View Filing Data

Effective portion of interest rate contracts

$ 216,312

$ 115,564

Other comprehensive income (loss):

180

Amortization of interest rate contracts

^[1]

1,666

1,306

Other comprehensive income

1,666

1,486

Comprehensive income

217,978

117,050

Comprehensive income attributable to noncontrolling interests

(37,666)

(15,856)

Other comprehensive loss attributable to noncontrolling interests

(299)

(218)

Comprehensive income attributable to the Company

180,013

100,976

Effective portion of interest rate contracts

220,766

117,711

Other comprehensive income (loss):

180

Amortization of interest rate contracts

^[2]

1,666

1,306

Other comprehensive income

1,666

1,486

Comprehensive income

222,432

119,197

Comprehensive income attributable to noncontrolling interests

(17,378)

(4,496)

Comprehensive income attributable to the Company

$ 205,054

$ 114,701

[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 [Member]
Equity, value at Dec. 31, 2016	$ 7,931,924	$ 1,538	$ 200,000	$ 6,333,424	$ (693,694)	$ (2,722)	$ (52,251)	$ 2,145,629
Equity, shares at Dec. 31, 2016		153,790,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units to Common Stock, shares		23,000
Conversion of operating partnership units to Common Stock, value	0	$ 0		793				(793)
Allocated net income for the year	115,564				99,708			15,856
Dividends/distributions declared	(131,665)				(118,012)			(13,653)
Shares issued pursuant to stock purchase plan, shares		3,000
Shares issued pursuant to stock purchase plan, value	373			373
Net activity from stock option and incentive plan, shares		33,000
Net activity from stock option and incentive plan, value	12,281	$ 0		996				11,285
Cumulative effect of a change in accounting principle	(2,035)				(272)			(1,763)
Contributions from noncontrolling interests in property partnerships	8,145							8,145
Distributions to noncontrolling interests in property partnerships	(13,635)							(13,635)
Effective portion of interest rate contracts	180						97	83
Amortization of interest rate contracts	1,306						1,171	135
Reallocation of noncontrolling interest	0			4,384				(4,384)
Equity, value at Mar. 31, 2017	7,922,438	$ 1,538	200,000	6,339,970	(712,270)	(2,722)	(50,983)	2,146,905
Equity, shares at Mar. 31, 2017		153,849,000
Equity, value at Dec. 31, 2017	$ 8,102,456	$ 1,543	200,000	6,377,908	(712,343)	(2,722)	(50,429)	2,288,499
Equity, shares at Dec. 31, 2017	154,325,286	154,325,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units to Common Stock, shares		24,000
Conversion of operating partnership units to Common Stock, value		$ 1		831				(832)
Allocated net income for the year	$ 216,312				178,646			37,666
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
Cumulative effect of a change in accounting principle	5,496				4,933			563
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	299
Reallocation of noncontrolling interest				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)	$ 2,305,062
Equity, shares at Mar. 31, 2018	154,362,303	154,362,000

Consolidated Statement of Partners' Capital Statement - USD ($) $ in Thousands	Total	Boston Properties Limited Partnership
Beginning Balance at Dec. 31, 2016		$ 3,811,717
Contributions		4,491
Net income allocable to general and limited partner units		101,855
Distributions		(118,012)
Other comprehensive income		1,268
Cumulative effect of a change in accounting principle	$ (2,035)	(272)
Unearned compensation		(3,122)
Conversion of redeemable partnership units		793
Adjustment to reflect redeemable partnership units at redemption value		(126,416)
Ending Balance at Mar. 31, 2017		3,672,302
Beginning Balance at Dec. 31, 2017		3,807,630
Contributions		1,452
Net income allocable to general and limited partner units		183,100
Distributions		(126,115)
Other comprehensive income		1,367
Cumulative effect of a change in accounting principle	$ 5,496	4,933
Unearned compensation		(1,208)
Conversion of redeemable partnership units		832
Adjustment to reflect redeemable partnership units at redemption value		115,432
Ending Balance at Mar. 31, 2018		$ 3,987,423

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 216,312	$ 115,564
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	165,797	159,205
Non-cash compensation expense	14,772	10,802
Income from unconsolidated joint ventures	(461)	(3,084)
Distributions of net cash flow from operations of unconsolidated joint ventures	847	1,861
Losses (gains) from investments in securities	126	(1,042)
Non-cash portion of interest expense	5,299	(7,729)
Gains on sales of real estate	(96,397)	(133)
Change in assets and liabilities:
Tenant and other receivables, net	22,790	19,023
Accrued rental income, net	(26,319)	(9,158)
Prepaid expenses and other assets	(66,968)	(21,197)
Accounts payable and accrued expenses	(13,913)	(16,306)
Accrued interest payable	12,399	22,781
Other liabilities	23,089	(7,104)
Tenant leasing costs	(31,595)	(23,631)
Total adjustments	9,466	124,288
Net cash provided by operating activities	225,778	239,852
Cash flows from investing activities:
Construction in progress	(150,060)	(154,518)
Building and other capital improvements	(53,550)	(43,687)
Tenant improvements	(47,157)	(50,810)
Proceeds from sales of real estate	116,120	133
Capital contributions to unconsolidated joint ventures	(48,823)	(17,980)
Investments in securities, net	(318)	(961)
Net cash used in investing activities	(183,788)	(267,823)
Cash flows from financing activities:
Repayments of mortgage notes payable	(5,333)	(5,038)
Borrowings on unsecured line of credit	260,000	175,000
Repayments of unsecured line of credit	(190,000)	(70,000)
Payments on capital lease obligations	(3)	(22)
Payments on real estate financing transactions	(444)	(480)
Deferred financing costs	(16)	0
Net proceeds from equity transactions	(723)	(183)
Dividends and distributions	(140,288)	(131,555)
Contributions from noncontrolling interests in property partnerships	15,267	8,145
Distributions to noncontrolling interests in property partnerships	(30,690)	(13,801)
Net cash used in financing activities	(92,230)	(37,934)
Net decrease in cash and cash equivalents and cash held in escrows	(50,240)	(65,905)
Cash and cash equivalents and cash held in escrows, beginning of period	505,369	420,088
Cash and cash equivalents and cash held in escrows, end of period	455,129	354,183
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	434,767	356,914
Cash held in escrows, beginning of period	70,602	63,174
Cash and Cash Equivalents, end of period	294,571	302,939
Cash held in escrows, end of period	160,558	51,244
Supplemental disclosures:
Cash paid for interest	89,412	92,774
Interest capitalized	17,378	12,345
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(29,609)	(49,292)
Additions to real estate included in accounts payable and accrued expenses	35,245	44,708
Dividends and distributions declared but not paid	139,218	130,418
Conversions of noncontrolling interests to stockholders’ equity	832	793
Issuance of restricted securities to employees	36,433	34,592
Boston Properties Limited Partnership
Cash flows from operating activities:
Net income	220,766	117,711
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	163,853	157,058
Non-cash compensation expense	14,772	10,802
Income from unconsolidated joint ventures	(461)	(3,084)
Distributions of net cash flow from operations of unconsolidated joint ventures	847	1,861
Losses (gains) from investments in securities	126	(1,042)
Non-cash portion of interest expense	5,299	(7,729)
Gains on sales of real estate	(98,907)	(133)
Change in assets and liabilities:
Tenant and other receivables, net	22,790	19,023
Accrued rental income, net	(26,319)	(9,158)
Prepaid expenses and other assets	(66,968)	(21,197)
Accounts payable and accrued expenses	(13,913)	(16,306)
Accrued interest payable	12,399	22,781
Other liabilities	23,089	(7,104)
Tenant leasing costs	(31,595)	(23,631)
Total adjustments	5,012	122,141
Net cash provided by operating activities	225,778	239,852
Cash flows from investing activities:
Construction in progress	(150,060)	(154,518)
Building and other capital improvements	(53,550)	(43,687)
Tenant improvements	(47,157)	(50,810)
Proceeds from sales of real estate	116,120	133
Capital contributions to unconsolidated joint ventures	(48,823)	(17,980)
Investments in securities, net	(318)	(961)
Net cash used in investing activities	(183,788)	(267,823)
Cash flows from financing activities:
Repayments of mortgage notes payable	(5,333)	(5,038)
Borrowings on unsecured line of credit	260,000	175,000
Repayments of unsecured line of credit	(190,000)	(70,000)
Payments on capital lease obligations	(3)	(22)
Payments on real estate financing transactions	(444)	(480)
Deferred financing costs	(16)	0
Net proceeds from equity transactions	(723)	(183)
Dividends and distributions	(140,288)	(131,555)
Contributions from noncontrolling interests in property partnerships	15,267	8,145
Distributions to noncontrolling interests in property partnerships	(30,690)	(13,801)
Net cash used in financing activities	(92,230)	(37,934)
Net decrease in cash and cash equivalents and cash held in escrows	(50,240)	(65,905)
Cash and cash equivalents and cash held in escrows, beginning of period	505,369	420,088
Cash and cash equivalents and cash held in escrows, end of period	455,129	354,183
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	434,767	356,914
Cash held in escrows, beginning of period	70,602	63,174
Cash and Cash Equivalents, end of period	294,571	302,939
Cash held in escrows, end of period	160,558	51,244
Supplemental disclosures:
Cash paid for interest	89,412	92,774
Interest capitalized	17,378	12,345
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(29,609)	(49,292)
Additions to real estate included in accounts payable and accrued expenses	35,245	44,708
Dividends and distributions declared but not paid	139,218	130,418
Conversions of noncontrolling interests to stockholders’ equity	832	793
Issuance of restricted securities to employees	$ 36,433	$ 34,592

