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Development and management services

^[1]

8,938,000

9,102,000

9,277,000

8,405,000

725,767,000

661,151,000

Expenses

Rental

257,517,000

240,329,000

General and administrative

7,863,000

8,073,000

41,762,000

35,894,000

460,000

21,000

164,594,000

165,797,000

475,591,000

452,999,000

Other income (expense)

213,000

461,000

(905,000)

96,397,000

3,753,000

1,648,000

2,969,000

(126,000)

(24,038,000)

(101,009,000)

(90,220,000)

Net income attributable to noncontrolling interests

131,159,000

216,312,000

Noncontrolling interests in property partnerships

(18,830,000)

(17,234,000)

Noncontrolling interest—common units of Boston Properties Limited Partnership

(11,599,000)

(20,432,000)

Net income attributable to the Company

100,730,000

178,646,000

Preferred dividends / distributions

(2,625,000)

Net income attributable to the Company's common shareholders / unitholders

$ 98,105,000

$ 176,021,000

Basic earnings per common share / unit attributable to the Company's common shareholders / unitholders

Net income (in dollars per share / unit)

$ 0.63

$ 1.14

Weighted average number of common shares / units outstanding

154,525

154,385

Diluted earnings per common share / unit attributable to the Company's common shareholders / unitholders

Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)

$ 0.63

$ 1.14

Weighted average number of common and common equivalent shares / units outstanding (in shares / units)

154,844

154,705

Development and management services

Revenue

Lease

$ 679,251,000

$ 0

Base rent

519,507,000

Recoveries from tenants

95,118,000

9,277,000

8,405,000

General and administrative

725,767,000

661,151,000

Expenses

Rental

257,517,000

240,329,000

41,762,000

35,894,000

460,000

21,000

162,682,000

163,853,000

473,679,000

451,055,000

Other income (expense)

213,000

461,000

(905,000)

98,907,000

3,753,000

1,648,000

2,969,000

(126,000)

(22,272,000)

(101,009,000)

(90,220,000)

Net income attributable to noncontrolling interests

134,837,000

220,766,000

Noncontrolling interests in property partnerships

(18,830,000)

(17,234,000)

Net income attributable to the Company

116,007,000

203,532,000

Preferred dividends / distributions

(2,625,000)

Net income attributable to the Company's common shareholders / unitholders

$ 113,382,000

$ 200,907,000

Basic earnings per common share / unit attributable to the Company's common shareholders / unitholders

Net income (in dollars per share / unit)

$ 0.66

$ 1.17

Weighted average number of common shares / units outstanding

172,131

171,867

Diluted earnings per common share / unit attributable to the Company's common shareholders / unitholders

Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)

$ 0.66

$ 1.17

Weighted average number of common and common equivalent shares / units outstanding (in shares / units)

172,450

172,187

Parking and Other [Member]

Revenue

Parking and Other [Member] | Boston Properties Limited Partnership

$ 24,906,000

$ 26,134,000

Revenue

24,906,000

26,134,000

Hotel [Member]

Revenue

8,938,000

9,102,000

Expenses

Hotel [Member] | Boston Properties Limited Partnership

7,863,000

8,073,000

Revenue

8,938,000

9,102,000

Expenses

Management Service [Member]

7,863,000

8,073,000

Revenue

3,395,000

2,885,000

Expenses

Management Service [Member] | Boston Properties Limited Partnership

3,395,000

2,885,000

Revenue

3,395,000

2,885,000

Expenses

$ 3,395,000

$ 2,885,000

[1]	Rental Revenue is equal to total Revenue per the Company's Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Consolidated Statements Of Comprehensive Income - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

Effective portion of interest rate contracts

$ 131,159

$ 216,312

Other comprehensive income (loss):

(2,628)

Amortization of interest rate contracts

^[1]

1,666

Other comprehensive income (loss)

(962)

1,666

Comprehensive income

130,197

217,978

Comprehensive income attributable to noncontrolling interests

(30,429)

(37,666)

Other comprehensive (income) loss attributable to noncontrolling interests

(31)

(299)

Comprehensive income attributable to the Company

99,737

180,013

Effective portion of interest rate contracts

134,837

220,766

Other comprehensive income (loss):

(2,628)

Amortization of interest rate contracts

^[2]

1,666

Other comprehensive income (loss)

(962)

1,666

Comprehensive income

133,875

222,432

Comprehensive income attributable to noncontrolling interests

(18,974)

(17,378)

Comprehensive income attributable to the Company

$ 114,901

$ 205,054

[1]	Amounts reclassified from comprehensive income primarily to interest expense within the Boston Properties, Inc.’s Consolidated Statements of Operations.
[2]	Amounts reclassified from comprehensive income primarily to interest expense within the Boston Properties Limited Partnership's Consolidated Statements of Operations.

Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Dividends In Excess Of Earnings [Member]	Treasury Stock, At Cost [Member]	Accumulated Other Comprehensive (Income) Loss [Member]	Noncontrolling Interests - Common units [Member]	Noncontrolling interest - property partnerships [Member]
Equity, value at Dec. 31, 2017	$ 8,102,456	$ 1,543	$ 200,000	$ 6,377,908	$ (712,343)	$ (2,722)	$ (50,429)	$ 604,739	$ 1,683,760
Equity, shares at Dec. 31, 2017		154,325,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	5,496				4,933			563
Conversion of operating partnership units to Common Stock, shares		24,000
Conversion of operating partnership units to Common Stock, value	0	$ 1		831				(832)
Allocated net income for the year	216,312				178,646			20,432	17,234
Dividends/distributions declared	(140,466)				(126,115)			(14,351)
Shares issued pursuant to stock purchase plan, shares		3,000
Shares issued pursuant to stock purchase plan, value	429			429
Net activity from stock option and incentive plan, shares		10,000
Net activity from stock option and incentive plan, value	13,620			(185)				13,805
Contributions from noncontrolling interests in property partnerships	15,267								15,267
Distributions to noncontrolling interests in property partnerships	(30,690)								(30,690)
Amortization of interest rate contracts	1,666						1,367	155	144
Reallocation of noncontrolling interest	0			5,164				(5,164)
Equity, value at Mar. 31, 2018	8,184,090	$ 1,544	200,000	6,384,147	(654,879)	(2,722)	(49,062)	619,347	1,685,715
Equity, shares at Mar. 31, 2018		154,362,000
Equity, value at Dec. 31, 2018	$ 8,213,968	$ 1,545	200,000	6,407,623	(675,534)	(2,722)	(47,741)	619,352	1,711,445
Equity, shares at Dec. 31, 2018	154,458,478	154,458,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	$ (4,379)				(3,864)			(445)	(70)
Conversion of operating partnership units to Common Stock, shares		14,000
Conversion of operating partnership units to Common Stock, value	0			492				(492)
Allocated net income for the year	131,159				100,730			11,599	18,830
Dividends/distributions declared	(166,600)				(149,415)			(17,185)
Shares issued pursuant to stock purchase plan, shares		4,000
Shares issued pursuant to stock purchase plan, value	373			373
Net activity from stock option and incentive plan, shares		39,000
Net activity from stock option and incentive plan, value	16,469			3,059				13,410
Contributions from noncontrolling interests in property partnerships	4,387								4,387
Distributions to noncontrolling interests in property partnerships	(24,128)								(24,128)
Effective portion of interest rate contracts	(2,628)						(2,359)	(269)
Amortization of interest rate contracts	1,666						1,366	156	144
Reallocation of noncontrolling interest	0			3,065				(3,065)
Equity, value at Mar. 31, 2019	$ 8,170,287	$ 1,545	$ 200,000	$ 6,414,612	$ (728,083)	$ (2,722)	$ (48,734)	$ 623,061	$ 1,710,608
Equity, shares at Mar. 31, 2019	154,515,486	154,515,000

Consolidated Statement of Partners' Capital Statement - USD ($) $ in Thousands	Total	General Partner [Member]	Limited Partner [Member]	Partners' Capital (General and Limited Partners) [Member]	Preferred Units [Member]	Accumulated Other Comprehensive (Income) Loss [Member]	Noncontrolling interest - property partnerships [Member]	Noncontrolling interest - property partnerships [Member] Boston Properties Limited Partnership	Total Capital [Member]	Noncontrolling interest - Redeemable partnership units [Member]
Common Stock, Shares, Outstanding		1,720,000	152,606,000
Beginning Balance at Dec. 31, 2017				$ 3,664,436	$ 193,623	$ (50,429)	$ 1,683,760		$ 5,491,390	$ 2,292,263
Cumulative effect of a change in accounting principle	$ 5,496			4,933					4,933	563
Contributions		1,000	11,000
Contributions				1,452					1,452	34,258
Allocated net income for the year				180,475	2,625		17,234		200,334	20,432
Distributions				(123,490)	(2,625)				(126,115)	(14,351)
Unearned compensation				(1,208)					(1,208)	(20,453)
Converstion of redeemable partnership units		1,000	23,000
Conversion of redeemable partnership units				832					832	(832)
Adjustment to reflect redeemable partnership units at redemption value				115,432					115,432	(115,432)
Amortization of interest rate contracts	1,666					1,367	144		1,511	155
Contributions from noncontrolling interests in property partnerships	15,267						15,267		15,267
Distributions to noncontrolling interests in property partnerships	$ (30,690)						(30,690)		(30,690)
Ending Balance at Mar. 31, 2018				3,842,862	193,623	(49,062)	1,685,715		5,673,138	2,196,603
Common Stock, Shares, Outstanding		1,722,000	152,640,000
Common Stock, Shares, Outstanding	154,458,478	1,722,000	152,736,000
Beginning Balance at Dec. 31, 2018				4,054,996	193,623	(47,741)	1,711,445		5,912,323	2,000,591
Cumulative effect of a change in accounting principle	$ (4,379)			(3,864)			(70)	$ 70	(3,934)	(445)
Contributions		2,000	41,000
Contributions				4,820					4,820	34,400
Allocated net income for the year				101,783	2,625		18,830		123,238	11,599
Distributions				(146,790)	(2,625)				(149,415)	(17,185)
Unearned compensation				(1,388)					(1,388)	(20,990)
Converstion of redeemable partnership units		1,000	13,000
Conversion of redeemable partnership units				492					492	(492)
Adjustment to reflect redeemable partnership units at redemption value				(406,875)					(406,875)	406,875
Effective portion of interest rate contracts	(2,628)					(2,359)			(2,359)	(269)
Amortization of interest rate contracts	1,666					1,366	144		1,510	156
Contributions from noncontrolling interests in property partnerships	4,387						4,387		4,387
Distributions to noncontrolling interests in property partnerships	$ (24,128)						(24,128)		(24,128)
Ending Balance at Mar. 31, 2019				$ 3,603,174	$ 193,623	$ (48,734)	$ 1,710,608		$ 5,458,671	$ 2,414,240
Common Stock, Shares, Outstanding	154,515,486	1,725,000	152,790,000

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 131,159	$ 216,312
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	164,594	165,797
Amortization of right of use assets - operating leases	605	0
Impairment loss	24,038	0
Non-cash compensation expense	15,050	14,772
Income from unconsolidated joint ventures	(213)	(461)
Distributions of net cash flow from operations of unconsolidated joint ventures	2,650	847
(Gains) losses from investments in securities	(2,969)	126
Non-cash portion of interest expense	5,447	5,299
Losses (gains) on sales of real estate	905	(96,397)
Change in assets and liabilities:
Tenant and other receivables, net	(14,000)	22,790
Note receivable	(125)	0
Accrued rental income, net	(15,570)	(26,319)
Prepaid expenses and other assets	(68,554)	(66,968)
Lease liabilities - operating leases	370	0
Accounts payable and accrued expenses	258	(13,913)
Accrued interest payable	(160)	12,399
Other liabilities	(17,831)	23,089
Tenant leasing costs	(18,420)	(31,595)
Total adjustments	76,075	9,466
Net cash provided by operating activities	207,234	225,778
Cash flows from investing activities:
Acquisitions of real estate	(43,061)	0
Construction in progress	(85,632)	(150,060)
Building and other capital improvements	(32,719)	(53,550)
Tenant improvements	(54,242)	(47,157)
Proceeds from sales of real estate	20,019	116,120
Capital contributions to unconsolidated joint ventures	(26,995)	(48,823)
Investments in securities, net	(885)	(318)
Net cash used in investing activities	(223,515)	(183,788)
Cash flows from financing activities:
Repayments of mortgage notes payable	(5,645)	(5,333)
Borrowings on unsecured line of credit	50,000	260,000
Repayments of unsecured line of credit	(50,000)	(190,000)
Payments on finance lease obligations	(470)	0
Payments on capital lease obligations	0	(3)
Payments on real estate financing transactions	0	(444)
Deferred financing costs	(186)	(16)
Net proceeds from equity transactions	1,792	(723)
Dividends and distributions	(166,362)	(140,288)
Contributions from noncontrolling interests in property partnerships	4,387	15,267
Distributions to noncontrolling interests in property partnerships	(24,128)	(30,690)
Net cash used in financing activities	(190,612)	(92,230)
Net decrease in cash and cash equivalents and cash held in escrows	(206,893)	(50,240)
Cash and cash equivalents and cash held in escrows, beginning of period	639,191	505,369
Cash and cash equivalents and cash held in escrows, end of period	432,298	455,129
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	543,359	434,767
Cash held in escrows, beginning of period	95,832	70,602
Cash and Cash Equivalents, end of period	360,091	294,571
Cash held in escrows, end of period	72,207	160,558
Supplemental disclosures:
Cash paid for interest	107,094	89,412
Interest capitalized	11,813	17,378
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(31,640)	(29,609)
Additions to real estate included in accounts payable and accrued expenses	49,689	35,245
Real estate acquired through finance lease	122,563	0
Dividends and distributions declared but not paid	165,352	139,218
Conversions of noncontrolling interests to stockholders’ equity / partners' capital	492	832
Issuance of restricted securities to employees	37,428	36,433
Boston Properties Limited Partnership
Cash flows from operating activities:
Net income	134,837	220,766
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	162,682	163,853
Amortization of right of use assets - operating leases	605	0
Impairment loss	22,272	0
Non-cash compensation expense	15,050	14,772
Income from unconsolidated joint ventures	(213)	(461)
Distributions of net cash flow from operations of unconsolidated joint ventures	2,650	847
(Gains) losses from investments in securities	(2,969)	126
Non-cash portion of interest expense	5,447	5,299
Losses (gains) on sales of real estate	905	(98,907)
Change in assets and liabilities:
Tenant and other receivables, net	(14,000)	22,790
Note receivable	(125)	0
Accrued rental income, net	(15,570)	(26,319)
Prepaid expenses and other assets	(68,554)	(66,968)
Lease liabilities - operating leases	370	0
Accounts payable and accrued expenses	258	(13,913)
Accrued interest payable	(160)	12,399
Other liabilities	(17,831)	23,089
Tenant leasing costs	(18,420)	(31,595)
Total adjustments	72,397	5,012
Net cash provided by operating activities	207,234	225,778
Cash flows from investing activities:
Acquisitions of real estate	(43,061)	0
Construction in progress	(85,632)	(150,060)
Building and other capital improvements	(32,719)	(53,550)
Tenant improvements	(54,242)	(47,157)
Proceeds from sales of real estate	20,019	116,120
Capital contributions to unconsolidated joint ventures	(26,995)	(48,823)
Investments in securities, net	(885)	(318)
Net cash used in investing activities	(223,515)	(183,788)
Cash flows from financing activities:
Repayments of mortgage notes payable	(5,645)	(5,333)
Borrowings on unsecured line of credit	50,000	260,000
Repayments of unsecured line of credit	(50,000)	(190,000)
Payments on finance lease obligations	(470)	0
Payments on capital lease obligations	0	(3)
Payments on real estate financing transactions	0	(444)
Deferred financing costs	(186)	(16)
Net proceeds from equity transactions	1,792	(723)
Dividends and distributions	(166,362)	(140,288)
Contributions from noncontrolling interests in property partnerships	4,387	15,267
Distributions to noncontrolling interests in property partnerships	(24,128)	(30,690)
Net cash used in financing activities	(190,612)	(92,230)
Net decrease in cash and cash equivalents and cash held in escrows	(206,893)	(50,240)
Cash and cash equivalents and cash held in escrows, beginning of period	639,191	505,369
Cash and cash equivalents and cash held in escrows, end of period	432,298	455,129
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	543,359	434,767
Cash held in escrows, beginning of period	95,832	70,602
Cash and Cash Equivalents, end of period	360,091	294,571
Cash held in escrows, end of period	72,207	160,558
Supplemental disclosures:
Cash paid for interest	107,094	89,412
Interest capitalized	11,813	17,378
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(31,640)	(29,609)
Additions to real estate included in accounts payable and accrued expenses	49,689	35,245
Real estate acquired through finance lease	122,563	0
Dividends and distributions declared but not paid	165,352	139,218
Conversions of noncontrolling interests to stockholders’ equity / partners' capital	492	832
Issuance of restricted securities to employees	$ 37,428	$ 36,433

Organization

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization

1. Organization

Boston Properties, Inc., a Delaware corporation, is a fully integrated, self-administered and self-managed real estate investment trust (“REIT”). Boston Properties, Inc. is the sole general partner of Boston Properties Limited Partnership, its operating partnership, and at March 31, 2019 owned an approximate 89.5% (89.7% at December 31, 2018) general and limited partnership interest in Boston Properties Limited Partnership. Unless stated otherwise or the context requires, the “Company” refers to Boston Properties, Inc. and its subsidiaries, including Boston Properties Limited Partnership, and its consolidated subsidiaries. Partnership interests in Boston Properties Limited Partnership include:


•	common units of partnership interest (also referred to as “OP Units”),


•	long term incentive units of partnership interest (also referred to as “LTIP Units”), and


•	preferred units of partnership interest (also referred to as “Preferred Units”).

Unless specifically noted otherwise, all references to OP Units exclude units held by Boston Properties, Inc. A holder of an OP Unit may present such OP Unit to Boston Properties Limited Partnership for redemption at any time (subject to restrictions agreed upon at the time of issuance of OP Units to particular holders that may restrict such redemption right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, Boston Properties Limited Partnership is obligated to redeem the OP Unit for cash equal to the value of a share of common stock of Boston Properties, Inc. (“Common Stock”). In lieu of a cash redemption, Boston Properties, Inc. may elect to acquire the OP Unit for one share of Common Stock. Because the number of shares of Common Stock outstanding at all times equals the number of OP Units that Boston Properties, Inc. owns, one share of Common Stock is generally the economic equivalent of one OP Unit, and the quarterly distribution that may be paid to the holder of an OP Unit equals the quarterly dividend that may be paid to the holder of a share of Common Stock.