Organization

3 Months Ended

Mar. 31, 2018

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, 2018 owned an approximate 89.6% (89.7% at December 31, 2017) 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 such OP Unit for cash equal to the value of a share of common stock of Boston Properties, Inc. (“Common Stock”) at such time. 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 and 2018 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 and 2015 MYLTIP Units expired on February 6, 2015, February 4, 2016, February 3, 2017 and February 4, 2018, 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 2016, 2017 and 2018 MYLTIP Units differ from other LTIP Units granted to employees (including the 2012 OPP Units, the 2013 MYLTIP Units, the 2014 MYLTIP Units and the 2015 MYLTIP Units, which have been earned). Therefore, unless specifically noted otherwise, all references to LTIP Units exclude the 2016, 2017 and 2018 MYLTIP Units. LTIP Units (including the 2012 OPP Units, the 2013 MYLTIP Units, the 2014 MYLTIP Units and the 2015 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, 2018, 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, 2018, the Company owned or had interests in a portfolio of 179 commercial real estate properties (the “Properties”) aggregating approximately 50.3 million net rentable square feet of primarily Class A office properties, including thirteen properties under construction/redevelopment totaling approximately 6.5 million net rentable square feet. At March 31, 2018, the Properties consisted of:


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


•	six residential properties (including four properties under construction);


•	five retail properties 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, 2018

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, 2017.

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," the accounting standards for Fair Value Measurements and Disclosures) 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 the accounting standards for Fair Value Measurements and Disclosures) if trading volumes are low. The Company determines the fair value of its mortgage notes payable using discounted cash flow analysis by discounting the spread between the future contractual interest payments and hypothetical future interest payments on 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 mortgage notes payable and mezzanine notes payable are categorized at a Level 3 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) 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, 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 mortgage notes payable, net, unsecured line of credit and unsecured senior notes, net and the Company’s corresponding estimate of fair value as of March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018				December 31, 2017
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Mortgage notes payable, net	$	2,974,930	$	2,957,054	$	2,979,281	$	3,042,920
Unsecured senior notes, net	7,249,383		7,262,443		7,247,330		7,461,615
Unsecured line of credit	115,000		115,000		45,000		45,000
Total	$	10,339,313	$	10,334,497	$	10,271,611	$	10,549,535

Variable Interest Entities (VIEs)

Consolidated VIEs are those where 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 nine entities that are VIEs.

Consolidated Variable Interest Entities

As of March 31, 2018, Boston Properties, Inc. has identified seven consolidated VIEs, including Boston Properties Limited Partnership. The VIEs own (1) the following five in-service properties: 767 Fifth Avenue (the General Motors Building), Times Square Tower, 601 Lexington Avenue, Atlantic Wharf Office Building and 100 Federal Street and (2) Salesforce Tower, which was partially placed in-service on December 1, 2017.

The Company consolidates these VIEs because it is the primary beneficiary. The third parties’ interests in these consolidated entities, with the exception of Boston Properties Limited Partnership, 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 Residential Tower Developer LLC joint ventures, which own 7750 Wisconsin Avenue and The Hub on Causeway - Residential, respectively, are VIEs. 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

Revenue from Contracts with Customers

In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). The objective of ASU 2014-09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers, which supersedes most of the existing revenue recognition guidance, including industry-specific guidance. The core principle is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying ASU 2014-09, companies will perform a five-step analysis of transactions to determine when and how revenue is recognized. The five-step analysis consists of the following: (i) identifying the contract with a customer, (ii) identifying the performance obligations in the contract, (iii) determining the transaction price, (iv) allocating the transaction price to the performance obligations in the contract and (v) recognizing revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB’s ASC. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date” (“ASU 2015-14”), which delayed the effective date of ASU 2014-09 by one year making it effective for the first interim period within annual reporting periods beginning after December 15, 2017. Early adoption was permitted as of the original effective date. In May 2016, the FASB issued ASU No. 2016-12, “Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients” (“ASU 2016-12”). ASU 2016-12 is intended to clarify and provide practical expedients for certain aspects of ASU 2014-09 and notes that lease contracts with customers are a scope exception. ASU 2014-09 was effective for the Company for reporting periods beginning after December 15, 2017.

The Company adopted ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The adoption of ASU 2014-09 did not have a material impact on the Company’s consolidated financial statements. The Company applied the guidance only to contracts that were not completed as of January 1, 2018. The Company does not have material contract assets and liabilities within the scope of ASC 606. The adoption of ASU 2014-09 resulted in a change to the timing pattern of revenue recognized, but not the total revenue recognized over time for certain of the Company’s development services contracts. As a result, the modified retrospective approach resulted in the Company recognizing on January 1, 2018 the cumulative effect of adopting ASU 2014-09 aggregating approximately $4.9 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners’ Capital of Boston Properties Limited Partnership and approximately $0.6 million to Noncontrolling Interests - Common Units of Boston Properties, Inc. and Noncontrolling Interests - Redeemable Partnership Units of Boston Properties Limited Partnership on the corresponding Consolidated Balance Sheets.

The Company disaggregates its revenue by source within its Consolidated Statements of Operations. As an owner and operator of real estate, the Company derives the majority of its revenue from leasing space to tenants at its properties. As a result, the majority of the Company’s revenue is accounted for pursuant to ASC 840 “Leases” (“ASC 840”) and is reflected within Base Rent in the Consolidated Statements of Operations. In addition, the Company earns revenue from recoveries from tenants, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs. Revenue from recoveries from tenants is recognized under the guidance within ASC 840 until the adoption of ASC 842 "Leases" in 2019 at which time it may fall within the guidance under ASC 606 pending a final determination from the FASB.

The Company also earns revenue from the following sources; parking and other revenue, hotel revenue and development and management services revenue.

Parking and other revenue is derived primarily from monthly and transient daily parking. In addition, the Company has certain lease arrangements for parking accounted for under the guidance in ASC 840. The monthly and transient daily parking revenue falls within the scope of ASC 606 and is accounted for at the point in time when control of the goods or services transfers to the customer and the Company’s performance obligation is satisfied, consistent with the Company’s previous accounting.

Hotel revenue is derived from room rentals and other sources such as charges to guests for telephone service, movie and vending commissions, meeting and banquet room revenue and laundry services. Hotel revenue also falls within the scope of ASC 606 and is accounted for at the point in time when control of the goods or services transfers to the customer and the Company’s performance obligation is satisfied, consistent with the Company’s previous accounting.

Development and management services revenue is earned from unconsolidated joint venture entities and third party property owners. The Company determined that the performance obligations associated with its development services contracts are satisfied over time and that the Company would recognize its development services revenue under the output method evenly over time from the development commencement date through the substantial completion date of the development management services project due to the stand-ready nature of the contracts. Significant judgments impacting the amount and timing of revenue recognized from the Company's development services contracts include estimates of total development project costs from which the fees are typically derived and estimates of the period of time until substantial completion of the development project, the period of time over which the development services are required to be performed. As a result, the pattern of revenue recognized over time under ASC 606 differs from the Company’s previous accounting. The Company recognizes development fees earned from unconsolidated joint venture projects equal to its cost plus profit to the extent of the third party partners’ ownership interest. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis, because such fees are contingent upon the collection of rents. The revenue recognized under property management services contracts is recognized consistent with the Company's previous accounting.

ASU 2014-09 also updates the principal versus agent considerations and as a result the Company determined that amounts reimbursed for payroll and related costs received from unconsolidated joint venture entities and third party property owners in connection with management services contracts should be reflected on a gross basis instead of on a net basis as the Company has determined that it is the principal under these arrangements. During the three months ended March 31, 2018, the Company recognized approximately $2.9 million of expenses consisting of payroll and related costs from management services contracts and recognized corresponding revenue of approximately $2.9 million reflecting the direct reimbursements of such costs from the unconsolidated joint venture entities and third party property owners.

Statement of Cash Flows

In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2016-15”). ASU 2016-15 is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. The areas addressed in the new guidance related to debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned and bank-owned life insurance policies, distributions received from equity method investments, beneficial interest in securitization transactions, and separately identifiable cash flows and application of the predominance principle. ASU 2016-15 was effective for the Company for reporting periods beginning after December 15, 2017, with early adoption permitted (provided that all of the amendments are adopted in the same period), and was required to be applied retrospectively to all periods presented. The Company adopted ASU 2016-15 effective January 1, 2018. The adoption of ASU 2016-15 did not have a material impact on the Company’s consolidated financial statements. The adoption of ASU 2016-15 will result in the retrospective classification of debt prepayment costs as a component of financing activities instead of as a component of operating activities in the Company's Consolidated Statements of Cash Flows.

In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2016-18”). ASU 2016-18 requires companies to include restricted cash and restricted cash equivalents with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 also requires a disclosure of a reconciliation between the statement of financial position and the statement of cash flows when the statement of financial position includes more than one line item for cash, cash equivalents, restricted cash and restricted cash equivalents. Entities with material restricted cash and restricted cash equivalents balances are required to disclose the nature of the restrictions. ASU 2016-18 was effective for reporting periods beginning after December 15, 2017, with early adoption permitted, and is required to be applied retrospectively to all periods presented. The Company adopted ASU 2016-18 effective January 1, 2018. The adoption of ASU 2016-18 did not have a material impact on the Company’s consolidated financial statements. The retrospective adoption of ASU 2016-18 resulted in a decrease to net cash provided by operating activities totaling approximately $6.7 million, an increase to net cash used in investing activities totaling approximately $5.2 million and a corresponding increase to the net decrease in cash and cash equivalents and cash held in escrows totaling approximately $11.9 million from amounts previously reported for the three months ended March 31, 2017. Cash held in escrows include amounts established pursuant to various agreements for security deposits, property taxes, insurance and other costs. Cash held in escrows also include cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties.

Sales of Real Estate

In February 2017, the FASB issued ASU No. 2017-05, “Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets” (“ASU 2017-05”). ASU 2017-05 updates the definition of an “in substance nonfinancial asset” and clarifies the derecognition guidance for nonfinancial assets to conform with the new revenue recognition standard. The effective date and transition methods of ASU 2017-05 are aligned with ASU 2014-09 described above and were effective for the first interim period within annual reporting periods beginning after December 15, 2017. The Company adopted ASU 2017-05 effective January 1, 2018 using the modified retrospective approach. The adoption of ASU 2017-05 did not have a material impact on the Company's consolidated financial statements. See also Note 3.

Stock Compensation

In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting” (“ASU 2017-09”). ASU 2017-09 is intended to provide clarity and reduce (1) diversity in practice, (2) cost and (3) complexity when applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award. ASU 2017-09 was effective for public entities for fiscal years and interim periods beginning after December 15, 2017. The Company adopted ASU 2017-09 effective January 1, 2018. The adoption of ASU 2017-09 did not have a material impact on the Company's consolidated financial statements.

Derivatives and Hedging

In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities” (“ASU 2017-12”). ASU 2017-12 was issued with the objective of improving the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. ASU 2017-12 also makes certain targeted improvements to simplify the application of the hedge accounting guidance. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company early adopted ASU 2017-12 effective January 1, 2018. The adoption of ASU 2017-12 did not have a material impact on the Company's consolidated financial statements. As of March 31, 2018, the Company does not have any outstanding hedges, but continues to reclassify into earnings as an increase primarily to interest expense approximately $1.7 million per quarter relating to previously settled interest rate contracts.