The Company uses LTIP Units as a form of equity-based award for annual long-term incentive equity compensation. The Company has also issued LTIP Units to employees in the form of (1) 2012 outperformance plan awards (“2012 OPP Units”) and (2) 2013, 2014, 2015, 2016, 2017, 2018 and 2019 multi-year, long-term incentive program awards (also referred to as “MYLTIP Units”), each of which, upon the satisfaction of certain performance and vesting conditions, is convertible into one OP Unit. The three-year measurement periods for the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units expired on February 6, 2015, February 4, 2016, February 3, 2017, February 4, 2018 and February 9, 2019, respectively, and Boston Properties, Inc.’s total stockholder return (“TSR”) was sufficient for employees to earn and therefore become eligible to vest in a portion of the awards. Unless and until they are earned, the rights, preferences and privileges of the 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units differ from other LTIP Units granted to employees (including the 2012 OPP Units, the 2013 MYLTIP Units, the 2014 MYLTIP Units, the 2015 MYLTIP Units and the 2016 MYLTIP Units, which have been earned). Therefore, unless specifically noted otherwise, all references to LTIP Units exclude the 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units. LTIP Units (including the earned 2012 OPP Units, the 2013 MYLTIP Units, the 2014 MYLTIP Units, the 2015 MYLTIP Units and 2016 MYLTIP Units), whether vested or not, will receive the same quarterly per unit distributions as OP Units, which equal per share dividends on Common Stock (See Notes 7, 8 and 10).

At March 31, 2019, there was one series of Preferred Units outstanding (i.e., Series B Preferred Units). The Series B Preferred Units were issued to Boston Properties, Inc. on March 27, 2013 in connection with the issuance of 80,000 shares (8,000,000 depositary shares each representing 1/100th of a share) of 5.25% Series B Cumulative Redeemable Preferred Stock (the “Series B Preferred Stock”). Boston Properties, Inc. contributed the net proceeds from the offering to Boston Properties Limited Partnership in exchange for 80,000 Series B Preferred Units having terms and preferences generally mirroring those of the Series B Preferred Stock (See Note 8).

Properties

At March 31, 2019, the Company owned or had interests in a portfolio of 196 commercial real estate properties (the “Properties”) aggregating approximately 51.4 million net rentable square feet of primarily Class A office properties, including eleven properties under construction/redevelopment totaling approximately 5.3 million net rentable square feet. At March 31, 2019, the Properties consisted of:


•	177 office properties (including nine properties under construction/redevelopment);


•	twelve retail properties;


•	six residential properties (including two properties under construction); and


•	one hotel.

The Company considers Class A office properties to be well-located buildings that are professionally managed and maintained, attract high-quality tenants and command upper-tier rental rates, and that are modern structures or have been modernized to compete with newer buildings.

Basis Of Presentation And Summary Of Significant Accounting Policies

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Basis Of Presentation And Summary Of Significant Accounting Policies

2. Basis of Presentation and Summary of Significant Accounting Policies

Boston Properties, Inc. does not have any other significant assets, liabilities or operations, other than its investment in Boston Properties Limited Partnership, nor does it have employees of its own. Boston Properties Limited Partnership, not Boston Properties, Inc., generally executes all significant business relationships other than transactions involving securities of Boston Properties, Inc. All majority-owned subsidiaries and joint ventures over which the Company has financial and operating control and variable interest entities (“VIEs”) in which the Company has determined it is the primary beneficiary are included in the consolidated financial statements. All significant intercompany balances and transactions have been eliminated in consolidation. The Company accounts for all other unconsolidated joint ventures using the equity method of accounting. Accordingly, the Company’s share of the earnings of these joint ventures and companies is included in consolidated net income.

The accompanying interim financial statements are unaudited; however, the financial statements have been prepared in accordance with generally accepted accounting principles (“GAAP”) for interim financial information and in conjunction with the rules and regulations of the Securities and Exchange Commission. Accordingly, they do not include all of the disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting solely of normal recurring matters) necessary for a fair statement of the financial statements for these interim periods have been included. The results of operations for the interim periods are not necessarily indicative of the results to be obtained for other interim periods or for the full fiscal year. The year-end consolidated balance sheet data was derived from audited financial statements, but does not include all disclosure required by GAAP. These financial statements should be read in conjunction with the Company’s financial statements and notes thereto contained in the Company’s Annual Report in the Company’s Form 10-K for its fiscal year ended December 31, 2018.

Fair Value of Financial Instruments

The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. Boston Properties Limited Partnership determines the fair value of its unsecured senior notes using market prices. The inputs used in determining the fair value of Boston Properties Limited Partnership’s unsecured senior notes is categorized at a Level 1 basis (as defined in Accounting Standards Codification ("ASC") 820 “Fair Value Measurements and Disclosures” (“ASC 820”)) due to the fact that it uses quoted market rates to value these instruments. However, the inputs used in determining the fair value could be categorized at a Level 2 basis (as defined in ASC 820) if trading volumes are low. The Company determines the fair value of its related party note receivable, note receivable and mortgage notes payable using discounted cash flow analysis by discounting the spread between the future contractual interest payments and hypothetical future interest payments on note receivables / mortgage debt based on current market rates for similar securities. In determining the current market rates, the Company adds its estimates of market spreads to the quoted yields on federal government treasury securities with similar maturity dates to its debt. The inputs used in determining the fair value of the Company’s related party note receivable, note receivable, and mortgage notes payable are categorized at a Level 3 basis (as defined in ASC 820) due to the fact that the Company considers the rates used in the valuation techniques to be unobservable inputs. To the extent that there are outstanding borrowings under the unsecured line of credit or unsecured term loan, the Company utilizes a discounted cash flow methodology in order to estimate the fair value. To the extent that credit spreads have changed since the origination, the net present value of the difference between future contractual interest payments and future interest payments based on the Company’s estimate of a current market rate would represent the difference between the book value and the fair value. The Company’s estimate of a current market rate is based upon the rate, considering current market conditions and Boston Properties Limited Partnership's specific credit profile, at which it estimates it could obtain similar borrowings. To the extent there are outstanding borrowings, this current market rate is estimated and therefore would be primarily based upon a Level 3 input.

Because the Company’s valuations of its financial instruments are based on these types of estimates, the actual fair values of its financial instruments may differ materially if the Company’s estimates do not prove to be accurate, and the Company’s estimated fair values for these instruments as of the end of the applicable reporting period are not necessarily indicative of estimated or actual fair values in future reporting periods. The following table presents the aggregate carrying value of the Company’s related party note receivable, note receivable, mortgage notes payable, net, unsecured senior notes, net, unsecured line of credit and unsecured term loan, net and the Company’s corresponding estimate of fair value as of March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Related party note receivable	$	80,000	$	80,060	$	80,000	$	80,000
Note receivable	19,593		17,723		19,468		19,468
	$	99,593	$	97,783	$	99,468	$	99,468

Mortgage notes payable, net	$	2,959,908	$	2,948,057	$	2,964,572	$	2,903,925
Unsecured senior notes, net	7,547,043		7,584,456		7,544,697		7,469,338
Unsecured line of credit	—		—		—		—
Unsecured term loan, net	498,607		500,728		498,488		500,783
Total	$	11,005,558	$	11,033,241	$	11,007,757	$	10,874,046

Variable Interest Entities (VIEs)

Consolidated VIEs are those for which the Company is considered to be the primary beneficiary of a VIE. The primary beneficiary is the entity that has a controlling financial interest in the VIE, which is defined by the entity having both of the following characteristics: (1) the power to direct the activities that, when taken together, most significantly impact the VIE’s performance and (2) the obligation to absorb losses or the right to receive the returns from the VIE that could potentially be significant to the VIE. The Company has determined that it is the primary beneficiary for seven of the ten entities that are VIEs.

Consolidated Variable Interest Entities

As of March 31, 2019, Boston Properties, Inc. has identified seven consolidated VIEs, including Boston Properties Limited Partnership. Excluding Boston Properties Limited Partnership, the VIEs consisted of the following six in-service properties: 767 Fifth Avenue (the General Motors Building), Times Square Tower, 601 Lexington Avenue, Atlantic Wharf Office Building, 100 Federal Street and Salesforce Tower (See Note 12).

The Company consolidates these VIEs because it is the primary beneficiary. The third parties’ interests in these consolidated entities (i.e., excluding Boston Properties Limited Partnership's interest) are reflected as noncontrolling interest in property partnerships in the accompanying Consolidated Financial Statements (See Note 7).

In addition, Boston Properties, Inc.’s only significant asset is its investment in Boston Properties Limited Partnership and, consequently, substantially all of Boston Properties, Inc.’s assets and liabilities are the assets and liabilities of Boston Properties Limited Partnership.

Variable Interest Entities Not Consolidated

The Company has determined that its 7750 Wisconsin Avenue LLC and Office Tower Developer LLC joint ventures, which own 7750 Wisconsin Avenue and 100 Causeway Street (which is the office component of The Hub on Causeway mixed-use development project), respectively, are VIEs. The Company also determined that the landlord entity for its Platform 16 ground lease is a VIE. The Company does not consolidate these entities as the Company does not have the power to direct the activities that, when taken together, most significantly impact the VIE’s performance and, therefore, the Company is not considered to be the primary beneficiary.

New Accounting Pronouncements

New Accounting Pronouncements Adopted

Leases

On January 1, 2019, the Company adopted Accounting Standards Update ("ASU") 2016-02, “Leases (Topic 842)” (“ASU 2016-02” or "Topic 842"). For information pertaining to the Company's adoption and disclosures with respect to leases, see Note 4.

Real Estate

3 Months Ended

Mar. 31, 2019

Real Estate [Abstract]

Real Estate

3. Real Estate

Boston Properties, Inc.

Real estate consisted of the following at March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019			December 31, 2018
Land	$	5,061,532		$	5,072,568
Right of use assets - finance leases	187,292			—
Right of use assets - operating leases	151,166			—
Land held for future development (1)	258,221			200,498
Buildings and improvements	13,286,605			13,356,751
Tenant improvements	2,444,358			2,396,932
Furniture, fixtures and equipment	43,080			44,351
Construction in progress	647,469			578,796
Total	22,079,723			21,649,896
Less: Accumulated depreciation	(4,962,959		)	(4,897,777		)
	$	17,116,764		$	16,752,119

_______________


(1)	Includes pre-development costs.

Boston Properties Limited Partnership

Real estate consisted of the following at March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019			December 31, 2018
Land	$	4,961,028		$	4,971,475
Right of use assets - finance leases	187,292			—
Right of use assets - operating leases	151,166			—
Land held for future development (1)	258,221			200,498
Buildings and improvements	12,991,108			13,059,488
Tenant improvements	2,444,358			2,396,932
Furniture, fixtures and equipment	43,080			44,351
Construction in progress	647,469			578,796
Total	21,683,722			21,251,540
Less: Accumulated depreciation	(4,864,334		)	(4,800,475		)
	$	16,819,388		$	16,451,065

_______________


(1)	Includes pre-development costs.

Development

On February 14, 2019, the Company announced that it had entered into a 15-year lease with Google, LLC for approximately 362,000 net rentable square feet of Class A office space in a build-to-suit development project to be located at the Company’s 325 Main Street property at Kendall Center in Cambridge, Massachusetts. 325 Main Street currently consists of an approximately 115,000 net rentable square foot Class A office property that will be demolished and developed into an approximately 400,000 net rentable square foot Class A office property, including approximately 38,000 net rentable square feet of retail space. There can be no assurance that the project will commence.

Ground Lease

On January 24, 2019, the ground lessor under the Company's 65-year ground lease for land totaling approximately 5.6 acres at Platform 16 located in San Jose, California, which will support approximately 1.1 million square feet of commercial office space, made available for lease to the Company the remaining land parcels. As a result, the Company recognized the remaining portion of the right of use finance lease asset and finance lease liability. The ground lease provides the Company with the right to purchase the land during a 12-month period commencing February 1, 2020 at a purchase price of approximately $134.8 million. The Company is reasonably certain that it will exercise the option to purchase the land and as a result, the Company has concluded that the lease should be accounted for as a finance lease. As a result, the Company recorded an approximately $122.6 million right of use asset - finance lease and a lease liability - finance lease on the Company’s Consolidated Balance Sheets. Finance lease assets and liabilities are accounted for at the lower of fair market value or the present value of future lease payments. The finance lease is for land only. Therefore, the Company will not depreciate the right of use asset - finance lease because land is assumed to have an indefinite life.

As of January 24, 2019, the lease payments from the finance lease are as follows (in thousands):



Period from January 24, 2019 through December 31, 2019	$	17,918
2020	109,460
Total expected minimum lease payments	127,378
Interest portion	(4,815		)
Present value of expected net lease payments	$	122,563

Acquisitions

On January 10, 2019, the Company acquired land parcels at its Carnegie Center property located in Princeton, New Jersey for a gross purchase price of approximately $51.5 million, which includes an aggregate of approximately $8.6 million of additional amounts that are payable in the future to the seller upon the development or sale of each of the parcels. The land parcels could support approximately 1.7 million square feet of development.

Dispositions

On January 24, 2019, the Company completed the sale of its 2600 Tower Oaks Boulevard property located in Rockville, Maryland for a gross sales price of approximately $22.7 million. Net cash proceeds totaled approximately $21.4 million, resulting in a loss on sale of real estate totaling approximately $0.6 million. The Company recognized an impairment loss totaling approximately $3.1 million for Boston Properties, Inc. and approximately $1.5 million for Boston Properties Limited Partnership during the year ended December 31, 2018. 2600 Tower Oaks Boulevard is an approximately 179,000 net rentable square foot Class A office property. 2600 Tower Oaks contributed approximately $(0.2) million of net loss to the Company for the period from January 1, 2019 through January 23, 2019 and contributed approximately $(0.2) million of net loss to the Company for the three months ended March 31, 2018.

At March 31, 2019, the Company evaluated the expected hold period of its One Tower Center property and based on a shorter than expected hold period, the Company reduced the carrying value of the property to its estimated fair value at March 31, 2019 and recognized an impairment loss totaling approximately $24.0 million for Boston Properties, Inc. and approximately $22.3 million for Boston Properties Limited Partnership. The Company’s estimated fair value was based on a pending offer from a third party to acquire the property and the subsequent execution of a purchase and sale agreement on April 18, 2019 for a gross sale price of approximately $38.0 million (See Note 12). One Tower Center is an approximately 410,000 net rentable square foot Class A office property located in East Brunswick, New Jersey.

Leases

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Leases of Lessee Disclosure

4. Leases

General Adoption

In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease for accounting purposes is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to the prior guidance in ASC 840 -“Leases” (“Topic 840”). ASU 2016-02 requires lessors to account for leases using an approach that is substantially equivalent to Topic 840 for sales-type leases, direct financing leases and operating leases. ASU 2016-02 supersedes previous leasing standards.

On July 30, 2018, the FASB issued ASU 2018-11, “Leases (Topic 842): Targeted Improvements” (“ASU 2018-11”), that (1) simplifies transition requirements for both lessees and lessors by adding an option that permits an organization to apply the transition provisions of the new standard at its adoption date instead of at the earliest comparative period presented in its financial statements and (2) allows lessors to elect, as a practical expedient, by class of underlying asset, to not separate nonlease components from the associated lease component and, instead, to account for those components as a single component if the nonlease components otherwise would be accounted for under the revenue guidance (ASU 2014-09, “Revenue from Contracts with Customers (Topic 606) ("ASC 606")) that was adopted on January 1, 2018, and both of the following are met:

(1) the timing and pattern of transfer of the nonlease component(s) and associated lease components are the same; and

(2) the lease component, if accounted for separately, would be classified as an operating lease.

If the nonlease component or components associated with the lease component are the predominant component of the combined component, an entity is required to account for the combined component in accordance with ASC 606.

The Company adopted ASU 2016-02 and ASU 2018-11 effective January 1, 2019. For purposes of transition, the Company elected the practical expedient package, which has been applied consistently to all of its leases but did not elect the hindsight practical expedient. The practical expedient package did not require the Company to reassess the following: (i) whether an expired or existing contract meets the definition of a lease; (ii) the lease classification at the adoption date for existing leases; and (iii) whether costs previously capitalized as initial direct costs would continue to be amortized. This allows the Company to continue to account for its ground leases as operating leases. However, as of January 1, 2019, any new or modified ground leases may be classified as financing leases unless they meet certain conditions. The Company also elected to apply the transition provisions as of the adoption date, January 1, 2019, and not change its comparative statements. The Company recorded an adjustment to the opening balance of retained earnings related to initial direct costs that, as of January 1, 2019, had not started to amortize and are no longer allowed to be capitalized in accordance with ASU 2016-02, totaling approximately $3.9 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners' Capital of Boston Properties Limited Partnership, approximately $0.4 million to Noncontrolling interests - Common Units of Boston Properties, Inc. and Noncontrolling Interest - Redeemable Partnership Units of Boston Properties Limited Partnership and $70,000 to Noncontrolling Interests - Property Partnerships of Boston Properties, Inc. and Noncontrolling Interests in Property Partnerships of Boston Properties Limited Partnership on the corresponding Consolidated Balance Sheets.

The Company made the policy election, when it is the lessee, to not apply the revenue recognition requirements of Topic 842 to short term leases. This policy election is made by class of underlying assets and as described below, the Company considers real estate to be a class of underlying assets, and will not be further delineating it into specific uses of the real estate asset as the risk profiles are similar in nature. The Company will recognize the lease payments in net income on a straight-line basis over the lease term.

Lease payments from operating leases are recognized on a straight-line basis over the term of the leases. The cumulative difference between lease revenue recognized under this method and the contractual lease payment terms is recorded as deferred rent receivable on our consolidated balance sheets. The Company reviews its trade accounts receivable, including its straight-line rent receivable, related to base rents, straight-line rent, expense reimbursements and other revenues for collectability. The Company analyzes its accounts receivable, customer credit worthiness and current economic trends when evaluating the adequacy of the collectability of the lessee’s total accounts receivable balance on a lease by lease basis. In addition, tenants in bankruptcy are analyzed and considerations are made in connection with the expected recovery of pre-petition and post-petition claims. If a lessee’s accounts receivable balance is considered uncollectible the Company will write-off the receivable balances associated with the lease to Lease revenue and cease to recognize lease income, including straight-line rent unless cash is received. If the Company subsequently determines that it is probable it will collect substantially all the remaining lessee’s lease payments under the lease term, the Company will then reinstate the straight-line balance adjusting for the amount related to the period when the lease payments were considered not probable. The Company’s reported net earnings are directly affected by management’s estimate of the collectability of its trade accounts receivable.