New Accounting Pronouncements Issued but not yet Adopted

Leases

In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“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 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 existing guidance for operating leases today. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. ASU 2016-02 supersedes previous leasing standards. ASU 2016-02 is effective for the Company for reporting periods beginning after December 15, 2018, with early adoption permitted. The Company will adopt ASU 2016-02 effective January 1, 2019 using the modified retrospective approach. The Company is in the process of evaluating whether it will elect to apply the practical expedients. The Company is in the process of adopting ASU 2016-02, with its project team compiling an inventory of its leases that will be impacted by the adoption of ASU 2016-02. The Company continues to assess the impact of adopting ASU 2016-02. However, the Company will account for operating leases under which it is the lessor on its balance sheet in a manner similar to its current accounting with the underlying leased asset recognized as real estate. In January 2018, the FASB issued a proposed ASU that would allow lessors to elect, as a practical expedient, not to allocate the total consideration to lease and non-lease components based on their relative standalone selling prices. If issued, this practical expedient will allow lessors to elect a combined single lease component presentation if (i) the timing and pattern of the revenue recognition of the combined single lease component is the same, and (ii) the related lease component and, the combined single lease component would be classified as an operating lease. If the practical expedient in the proposed ASU is issued, it could allow for tenant recoveries that qualify as non-lease components to be presented under a single lease component presentation. However, without the proposed practical expedient, tenant recoveries would be separated into lease and non-lease components. For leases in which the Company is the lessee, primarily consisting of ground leases, the Company will recognize a right-of-use asset and a lease liability equal to the present value of the minimum lease payments with rental payments being applied to the lease liability and to interest expense and the right-of-use asset being amortized to expense over the term of the lease. In addition, under ASU 2016-02, lessors will only capitalize incremental direct leasing costs. As a result, the Company will no longer be able to capitalize legal costs and internal leasing wages and instead will be required to expense these and other non-incremental costs as incurred. 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 current 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.

Real Estate

3 Months Ended

Mar. 31, 2018

Real Estate [Abstract]

Real Estate

3. Real Estate

Boston Properties, Inc.

Real estate consisted of the following at March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Land	$	5,105,376		$	5,080,679
Land held for future development (1)	204,506			204,925
Buildings and improvements	12,435,573			12,284,164
Tenant improvements	2,266,796			2,219,608
Furniture, fixtures and equipment	41,507			37,928
Construction in progress	1,262,886			1,269,338
Total	21,316,644			21,096,642
Less: Accumulated depreciation	(4,674,838		)	(4,589,634		)
	$	16,641,806		$	16,507,008

_______________


(1)	Includes pre-development costs.

Boston Properties Limited Partnership

Real estate consisted of the following at March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Land	$	5,001,810		$	4,976,303
Land held for future development (1)	204,506			204,925
Buildings and improvements	12,130,901			11,977,062
Tenant improvements	2,266,796			2,219,608
Furniture, fixtures and equipment	41,507			37,928
Construction in progress	1,262,886			1,269,338
Total	20,908,406			20,685,164
Less: Accumulated depreciation	(4,580,949		)	(4,496,959		)
	$	16,327,457		$	16,188,205

_______________


(1)	Includes pre-development costs.

Development

On January 24, 2018, the Company entered into a lease agreement with Leidos for a build-to-suit project with approximately 276,000 net rentable square feet of Class A office space at the Company's 17Fifty Presidents Street development project located in Reston, Virginia. Concurrently with the execution of the lease, the Company commenced development of the project and expects the building to be completed and available for occupancy during the second quarter of 2020.

On January 31, 2018, the Company partially placed in-service its Signature at Reston development project comprised of 508 apartment units and retail space aggregating approximately 515,000 square feet located in Reston, Virginia.

On February 23, 2018, the Company entered into a lease agreement with Fannie Mae to lease approximately 850,000 net rentable square feet of Class A office space at the Company's Reston Gateway development project located in Reston, Virginia. The initial phase of the project will consist of approximately 1.1 million net rentable square feet. The Company expects to begin construction in the second half of 2018 upon receipt of all necessary approvals.

Dispositions

On January 9, 2018, the Company completed the sale of its 500 E Street, S.W. property located in Washington, DC for a net contract sale price of approximately $118.6 million. Net cash proceeds totaled approximately $116.1 million, resulting in a gain on sale of real estate totaling approximately $96.4 million for Boston Properties, Inc. and approximately $98.9 million for Boston Properties Limited Partnership. 500 E Street, S.W. is an approximately 262,000 net rentable square foot Class A office property. 500 E Street, S.W. contributed approximately $0.1 million of net income to the Company for the period from January 1, 2018 through January 8, 2018 and contributed approximately $1.6 million of net income to the Company for the three months ended March 31, 2017.

Investments in Unconsolidated Joint Ventures

3 Months Ended

Mar. 31, 2018

Investments In Unconsolidated Joint Ventures [Abstract]

Investments In Unconsolidated Joint Ventures

4. Investments in Unconsolidated Joint Ventures

The investments in unconsolidated joint ventures consist of the following at March 31, 2018 and December 31, 2017:



		Nominal % Ownership			Carrying Value of Investment (1)
Entity	Properties	Nominal % Ownership			March 31, 2018			December 31, 2017
					(in thousands)
Square 407 Limited Partnership	Market Square North	50.0	%		$	(7,811	)	$	(8,258	)
The Metropolitan Square Associates LLC	Metropolitan Square	20.0	%		3,372			3,339
BP/CRF 901 New York Avenue LLC	901 New York Avenue	25.0	%	(2)	(13,262		)	(13,811		)
WP Project Developer LLC	Wisconsin Place Land and Infrastructure	33.3	%	(3)	39,340			39,710
Annapolis Junction NFM, LLC	Annapolis Junction	50.0	%	(4)	17,974			18,381
540 Madison Venture LLC	540 Madison Avenue	60.0	%		66,259			66,179
500 North Capitol Venture LLC	500 North Capitol Street, NW	30.0	%		(4,129		)	(3,876		)
501 K Street LLC	1001 6th Street	50.0	%	(5)	42,636			42,657
Podium Developer LLC	The Hub on Causeway	50.0	%		67,883			67,120
Residential Tower Developer LLC	The Hub on Causeway - Residential	50.0	%	(6)	29,752			28,212
Hotel Tower Developer LLC	The Hub on Causeway - Hotel Air Rights	50.0	%		1,751			1,690
1265 Main Office JV LLC	1265 Main Street	50.0	%		4,539			4,641
BNY Tower Holdings LLC	Dock 72 at the Brooklyn Navy Yard	50.0	%		71,582			72,104
CA-Colorado Center Limited Partnership	Colorado Center	50.0	%		254,226			254,440
7750 Wisconsin Avenue LLC	7750 Wisconsin Avenue	50.0	%	(6)	67,404			21,452
					$	641,516		$	593,980

_______________


(1)	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, 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 four 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 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 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, 2018		December 31, 2017
	(in thousands)
ASSETS
Real estate and development in process, net	$	1,844,695	$	1,768,996
Other assets	376,127		367,743
Total assets	$	2,220,822	$	2,136,739
LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
Mortgage and notes payable, net	$	1,471,762	$	1,437,440
Other liabilities	95,597		99,215
Members’/Partners’ equity	653,463		600,084
Total liabilities and members’/partners’ equity	$	2,220,822	$	2,136,739
Company’s share of equity	$	335,580	$	286,495
Basis differentials (1)	305,936		307,485
Carrying value of the Company’s investments in unconsolidated joint ventures (2)	$	641,516	$	593,980

_______________

(1)

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, 2018 and December 31, 2017, there was an aggregate basis differential of approximately $321.1 million and $322.5 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.