In January 2018, the FASB issued ASU 2018-01, “Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842” (“ASU 2018-01”), which provides an optional transition practical expedient to not evaluate, under Topic 842, existing or expired land easements that were not previously accounted for as leases under the leases guidance in Topic 840. An entity that elects this practical expedient should evaluate new or modified land easements under Topic 842 beginning at the date that the entity adopts Topic 842. An entity that does not elect this practical expedient should evaluate all existing or expired land easements in connection with the adoption of the new lease requirements in Topic 842 to assess whether they meet the definition of a lease. The effective date and transition requirements for ASU 2018-01 are the same as the effective date and transition requirements in ASU 2016-02. The Company adopted ASU 2018-01 on January 1, 2019.

Lessee

For leases in which the Company is the lessee, (generally ground leases), on January 1, 2019, the Company recognized a right-of-use asset and a lease liability of approximately $151.8 million and $199.3 million, respectively. The leases liability was equal to the present value of the minimum lease payments in accordance with Topic ASC 840. In addition, the Company did not know the rate implicit in any of its ground leases which were classified as operating leases, and accordingly used the Company's incremental borrowing rate ("IBR") to determine the net present value of the minimum lease payments.

In order to determine the IBR, the Company utilized a market-based approach to estimate the incremental borrowing rate for each individual lease. The approach required significant judgment. Therefore, the Company utilized different data sets to estimate base IBRs via an analysis of the following weighted-components:


•	The interpolated rates from yields on outstanding U.S. Treasury issuances for up to 30 years and for years 31 and beyond, longer term publicly traded educational institution debt issued by high credit quality educational institutions with maturity dates up to 2116,


•	Observable mortgage rates spread over U.S. Treasury issuances, and


•	Unlevered property yields and discount rates.

The Company then applied adjustments to account for considerations related to term and interpolated the IBR.

The Company has four non-cancelable ground lease obligations, which were classified as operating leases, with various initial term expiration dates through 2114. The Company recognizes ground rent expense on a straight-line basis over the term of the respective ground lease agreements. None of the amounts disclosed below for these ground leases contain variable payments, extension options or residual value guarantees. One of the ground leases does have an extension option. However, lease payments for this ground lease are based on fair market value and as such have not been included in the analysis below.

The Company has four finance lease obligations with various initial term expiration dates through 2036.

The following tables provide quantitative information for the Company's operating and finance leases as of March 31, 2019 (dollars in thousands):



	Three months ended March 31, 2019
Lease costs
Operating lease costs	$	3,677
Finance lease costs
Amortization of right of use asset (1)	$	16
Interest on lease liabilities (2)	$	12

	March 31, 2019
Other information
Weighted-average remaining lease term (in years)
Operating leases	52
Finance leases	5
Weighted-average discount rate
Operating leases	5.7		%
Finance leases	4.1		%

_______________


(1)	The finance leases relate to either land, building or assets that remain in development. The Company's policy is not to depreciate finance lease assets related to land because it is assumed to have an indefinite life. For assets under development, depreciation may commence once the asset is placed in-service and depreciation would be recognized in accordance with the Company's policy.


(2)	Three of the finance leases relate to assets under development and as such the entire interest amount was capitalized.

The following table provides a maturity analysis for the Company's future contractual minimum lease payments to be made by the Company as of December 31, 2018, under non-cancelable ground leases which expire on various dates through 2114:



Years Ending December 31,	(in thousands)
2019	$	11,425
2020	18,425
2021	25,310
2022	8,894
2023	9,084
Thereafter	567,232

The following table provides a maturity analysis for the Company's future minimum lease payments, as of December 31, 2018, related to the four capital leases, through 2036:



Years Ending December 31,	(in thousands)
2019	$	1,441
2020	12,682
2021	2,123
2022	1,253
2023	944
Thereafter	73,241
Total expected minimum lease payments	91,684
Interest portion	(27,497		)
Present value of expected net minimum lease payments	$	64,187

The following table provides a maturity analysis for the Company's lease liabilities related to its operating and finance leases as of March 31, 2019 (in thousands):



	Operating			Finance (1)
April 1, 2019 - December 31, 2019	$	7,317		$	4,401
2020	17,488			122,070
2021	25,403			2,130
2022	11,376			1,121
2023	9,084			944
Thereafter	567,232			73,241
Total lease payments	637,900			203,907
Less: interest portion	(438,247		)	(30,784		)
Present value of lease payments	$	199,653		$	173,123

_______________


(1)	Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million, respectively, related to purchase options that the Company is reasonably certain that it will exercise.

Lessor, Operating Leases

Lessor

The Company leases primarily Class A office, retail and residential space to tenants. These leases may contain extension and termination options, that are predominately at the sole discretion of the tenant. In a few instances, the leases also contain purchase options, which would be exercisable at fair market value. Also, certain of the Company's leases include rental payments that are based on a percentage of the tenant sales in excess of contractual amounts.

ASU 2018-11 provides lessors a practical expedient to not separate nonlease components from the associated lease component if certain criteria stated above are met for each class of underlying assets. The guidance in Topic 842 defines "underlying asset" as "an asset that is the subject of a lease for which a right to use that asset has been conveyed to a lessee. The underlying asset could be a physically distinct portion of a single asset." Based on the above guidance, the Company considers real estate assets as a class of underlying assets and will not be further delineating it into specific uses of the real estate asset as the risk profiles are similar in nature.

Lease components are elements of an arrangement that provide the customer with the right to use an identified asset. Nonlease components are distinct elements of a contract that are not related to securing the use of the leased asset and revenue is recognized in accordance with ASC 606. The Company considers common area maintenance (CAM) and service income associated with tenant work orders to be nonlease components because they represent delivery of a separate service but are not considered a cost of securing the identified asset. In the case of the Company's business, the identified asset would be the leased real estate (office, retail or residential).

The Company assessed and concluded that the timing and pattern of transfer for nonlease components and the associated lease component are the same. The Company determined that the predominate component was the lease component and as such its leases will continue to qualify as operating leases and the Company has made a policy election to account for and present the lease component and the nonlease component as a single component in the revenue section of the Consolidated Statements of Operations labeled Lease. Prior to the adoption of Topic 842, nonlease components had been included within Recoveries from Tenants Revenue, Parking and Other Revenue and Development and Management Services Revenue on the Company's Consolidated Statements of Operations.

In addition, under ASU 2016-02, lessors will only capitalize incremental direct leasing costs. As a result, starting January 1, 2019, the Company no longer capitalizes non-incremental legal costs and internal leasing wages. These costs are expensed as incurred. The expensing of these items is included within General and Administrative Expense on the Consolidated Statements of Operations.

The following table summarizes the components of lease revenue recognized during the three months ended March 31, 2019 included within the Company's Consolidated Statements of Operations (in thousands):



Lease Revenue	Three months ended March 31, 2019
Fixed Contractual Payments	$	553,986
Variable lease payments	125,265
	$	679,251

The Company's properties are leased to tenants under operating leases with initial term expiration dates ranging from 2019 to 2049.

The future contractual minimum lease payments to be received (excluding operating expense reimbursements) by the Company as of December 31, 2018, under non-cancelable operating leases which expire on various dates through 2049:



Years Ending December 31,	(in thousands)
2019	$	2,088,171
2020	2,106,963
2021	2,015,031
2022	1,838,699
2023	1,736,636
Thereafter	12,295,464

The future contractual lease payments to be received (excluding operating expense reimbursements) by the Company as of March 31, 2019, under non-cancelable operating leases which expire on various dates through 2049:



	(in thousands)
April 1, 2019 - December 31, 2019	$	1,573,871
2020	2,147,464
2021	2,076,969
2022	1,910,362
2023	1,811,936
Thereafter	12,821,229

Investments in Unconsolidated Joint Ventures

3 Months Ended

Mar. 31, 2019

Investments In Unconsolidated Joint Ventures [Abstract]

Investments In Unconsolidated Joint Ventures

5. Investments in Unconsolidated Joint Ventures

The investments in unconsolidated joint ventures consist of the following at March 31, 2019 and December 31, 2018:



		Nominal % Ownership			Carrying Value of Investment (1)
Entity	Properties	Nominal % Ownership			March 31, 2019			December 31, 2018
					(in thousands)
Square 407 Limited Partnership	Market Square North	50.0	%		$	(5,948	)	$	(6,424	)
The Metropolitan Square Associates LLC	Metropolitan Square	20.0	%		3,146			2,644
BP/CRF 901 New York Avenue LLC	901 New York Avenue	25.0	%	(2)	(13,215		)	(13,640		)
WP Project Developer LLC	Wisconsin Place Land and Infrastructure	33.3	%	(3)	37,821			38,214
Annapolis Junction NFM LLC	Annapolis Junction	50.0	%	(4)	25,284			25,268
540 Madison Venture LLC	540 Madison Avenue	60.0	%		66,452			66,391
500 North Capitol Venture LLC	500 North Capitol Street, NW	30.0	%		(4,781		)	(5,026		)
501 K Street LLC	1001 6th Street	50.0	%	(5)	42,500			42,557
Podium Developer LLC	The Hub on Causeway - Podium	50.0	%		69,849			69,302
Residential Tower Developer LLC	The Hub on Causeway - Residential	50.0	%		47,795			47,505
Hotel Tower Developer LLC	The Hub on Causeway - Hotel Air Rights	50.0	%		3,343			3,022
Office Tower Developer LLC	100 Causeway Street	50.0	%	(6)	46,881			23,804
1265 Main Office JV LLC	1265 Main Street	50.0	%		4,030			3,918
BNY Tower Holdings LLC	Dock 72	50.0	%		83,291			82,520
CA-Colorado Center Limited Partnership	Colorado Center	50.0	%		252,762			253,495
7750 Wisconsin Avenue LLC	7750 Wisconsin Avenue	50.0	%	(6)	70,147			69,724
BP-M 3HB Venture LLC	3 Hudson Boulevard	25.0	%		47,480			46,993
SMBP Venture LP	Santa Monica Business Park	55.0	%		175,799			180,952
					$	952,636		$	931,219

_______________


(1)	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.


(2)	The Company’s economic ownership has increased based on the achievement of certain return thresholds.


(3)	The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.


(4)	The joint venture owns three in-service buildings and two undeveloped land parcels.


(5)	Under the joint venture agreement for this land parcel, the partner will be entitled to up to two additional payments from the venture based on increases in total entitled square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.


(6)	This entity is a VIE (See Note 2).

Certain of the Company’s unconsolidated joint venture agreements provide that, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exceptions, under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. Under certain of the Company’s joint venture agreements, if certain return thresholds are achieved, the partners will be entitled to an additional promoted interest or payments.

The combined summarized balance sheets of the Company’s unconsolidated joint ventures are as follows:



	March 31, 2019		December 31, 2018
	(in thousands)
ASSETS
Real estate and development in process, net (1)	$	3,660,439	$	3,545,906
Other assets	534,534		543,512
Total assets	$	4,194,973	$	4,089,418
LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
Mortgage and notes payable, net	$	2,074,473	$	2,017,609
Other liabilities (2)	604,280		582,006
Members’/Partners’ equity	1,516,220		1,489,803
Total liabilities and members’/partners’ equity	$	4,194,973	$	4,089,418
Company’s share of equity	$	642,564	$	622,498
Basis differentials (3)	310,072		308,721
Carrying value of the Company’s investments in unconsolidated joint ventures (4)	$	952,636	$	931,219

_______________


(1)	At March 31, 2019, this amount includes right of use assets - finance leases and right of use assets - operating leases totaling approximately $248.9 million and $12.7 million, respectively.


(2)	At March 31, 2019, this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.9 million and $17.2 million, respectively.

(3)

This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At March 31, 2019 and December 31, 2018, there was an aggregate basis differential of approximately $315.3 million and $316.7 million, respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities.


(4)	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

The combined summarized statements of operations of the Company’s unconsolidated joint ventures are as follows:



	Three months ended March 31,
	2019			2018
	(in thousands)
Total revenue (1)	$	82,955		$	56,486
Expenses
Operating	30,499			22,849
Depreciation and amortization	28,646			14,725
Total expenses	59,145			37,574
Other expense
Interest expense	20,757			14,424
Net income	$	3,053		$	4,488

Company’s share of net income	$	1,584		$	1,826
Basis differential (2)	(1,371		)	(1,365		)
Income from unconsolidated joint ventures	$	213		$	461

_______________


(1)	Includes straight-line rent adjustments of approximately $5.8 million and $1.8 million for the three months ended March 31, 2019 and 2018, respectively.


(2)	Includes straight-line rent adjustments of approximately $0.5 million and $0.7 million for the three months ended March 31, 2019 and 2018, respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.4 million for the three months ended March 31, 2019 and 2018, respectively.

On January 24, 2019, a joint venture in which the Company has a 50% interest extended the loan collateralized by its Annapolis Junction Building Six property. At the time of the extension, the outstanding balance of the loan totaled approximately $13.0 million and was scheduled to mature on November 17, 2019, with one, one-year extension option, subject to certain conditions. The extended loan has a total commitment amount of approximately $14.3 million, bears interest at a variable rate equal to LIBOR plus 2.00% per annum and matures on November 17, 2020. Annapolis Junction Building Six is a Class A office property with approximately 119,000 net rentable square feet located in Annapolis, Maryland.

Commitments And Contingencies	3 Months Ended
Commitments And Contingencies	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	6. Commitments and Contingencies General In the normal course of business, the Company guarantees its performance of services or indemnifies third parties against its negligence. In addition, in the normal course of business, the Company guarantees to certain tenants the obligations of its subsidiaries for the payment of tenant improvement allowances and brokerage commissions in connection with their leases and limited costs arising from delays in delivery of their premises. The Company has letter of credit and performance obligations related to lender and development requirements that total approximately $7.7 million. Certain of the Company’s joint venture agreements include provisions whereby, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exception, under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. From time to time, under certain of the Company’s joint venture agreements, if certain return thresholds are achieved, either the Company or its partners will be entitled to an additional promoted interest or payments. See also Note 7. From time to time, the Company (or ventures in which the Company has an ownership interest) has agreed, and may in the future agree, to (1) guarantee portions of the principal, interest and other amounts in connection with their borrowings, (2) provide customary environmental indemnifications and nonrecourse carve-outs (e.g., guarantees against fraud, misrepresentation and bankruptcy) in connection with their borrowings and (3) provide guarantees to lenders, tenants and other third parties for the completion of development projects. The Company has agreements with its outside partners whereby the partners agree to reimburse the joint venture for their share of any payments made under the guarantee. In some cases, the Company earns a fee from the applicable joint venture for providing the guarantee. In connection with the refinancing of 767 Fifth Avenue’s (the General Motors Building) secured loan by the Company’s consolidated joint venture entity, 767 Venture, LLC, the Company guaranteed the consolidated entity’s obligation to fund various reserves for tenant improvement costs and allowances, leasing commissions and free rent obligations in lieu of cash deposits. As of March 31, 2019, the maximum funding obligation under the guarantee was approximately $110.5 million. The Company earns a fee from the joint venture for providing the guarantee and has an agreement with the outside partners to reimburse the joint venture for their share of any payments made under the guarantee. As of March 31, 2019, no amounts related to the guarantee are recorded as liabilities in the Company’s consolidated financial statements. Pursuant to the lease agreement with Marriott, the Company has guaranteed the completion of the office building and parking garage on behalf of its 7750 Wisconsin Avenue joint venture and has also agreed to provide any financing guaranty that may be required with respect to third-party construction financing. The Company earns fees from the joint venture for providing the guarantees and any amounts the Company pays under the guarantee(s) will be deemed to be capital contributions by the Company to the joint venture. The Company has also agreed to fund construction costs through capital contributions to the joint venture in the event of unavailability or insufficiency of third-party construction financing. In addition, the Company has guaranteed to Marriott, as hotel manager, the completion of a hotel being developed by an affiliate of The Bernstein Companies (the Company's partner in the 7750 Wisconsin Avenue joint venture) adjacent to the office property, for which the Company earns a fee from the affiliate of The Bernstein Companies. In addition, the Company entered into agreements with affiliates of The Bernstein Companies whereby the Company could be required to act as a mezzanine and/or mortgage lender and finance the construction of the hotel property. To secure such financing arrangements, affiliates of The Bernstein Companies are required to provide certain security, which varies depending on the specific loan, by pledges of their equity interest in the office property, a fee mortgage on the hotel property, or both. As of March 31, 2019, no amounts related to the contingent aspect of any of the guarantees are recorded as liabilities in the Company’s consolidated financial statements. In connection with the sale and development of the Company's 6595 Springfield Center Drive development project, the Company has guaranteed the completion of the project and the payment of certain cost overruns in accordance with the development management agreement with the buyer. Although the project has been sold and the lease with the federal government tenant has been assigned to the buyer, pursuant to the terms of the Federal Government lease, the Federal Government tenant is not obligated to release the prior owner/landlord from such landlord’s obligations under the lease until completion of the construction. As a result, the entity which previously owned the land remains liable to the Federal Government tenant for the completion of the construction obligations under the lease. The buyer is obligated to fund the balance of the costs to meet such construction obligations, subject to the Company’s obligation to fund cost overruns (if any), as noted above. An affiliate of the buyer has provided a guaranty of the obligations of the buyer to fund such construction costs and the buyer has agreed to use commercially reasonable efforts to require the construction lender to provide certain remedies to the Company in the event the buyer does not fund such construction obligations. As of March 31, 2019, no amounts related to the contingent aspect of the guarantee are recorded as a liability in the Company’s consolidated financial statements. In 2009, the Company filed a general unsecured creditor’s claim against Lehman Brothers, Inc. for approximately $45.3 million related to its rejection of a lease at 399 Park Avenue in New York City. On January 10, 2014, the trustee for the liquidation of the business of Lehman Brothers allowed the Company’s claim in the amount of approximately $45.2 million. During 2014, 2015, 2016, 2017 and 2018, the Company received distributions of approximately $7.7 million, $8.1 million, $1.4 million, $0.4 million and $0.3 million, respectively. The Company has a remaining claim of approximately $27.2 million. The Company will continue to evaluate whether to attempt to sell the remaining claim or wait until the trustee distributes proceeds from the Lehman Brothers estate. Given the inherent uncertainties in bankruptcy proceedings, there can be no assurance as to the timing or amount of additional proceeds, if any, that the Company may ultimately realize on the remaining claim, whether by sale to a third party or by one or more distributions from the trustee. Accordingly, the Company has not recorded any estimated recoveries associated with this gain contingency within its Consolidated Financial Statements at March 31, 2019. Insurance The Company’s property insurance program per occurrence limits are $1.0 billion for its portfolio insurance program, including coverage for acts of terrorism other than nuclear, biological, chemical or radiological terrorism (“Terrorism Coverage”). The Company also carries $250 million of Terrorism Coverage for 601 Lexington Avenue, New York, New York (“601 Lexington Avenue”) in excess of the $1.0 billion of coverage in the Company’s property insurance program. Certain properties, including the General Motors Building located at 767 Fifth Avenue in New York, New York (“767 Fifth Avenue”), are currently insured in separate insurance programs. The property insurance program per occurrence limits for 767 Fifth Avenue are $1.625 billion, including Terrorism Coverage. The Company also currently carries nuclear, biological, chemical and radiological terrorism insurance coverage for acts of terrorism certified under the Federal Terrorism Risk Insurance Act (as amended, “TRIA”) (“NBCR Coverage”), which is provided by IXP as a direct insurer, for the properties in the Company's portfolio, including 767 Fifth Avenue, but excluding certain other properties owned in joint ventures with third parties or which the Company manages. The per occurrence limit for NBCR Coverage is $1.0 billion. Under TRIA, after the payment of the required deductible and coinsurance, the NBCR Coverage provided by IXP is backstopped by the Federal Government if the aggregate industry insured losses resulting from a certified act of terrorism exceed a “program trigger.” In 2019, the program trigger is $180 million and the coinsurance is 19%, however, both will increase in subsequent years pursuant to TRIA. If the Federal Government pays out for a loss under TRIA, it is mandatory that the Federal Government recoup the full amount of the loss from insurers offering TRIA coverage after the payment of the loss pursuant to a formula in TRIA. The Company may elect to terminate the NBCR Coverage if the Federal Government seeks recoupment for losses paid under TRIA, if TRIA is not extended after its expiration on December 31, 2020, if there is a change in its portfolio or for any other reason. The Company intends to continue to monitor the scope, nature and cost of available terrorism insurance. The Company also currently carries earthquake insurance on its properties located in areas known to be subject to earthquakes. In addition, this insurance is subject to a deductible in the amount of 3% of the value of the affected property. Specifically, the Company currently carries earthquake insurance which covers its San Francisco and Los Angeles regions with a $240 million per occurrence limit, and a $240 million annual aggregate limit, $20 million of which is provided by IXP, as a direct insurer. The amount of the Company’s earthquake insurance coverage may not be sufficient to cover losses from earthquakes. In addition, the amount of earthquake coverage could impact the Company’s ability to finance properties subject to earthquake risk. The Company may discontinue earthquake insurance or change the structure of its earthquake insurance program on some or all of its properties in the future if the premiums exceed the Company’s estimation of the value of the coverage. IXP, a captive insurance company which is a wholly-owned subsidiary of the Company, acts as a direct insurer with respect to a portion of the Company’s earthquake insurance coverage for its Greater San Francisco and Los Angeles properties and the Company’s NBCR Coverage. Insofar as the Company owns IXP, it is responsible for its liquidity and capital resources, and the accounts of IXP are part of the Company’s consolidated financial statements. In particular, if a loss occurs which is covered by the Company’s NBCR Coverage but is less than the applicable program trigger under TRIA, IXP would be responsible for the full amount of the loss without any backstop by the Federal Government. IXP would also be responsible for any recoupment charges by the Federal Government in the event losses are paid out and its insurance policy is maintained after the payout by the Federal Government. If the Company experiences a loss and IXP is required to pay under its insurance policy, the Company would ultimately record the loss to the extent of the required payment. Therefore, insurance coverage provided by IXP should not be considered as the equivalent of third-party insurance, but rather as a modified form of self-insurance. In addition, Boston Properties Limited Partnership has issued a guarantee to cover liabilities of IXP in the amount of $20.0 million. The mortgages on the Company’s properties typically contain requirements concerning the financial ratings of the insurers who provide policies covering the property. The Company provides the lenders on a regular basis with the identity of the insurance companies in the Company’s insurance programs. The ratings of some of the Company’s insurers are below the rating requirements in some of the Company’s loan agreements and the lenders for these loans could attempt to claim that an event of default has occurred under the loan. The Company believes it could obtain insurance with insurers which satisfy the rating requirements. Additionally, in the future, the Company’s ability to obtain debt financing secured by individual properties, or the terms of such financing, may be adversely affected if lenders generally insist on ratings for insurers or amounts of insurance which are difficult to obtain or which result in a commercially unreasonable premium. There can be no assurance that a deficiency in the financial ratings of one or more of the Company’s insurers will not have a material adverse effect on the Company. The Company continues to monitor the state of the insurance market in general, and the scope and costs of coverage for acts of terrorism and California earthquake risk in particular, but the Company cannot anticipate what coverage will be available on commercially reasonable terms in future policy years. There are other types of losses, such as from wars, for which the Company cannot obtain insurance at all or at a reasonable cost. With respect to such losses and losses from acts of terrorism, earthquakes or other catastrophic events, if the Company experiences a loss that is uninsured or that exceeds policy limits, the Company could lose the capital invested in the damaged properties, as well as the anticipated future revenues from those properties. Depending on the specific circumstances of each affected property, it is possible that the Company could be liable for mortgage indebtedness or other obligations related to the property. Any such loss could materially and adversely affect the Company’s business and financial condition and results of operations.

Noncontrolling Interests

3 Months Ended

Mar. 31, 2019

Noncontrolling Interest [Abstract]

Noncontrolling Interests

7. Noncontrolling Interests

Noncontrolling interests relate to the interests in Boston Properties Limited Partnership not owned by Boston Properties, Inc. and interests in consolidated property partnerships not wholly-owned by the Company. As of March 31, 2019, the noncontrolling interests in Boston Properties Limited Partnership consisted of 16,844,947 OP Units, 1,187,919 LTIP Units (including 118,067 2012 OPP Units, 68,659 2013 MYLTIP Units, 23,100 2014 MYLTIP Units, 28,724 2015 MYLTIP Units and 98,706 2016 MYLTIP Units), 394,921 2017 MYLTIP Units, 336,195 2018 MYLTIP Units and 220,734 2019 MYLTIP Units held by parties other than Boston Properties, Inc.

Noncontrolling Interest—Common Units

During the three months ended March 31, 2019, 14,129 OP Units were presented by the holders for redemption (including 12,929 OP Units issued upon conversion of LTIP Units, 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units) and were redeemed by Boston Properties, Inc. in exchange for an equal number of shares of Common Stock.

At March 31, 2019, Boston Properties Limited Partnership had outstanding 394,921 2017 MYLTIP Units, 336,195 2018 MYLTIP Units and 220,734 2019 MYLTIP Units. Prior to the applicable measurement date (February 6, 2020 for the 2017 MYLTIP Units, February 5, 2021 for the 2018 MYLTIP Units and February 4, 2022 for the 2019 MYLTIP Units), holders of MYLTIP Units will be entitled to receive per unit distributions equal to one-tenth (10%) of the regular quarterly distributions payable on an OP Unit, but will not be entitled to receive any special distributions. After the measurement date, the number of MYLTIP Units, both vested and unvested, that MYLTIP award recipients have earned, if any, based on the establishment of a performance pool, will be entitled to receive distributions in an amount per unit equal to distributions, both regular and special, payable on an OP Unit.

On February 9, 2019, the measurement period for the Company’s 2016 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 69.5% of target or an aggregate of approximately $13.6 million (after giving effect to voluntary employee separations). As a result, an aggregate of 364,980 2016 MYLTIP Units that had been previously granted were automatically forfeited.

The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and 2015 MYLTIP Units and, after the February 9, 2019 measurement date, the 2016 MYLTIP Units) and its distributions on the 2016 MYLTIP Units (prior to the February 9, 2019 measurement date), 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units (after the February 5, 2019 issuance date) paid in 2019:



Record Date	Payment Date	Distributions per OP Unit and LTIP Unit		Distributions per MYLTIP Unit
March 29, 2019	April 30, 2019		$0.95		$0.095
December 31, 2018	January 30, 2019		$0.95		$0.095

The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and, after the February 4, 2018 measurement date, the 2015 MYLTIP Units) and its distributions on the 2015 MYLTIP Units (prior to the February 4, 2018 measurement date), 2016 MYLTIP Units, 2017 MYLTIP Units and 2018 MYLTIP Units (after the February 6, 2018 issuance date) that occurred during the first quarter of 2018:



Record Date	Payment Date	Distributions per OP Unit and LTIP Unit		Distributions per MYLTIP Unit
March 29, 2018	April 30, 2018		$0.80		$0.080
December 31, 2017	January 30, 2018		$0.80		$0.080

A holder of an OP Unit may present the OP Unit to Boston Properties Limited Partnership for redemption at any time (subject to restrictions agreed upon at the time of issuance of OP Units to particular holders that may restrict such redemption right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, Boston Properties Limited Partnership must redeem the OP Unit for cash equal to the then value of a share of common stock of Boston Properties, Inc. Boston Properties, Inc. may, in its sole discretion, elect to assume and satisfy the redemption obligation by paying either cash or issuing one share of Common Stock. The value of the OP Units not owned by Boston Properties, Inc. and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units), assuming that all conditions had been met for the conversion thereof, had all of such units been redeemed at March 31, 2019 was approximately $2.4 billion based on the last reported price of a share of Common Stock on the New York Stock Exchange of $133.88 per share on March 29, 2019.

Noncontrolling Interests—Property Partnerships

The noncontrolling interests in property partnerships consist of the outside equity interests in ventures that are consolidated with the financial results of the Company because the Company exercises control over the entities that own the properties. The equity interests in these ventures that are not owned by the Company, totaling approximately $1.7 billion at March 31, 2019 and December 31, 2018, are included in Noncontrolling Interests—Property Partnerships in the accompanying Consolidated Balance Sheets.

On May 12, 2016, the partners in the Company’s consolidated entity that owns Salesforce Tower located in San Francisco, California amended the venture agreement. Under the original venture agreement, if the Company elects to fund the construction of Salesforce Tower without a construction loan (or a construction loan of less than 50% of project costs) and the venture has commenced vertical construction of the project, then the partner’s capital funding obligation shall be limited, in which event the Company shall fund up to 2.5% of the total project costs (i.e., 50% of the partner’s 5% interest in the venture) in the form of a loan to the partner. This loan would bear interest at the then prevailing market interest rates for construction loans. Under the amended agreement, the partners have agreed to structure this funding by the Company as preferred equity rather than a loan. The preferred equity contributed by the Company earns a preferred return equal to LIBOR plus 3.00% per annum and is payable to the Company out of any distributions to which the partner would otherwise be entitled until such preferred equity and preferred return have been repaid to the Company. As of March 31, 2019, the Company had contributed an aggregate of approximately $22.6 million of preferred equity to the venture. Also, under the joint venture agreement, (a) from and after the stabilization date, the partner has the right to cause the Company to purchase all (but not less than all) of the partner’s interest and (b) from and after the third anniversary of the stabilization date, the Company has the right to acquire all (but not less than all) of the partner’s interest, in each case at an agreed upon purchase price or appraised value. In addition, if certain threshold returns are achieved the partner will be entitled to receive an additional promoted interest with respect to cash flow distributions. The term stabilization date is defined in the agreement to generally mean the first date after completion upon which Salesforce Tower is (1) at least 90% leased and (2) 50% occupied by tenants that are paying rent.

On January 18, 2019, the Company and its partner amended the venture agreement. Per the amendment, the partner exercised its right to cause the Company to purchase on April 1, 2019 its 5% ownership interest and promoted profits interest in the venture for cash totaling approximately $210.9 million, which amount shall be reduced by approximately $24.1 million, consisting of the repayment of the Company's preferred equity and preferred return as provided for in the venture agreement. As part of the original agreement, the partner was required to contribute 5% of the equity and was entitled to receive an additional promoted payment based on the success of the property (See Note 12).

Stockholders' Equity / Partners' Capital

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Stockholders' Equity / Partners' Capital

8. Stockholders’ Equity / Partners’ Capital

As of March 31, 2019, Boston Properties, Inc. had 154,515,486 shares of Common Stock outstanding.

As of March 31, 2019, Boston Properties, Inc. owned 1,725,484 general partnership units and 152,790,002 limited partnership units of Boston Properties Limited Partnership.

On June 2, 2017, Boston Properties, Inc. renewed its “at the market” (“ATM”) stock offering program through which it may sell from time to time up to an aggregate of $600.0 million of its common stock through sales agents over a three-year period. This program replaced the Company’s prior $600.0 million ATM stock offering program that was scheduled to expire on June 3, 2017. The Company intends to use the net proceeds from any offering for general business purposes, which may include investment opportunities and debt reduction. No shares of common stock have been issued under this ATM stock offering program.

During the three months ended March 31, 2019, Boston Properties, Inc. issued 14,129 shares of Common Stock in connection with the redemption of an equal number of redeemable OP Units from limited partners.

The following table presents Boston Properties, Inc.’s dividends per share and Boston Properties Limited Partnership’s distributions per OP Unit and LTIP Unit paid in 2019 and occurred during the first quarter of 2018:



Record Date	Payment Date	Dividend (Per Share)		Distribution (Per Unit)
March 29, 2019	April 30, 2019		$0.95		$0.95
December 31, 2018	January 30, 2019		$0.95		$0.95

March 29, 2018	April 30, 2018		$0.80		$0.80
December 31, 2017	January 30, 2018		$0.80		$0.80

Preferred Stock

As of March 31, 2019, Boston Properties, Inc. had 80,000 shares (8,000,000 depositary shares each representing 1/100th of a share) outstanding of its 5.25% Series B Cumulative Redeemable Preferred Stock with a liquidation preference of $2,500.00 per share ($25.00 per depositary share). Boston Properties, Inc. pays cumulative cash dividends on the Series B Preferred Stock at a rate of 5.25% per annum of the $2,500.00 liquidation preference per share. Boston Properties, Inc. did not have the right to redeem the Series B Preferred Stock prior to March 27, 2018, except in certain circumstances relating to the preservation of Boston Properties, Inc.’s REIT status. On and after March 27, 2018, Boston Properties, Inc., at its option, may redeem the Series B Preferred Stock for a cash redemption price of $2,500.00 per share ($25.00 per depositary share), plus all accrued and unpaid dividends. The Series B Preferred Stock is not redeemable by the holders, has no maturity date and is not convertible into any other security of Boston Properties, Inc. or its affiliates.

The following table presents Boston Properties Inc.’s dividends per share on its outstanding Series B Preferred Stock paid during 2019 and occurred during the first quarter of 2018:



Record Date	Payment Date	Dividend (Per Share)
May 3, 2019	May 15, 2019		$32.8125
February 4, 2019	February 15, 2019		$32.8125

May 4, 2018	May 15, 2018		$32.8125
February 2, 2018	February 15, 2018		$32.8125

Earnings Per Share / Common Unit

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Earnings Per Share / Common Unit

9. Earnings Per Share / Common Unit

Boston Properties, Inc.

The following table provides a reconciliation of both the net income attributable to Boston Properties, Inc. common shareholders and the number of common shares used in the computation of basic earnings per share (“EPS”), which is calculated by dividing net income attributable to Boston Properties, Inc. common shareholders by the weighted-average number of common shares outstanding during the period. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are also participating securities. As such, unvested restricted common stock of Boston Properties, Inc. and Boston Properties Limited Partnership's LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic EPS of Boston Properties, Inc. using the two-class method. Participating securities are included in the computation of diluted EPS of Boston Properties, Inc. using the if-converted method if the impact is dilutive. Because the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units required, and the 2017-2019 MYLTIP Units require, Boston Properties, Inc. to outperform absolute and relative return thresholds, unless such thresholds have been met by the end of the applicable reporting period, Boston Properties, Inc. excludes such units from the diluted EPS calculation. Other potentially dilutive common shares, including stock options, restricted stock and other securities of Boston Properties Limited Partnership that are exchangeable for Boston Properties, Inc.’s Common Stock, and the related impact on earnings, are considered when calculating diluted EPS.



	Three months ended March 31, 2019
	Income (Numerator)			Shares (Denominator)	Per Share Amount
	(in thousands, except for per share amounts)
Basic Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	98,105		154,525	$	0.63
Effect of Dilutive Securities:
Stock Based Compensation	—			319	—
Diluted Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	98,105		154,844	$	0.63

	Three months ended March 31, 2018
	Income (Numerator)			Shares (Denominator)	Per Share Amount
	(in thousands, except for per share amounts)
Basic Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	176,021		154,385	$	1.14
Allocation of undistributed earnings to participating securities	(127		)	—	—
Net income attributable to Boston Properties, Inc. common shareholders	$	175,894		154,385	$	1.14
Effect of Dilutive Securities:
Stock Based Compensation	—			320	—
Diluted Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	175,894		154,705	$	1.14

Boston Properties Limited Partnership

The following table provides a reconciliation of both the net income attributable to Boston Properties Limited Partnership common unitholders and the number of common units used in the computation of basic earnings per common unit, which is calculated by dividing net income attributable to Boston Properties Limited Partnership common unitholders by the weighted-average number of common units outstanding during the period. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are also participating securities. As such, unvested restricted common stock of Boston Properties, Inc. and Boston Properties Limited Partnership’s LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic earnings per common unit using the two-class method. Participating securities are included in the computation of diluted earnings per common unit using the if-converted method if the impact is dilutive. Because the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units required, and the 2017-2019 MYLTIP Units require, Boston Properties, Inc. to outperform absolute and relative return thresholds, unless such thresholds have been met by the end of the applicable reporting period, Boston Properties Limited Partnership excludes such units from the diluted earnings per common unit calculation. Other potentially dilutive common units and the related impact on earnings are considered when calculating diluted earnings per common unit. Included in the number of units (the denominator) below are approximately 17,606,000 and 17,482,000 redeemable common units for the three months ended March 31, 2019 and 2018, respectively.