(2)	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, 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,
	2018			2017
	(in thousands)
Total revenue (1)	$	56,486		$	54,761
Expenses
Operating	22,849			22,079
Depreciation and amortization	14,725			14,309
Total expenses	37,574			36,388
Operating income	18,912			18,373
Other expense
Interest expense	14,424			9,300
Net income	$	4,488		$	9,073

Company’s share of net income	$	1,826		$	4,323
Basis differential (2)	(1,365		)	(1,239		)
Income from unconsolidated joint ventures	$	461		$	3,084

_______________


(1)	Includes straight-line rent adjustments of approximately $1.8 million and $7.0 million for the three months ended March 31, 2018 and 2017, respectively.


(2)	Includes straight-line rent adjustments of approximately $0.7 million and $0.7 million for the three months ended March 31, 2018 and 2017, 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, 2018 and 2017, respectively.

Debt (Notes)	3 Months Ended
Debt (Notes)	Mar. 31, 2018
Debt [Abstract]
Debt Disclosure [Text Block]	5. Debt Credit Facility On April 24, 2017, Boston Properties Limited Partnership amended and restated its unsecured revolving credit agreement (as amended and restated, the "2017 Credit Facility"). Among other things, the 2017 Credit Facility (1) increased the total commitment of the revolving line of credit (the "Revolving Facility") from $1.0 billion to $1.5 billion, (2) extended the maturity date from July 26, 2018 to April 24, 2022, (3) reduced the per annum variable interest rates, and (4) added a $500.0 million delayed draw term loan facility (the "Delayed Draw Facility") that permits Boston Properties Limited Partnership to draw until the first anniversary of the closing date (See Note 12). Based on Boston Properties Limited Partnership’s current credit rating, (1) the applicable Eurocurrency margins for the Revolving Facility and Delayed Draw Facility are 82.5 basis points and 90 basis points, respectively, and (2) the facility fee on the Revolving Facility commitment is 0.125% per annum. The Delayed Draw Facility has a fee on unused commitments equal to 0.15% per annum. As of March 31, 2018, Boston Properties Limited Partnership had $115.0 million of borrowings and outstanding letters of credit totaling approximately $1.6 million outstanding under the 2017 Credit Facility, with the ability to borrow approximately $1.9 billion.

Commitments And Contingencies	3 Months Ended
Commitments And Contingencies	Mar. 31, 2018
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 $9.1 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, the 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 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, 2018, the maximum funding obligation under the guarantee was approximately $171.7 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, 2018, 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 a fee 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, 2018, no amounts related to the contingent aspect of any of the guarantees are recorded as liabilities 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 and 2016, the Company received distributions of approximately $7.7 million, $8.1 million and $1.4 million, respectively. On May 19, 2017, the Company received a fifth interim distribution totaling approximately $0.4 million, leaving a remaining claim of approximately $27.6 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, 2018. 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 2018, the program trigger is $160 million and the coinsurance is 18%, 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, 2018

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, 2018, the noncontrolling interests in Boston Properties Limited Partnership consisted of 16,804,390 OP Units, 1,022,287 LTIP Units (including 118,067 2012 OPP Units, 85,042 2013 MYLTIP Units, 25,074 2014 MYLTIP Units and 28,771 2015 MYLTIP Units), 473,360 2016 MYLTIP Units, 400,000 2017 MYLTIP Units and 342,659 2018 MYLTIP Units held by parties other than Boston Properties, Inc.

Noncontrolling Interest—Common Units

During the three months ended March 31, 2018, 24,265 OP Units were presented by the holders for redemption (including 21,265 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, 2018, Boston Properties Limited Partnership had outstanding 473,360 2016 MYLTIP Units, 400,000 2017 MYLTIP Units and 342,659 2018 MYLTIP Units. Prior to the applicable measurement date (February 9, 2019 for 2016 MYLTIP Units, February 6, 2020 for 2017 MYLTIP Units and February 5, 2021 for the 2018 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 4, 2018, the measurement period for the Company’s 2015 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 22.0% of target or an aggregate of approximately $3.6 million (after giving effect to voluntary employee separations). As a result, an aggregate of 337,847 2015 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 and 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) paid in 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 29, 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 and 2015 MYLTIP Units), assuming that all conditions had been met for the conversion thereof, had all of such units been redeemed at March 31, 2018 was approximately $2.2 billion based on the last reported price of a share of Common Stock on the New York Stock Exchange of $123.22 per share on March 29, 2018.

Boston Properties Limited Partnership

The following table reflects the activity of noncontrolling interests—redeemable partnership units of Boston Properties Limited Partnership for the three months ended March 31, 2018 and 2017 (in thousands):



Balance at December 31, 2017	$	2,292,263
Contributions	34,258
Net income	20,432
Distributions	(14,351		)
Conversion of redeemable partnership units	(832		)
Unearned compensation	(20,453		)
Cumulative effect of a change in accounting principle	563
Other comprehensive income	155
Adjustment to reflect redeemable partnership units at redemption value	(115,432		)
Balance at March 31, 2018	$	2,196,603

Balance at December 31, 2016	$	2,262,040
Contributions	29,918
Net income	11,432
Distributions	(13,653		)
Conversion of redeemable partnership units	(793		)
Unearned compensation	(18,633		)
Cumulative effect of a change in accounting principle	(1,763		)
Other comprehensive income	146
Adjustment to reflect redeemable partnership units at redemption value	126,416
Balance at March 31, 2017	$	2,395,110

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, 2018 and December 31, 2017, 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, 2018, the Company had contributed an aggregate of approximately $17.2 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. 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. The stabilization date is expected to occur in the second half of 2018.

The following table reflects the activity of the noncontrolling interests—property partnerships for the three months ended March 31, 2018 and 2017 (in thousands):



Balance at December 31, 2017	$	1,683,760
Capital contributions	15,267
Net income	17,234
Accumulated other comprehensive income	144
Distributions	(30,690		)
Balance at March 31, 2018	$	1,685,715

Balance at December 31, 2016	$	1,530,647
Capital contributions	8,145
Net income	4,424
Accumulated other comprehensive income	72
Distributions	(13,635		)
Balance at March 31, 2017	$	1,529,653

Stockholders' Equity / Partners' Capital

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Stockholders' Equity / Partners' Capital

8. Stockholders’ Equity / Partners’ Capital

As of March 31, 2018, Boston Properties, Inc. had 154,362,303 shares of Common Stock outstanding.

As of March 31, 2018, Boston Properties, Inc. owned 1,721,890 general partnership units and 152,640,413 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, 2018, Boston Properties, Inc. issued 24,265 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 2018:



Record Date	Payment Date	Dividend (Per Share)		Distribution (Per Unit)
March 29, 2018	April 30, 2018		$0.80		$0.80
December 29, 2017	January 30, 2018		$0.80		$0.80

Preferred Stock

As of March 31, 2018, 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 2018:

Earnings Per Share / Common Unit

3 Months Ended

Mar. 31, 2018

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, 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 and 2015 MYLTIP Units required, and the 2016-2018 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 the Boston Properties, Inc.’s Common Stock, and the related impact on earnings, are considered when calculating diluted EPS.



	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



	Three months ended March 31, 2017
	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	$	97,083	153,860	$	0.63
Effect of Dilutive Securities:
Stock Based Compensation	—		354	—
Diluted Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	97,083	154,214	$	0.63

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 and 2015 MYLTIP Units required, and the 2016-2018 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 17,482,000 and 17,721,000 redeemable common units for the three months ended March 31, 2018 and 2017, respectively.



	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



	Three months ended March 31, 2017
	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	$	110,662	171,581	$	0.64
Effect of Dilutive Securities:
Stock Based Compensation	—		354	—
Diluted Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	110,662	171,935	$	0.64

Stock Option and Incentive Plan	3 Months Ended
Stock Option and Incentive Plan	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	10. Stock Option and Incentive Plan On February 6, 2018, Boston Properties, Inc.’s Compensation Committee approved the 2018 MYLTIP awards under Boston Properties, Inc.’s 2012 Plan to certain officers and employees of Boston Properties, Inc. The 2018 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 (i) the Cohen & Steers Realty Majors Portfolio Index (50% weight) and (ii) the Nareit Office Index adjusted to include Vornado Realty Trust (50% weight). Earned awards will range from zero to a maximum of approximately $32.3 million depending on Boston Properties, Inc.’s TSR relative to the two indices, with a target of approximately $16.2 million and linear interpolation between zero and maximum. Earned awards measured on the basis of relative TSR performance are subject to an absolute TSR component in the form of relatively simple modifiers that (A) reduce the level of earned awards in the event Boston Properties, Inc.’s annualized TSR is less than 0% and (B) cause some awards to be earned in the event Boston Properties, Inc.’s annualized TSR is more than 12% even though on a relative basis alone Boston Properties, Inc.’s TSR would not result in any earned awards. Earned awards (if any) will vest 50% on February 5, 2021 and 50% on February 5, 2022, 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 5, 2021, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2018 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, the 2018 MYLTIP awards have an aggregate value of approximately $13.3 million, which amount will generally be amortized into earnings over the four-year plan period under the graded vesting method. On February 4, 2018, the measurement period for the Company’s 2015 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 22.0% of target or an aggregate of approximately $3.6 million (after giving effect to voluntary employee separations). As a result, an aggregate of 337,847 2015 MYLTIP Units that had been previously granted were automatically forfeited. During the three months ended March 31, 2018, Boston Properties, Inc. issued 18,226 shares of restricted common stock and Boston Properties Limited Partnership issued 195,546 LTIP Units and 342,659 2018 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 2018 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. Grants of restricted stock and LTIP Units to employees vest in four equal annual installments. Restricted 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 stock granted during the three months ended March 31, 2018 were valued at approximately $2.2 million ($118.98 per share weighted-average). The LTIP Units granted were valued at approximately $21.5 million (approximately $109.88 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 2.63% 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 and 2018 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 and 2018 MYLTIP Units was approximately $14.2 million and $10.3 million for the three months ended March 31, 2018 and 2017, respectively. At March 31, 2018, there was (1) an aggregate of approximately $36.5 million of unrecognized compensation expense related to unvested restricted stock, LTIP Units and 2015 MYLTIP Units and (2) an aggregate of approximately $26.0 million of unrecognized compensation expense related to unvested 2016 MYLTIP Units, 2017 MYLTIP Units and 2018 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 2.8 years.

Segment Information

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Segment Information

11. Segment Information

The following tables present reconciliations of Net Income Attributable to Boston Properties, Inc. Common Shareholders to Net Operating Income and Net Income Attributable to Boston Properties Limited Partnership Common Unitholders to Net Operating Income for the three months ended March 31, 2018 and 2017.

Boston Properties, Inc.



	Three months ended March 31,
	2018		2017
	(in thousands)
Net income attributable to Boston Properties, Inc. common shareholders	$	176,021	$	97,083
Add:
Preferred dividends	2,625		2,625
Noncontrolling interest—common units of Boston Properties Limited Partnership	20,432		11,432
Noncontrolling interests in property partnerships	17,234		4,424
Interest expense	90,220		95,534
Losses (gains) from investments in securities	126		(1,042		)
Depreciation and amortization expense	165,797		159,205
Transaction costs	21		34
Payroll and related costs from management services contracts	2,885		—
General and administrative expense	35,894		31,386
Less:
Gains on sales of real estate	96,397		133
Interest and other income	1,648		614
Income from unconsolidated joint ventures	461		3,084
Direct reimbursements of payroll and related costs from management services contracts	2,885		—
Development and management services revenue	8,405		6,472
Net Operating Income	$	401,459	$	390,378

Boston Properties Limited Partnership



	Three months ended March 31,
	2018		2017
	(in thousands)
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,907	$	110,662
Add:
Preferred distributions	2,625		2,625
Noncontrolling interests in property partnerships	17,234		4,424
Interest expense	90,220		95,534
Losses (gains) from investments in securities	126		(1,042		)
Depreciation and amortization expense	163,853		157,058
Transaction costs	21		34
Payroll and related costs from management services contracts	2,885		—
General and administrative expense	35,894		31,386
Less:
Gains on sales of real estate	98,907		133
Interest and other income	1,648		614
Income from unconsolidated joint ventures	461		3,084
Direct reimbursements of payroll and related costs from management services contracts	2,885		—
Development and management services revenue	8,405		6,472
Net Operating Income	$	401,459	$	390,378

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, losses (gains) from investments in securities, depreciation and amortization expense, transaction costs, payroll and related costs from management service contracts and corporate general and administrative expense less (2) gains on sales of real estate, interest and other income, 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.

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, net income attributable to noncontrolling interests, interest expense, losses (gains) from investments in securities, depreciation and amortization expense, transactions costs, payroll and related costs from management services contracts, corporate general and administrative expense, gains on sales of real estate, interest and other income, income from unconsolidated joint ventures, direct reimbursements of payroll and related costs from management services contracts and development and management services revenue are not included in NOI as internal reporting addresses these items on a corporate level.