	Three months ended March 31, 2019
	Income (Numerator)		Units (Denominator)	Per Unit Amount
	(in thousands, except for per unit amounts)
Basic Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	113,382	172,131	$	0.66
Effect of Dilutive Securities:
Stock Based Compensation	—		319	—
Diluted Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	113,382	172,450	$	0.66



	Three months ended March 31, 2018
	Income (Numerator)			Units (Denominator)	Per Unit Amount
	(in thousands, except for per unit amounts)
Basic Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,907		171,867	$	1.17
Allocation of undistributed earnings to participating securities	(141		)	—	—
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,766		171,867	$	1.17
Effect of Dilutive Securities:
Stock Based Compensation	—			320	—
Diluted Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,766		172,187	$	1.17

Stock Option and Incentive Plan	3 Months Ended
Stock Option and Incentive Plan	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	10. Stock Option and Incentive Plan On February 5, 2019, Boston Properties, Inc.’s Compensation Committee approved the 2019 MYLTIP awards under Boston Properties, Inc.’s 2012 Stock Option and Incentive Plan (the "2012 Plan") to certain officers and employees of Boston Properties, Inc. The 2019 MYLTIP awards utilize Boston Properties, Inc.’s TSR over a three-year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will be based on Boston Properties, Inc.’s TSR relative to the Nareit Office Index adjusted to include Vornado Realty Trust. Earned awards will range from zero to a maximum of 220,734 LTIP Units depending on Boston Properties, Inc.’s TSR relative to the Nareit Office Index adjusted to include Vornado Realty Trust, with a target of approximately 110,367 LTIP Units and linear interpolation between zero and maximum. Earned awards (if any) will vest 50% on February 4, 2022 and 50% on February 4, 2023, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by Boston Properties, Inc. without cause, or termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 4, 2022, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2019 MYLTIP awards are in the form of LTIP Units issued on the grant date which (i) are subject to forfeiture to the extent awards are not earned and (ii) prior to the performance measurement date are only entitled to one-tenth (10%) of the regular quarterly distributions payable on common partnership units. Under ASC 718 "Compensation - Stock Compensation", the 2019 MYLTIP awards have an aggregate value of approximately $13.5 million, which amount will generally be amortized into earnings over the four-year plan period under the graded vesting method. On February 9, 2019, the measurement period for the Company’s 2016 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 69.5% of target or an aggregate of approximately $13.6 million (after giving effect to voluntary employee separations). As a result, an aggregate of 364,980 2016 MYLTIP Units that had been previously granted were automatically forfeited. During the three months ended March 31, 2019, Boston Properties, Inc. issued 23,083 shares of restricted common stock and Boston Properties Limited Partnership issued 172,166 LTIP Units and 220,734 2019 MYLTIP Units to employees under the 2012 Plan. Employees paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit and 2019 MYLTIP Unit. When issued, LTIP Units are not economically equivalent in value to a share of Common Stock, but over time can increase in value to one-for-one parity with Common Stock if there is sufficient appreciation in the value of the Company’s assets. The aggregate value of the LTIP Units is included in noncontrolling interests in the Consolidated Balance Sheets. A substantial majority of the grants of restricted common stock and LTIP Units to employees vest in four equal annual installments. Restricted common stock is measured at fair value on the date of grant based on the number of shares granted and the closing price of Boston Properties, Inc.’s Common Stock on the date of grant as quoted on the New York Stock Exchange. Such value is recognized as an expense ratably over the corresponding employee service period. The shares of restricted common stock granted during the three months ended March 31, 2019 were valued at approximately $3.0 million ($131.23 per share weighted-average). The LTIP Units granted were valued at approximately $20.9 million (approximately $121.41 per unit weighted-average fair value) using a Monte Carlo simulation method model. The per unit fair values of the LTIP Units granted were estimated on the dates of grant and for a substantial majority of such units were valued using the following assumptions: an expected life of 5.7 years, a risk-free interest rate of 2.68% and an expected price volatility of 27.0%. Because the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units, 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units are subject to both a service condition and a market condition, the Company recognizes the related compensation expense under the graded vesting attribution method. Under the graded vesting attribution method, each portion of the award that vests at a different date is accounted for as a separate award and recognized over the period appropriate to that portion so that the compensation cost for each portion should be recognized in full by the time that portion vests. The Company recognizes forfeitures as they occur on its awards of stock-based compensation. Dividends paid on both vested and unvested shares of restricted stock are charged directly to Dividends in Excess of Earnings in Boston Properties, Inc.’s Consolidated Balance Sheets and Partners’ Capital in Boston Properties Limited Partnership’s Consolidated Balance Sheets. Aggregate stock-based compensation expense associated with restricted stock, non-qualified stock options, LTIP Units, 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units, 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units was approximately $14.8 million and $14.2 million for the three months ended March 31, 2019 and 2018, respectively. At March 31, 2019, there was (1) an aggregate of approximately $38.4 million of unrecognized compensation expense related to unvested restricted stock, LTIP Units and 2016 MYLTIP Units and (2) an aggregate of approximately $22.6 million of unrecognized compensation expense related to unvested 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 2.9 years.

Segment Information

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Segment Information

11. Segment Information

The following tables present reconciliations of Net Income Attributable to Boston Properties, Inc. Common Shareholders to the Company's share of Net Operating Income and Net Income Attributable to Boston Properties Limited Partnership Common Unitholders to the Company's share of Net Operating Income for the three months ended March 31, 2019 and 2018.

Boston Properties, Inc.



	Three months ended March 31,
	2019			2018
	(in thousands)
Net income attributable to Boston Properties, Inc. common shareholders	$	98,105		$	176,021
Add:
Preferred dividends	2,625			2,625
Noncontrolling interest—common units of Boston Properties Limited Partnership	11,599			20,432
Noncontrolling interests in property partnerships	18,830			17,234
Interest expense	101,009			90,220
Impairment loss	24,038			—
Net operating income from unconsolidated joint ventures	25,349			16,060
Depreciation and amortization expense	164,594			165,797
Transaction costs	460			21
Payroll and related costs from management services contracts	3,395			2,885
General and administrative expense	41,762			35,894
Less:
Net operating income attributable to noncontrolling interests in property partnerships	47,085			45,909
Gains (losses) from investments in securities	2,969			(126		)
Interest and other income	3,753			1,648
(Losses) gains on sales of real estate	(905		)	96,397
Income from unconsolidated joint ventures	213			461
Direct reimbursements of payroll and related costs from management services contracts	3,395			2,885
Development and management services revenue	9,277			8,405
Company's share of Net Operating Income	$	425,979		$	371,610

Boston Properties Limited Partnership



	Three months ended March 31,
	2019			2018
	(in thousands)
Net income attributable to Boston Properties Limited Partnership common unitholders	$	113,382		$	200,907
Add:
Preferred distributions	2,625			2,625
Noncontrolling interests in property partnerships	18,830			17,234
Interest expense	101,009			90,220
Impairment loss	22,272			—
Net operating income from unconsolidated joint ventures	25,349			16,060
Depreciation and amortization expense	162,682			163,853
Transaction costs	460			21
Payroll and related costs from management services contracts	3,395			2,885
General and administrative expense	41,762			35,894
Less:
Net operating income attributable to noncontrolling interests in property partnerships	47,085			45,909
Gains (losses) from investments in securities	2,969			(126		)
Interest and other income	3,753			1,648
(Losses) gains on sales of real estate	(905		)	98,907
Income from unconsolidated joint ventures	213			461
Direct reimbursements of payroll and related costs from management services contracts	3,395			2,885
Development and management services revenue	9,277			8,405
Company's share of Net Operating Income	$	425,979		$	371,610

Net operating income (“NOI”) is a non-GAAP financial measure equal to net income attributable to Boston Properties, Inc. common shareholders and net income attributable to Boston Properties Limited Partnership common unitholders, as applicable, the most directly comparable GAAP financial measures, plus (1) preferred dividends/distributions, net income attributable to noncontrolling interests, interest expense, impairment loss, depreciation and amortization expense, transaction costs, payroll and related costs from management services contracts and corporate general and administrative expense less (2) gains (losses) from investments in securities, interest and other income, (losses) gains on sales of real estate, income from unconsolidated joint ventures, direct reimbursements of payroll and related costs from management services contracts and development and management services revenue. The Company believes NOI is useful to investors as a performance measure and believes it provides useful information to investors regarding the Company's results of operations and financial condition because, when compared across periods, it reflects the impact on operations from trends in occupancy rates, rental rates, operating costs and acquisition and development activity on an unleveraged basis, providing perspective not immediately apparent from net income attributable to Boston Properties, Inc. common shareholders and net income attributable to Boston Properties Limited Partnership common unitholders. For example, interest expense is not necessarily linked to the operating performance of a real estate asset and is often incurred at the corporate level as opposed to the property level. Similarly, interest expense may be incurred at the property level even though the financing proceeds may be used at the corporate level (e.g., used for other investment activity). In addition, depreciation and amortization expense, because of historical cost accounting and useful life estimates, may distort operating performance measures at the property level. NOI presented by the Company may not be comparable to NOI reported by other REITs or real estate companies that define NOI differently.

The Company's internal reporting utilizes its share of NOI, which includes its share of NOI from consolidated and unconsolidated joint ventures, which is a non-GAAP financial measure that is calculated as the consolidated amount, plus the Company's share of the amount from the Company's unconsolidated joint ventures (calculated based upon the Company’s percentage ownership interest and, in some cases, after priority allocations), minus the Company’s partners’ share of the amount from the Company's consolidated joint ventures (calculated based upon the partners’ percentage ownership interests and, in some cases, after priority allocations and their share of fees due to the Company). Management utilizes its share of NOI in assessing its performance as the Company has several significant joint ventures and in some cases, the Company exercises significant influence over, but does not control, the joint venture, in which case GAAP requires that the Company account for the joint venture entity using the equity method of accounting and the Company does not consolidate it for financial reporting purposes. In other cases, GAAP requires that the Company consolidate the venture even though the Company's partner(s) owns a significant percentage interest. As a result, the presentations of the Company’s share of NOI should not be considered a substitute for, and should only be considered together with and as a supplement to, the Company's financial information presented in accordance with GAAP.

Asset information by segment is not reported because the Company does not use this measure to assess performance. Therefore, depreciation and amortization expense is not allocated among segments. Preferred dividends/distributions, interest expense, impairment loss, depreciation and amortization expense, transaction costs, payroll and related costs from management services contracts, corporate general and administrative expense, gains (losses) from investments in securities, interest and other income, (losses) gains on sales of real estate, direct reimbursements of payroll and related costs from management services contracts and development and management services revenue are not included in NOI and are provided as reconciling items to the Company's reconciliations of its share of NOI to net income attributable to common shareholders/unitholders.

The Company’s segments are based on the Company’s method of internal reporting which classifies its operations by geographic area. The Company’s segments by geographic area are Boston, Los Angeles, New York, San Francisco and Washington, DC. The Company also presents information for each segment by property type including Office, Residential and Hotel.

The Company has modified the presentation of its geographic area classification for all periods presented to include the Los Angeles geographic area to align with its method of internal reporting. The Company has expanded its presence in the Los Angeles geographic area with its equity method investment in Santa Monica Business Park located in Santa Monica, California. The Company now has equity interests in a portfolio of 27 office and retail properties in the Los Angeles geographic area aggregating approximately 2.3 million net rentable square feet, all of which are owned through investments in unconsolidated joint ventures. The Company is now presenting the Los Angeles geographic area as a reportable segment to align with its method of internal reporting given the increased significance as a result of commencing a full reporting period of ownership of the Santa Monica Business Park portfolio. The inclusion of the Los Angeles geographic area has also resulted in a change in the reported measure of segment profit or loss from NOI to the Company's share of NOI. This change has been reflected in all periods presented and the impact of the change can been seen within the tables below. The Company has not presented rental revenue and rental expenses for properties owned through investments in unconsolidated joint ventures, including those in the Los Angeles geographic area, as the Company accounts for these properties using the equity method of accounting.

Information by geographic area (dollars in thousands):

For the three months ended March 31, 2019:



	Boston			Los Angeles			New York			San Francisco			Washington, DC			Total
Rental Revenue: (1)
Office	$	217,411		$	—		$	258,631		$	124,055		$	96,345		$	696,442
Residential	2,701			—			—			—			5,014			7,715
Hotel	8,938			—			—			—			—			8,938
Total	229,050			—			258,631			124,055			101,359			713,095
% of Grand Totals	32.12		%	—		%	36.27		%	17.40		%	14.21		%	100.00		%
Rental Expenses:
Office	79,500			—			96,971			41,125			36,147			253,743
Residential	1,206			—			—			—			2,568			3,774
Hotel	7,863			—			—			—			—			7,863
Total	88,569			—			96,971			41,125			38,715			265,380
% of Grand Totals	33.37		%	—		%	36.54		%	15.50		%	14.59		%	100.00		%
Net operating income	$	140,481		$	—		$	161,660		$	82,930		$	62,644		$	447,715
% of Grand Totals	31.38		%	—		%	36.11		%	18.52		%	13.99		%	100.00		%
Less: Net operating income attributable to noncontrolling interests in property partnerships	(9,373		)	—			(37,264		)	(448		)	—			(47,085		)
Add: Company's share of net operating income from unconsolidated joint ventures	772			15,708			1,786			—			7,083			25,349
Company's share of net operating income	$	131,880		$	15,708		$	126,182		$	82,482		$	69,727		$	425,979
% of Grand Totals	30.96		%	3.69		%	29.62		%	19.36		%	16.37		%	100.00		%

_______________


(1)	Rental Revenue is equal to total Revenue per the Company's Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

For the three months ended March 31, 2018:



	Boston			Los Angeles			New York			San Francisco			Washington, DC			Total
Rental Revenue: (1)
Office	$	204,997		$	—		$	242,398		$	89,893		$	99,312		$	636,600
Residential	1,152			—			—			—			3,007			4,159
Hotel	9,102			—			—			—			—			9,102
Total	215,251			—			242,398			89,893			102,319			649,861
% of Grand Totals	33.12		%	—		%	37.31		%	13.83		%	15.74		%	100.00		%
Rental Expenses:
Office	80,324			—			93,762			27,628			36,343			238,057
Residential	514			—			—			—			1,758			2,272
Hotel	8,073			—			—			—			—			8,073
Total	88,911			—			93,762			27,628			38,101			248,402
% of Grand Totals	35.79		%	—		%	37.75		%	11.12		%	15.34		%	100.00		%
Net operating income	$	126,340		$	—		$	148,636		$	62,265		$	64,218		$	401,459
% of Grand Totals	31.47		%	—		%	37.02		%	15.51		%	16.00		%	100.00		%
Less: Net operating income attributable to noncontrolling interests in property partnerships	(8,129		)	—			(37,946		)	166			—			(45,909		)
Add: Company's share of net operating income from unconsolidated joint ventures	534			7,074			1,661			—			6,791			16,060
Company's share of net operating income	$	118,745		$	7,074		$	112,351		$	62,431		$	71,009		$	371,610
% of Grand Totals	31.96		%	1.90		%	30.23		%	16.80		%	19.11		%	100.00		%

_______________


(1)	Rental Revenue is equal to total Revenue per the Company's Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	12. Subsequent Events On April 1, 2019, the Company completed the acquisition of its partner's 5% ownership interest and promoted profits interest in the consolidated entity that owns Salesforce Tower located in San Francisco, California for cash totaling approximately $210.9 million, which amount was reduced by approximately $24.1 million, consisting of the repayment of the Company's preferred equity and preferred return in the venture. The partner was entitled to receive an additional promoted payment based on the success of the property. Salesforce Tower is an approximately 1,421,000 net rentable square foot Class A office property (See Note 7). On April 18, 2019, the Company entered into an agreement to sell its One Tower Center property located in East Brunswick, New Jersey for a gross sale price of approximately $38.0 million. One Tower Center is an approximately 410,000 net rentable square foot Class A office property. The closing is subject to customary closing conditions and termination rights for transactions of this type. There can be no assurance that the sale will be completed on the terms currently contemplated or at all (See Note 3). On April 26, 2019, a joint venture in which the Company has a 50% interest obtained construction financing with a total commitment of $255.0 million collateralized by its 7750 Wisconsin Avenue development project located in Bethesda, Maryland. The construction financing bears interest at a variable rate equal to LIBOR plus 1.25% per annum and matures on April 26, 2023, with two, one-year extension options, subject to certain conditions. There have been no amounts drawn under the loan to date. 7750 Wisconsin Avenue is a 734,000 net rentable square foot build-to-suit Class A office project and below-grade parking garage.

Basis Of Presentation And Summary Of Significant Accounting Policies New Accounting Pronouncements (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Pronouncements New Accounting Pronouncements Adopted Leases On January 1, 2019, the Company adopted Accounting Standards Update ("ASU") 2016-02, “Leases (Topic 842)” (“ASU 2016-02” or "Topic 842"). For information pertaining to the Company's adoption and disclosures with respect to leases, see Note 4.

Basis Of Presentation And Summary Of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value

March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Related party note receivable	$	80,000	$	80,060	$	80,000	$	80,000
Note receivable	19,593		17,723		19,468		19,468
	$	99,593	$	97,783	$	99,468	$	99,468

Mortgage notes payable, net	$	2,959,908	$	2,948,057	$	2,964,572	$	2,903,925
Unsecured senior notes, net	7,547,043		7,584,456		7,544,697		7,469,338
Unsecured line of credit	—		—		—		—
Unsecured term loan, net	498,607		500,728		498,488		500,783
Total	$	11,005,558	$	11,033,241	$	11,007,757	$	10,874,046

Real Estate (Tables)

3 Months Ended

Mar. 31, 2019

Schedule of Real Estate Properties [Table Text Block]

Boston Properties, Inc.

Real estate consisted of the following at March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019			December 31, 2018
Land	$	5,061,532		$	5,072,568
Right of use assets - finance leases	187,292			—
Right of use assets - operating leases	151,166			—
Land held for future development (1)	258,221			200,498
Buildings and improvements	13,286,605			13,356,751
Tenant improvements	2,444,358			2,396,932
Furniture, fixtures and equipment	43,080			44,351
Construction in progress	647,469			578,796
Total	22,079,723			21,649,896
Less: Accumulated depreciation	(4,962,959		)	(4,897,777		)
	$	17,116,764		$	16,752,119

_______________


(1)	Includes pre-development costs.

Finance Lease, Liability, Maturity [Table Text Block]

The following table provides a maturity analysis for the Company's lease liabilities related to its operating and finance leases as of March 31, 2019 (in thousands):



	Operating			Finance (1)
April 1, 2019 - December 31, 2019	$	7,317		$	4,401
2020	17,488			122,070
2021	25,403			2,130
2022	11,376			1,121
2023	9,084			944
Thereafter	567,232			73,241
Total lease payments	637,900			203,907
Less: interest portion	(438,247		)	(30,784		)
Present value of lease payments	$	199,653		$	173,123

The Company recorded an adjustment to the opening balance of retained earnings related to initial direct costs that, as of January 1, 2019, had not started to amortize and are no longer allowed to be capitalized in accordance with ASU 2016-02, totaling approximately to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners' Capital of Boston Properties Limited Partnership, approximately $0.4 million to Noncontrolling interests - Common Units of Boston Properties, Inc. and Noncontrolling Interest - Redeemable Partnership Units of Boston Properties Limited Partnership and $70,000 to Noncontrolling Interests - Property Partnerships of Boston Properties, Inc. and Noncontrolling Interests in Property Partnerships of Boston Properties Limited Partnership on the corresponding Consolidated Balance Sheets.

$3.9 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners' Capital of Boston Properties Limited Partnership, approximately $0.4 million



52		P52Y0M0D
5		P5Y0M0D

Schedule of Real Estate Properties [Table Text Block]

Boston Properties Limited Partnership

Real estate consisted of the following at March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019			December 31, 2018
Land	$	4,961,028		$	4,971,475
Right of use assets - finance leases	187,292			—
Right of use assets - operating leases	151,166			—
Land held for future development (1)	258,221			200,498
Buildings and improvements	12,991,108			13,059,488
Tenant improvements	2,444,358			2,396,932
Furniture, fixtures and equipment	43,080			44,351
Construction in progress	647,469			578,796
Total	21,683,722			21,251,540
Less: Accumulated depreciation	(4,864,334		)	(4,800,475		)
	$	16,819,388		$	16,451,065

_______________


(1)	Includes pre-development costs.

Platform 16 [Member]

Finance Lease, Liability, Maturity [Table Text Block]

As of January 24, 2019, the lease payments from the finance lease are as follows (in thousands):



Period from January 24, 2019 through December 31, 2019	$	17,918
2020	109,460
Total expected minimum lease payments	127,378
Interest portion	(4,815		)
Present value of expected net lease payments	$	122,563

Leases (Tables)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Finance Lease, Liability, Maturity [Table Text Block]

The following table provides a maturity analysis for the Company's lease liabilities related to its operating and finance leases as of March 31, 2019 (in thousands):



	Operating			Finance (1)
April 1, 2019 - December 31, 2019	$	7,317		$	4,401
2020	17,488			122,070
2021	25,403			2,130
2022	11,376			1,121
2023	9,084			944
Thereafter	567,232			73,241
Total lease payments	637,900			203,907
Less: interest portion	(438,247		)	(30,784		)
Present value of lease payments	$	199,653		$	173,123

$3.9 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners' Capital of Boston Properties Limited Partnership, approximately $0.4 million



52		P52Y0M0D
5		P5Y0M0D

Lease, Cost [Table Text Block]

The following tables provide quantitative information for the Company's operating and finance leases as of March 31, 2019 (dollars in thousands):



	Three months ended March 31, 2019
Lease costs
Operating lease costs	$	3,677
Finance lease costs
Amortization of right of use asset (1)	$	16
Interest on lease liabilities (2)	$	12

	March 31, 2019
Other information
Weighted-average remaining lease term (in years)
Operating leases	52
Finance leases	5
Weighted-average discount rate
Operating leases	5.7		%
Finance leases	4.1		%

_______________


(1)	The finance leases relate to either land, building or assets that remain in development. The Company's policy is not to depreciate finance lease assets related to land because it is assumed to have an indefinite life. For assets under development, depreciation may commence once the asset is placed in-service and depreciation would be recognized in accordance with the Company's policy.


(2)	Three of the finance leases relate to assets under development and as such the entire interest amount was capitalized.

Operating Lease, Lease Income [Table Text Block]



Lease Revenue	Three months ended March 31, 2019
Fixed Contractual Payments	$	553,986
Variable lease payments	125,265
	$	679,251

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]



Years Ending December 31,	(in thousands)
2019	$	11,425
2020	18,425
2021	25,310
2022	8,894
2023	9,084
Thereafter	567,232

Capital Leases in Financial Statements of Lessee Disclosure [Text Block]

The following table provides a maturity analysis for the Company's future minimum lease payments, as of December 31, 2018, related to the four capital leases, through 2036:



Years Ending December 31,	(in thousands)
2019	$	1,441
2020	12,682
2021	2,123
2022	1,253
2023	944
Thereafter	73,241
Total expected minimum lease payments	91,684
Interest portion	(27,497		)
Present value of expected net minimum lease payments	$	64,187

Lessor, Operating Lease, Payments to be Received, Maturity [Table Text Block]



Years Ending December 31,	(in thousands)
2019	$	2,088,171
2020	2,106,963
2021	2,015,031
2022	1,838,699
2023	1,736,636
Thereafter	12,295,464



	(in thousands)
April 1, 2019 - December 31, 2019	$	1,573,871
2020	2,147,464
2021	2,076,969
2022	1,910,362
2023	1,811,936
Thereafter	12,821,229

Lessee, Operating Lease, Liability, Maturity [Table Text Block]

The following table provides a maturity analysis for the Company's lease liabilities related to its operating and finance leases as of March 31, 2019 (in thousands):



	Operating			Finance (1)
April 1, 2019 - December 31, 2019	$	7,317		$	4,401
2020	17,488			122,070
2021	25,403			2,130
2022	11,376			1,121
2023	9,084			944
Thereafter	567,232			73,241
Total lease payments	637,900			203,907
Less: interest portion	(438,247		)	(30,784		)
Present value of lease payments	$	199,653		$	173,123

_______________


(1)	Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million, respectively, related to purchase options that the Company is reasonably certain that it will exercise.

Investments in Unconsolidated Joint Ventures (Tables)

3 Months Ended

Mar. 31, 2019

Schedule of Equity Method Investments [Line Items]

Investments In Unconsolidated Joint Ventures

The investments in unconsolidated joint ventures consist of the following at March 31, 2019 and December 31, 2018:



		Nominal % Ownership			Carrying Value of Investment (1)
Entity	Properties	Nominal % Ownership			March 31, 2019			December 31, 2018
					(in thousands)
Square 407 Limited Partnership	Market Square North	50.0	%		$	(5,948	)	$	(6,424	)
The Metropolitan Square Associates LLC	Metropolitan Square	20.0	%		3,146			2,644
BP/CRF 901 New York Avenue LLC	901 New York Avenue	25.0	%	(2)	(13,215		)	(13,640		)
WP Project Developer LLC	Wisconsin Place Land and Infrastructure	33.3	%	(3)	37,821			38,214
Annapolis Junction NFM LLC	Annapolis Junction	50.0	%	(4)	25,284			25,268
540 Madison Venture LLC	540 Madison Avenue	60.0	%		66,452			66,391
500 North Capitol Venture LLC	500 North Capitol Street, NW	30.0	%		(4,781		)	(5,026		)
501 K Street LLC	1001 6th Street	50.0	%	(5)	42,500			42,557
Podium Developer LLC	The Hub on Causeway - Podium	50.0	%		69,849			69,302
Residential Tower Developer LLC	The Hub on Causeway - Residential	50.0	%		47,795			47,505
Hotel Tower Developer LLC	The Hub on Causeway - Hotel Air Rights	50.0	%		3,343			3,022
Office Tower Developer LLC	100 Causeway Street	50.0	%	(6)	46,881			23,804
1265 Main Office JV LLC	1265 Main Street	50.0	%		4,030			3,918
BNY Tower Holdings LLC	Dock 72	50.0	%		83,291			82,520
CA-Colorado Center Limited Partnership	Colorado Center	50.0	%		252,762			253,495
7750 Wisconsin Avenue LLC	7750 Wisconsin Avenue	50.0	%	(6)	70,147			69,724
BP-M 3HB Venture LLC	3 Hudson Boulevard	25.0	%		47,480			46,993
SMBP Venture LP	Santa Monica Business Park	55.0	%		175,799			180,952
					$	952,636		$	931,219

_______________


(1)	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.


(2)	The Company’s economic ownership has increased based on the achievement of certain return thresholds.


(3)	The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.


(4)	The joint venture owns three in-service buildings and two undeveloped land parcels.


(5)	Under the joint venture agreement for this land parcel, the partner will be entitled to up to two additional payments from the venture based on increases in total entitled square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.


(6)	This entity is a VIE (See Note 2).

Schedule Of Balance Sheets Of The Unconsolidated Joint Ventures [Text Block]

The combined summarized balance sheets of the Company’s unconsolidated joint ventures are as follows:



	March 31, 2019		December 31, 2018
	(in thousands)
ASSETS
Real estate and development in process, net (1)	$	3,660,439	$	3,545,906
Other assets	534,534		543,512
Total assets	$	4,194,973	$	4,089,418
LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
Mortgage and notes payable, net	$	2,074,473	$	2,017,609
Other liabilities (2)	604,280		582,006
Members’/Partners’ equity	1,516,220		1,489,803
Total liabilities and members’/partners’ equity	$	4,194,973	$	4,089,418
Company’s share of equity	$	642,564	$	622,498
Basis differentials (3)	310,072		308,721
Carrying value of the Company’s investments in unconsolidated joint ventures (4)	$	952,636	$	931,219

_______________


(1)	At March 31, 2019, this amount includes right of use assets - finance leases and right of use assets - operating leases totaling approximately $248.9 million and $12.7 million, respectively.


(2)	At March 31, 2019, this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.9 million and $17.2 million, respectively.

(3)


(4)	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

Statements Of Operations Of The Joint Ventures

The combined summarized statements of operations of the Company’s unconsolidated joint ventures are as follows:



	Three months ended March 31,
	2019			2018
	(in thousands)
Total revenue (1)	$	82,955		$	56,486
Expenses
Operating	30,499			22,849
Depreciation and amortization	28,646			14,725
Total expenses	59,145			37,574
Other expense
Interest expense	20,757			14,424
Net income	$	3,053		$	4,488

Company’s share of net income	$	1,584		$	1,826
Basis differential (2)	(1,371		)	(1,365		)
Income from unconsolidated joint ventures	$	213		$	461

_______________


(1)	Includes straight-line rent adjustments of approximately $5.8 million and $1.8 million for the three months ended March 31, 2019 and 2018, respectively.


(2)	Includes straight-line rent adjustments of approximately $0.5 million and $0.7 million for the three months ended March 31, 2019 and 2018, respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.4 million for the three months ended March 31, 2019 and 2018, respectively.

Noncontrolling Interests (Tables)

3 Months Ended

Mar. 31, 2019

Noncontrolling Interest [Line Items]

Distributions Declared to OP, LTIP, OPP and MYLTIP Units [Table Text Block]



Record Date	Payment Date	Dividend (Per Share)		Distribution (Per Unit)
March 29, 2019	April 30, 2019		$0.95		$0.95
December 31, 2018	January 30, 2019		$0.95		$0.95

March 29, 2018	April 30, 2018		$0.80		$0.80
December 31, 2017	January 30, 2018		$0.80		$0.80

Noncontrolling Interests [Member]

Noncontrolling Interest [Line Items]

Distributions Declared to OP, LTIP, OPP and MYLTIP Units [Table Text Block]



Record Date	Payment Date	Distributions per OP Unit and LTIP Unit		Distributions per MYLTIP Unit
March 29, 2019	April 30, 2019		$0.95		$0.095
December 31, 2018	January 30, 2019		$0.95		$0.095

The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and, after the February 4, 2018 measurement date, the 2015 MYLTIP Units) and its distributions on the 2015 MYLTIP Units (prior to the February 4, 2018 measurement date), 2016 MYLTIP Units, 2017 MYLTIP Units and 2018 MYLTIP Units (after the February 6, 2018 issuance date) that occurred during the first quarter of 2018:



Record Date	Payment Date	Distributions per OP Unit and LTIP Unit		Distributions per MYLTIP Unit
March 29, 2018	April 30, 2018		$0.80		$0.080
December 31, 2017	January 30, 2018		$0.80		$0.080

Stockholders' Equity / Partners' Capital Tables (Tables)

3 Months Ended

Mar. 31, 2019

Class of Stock [Line Items]

Dividends Declared [Table Text Block]



Record Date	Payment Date	Dividend (Per Share)		Distribution (Per Unit)
March 29, 2019	April 30, 2019		$0.95		$0.95
December 31, 2018	January 30, 2019		$0.95		$0.95

March 29, 2018	April 30, 2018		$0.80		$0.80
December 31, 2017	January 30, 2018		$0.80		$0.80

Series B Cumulative Redeemable Preferred Stock [Member]

Class of Stock [Line Items]

Dividends Declared [Table Text Block]

The following table presents Boston Properties Inc.’s dividends per share on its outstanding Series B Preferred Stock paid during 2019 and occurred during the first quarter of 2018:



Record Date	Payment Date	Dividend (Per Share)
May 3, 2019	May 15, 2019		$32.8125
February 4, 2019	February 15, 2019		$32.8125

May 4, 2018	May 15, 2018		$32.8125
February 2, 2018	February 15, 2018		$32.8125

Earnings Per Share / Common Unit (Tables)

3 Months Ended

Mar. 31, 2019

Computation Of Basic And Diluted Earnings Per Share



	Three months ended March 31, 2019
	Income (Numerator)			Shares (Denominator)	Per Share Amount
	(in thousands, except for per share amounts)
Basic Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	98,105		154,525	$	0.63
Effect of Dilutive Securities:
Stock Based Compensation	—			319	—
Diluted Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	98,105		154,844	$	0.63

	Three months ended March 31, 2018
	Income (Numerator)			Shares (Denominator)	Per Share Amount
	(in thousands, except for per share amounts)
Basic Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	176,021		154,385	$	1.14
Allocation of undistributed earnings to participating securities	(127		)	—	—
Net income attributable to Boston Properties, Inc. common shareholders	$	175,894		154,385	$	1.14
Effect of Dilutive Securities:
Stock Based Compensation	—			320	—
Diluted Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	175,894		154,705	$	1.14

Computation Of Basic And Diluted Earnings Per Share



	Three months ended March 31, 2019
	Income (Numerator)		Units (Denominator)	Per Unit Amount
	(in thousands, except for per unit amounts)
Basic Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	113,382	172,131	$	0.66
Effect of Dilutive Securities:
Stock Based Compensation	—		319	—
Diluted Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	113,382	172,450	$	0.66



	Three months ended March 31, 2018
	Income (Numerator)			Units (Denominator)	Per Unit Amount
	(in thousands, except for per unit amounts)
Basic Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,907		171,867	$	1.17
Allocation of undistributed earnings to participating securities	(141		)	—	—
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,766		171,867	$	1.17
Effect of Dilutive Securities:
Stock Based Compensation	—			320	—
Diluted Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,766		172,187	$	1.17

Segment Information (Tables)

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Schedule Of Reconciliation Of Net Operating Income To Net Income

Boston Properties, Inc.



	Three months ended March 31,
	2019			2018
	(in thousands)
Net income attributable to Boston Properties, Inc. common shareholders	$	98,105		$	176,021
Add:
Preferred dividends	2,625			2,625
Noncontrolling interest—common units of Boston Properties Limited Partnership	11,599			20,432
Noncontrolling interests in property partnerships	18,830			17,234
Interest expense	101,009			90,220
Impairment loss	24,038			—
Net operating income from unconsolidated joint ventures	25,349			16,060
Depreciation and amortization expense	164,594			165,797
Transaction costs	460			21
Payroll and related costs from management services contracts	3,395			2,885
General and administrative expense	41,762			35,894
Less:
Net operating income attributable to noncontrolling interests in property partnerships	47,085			45,909
Gains (losses) from investments in securities	2,969			(126		)
Interest and other income	3,753			1,648
(Losses) gains on sales of real estate	(905		)	96,397
Income from unconsolidated joint ventures	213			461
Direct reimbursements of payroll and related costs from management services contracts	3,395			2,885
Development and management services revenue	9,277			8,405
Company's share of Net Operating Income	$	425,979		$	371,610

Boston Properties Limited Partnership



	Three months ended March 31,
	2019			2018
	(in thousands)
Net income attributable to Boston Properties Limited Partnership common unitholders	$	113,382		$	200,907
Add:
Preferred distributions	2,625			2,625
Noncontrolling interests in property partnerships	18,830			17,234
Interest expense	101,009			90,220
Impairment loss	22,272			—
Net operating income from unconsolidated joint ventures	25,349			16,060
Depreciation and amortization expense	162,682			163,853
Transaction costs	460			21
Payroll and related costs from management services contracts	3,395			2,885
General and administrative expense	41,762			35,894
Less:
Net operating income attributable to noncontrolling interests in property partnerships	47,085			45,909
Gains (losses) from investments in securities	2,969			(126		)
Interest and other income	3,753			1,648
(Losses) gains on sales of real estate	(905		)	98,907
Income from unconsolidated joint ventures	213			461
Direct reimbursements of payroll and related costs from management services contracts	3,395			2,885
Development and management services revenue	9,277			8,405
Company's share of Net Operating Income	$	425,979		$	371,610

Schedule Of Segment Information By Geographic Area And Property Type

Information by geographic area (dollars in thousands):

For the three months ended March 31, 2019:



	Boston			Los Angeles			New York			San Francisco			Washington, DC			Total
Rental Revenue: (1)
Office	$	217,411		$	—		$	258,631		$	124,055		$	96,345		$	696,442
Residential	2,701			—			—			—			5,014			7,715
Hotel	8,938			—			—			—			—			8,938
Total	229,050			—			258,631			124,055			101,359			713,095
% of Grand Totals	32.12		%	—		%	36.27		%	17.40		%	14.21		%	100.00		%
Rental Expenses:
Office	79,500			—			96,971			41,125			36,147			253,743
Residential	1,206			—			—			—			2,568			3,774
Hotel	7,863			—			—			—			—			7,863
Total	88,569			—			96,971			41,125			38,715			265,380
% of Grand Totals	33.37		%	—		%	36.54		%	15.50		%	14.59		%	100.00		%
Net operating income	$	140,481		$	—		$	161,660		$	82,930		$	62,644		$	447,715
% of Grand Totals	31.38		%	—		%	36.11		%	18.52		%	13.99		%	100.00		%
Less: Net operating income attributable to noncontrolling interests in property partnerships	(9,373		)	—			(37,264		)	(448		)	—			(47,085		)
Add: Company's share of net operating income from unconsolidated joint ventures	772			15,708			1,786			—			7,083			25,349
Company's share of net operating income	$	131,880		$	15,708		$	126,182		$	82,482		$	69,727		$	425,979
% of Grand Totals	30.96		%	3.69		%	29.62		%	19.36		%	16.37		%	100.00		%

_______________


(1)	Rental Revenue is equal to total Revenue per the Company's Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

For the three months ended March 31, 2018:



	Boston			Los Angeles			New York			San Francisco			Washington, DC			Total
Rental Revenue: (1)
Office	$	204,997		$	—		$	242,398		$	89,893		$	99,312		$	636,600
Residential	1,152			—			—			—			3,007			4,159
Hotel	9,102			—			—			—			—			9,102
Total	215,251			—			242,398			89,893			102,319			649,861
% of Grand Totals	33.12		%	—		%	37.31		%	13.83		%	15.74		%	100.00		%
Rental Expenses:
Office	80,324			—			93,762			27,628			36,343			238,057
Residential	514			—			—			—			1,758			2,272
Hotel	8,073			—			—			—			—			8,073
Total	88,911			—			93,762			27,628			38,101			248,402
% of Grand Totals	35.79		%	—		%	37.75		%	11.12		%	15.34		%	100.00		%
Net operating income	$	126,340		$	—		$	148,636		$	62,265		$	64,218		$	401,459
% of Grand Totals	31.47		%	—		%	37.02		%	15.51		%	16.00		%	100.00		%
Less: Net operating income attributable to noncontrolling interests in property partnerships	(8,129		)	—			(37,946		)	166			—			(45,909		)
Add: Company's share of net operating income from unconsolidated joint ventures	534			7,074			1,661			—			6,791			16,060
Company's share of net operating income	$	118,745		$	7,074		$	112,351		$	62,431		$	71,009		$	371,610
% of Grand Totals	31.96		%	1.90		%	30.23		%	16.80		%	19.11		%	100.00		%