The Company’s segments are based on the Company’s method of internal reporting which classifies its operations by both geographic area and property type. The Company’s segments by geographic area are Boston, New York, San Francisco and Washington, DC. Segments by property type include: Office, Residential and Hotel.

Information by geographic area and property type (dollars in thousands):

For the three months ended March 31, 2018:



	Boston			New York			San Francisco			Washington, DC			Total
Rental Revenue:
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		%

For the three months ended March 31, 2017:



	Boston			New York			San Francisco			Washington, DC			Total
Rental Revenue:
Office	$	185,436		$	241,570		$	84,641		$	102,733		$	614,380
Residential	1,139			—			—			2,817			3,956
Hotel	7,420			—			—			—			7,420
Total	193,995			241,570			84,641			105,550			625,756
% of Grand Totals	31.00		%	38.60		%	13.53		%	16.87		%	100.00		%
Rental Expenses:
Office	75,256			91,684			24,474			35,322			226,736
Residential	495			—			—			1,056			1,551
Hotel	7,091			—			—			—			7,091
Total	82,842			91,684			24,474			36,378			235,378
% of Grand Totals	35.19		%	38.95		%	10.40		%	15.46		%	100.00		%
Net operating income	$	111,153		$	149,886		$	60,167		$	69,172		$	390,378
% of Grand Totals	28.47		%	38.40		%	15.41		%	17.72		%	100.00		%

Subsequent Events (Notes)	3 Months Ended
Subsequent Events (Notes)	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	12. Subsequent Events On April 19, 2018, a joint venture in which the Company has a 50% interest obtained construction financing with a total commitment of $180.0 million collateralized by its Hub on Causeway - Residential development project. The construction financing bears interest at a variable rate equal to LIBOR plus 2.00% per annum and matures on April 19, 2022, with two, one-year extension options, subject to certain conditions. The joint venture has not yet drawn any funds under the loan. The Hub on Causeway - Residential is an approximately 320,000 square foot project comprised of 440 residential units located in Boston, Massachusetts. On April 23, 2018, the Company entered into an agreement to acquire Santa Monica Business Park in the Ocean Park neighborhood of Santa Monica, California for a net purchase price of approximately $616.0 million. Santa Monica Business Park is a 47-acre office park consisting of 21 buildings totaling approximately 1.2 million net rentable square feet. Approximately 70% of the rentable square footage is subject to a ground lease with 80 years remaining, including renewal periods. The ground lease provides the Company with the right to purchase the land underlying the properties subject to the ground lease in 2028 with subsequent purchase rights every 15 years. The closing is subject to customary closing conditions and termination rights for transactions of this type. There can be no assurance that the acquisition will be completed on the terms currently contemplated, or at all. On April 24, 2018, Boston Properties Limited Partnership exercised its option to draw $500.0 million on its Delayed Draw Facility. The Delayed Draw Facility totaling $500.0 million bears interest at a variable rate equal to LIBOR plus 0.90% per annum based on Boston Properties Limited Partnership's current credit rating and matures on April 24, 2022. On April 27, 2018, a joint venture in which the Company has a 60% interest refinanced the mortgage loan collateralized by its 540 Madison Avenue property located in New York City totaling $120.0 million. The mortgage loan bears interest at a variable rate equal to LIBOR plus 1.10% per annum and matures on June 5, 2023. The previous mortgage loan bore interest at a variable rate equal to LIBOR plus 1.50% per annum and was scheduled to mature on June 5, 2018. 540 Madison Avenue is an approximately 284,000 net rentable square foot Class A office property.