_______________


(1)	Rental Revenue is equal to total Revenue per the Company's Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Organization (Details) ft² in Millions	3 Months Ended	12 Months Ended
Organization (Details) ft² in Millions	Mar. 31, 2019 ft² Real_Estate_Properties series Buildings yr shares	Dec. 31, 2018 shares
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.50%	89.70%
Restriction on redemption of OP units from date of issuance (years) \| yr	1
One OP unit is equivalent to one share of Common Stock (in shares) \| shares	1
OP unit conversion rate (in shares) \| shares	1
Number Of Series Of Preferred Units Outstanding \| series	1
Commercial Real Estate Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	196
Net Rentable Area (in sf) \| ft²	51.4
Total Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	11
Net Rentable Area (in sf) \| ft²	5.3
Total Office Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	177
Office Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	9
Residential Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	6
Residential Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	2
Retail Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties \| Buildings	12
Hotel Property [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	1
Series B Cumulative Redeemable Preferred Stock [Member]
Real Estate Properties [Line Items]
Ratio of depository shares to shares of Series B Preferred Stock	0.01
Series B, Shares Outstanding (in shares) \| shares	80,000	80,000
Series B, Dividend Rate, Percentage	5.25%
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Real Estate Properties [Line Items]
Series B, Shares Outstanding (in shares) \| shares	8,000,000
Series B Preferred Units [Member]
Real Estate Properties [Line Items]
Series B, Shares Outstanding (in shares) \| shares	80,000

Basis Of Presentation And Summary Of Significant Accounting Policies (Carrying Value Of note receivable, Indebtedness And Corresponding Estimate Of Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable	$ 80,000	$ 80,000
Note receivable	19,593	19,468
Mortgage notes payable, net	2,959,908	2,964,572
Unsecured senior notes, net	7,547,043	7,544,697
Unsecured line of credit	0	0
Unsecured term loan, net	498,607	498,488
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable	80,000	80,000
Note receivable	19,593	19,468
Note and Related Party Receivables	99,593	99,468
Mortgage notes payable, net	2,959,908	2,964,572
Unsecured senior notes, net	7,547,043	7,544,697
Unsecured line of credit	0	0
Unsecured term loan, net	498,607	498,488
Total	11,005,558	11,007,757
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable	80,060	80,000
Note receivable	17,723	19,468
Note and Related Party Receivables	97,783	99,468
Mortgage notes payable, net	2,948,057	2,903,925
Unsecured senior notes, net	7,584,456	7,469,338
Unsecured line of credit	0	0
Unsecured term loan, net	500,728	500,783
Total	$ 11,033,241	$ 10,874,046

Real Estate Properties Table (Details) - USD ($)
$ in Thousands

Mar. 31, 2019

Jan. 01, 2019

Dec. 31, 2018

Land

$ 5,061,532

$ 5,072,568

187,292

Land held for future development

151,166

$ 151,800

^[1]

258,221

200,498

Buildings and improvements

13,286,605

13,356,751

Tenant improvements

2,444,358

2,396,932

Furniture, fixtures and equipment

43,080

44,351

Construction in progress

647,469

578,796

Total

22,079,723

21,649,896

Accumulated depreciation

(4,962,959)

(4,897,777)

Total real estate

17,116,764

16,752,119

Land

4,961,028

4,971,475

187,292

Land held for future development

151,166

^[1]

258,221

200,498

Buildings and improvements

12,991,108

13,059,488

Tenant improvements

2,444,358

2,396,932

Furniture, fixtures and equipment

43,080

44,351

Construction in progress

647,469

578,796

Total

21,683,722

21,251,540

Accumulated depreciation

(4,864,334)

(4,800,475)

Total real estate

$ 16,819,388

$ 16,451,065

[1]	Includes pre-development costs.

Real Estate Narrative (Details) $ in Thousands			1 Months Ended	3 Months Ended		12 Months Ended
Real Estate Narrative (Details) $ in Thousands	Feb. 14, 2019 ft² yr	Jan. 24, 2019 USD ($) ft² a	Jan. 23, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Apr. 18, 2019 USD ($) ft²	Jan. 10, 2019 USD ($) ft²
Real Estate [Line Items]
Right of use assets - finance leases				$ 187,292		$ 0
Proceeds from sales of real estate				20,019	$ 116,120
Gains (loss) on sales of real estate				905	(96,397)
Boston Properties Limited Partnership
Real Estate [Line Items]
Right of use assets - finance leases				187,292		0
Proceeds from sales of real estate				20,019	116,120
Gains (loss) on sales of real estate				905	(98,907)
325 Main Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²	115,000
Platform 16 [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²		1,100,000
Finance Lease fixed purchase price		$ 134,800
Right of use assets - finance leases		$ 122,600
Lessee, Finance Lease, Term of Contract		65 years
Area of Land \| a		5.6
Carnegie Center [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²								1,700,000
Aggregate purchase price								$ 51,500
Deferred purchase price								$ 8,600
One Tower Center [Member]
Real Estate [Line Items]
Impairment loss				24,000
One Tower Center [Member] \| Boston Properties Limited Partnership
Real Estate [Line Items]
Impairment loss				22,300
2600 Tower Oaks Boulevard [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²		179,000
Gross Sale Price		$ 22,700
Proceeds from sales of real estate		$ 21,400
Net income (loss)			$ (200)		$ (200)
Gains (loss) on sales of real estate				$ 600
Impairment loss						3,100
2600 Tower Oaks Boulevard [Member] \| Boston Properties Limited Partnership
Real Estate [Line Items]
Impairment loss						$ 1,500
Future Office Building [Member] \| 325 Main Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²	400,000
Square Footage Of Signed Lease \| ft²	362,000
Term of Lease Signed (in years) \| yr	15
Future Retail Building [Member] \| 325 Main Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²	38,000
Subsequent Event [Member] \| One Tower Center [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²							410,000
Gross Sale Price							$ 38,000

Real Estate Finance Lease Liability, Maturity - Platform 16 (Details) - USD ($)
$ in Thousands

Mar. 31, 2019

Jan. 24, 2019

Dec. 31, 2018

Total expected minimum lease payments

2019

$ 4,401

2020

^[1]

122,070

203,907

Interest portion

(30,784)

Present value of expected net lease payments

$ 173,123

$ 0

Platform 16 [Member]

Total expected minimum lease payments

2019

$ 17,918

2020

109,460

127,378

Interest portion

(4,815)

Present value of expected net lease payments

$ 122,563

[1]	(1)Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million, respectively, related to purchase options that the Company is reasonably certain that it will exercise.

Leases Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
Leases Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018
Cumulative effect of a change in accounting principle	$ 4,379	$ (5,496)
Right of use assets - operating leases	151,166		$ 151,800	$ 0
Lease liabilities - operating leases	199,653		$ 199,300	0
Boston Properties Limited Partnership
Right of use assets - operating leases	151,166			0
Lease liabilities - operating leases	199,653			$ 0
Dividends In Excess Of Earnings [Member]
Cumulative effect of a change in accounting principle	3,864	(4,933)
Dividends In Excess Of Earnings [Member] \| Boston Properties Limited Partnership
Cumulative effect of a change in accounting principle	3,900
Noncontrolling Interests - Common units [Member]
Cumulative effect of a change in accounting principle	445	$ (563)
Noncontrolling Interests - Common units [Member] \| Boston Properties Limited Partnership
Cumulative effect of a change in accounting principle	400
Noncontrolling interest - property partnerships [Member]
Cumulative effect of a change in accounting principle	70
Noncontrolling interest - property partnerships [Member] \| Boston Properties Limited Partnership
Cumulative effect of a change in accounting principle	$ (70)

Leases Lessee, Lease Costs and Other Information (Details)
$ in Thousands

3 Months Ended

Mar. 31, 2019

USD ($)

Leases [Abstract]

Operating lease costs

$ 3,677

Finance Lease, Amortization of right of use asset

^[1]

Finance Lease, Interest on lease liabilities

$ 12

^[2]

Operating Lease, Weighted Average Remaining Lease Term

52 years

Finance Lease, Weighted Average Remaining Lease Term

5 years

Operating Lease, Weighted Average Discount Rate, Percent

5.70%

Finance Lease, Weighted Average Discount Rate, Percent

4.10%

[1]	The finance leases relate to either land, building or assets that remain in development. The Company's policy is not to depreciate finance lease assets related to land because it is assumed to have an indefinite life. For assets under development, depreciation may commence once the asset is placed in-service and depreciation would be recognized in accordance with the Company's policy.
[2]	Three of the finance leases relate to assets under development and as such the entire interest amount was capitalized.

Leases Future Minimum Lease Payments for Ground Leases (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Leases [Abstract]
2019	$ 11,425
2020	18,425
2021	25,310
2022	8,894
2023	9,084
Thereafter	$ 567,232

Leases Future Minimum Lease Payments, Capital Leases (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Leases [Abstract]
2019	$ 1,441
2020	12,682
2021	2,123
2022	1,253
2023	944
Thereafter	73,241
Total expected minimum lease payments	91,684
Interest portion	(27,497)
Present value of expected net minimum lease payments	$ 64,187

Leases Lease Liability Maturity Schedule (Details) - USD ($)
$ in Thousands

Mar. 31, 2019

Jan. 01, 2019

Dec. 31, 2018

Operating Leases

April 1, 2019 - December 31, 2019

$ 7,317

17,488

25,403

11,376

9,084

567,232

637,900

Less: interest portion

(438,247)

Present value of lease payments

199,653

$ 199,300

$ 0

Finance Leases

April 1, 2019 - december 31, 2019

4,401

2020

^[1]

122,070

2,130

1,121

944

^[1]

73,241

Total lease payments

203,907

Interest portion

(30,784)

Present value of expected net lease payments

173,123

$ 0

Lessee, Finance Lease, Option to Extend, Reasonably Certain 2024

38,700

Lessee, Finance Lease, Option to Extend, Reasonably Certain 2020

$ 119,800

[1]	(1)Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million, respectively, related to purchase options that the Company is reasonably certain that it will exercise.

Leases Lessor, Lease Income Table (Details) - USD ($)	3 Months Ended
Leases Lessor, Lease Income Table (Details) - USD ($)	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Fixed Contractual Payments	$ 553,986,000
Variable lease payments	125,265,000
Lease	$ 679,251,000	$ 0

Leases Lessor , Future Minimum Rents (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
April 1, 2019 - December 31, 2019	$ 1,573,871
2019		$ 2,088,171
2020	2,147,464	2,106,963
2021	2,076,969	2,015,031
2022	1,910,362	1,838,699
2023	1,811,936	1,736,636
Thereafter	$ 12,821,229	$ 12,295,464

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details)
$ in Thousands

3 Months Ended

Mar. 31, 2019

USD ($)

ft²

Land_Parcels

Buildings

payments

Dec. 31, 2018

USD ($)

Schedule of Equity Method Investments [Line Items]

Carrying value of the Company's investments in unconsolidated joint ventures

$ (369,575)

$ (503,726)

$ 976,580

956,309

Square 407 Limited Partnership [Member]

Schedule of Equity Method Investments [Line Items]

Market Square North

50.00%

The Metropolitan Square Associates LLC [Member]

^[1]

$ (5,948)

(6,424)

Schedule of Equity Method Investments [Line Items]

Metropolitan Square

Carrying value of the Company's investments in unconsolidated joint ventures

20.00%

^[1]

$ 3,146

2,644

BP/CRF 901 New York Avenue LLC [Member]

Schedule of Equity Method Investments [Line Items]

901 New York Avenue

^[2]

25.00%

WP Project Developer LLC [Member]

^[1]

$ (13,215)

(13,640)

Schedule of Equity Method Investments [Line Items]

Wisconsin Place Land and Infrastructure

Carrying value of the Company's investments in unconsolidated joint ventures

^[3]

33.30%

^[1]

$ 37,821

38,214

Annapolis Junction NFM, LLC [Member]

Schedule of Equity Method Investments [Line Items]

Annapolis Junction

Carrying value of the Company's investments in unconsolidated joint ventures

^[4]

50.00%

^[1]

$ 25,284

25,268

Number of real estate properties | Buildings

Parcels of undeveloped land | Land_Parcels

540 Madison Venture LLC [Member]

Schedule of Equity Method Investments [Line Items]

540 Madison Avenue

Carrying value of the Company's investments in unconsolidated joint ventures

60.00%

^[1]

$ 66,452

66,391

500 North Capitol Venture LLC [Member]

Schedule of Equity Method Investments [Line Items]

500 North Capitol Street, NW

30.00%

501 K Street LLC [Member]

^[1]

$ (4,781)

(5,026)

Schedule of Equity Method Investments [Line Items]

1001 6th Street

Carrying value of the Company's investments in unconsolidated joint ventures

^[5]

50.00%

^[1]

$ 42,500

42,557

Potential additonal payments to joint venture partner | payments

Minimum square footage to make a potential additional payment to joint venture partner (in sqft) | ft²

520,000

Podium Developer LLC [Member]

Schedule of Equity Method Investments [Line Items]

The Hub on Causeway - Podium

Carrying value of the Company's investments in unconsolidated joint ventures

50.00%

^[1]

$ 69,849

69,302

Residential Tower Developer LLC [Member]

Schedule of Equity Method Investments [Line Items]

The Hub on Causeway - Residential

Carrying value of the Company's investments in unconsolidated joint ventures

50.00%

^[1]

$ 47,795

47,505

Hotel Tower Developer LLC [Member]

Schedule of Equity Method Investments [Line Items]

The Hub on Causeway - Hotel Air Rights

Carrying value of the Company's investments in unconsolidated joint ventures

50.00%

^[1]

$ 3,343

3,022

Office Tower Developer LLC [Member]

Schedule of Equity Method Investments [Line Items]

100 Causeway Street

Carrying value of the Company's investments in unconsolidated joint ventures

^[6]

50.00%

^[1]

$ 46,881

23,804

1265 Main Office JV LLC [Member]

Schedule of Equity Method Investments [Line Items]

1265 Main Street

Carrying value of the Company's investments in unconsolidated joint ventures

50.00%

^[1]

$ 4,030

3,918

BNY Tower Holdings LLC [Member]

Schedule of Equity Method Investments [Line Items]

Dock 72

Carrying value of the Company's investments in unconsolidated joint ventures

50.00%

^[1]

$ 83,291

82,520

CA-Colorado Center Limited Partnership [Member]

Schedule of Equity Method Investments [Line Items]

Colorado Center

Carrying value of the Company's investments in unconsolidated joint ventures

50.00%

^[1]

$ 252,762

253,495

7750 Wisconsin Avenue LLC [Member]

Schedule of Equity Method Investments [Line Items]

7750 Wisconsin Avenue

Carrying value of the Company's investments in unconsolidated joint ventures

^[6]

50.00%

^[1]

$ 70,147

69,724

BP-M 3HB Venture LLC [Member]

Schedule of Equity Method Investments [Line Items]

3 Hudson Boulevard

Carrying value of the Company's investments in unconsolidated joint ventures

25.00%

^[1]

$ 47,480

46,993

SMBP Venture LP [Member]

Schedule of Equity Method Investments [Line Items]

Santa Monica Business Park

Carrying value of the Company's investments in unconsolidated joint ventures

55.00%

^[1]

$ 175,799

180,952

Schedule of Equity Method Investments [Line Items]

23,900

25,100

Schedule of Equity Method Investments [Line Items]

Carrying value of the Company's investments in unconsolidated joint ventures

(604,280)

^[7]

(582,006)

^[1],[8]

$ 952,636

$ 931,219

[1]	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[2]	The Company’s economic ownership has increased based on the achievement of certain return thresholds.
[3]	The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.
[4]	The joint venture owns three in-service buildings and two undeveloped land parcels.
[5]	Under the joint venture agreement for this land parcel, the partner will be entitled to up to two additional payments from the venture based on increases in total entitled square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.
[6]	This entity is a VIE (See Note 2).
[7]	At March 31, 2019, this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.9 million and $17.2 million, respectively.
[8]	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheet

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($)
$ in Thousands

Mar. 31, 2019

Jan. 01, 2019

Dec. 31, 2018

ASSETS

Real estate and development in process, net

$ 17,116,764

$ 16,752,119

Liabilities and Members'/Partners' Equity [Abstract]

Mortgage notes payable, net

2,959,908

2,964,572

Other Liabilities

369,575

503,726

Total liabilities and equity / capital

20,501,604

20,256,477

Carrying value of the Company's investments in unconsolidated joint ventures

976,580

956,309

187,292

Lease liabilities - finance leases

151,166

$ 151,800

173,123

Lease liabilities - operating leases

199,653

$ 199,300

Real estate and development in process, net

ASSETS

3,660,439

^[1]

3,545,906

Other assets

534,534

543,512

Total assets

4,194,973

4,089,418

Liabilities and Members'/Partners' Equity [Abstract]

Mortgage notes payable, net

2,074,473

2,017,609

Other Liabilities

604,280

^[2]

582,006

Members'/Partners' equity

1,516,220

1,489,803

Total liabilities and equity / capital

4,194,973

4,089,418

Company's share of equity

642,564

622,498

Basis differentials

^[3]

310,072

308,721

Carrying value of the Company's investments in unconsolidated joint ventures

^[4],[5]

952,636

931,219

Liabilities and Members'/Partners' Equity [Abstract]

Other Liabilities

(23,900)

(25,100)

Basis differentials

315,300

$ 316,700

248,900

Lease liabilities - finance leases

12,700

393,900

Lease liabilities - operating leases

$ 17,200

[1]	(1)At March 31, 2019, this amount includes right of use assets - finance leases and right of use assets - operating leases totaling approximately $248.9 million and $12.7 million, respectively.
[2]	At March 31, 2019, this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.9 million and $17.2 million, respectively.
[3]	This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At March 31, 2019 and December 31, 2018, there was an aggregate basis differential of approximately $315.3 million and $316.7 million, respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities.
[4]	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheet
[5]	Investments with deficit balances aggregating approximately $23.9 million and $25.1 million at March 31, 2019 and December 31, 2018, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

Schedule of Equity Method Investments [Line Items]

$ 725,767

$ 661,151

Expenses

164,594

165,797

475,591

452,999

Other expense

101,009

90,220

131,159

216,312

213

461

Schedule of Equity Method Investments [Line Items]

^[1]

82,955

56,486

Expenses

Operating

30,499

22,849

28,646

14,725

59,145

37,574

Other expense

20,757

14,424

Company's share of net income (loss)

3,053

4,488

1,584

1,826

Basis differential

^[2]

(1,371)

(1,365)

Straight-line rent adjustments

213

461

5,800

1,800

Colorado Center [Member] | Unconsolidated Joint Ventures [Member]

Other expense

Straight-line rent adjustments

500

700

"Above" and "below" market rent adjustments, net

$ 400

[1]	Includes straight-line rent adjustments of approximately $5.8 million and $1.8 million for the three months ended March 31, 2019 and 2018, respectively
[2]	Includes straight-line rent adjustments of approximately $0.5 million and $0.7 million for the three months ended March 31, 2019 and 2018, respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.4 million for the three months ended March 31, 2019 and 2018, respectively

Investments in Unconsolidated Joint Ventures Narrative (Details) $ in Thousands	Jan. 24, 2019 USD ($) ft²	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Mortgage notes payable, net		$ 2,959,908	$ 2,964,572
Annapolis Junction Building Six [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%
Mortgage notes payable, net	$ 13,000
Debt Instrument, Basis Spread on Variable Rate	2.00%
Number of extensions	1
Extension Option (in years)	1
Debt instrument, borrowing capacity	$ 14,300
Net Rentable Area (in sf) \| ft²	119,000

Commitments And Contingencies (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2009	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 10, 2014
Commitments And Contingencies [Line Items]
Letter of credit and performance obligations	$ 7.7
Property insurance program per occurrence limits	1,000.0
Per occurrence limit for NBCR Coverage	1,000.0
Value of program trigger	$ 180.0
Coinsurance of program trigger	19.00%
Deductible in insurance as a percentage of the value of the affected property, San Francisco and Los Angeles	3.00%
Per occurrence limit of the earthquake insurance which covers San Francisco and Los Angeles regions	$ 240.0
Annual aggregate limit of the earthquake insurance which covers San Francisco and Los Angeles regions	240.0
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco and Los Angeles	20.0
767 Venture, LLC [Member]
Commitments And Contingencies [Line Items]
Maximum funding obligation	110.5
Property insurance program per occurrence limits	1,625.0
Lehman [Member]
Commitments And Contingencies [Line Items]
Bankruptcy claim, amount filed by general creditor		$ 45.3
Bankruptcy claim amount allowed by court to creditor								$ 45.2
Bankruptcy Claims, Amount of Claims Settled			$ 0.3	$ 0.4	$ 1.4	$ 8.1	$ 7.7
Bankruptcy remaining claim amount allowed by court to creditor	27.2
601 Lexington Avenue [Member]
Commitments And Contingencies [Line Items]
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP	250.0
Boston Properties Limited Partnership
Commitments And Contingencies [Line Items]
Operating partnership guarantee to cover liabilities of IXP	$ 20.0

Noncontrolling Interests (Narrative) (Details) - Boston Properties Limited Partnership	Mar. 31, 2019 shares
Noncontrolling Interests [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operating Partnership (OP) Units (in shares)	16,844,947
Long-Term Incentive Plan (LTIP) Units (in shares)	1,187,919
OPP Units 2012 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards in LTIP Units (in shares)	118,067
2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP (in units)	68,659
2014 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP (in units)	23,100
2015 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIPS (in units)	28,724
2016 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIPs (in units)	98,706
2017 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP (in units)	394,921
2018 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP	336,195
2019 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS	220,734

(Common Units) (Narrative) (Details) $ / shares in Units, $ in Millions		3 Months Ended
	Feb. 09, 2019 USD ($) shares	Mar. 31, 2019 USD ($) shares yr	Mar. 29, 2019 $ / shares
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)		14,129
Redemption of OP units issued on conversion of LTIP Units (in shares)		12,929
Restriction on redemption of OP Unit to Common Stock (in years) \| yr		1
Redemption of OP Unit equivalent to Common Stock (in shares)		1
Common units of operating partnership if converted value \| $		$ 2,400.0
Closing price of common stock (in dollars per share) \| $ / shares			$ 133.88
2016 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target	69.50%
Value of MYLTIP Awards \| $	$ 13.6
2016 MYLTIP Units Forfeited	364,980
Boston Properties Limited Partnership \| OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
MYLTIP distribution prior to measurement date		10.00%
Boston Properties Limited Partnership \| 2017 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP (in units)		394,921
Boston Properties Limited Partnership \| 2018 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP		336,195
Boston Properties Limited Partnership \| 2019 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS		220,734

Noncontrolling Interests Common units distributions (Details) - Boston Properties Limited Partnership - $ / shares	Jan. 30, 2019	Apr. 30, 2018	Jan. 30, 2018	Mar. 18, 2019
Dividends Payable [Line Items]
Distributions Declared To OP And LTIP Units Per Unit				$ 0.95
Distributions Declared To MYLTIP Units Per Unit (in dollars per unit)				$ 0.095
Distributions made to OP and LTIP units per unit (in dollars per unit)	$ 0.95	$ 0.80	$ 0.80
Distribution paid to MYLTIP Units (in dollars per unit)	$ 0.095	$ 0.080	$ 0.080

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) - USD ($) $ in Thousands			3 Months Ended
	Apr. 01, 2019	May 12, 2016	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Noncontrolling Interest [Line Items]
Noncontrolling Interest in Limited Partnerships			$ 1,710,608		$ 1,711,445
Payments to Noncontrolling Interests			24,128	$ 30,690
Salesforce Tower [Member] \| Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Portion of project costs covered by a construction loan		50.00%
Portion of costs funded (in percentage)		50.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		5.00%
Debt Instrument, Basis Spread on Variable Rate		3.00%
Salesforce Tower [Member] \| Parent Company [Member] \| Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Costs funded (in percentage)		2.50%
Preferred equity funded			$ 22,600
Salesforce Tower [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	5.00%
Payments to Noncontrolling Interests	$ 210,900
Repayment of Preferred Equity	$ 24,100

Stockholders' Equity / Partners' Capital Narrative (Details)		3 Months Ended
	Jun. 02, 2017 USD ($) yr	Mar. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Mar. 27, 2018 $ / shares	Jun. 03, 2014 USD ($)
Class of Stock [Line Items]
Common stock, shares outstanding		154,515,486	154,458,478
General Partners' Capital Account, Units Outstanding		1,725,484
Limited Partners' Capital Account, Units Outstanding		152,790,002
Shares of Common Stock in connection with the redemption of an equal number of OP Units (in shares)		14,129
Common Stock, Value, Issued \| $		$ 1,545,000	$ 1,545,000
ATM Program [Member]
Class of Stock [Line Items]
At the market stock offering program, aggregate value of common stock \| $	$ 600,000,000				$ 600,000,000
At Market Stock Offering Program Maximum Length Of Sale In Years \| yr	3
Common Stock, Value, Issued \| $		$ 0
Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		80,000	80,000
Series B, Dividend Rate, Percentage		5.25%
Series B, Liquidation Preference Per Share (dollars per share) \| $ / shares		$ 2,500.00	$ 2,500	$ 2,500.00
Ratio of depository shares to shares of Series B Preferred Stock		0.01
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		8,000,000
Series B, Liquidation Preference Per Share (dollars per share) \| $ / shares		$ 25.00		$ 25.00
Boston Properties Limited Partnership
Class of Stock [Line Items]
General Partners' Capital Account, Units Outstanding		1,725,484	1,722,336
Limited Partners' Capital Account, Units Outstanding		152,790,002	152,736,142
Boston Properties Limited Partnership \| Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		80,000	80,000
Series B, Liquidation Preference Per Share (dollars per share) \| $ / shares		$ 2,500	$ 2,500

Stockholders' Equity / Partners' Capital Stockholders' Equity / Partners' Capital Dividends / Distributions (Details) - $ / shares	Feb. 15, 2019	Jan. 30, 2019	May 15, 2018	Apr. 30, 2018	Feb. 15, 2018	Jan. 30, 2018	Mar. 18, 2019
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit							$ 0.95
Dividends, Per Share / Unit		$ 0.95		$ 0.80		$ 0.80
Boston Properties Limited Partnership
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit							0.95
Dividends, Per Share / Unit		$ 0.95		$ 0.80		$ 0.80
Series B Cumulative Redeemable Preferred Stock [Member]
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit							$ 32.8125
Dividends, Per Share / Unit	$ 32.8125		$ 32.8125		$ 32.8125

Earnings Per Share / Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basic Earnings:
Net income attributable to the Company's common shareholders / unitholders	$ 98,105	$ 176,021
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	154,525,000	154,385,000
Net income (in dollars per share / unit)	$ 0.63	$ 1.14
Allocation of undistributed earnings to participating securities (numerator)		$ (127)
Allocation of undistributed earnings to participating securities (in shares)		0
Allocation of undistributed earnings to participating securities (in dollars per shares / units)		$ 0
Net income attributable to the Company's common shareholders / unitholders		$ 175,894
Net income attributable to the Company's common shareholders / unitholders (in shares / units)		154,385,000
Net income attributable to the Company's common shareholders / unitholders (in dollars per share / unit)		$ 1.14
Effect of Dilutive Securities:
Stock Based Compensation, Income (Numerator)	$ 0	$ 0
Stock Based Compensation, Shares / Units (Denominator)	319,000	320,000
Stock Based Compensation, Per Share / Unit Amount (in dollars per share / unit)	$ 0.00	$ 0.00
Diluted Earnings:
Net income attributable to the Company's common shareholders / unitholders (Numerator)	$ 98,105	$ 175,894
Net income attributable to to the Company's shareholders / unitholder (number of shares)	154,844,000	154,705,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 0.63	$ 1.14
Boston Properties Limited Partnership
Entity Information [Line Items]
Redeemable Common Units	17,606,000	17,482,000
Basic Earnings:
Net income attributable to the Company's common shareholders / unitholders	$ 113,382	$ 200,907
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	172,131,000	171,867,000
Net income (in dollars per share / unit)	$ 0.66	$ 1.17
Allocation of undistributed earnings to participating securities (numerator)		$ (141)
Allocation of undistributed earnings to participating securities (in shares)		0
Allocation of undistributed earnings to participating securities (in dollars per shares / units)		$ 0
Net income attributable to the Company's common shareholders / unitholders		$ 200,766
Net income attributable to the Company's common shareholders / unitholders (in shares / units)		171,867,000
Net income attributable to the Company's common shareholders / unitholders (in dollars per share / unit)		$ 1.17
Effect of Dilutive Securities:
Stock Based Compensation, Income (Numerator)	$ 0	$ 0
Stock Based Compensation, Shares / Units (Denominator)	319,000	320,000
Stock Based Compensation, Per Share / Unit Amount (in dollars per share / unit)	$ 0.00	$ 0.00
Diluted Earnings:
Net income attributable to the Company's common shareholders / unitholders (Numerator)	$ 113,382	$ 200,766
Net income attributable to to the Company's shareholders / unitholder (number of shares)	172,450,000	172,187,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 0.66	$ 1.17

Stock Option and Incentive Plan Stock Option and Incentive Plan (Narrative) (Details) $ in Millions	Feb. 09, 2019 USD ($) shares	Feb. 05, 2019 USD ($) yr shares
2019 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Measurement, Years \| yr		3
Distributions Percent Before Measurement Date		10.00%
Value of MYLTIP Awards \| $		$ 13.5
MYLTIP Value Amortized Into Earnings, Years \| yr		4
2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards \| $	$ 13.6
Final awards percentage of target	69.50%
2016 MYLTIP Units Forfeited	364,980
Nareit Office Index adjusted [Member] \| 2019 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum earned awards		0
Maximum Earned Awards		220,734
Target Tier		110,367

Stock Option and Incentive Plan Restricted Stock (Narrative) (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued \| shares	154,594,386		154,537,378
Common Stock, Value, Issued	$ 1,545		$ 1,545
Stock based compensation expense	$ 14,800	$ 14,200
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued \| shares	23,083
Employee and director payment per share (in dollars per share) \| $ / shares	$ 0.01
Common Stock, Value, Issued	$ 3,000
Employee's weighted average cost per share (in dollars per share) \| $ / shares	$ 131.23
LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of LTIP units issued	$ 20,900
Per unit fair value weighted-average (in dollars per share) \| $ / shares	$ 121.41
Expected life assumed to calculate per unit fair value per LTIP unit (years)	5 years 8 months 12 days
Risk-free rate	2.68%
Expected price volatility	27.00%
LTIPs (including vested 2012 OPP Awards and vested MYLTIPS) And Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting annual installments	4
Unrecognized compensation expenses	$ 38,400
Unvested MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses	$ 22,600
Weighted-average period (years)	2 years 10 months 24 days
Boston Properties Limited Partnership \| LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP units issued (in shares) \| shares	172,166
Boston Properties Limited Partnership \| 2019 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued (in shares) \| shares	220,734
Boston Properties Limited Partnership \| LTIPs and 2019 MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee and director payment per share (in dollars per share) \| $ / shares	$ 0.25

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Net income attributable to the Company's common shareholders / unitholders

$ 98,105

$ 176,021

Noncontrolling interest-common units of the Operating Partnership

(2,625)

(11,599)

(20,432)

(18,830)

(17,234)

Net operating income from unconsolidated joint ventures

(101,009)

(90,220)

25,349

16,060

(164,594)

(165,797)

(460)

(21)

(7,863)

(8,073)

Net operating income attributable to noncontrolling interests in property partnerships

(41,762)

(35,894)

47,085

45,909

(2,969)

126

(3,753)

(1,648)

Direct reimbursement of payroll and related costs from management service contracts

(213)

(461)

^[1]

(8,938)

(9,102)

(9,277)

(8,405)

Business Intersegment, Eliminations [Member]

425,979

371,610

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Net income attributable to the Company's common shareholders / unitholders

98,105

176,021

Noncontrolling interest-common units of the Operating Partnership

2,625

11,599

20,432

18,830

17,234

101,009

90,220

Net operating income from unconsolidated joint ventures

24,038

25,349

16,060

164,594

165,797

460

3,395

2,885

Net operating income attributable to noncontrolling interests in property partnerships

41,762

35,894

47,085

45,909

2,969

(126)

3,753

1,648

(905)

96,397

Direct reimbursement of payroll and related costs from management service contracts

213

461

3,395

2,885

9,277

8,405

425,979

371,610

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Net income attributable to the Company's common shareholders / unitholders

113,382

200,907

(2,625)

(18,830)

(17,234)

(101,009)

(90,220)

(162,682)

(163,853)

(460)

(21)

(41,762)

(35,894)

(2,969)

126

(3,753)

(1,648)

(213)

(461)

Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member]

(9,277)

(8,405)

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Net income attributable to the Company's common shareholders / unitholders

113,382

200,907

2,625

18,830

17,234

101,009

90,220

Net operating income from unconsolidated joint ventures

22,272

25,349

16,060

162,682

163,853

460

3,395

2,885

Net operating income attributable to noncontrolling interests in property partnerships

41,762

35,894

47,085

45,909

2,969

(126)

3,753

1,648

(905)

98,907

Direct reimbursement of payroll and related costs from management service contracts

213

461

3,395

2,885

9,277

8,405

$ 425,979

$ 371,610

[1]	Rental Revenue is equal to total Revenue per the Company's Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2019

Mar. 31, 2018

^[1]

$ 696,442

$ 636,600

^[1]

7,715

4,159

^[1]

8,938

9,102

^[1]

$ 713,095

$ 649,861

100.00%

$ 253,743

$ 238,057

3,774

2,272

7,863

8,073

$ 265,380

$ 248,402

100.00%

$ 447,715

$ 401,459

Net operating income attributable to noncontrolling interests in property partnerships

100.00%

$ (47,085)

$ (45,909)

Company's share of net operating income from unconsolidated joint ventures

25,349

16,060

Company's Share of Net Operating Income: % of Grand Totals

$ 425,979

$ 371,610

100.00%

Boston [Member]

^[1]

$ 217,411

$ 204,997

^[1]

2,701

1,152

^[1]

8,938

9,102

^[1]

$ 229,050

$ 215,251

32.12%

33.12%

$ 79,500

$ 80,324

1,206

514

7,863

8,073

$ 88,569

$ 88,911

33.37%

35.79%

$ 140,481

$ 126,340

Net operating income attributable to noncontrolling interests in property partnerships

31.38%

31.47%

$ (9,373)

$ (8,129)

Company's share of net operating income from unconsolidated joint ventures

772

534

Company's Share of Net Operating Income: % of Grand Totals

$ 131,880

$ 118,745

30.96%

31.96%

Los Angeles [Member]

^[1]

$ 0

^[1]

^[1]

^[1]

$ 0

0.00%

$ 0

$ 0

0.00%

$ 0

Net operating income attributable to noncontrolling interests in property partnerships

0.00%

$ 0

Company's share of net operating income from unconsolidated joint ventures

15,708

7,074

Company's Share of Net Operating Income: % of Grand Totals

$ 15,708

$ 7,074

3.69%

1.90%

New York [Member]

^[1]

$ 258,631

$ 242,398

^[1]

^[1]

^[1]

$ 258,631

$ 242,398

36.27%

37.31%

$ 96,971

$ 93,762

$ 96,971

$ 93,762

36.54%

37.75%

$ 161,660

$ 148,636

Net operating income attributable to noncontrolling interests in property partnerships

36.11%

37.02%

$ (37,264)

$ (37,946)

Company's share of net operating income from unconsolidated joint ventures

1,786

1,661

Company's Share of Net Operating Income: % of Grand Totals

$ 126,182

$ 112,351

29.62%

30.23%

San Francisco [Member]

^[1]

$ 124,055

$ 89,893

^[1]

^[1]

^[1]

$ 124,055

$ 89,893

17.40%

13.83%

$ 41,125

$ 27,628

$ 41,125

$ 27,628

15.50%

11.12%

$ 82,930

$ 62,265

Net operating income attributable to noncontrolling interests in property partnerships

18.52%

15.51%

$ (448)

$ 166

Company's share of net operating income from unconsolidated joint ventures

Company's Share of Net Operating Income: % of Grand Totals

$ 82,482

$ 62,431

19.36%

16.80%

Washington, DC [Member]

^[1]

$ 96,345

$ 99,312

^[1]

5,014

3,007

^[1]

^[1]

$ 101,359

$ 102,319

14.21%

15.74%

$ 36,147

$ 36,343

2,568

1,758

$ 38,715

$ 38,101

14.59%

15.34%

$ 62,644

$ 64,218

Net operating income attributable to noncontrolling interests in property partnerships

13.99%

16.00%

$ 0

Company's share of net operating income from unconsolidated joint ventures

7,083

6,791