Basis Of Presentation And Summary Of Significant Accounting Policies Recent Accounting Pronouncements (Policies)	3 Months Ended
	Mar. 31, 2018
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncement [Policy Text Block]	New Accounting Pronouncements New Accounting Pronouncements Adopted Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). The objective of ASU 2014-09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers, which supersedes most of the existing revenue recognition guidance, including industry-specific guidance. The core principle is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying ASU 2014-09, companies will perform a five-step analysis of transactions to determine when and how revenue is recognized. The five-step analysis consists of the following: (i) identifying the contract with a customer, (ii) identifying the performance obligations in the contract, (iii) determining the transaction price, (iv) allocating the transaction price to the performance obligations in the contract and (v) recognizing revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB’s ASC. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date” (“ASU 2015-14”), which delayed the effective date of ASU 2014-09 by one year making it effective for the first interim period within annual reporting periods beginning after December 15, 2017. Early adoption was permitted as of the original effective date. In May 2016, the FASB issued ASU No. 2016-12, “Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients” (“ASU 2016-12”). ASU 2016-12 is intended to clarify and provide practical expedients for certain aspects of ASU 2014-09 and notes that lease contracts with customers are a scope exception. ASU 2014-09 was effective for the Company for reporting periods beginning after December 15, 2017. The Company adopted ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The adoption of ASU 2014-09 did not have a material impact on the Company’s consolidated financial statements. The Company applied the guidance only to contracts that were not completed as of January 1, 2018. The Company does not have material contract assets and liabilities within the scope of ASC 606. The adoption of ASU 2014-09 resulted in a change to the timing pattern of revenue recognized, but not the total revenue recognized over time for certain of the Company’s development services contracts. As a result, the modified retrospective approach resulted in the Company recognizing on January 1, 2018 the cumulative effect of adopting ASU 2014-09 aggregating approximately $4.9 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners’ Capital of Boston Properties Limited Partnership and approximately $0.6 million to Noncontrolling Interests - Common Units of Boston Properties, Inc. and Noncontrolling Interests - Redeemable Partnership Units of Boston Properties Limited Partnership on the corresponding Consolidated Balance Sheets. The Company disaggregates its revenue by source within its Consolidated Statements of Operations. As an owner and operator of real estate, the Company derives the majority of its revenue from leasing space to tenants at its properties. As a result, the majority of the Company’s revenue is accounted for pursuant to ASC 840 “Leases” (“ASC 840”) and is reflected within Base Rent in the Consolidated Statements of Operations. In addition, the Company earns revenue from recoveries from tenants, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs. Revenue from recoveries from tenants is recognized under the guidance within ASC 840 until the adoption of ASC 842 "Leases" in 2019 at which time it may fall within the guidance under ASC 606 pending a final determination from the FASB. The Company also earns revenue from the following sources; parking and other revenue, hotel revenue and development and management services revenue. Parking and other revenue is derived primarily from monthly and transient daily parking. In addition, the Company has certain lease arrangements for parking accounted for under the guidance in ASC 840. The monthly and transient daily parking revenue falls within the scope of ASC 606 and is accounted for at the point in time when control of the goods or services transfers to the customer and the Company’s performance obligation is satisfied, consistent with the Company’s previous accounting. Hotel revenue is derived from room rentals and other sources such as charges to guests for telephone service, movie and vending commissions, meeting and banquet room revenue and laundry services. Hotel revenue also falls within the scope of ASC 606 and is accounted for at the point in time when control of the goods or services transfers to the customer and the Company’s performance obligation is satisfied, consistent with the Company’s previous accounting. Development and management services revenue is earned from unconsolidated joint venture entities and third party property owners. The Company determined that the performance obligations associated with its development services contracts are satisfied over time and that the Company would recognize its development services revenue under the output method evenly over time from the development commencement date through the substantial completion date of the development management services project due to the stand-ready nature of the contracts. Significant judgments impacting the amount and timing of revenue recognized from the Company's development services contracts include estimates of total development project costs from which the fees are typically derived and estimates of the period of time until substantial completion of the development project, the period of time over which the development services are required to be performed. As a result, the pattern of revenue recognized over time under ASC 606 differs from the Company’s previous accounting. The Company recognizes development fees earned from unconsolidated joint venture projects equal to its cost plus profit to the extent of the third party partners’ ownership interest. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis, because such fees are contingent upon the collection of rents. The revenue recognized under property management services contracts is recognized consistent with the Company's previous accounting. ASU 2014-09 also updates the principal versus agent considerations and as a result the Company determined that amounts reimbursed for payroll and related costs received from unconsolidated joint venture entities and third party property owners in connection with management services contracts should be reflected on a gross basis instead of on a net basis as the Company has determined that it is the principal under these arrangements. During the three months ended March 31, 2018, the Company recognized approximately $2.9 million of expenses consisting of payroll and related costs from management services contracts and recognized corresponding revenue of approximately $2.9 million reflecting the direct reimbursements of such costs from the unconsolidated joint venture entities and third party property owners. Statement of Cash Flows In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2016-15”). ASU 2016-15 is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. The areas addressed in the new guidance related to debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned and bank-owned life insurance policies, distributions received from equity method investments, beneficial interest in securitization transactions, and separately identifiable cash flows and application of the predominance principle. ASU 2016-15 was effective for the Company for reporting periods beginning after December 15, 2017, with early adoption permitted (provided that all of the amendments are adopted in the same period), and was required to be applied retrospectively to all periods presented. The Company adopted ASU 2016-15 effective January 1, 2018. The adoption of ASU 2016-15 did not have a material impact on the Company’s consolidated financial statements. The adoption of ASU 2016-15 will result in the retrospective classification of debt prepayment costs as a component of financing activities instead of as a component of operating activities in the Company's Consolidated Statements of Cash Flows. In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2016-18”). ASU 2016-18 requires companies to include restricted cash and restricted cash equivalents with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 also requires a disclosure of a reconciliation between the statement of financial position and the statement of cash flows when the statement of financial position includes more than one line item for cash, cash equivalents, restricted cash and restricted cash equivalents. Entities with material restricted cash and restricted cash equivalents balances are required to disclose the nature of the restrictions. ASU 2016-18 was effective for reporting periods beginning after December 15, 2017, with early adoption permitted, and is required to be applied retrospectively to all periods presented. The Company adopted ASU 2016-18 effective January 1, 2018. The adoption of ASU 2016-18 did not have a material impact on the Company’s consolidated financial statements. The retrospective adoption of ASU 2016-18 resulted in a decrease to net cash provided by operating activities totaling approximately $6.7 million, an increase to net cash used in investing activities totaling approximately $5.2 million and a corresponding increase to the net decrease in cash and cash equivalents and cash held in escrows totaling approximately $11.9 million from amounts previously reported for the three months ended March 31, 2017. Cash held in escrows include amounts established pursuant to various agreements for security deposits, property taxes, insurance and other costs. Cash held in escrows also include cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties. Sales of Real Estate In February 2017, the FASB issued ASU No. 2017-05, “Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets” (“ASU 2017-05”). ASU 2017-05 updates the definition of an “in substance nonfinancial asset” and clarifies the derecognition guidance for nonfinancial assets to conform with the new revenue recognition standard. The effective date and transition methods of ASU 2017-05 are aligned with ASU 2014-09 described above and were effective for the first interim period within annual reporting periods beginning after December 15, 2017. The Company adopted ASU 2017-05 effective January 1, 2018 using the modified retrospective approach. The adoption of ASU 2017-05 did not have a material impact on the Company's consolidated financial statements. See also Note 3. Stock Compensation In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting” (“ASU 2017-09”). ASU 2017-09 is intended to provide clarity and reduce (1) diversity in practice, (2) cost and (3) complexity when applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award. ASU 2017-09 was effective for public entities for fiscal years and interim periods beginning after December 15, 2017. The Company adopted ASU 2017-09 effective January 1, 2018. The adoption of ASU 2017-09 did not have a material impact on the Company's consolidated financial statements. Derivatives and Hedging In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities” (“ASU 2017-12”). ASU 2017-12 was issued with the objective of improving the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. ASU 2017-12 also makes certain targeted improvements to simplify the application of the hedge accounting guidance. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company early adopted ASU 2017-12 effective January 1, 2018. The adoption of ASU 2017-12 did not have a material impact on the Company's consolidated financial statements. As of March 31, 2018, the Company does not have any outstanding hedges, but continues to reclassify into earnings as an increase primarily to interest expense approximately $1.7 million per quarter relating to previously settled interest rate contracts. New Accounting Pronouncements Issued but not yet Adopted Leases In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“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 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 existing guidance for operating leases today. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. ASU 2016-02 supersedes previous leasing standards. ASU 2016-02 is effective for the Company for reporting periods beginning after December 15, 2018, with early adoption permitted. The Company will adopt ASU 2016-02 effective January 1, 2019 using the modified retrospective approach. The Company is in the process of evaluating whether it will elect to apply the practical expedients. The Company is in the process of adopting ASU 2016-02, with its project team compiling an inventory of its leases that will be impacted by the adoption of ASU 2016-02. The Company continues to assess the impact of adopting ASU 2016-02. However, the Company will account for operating leases under which it is the lessor on its balance sheet in a manner similar to its current accounting with the underlying leased asset recognized as real estate. In January 2018, the FASB issued a proposed ASU that would allow lessors to elect, as a practical expedient, not to allocate the total consideration to lease and non-lease components based on their relative standalone selling prices. If issued, this practical expedient will allow lessors to elect a combined single lease component presentation if (i) the timing and pattern of the revenue recognition of the combined single lease component is the same, and (ii) the related lease component and, the combined single lease component would be classified as an operating lease. If the practical expedient in the proposed ASU is issued, it could allow for tenant recoveries that qualify as non-lease components to be presented under a single lease component presentation. However, without the proposed practical expedient, tenant recoveries would be separated into lease and non-lease components. For leases in which the Company is the lessee, primarily consisting of ground leases, the Company will recognize a right-of-use asset and a lease liability equal to the present value of the minimum lease payments with rental payments being applied to the lease liability and to interest expense and the right-of-use asset being amortized to expense over the term of the lease. In addition, under ASU 2016-02, lessors will only capitalize incremental direct leasing costs. As a result, the Company will no longer be able to capitalize legal costs and internal leasing wages and instead will be required to expense these and other non-incremental costs as incurred. 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 current 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.
Revenue Recognition, Policy [Policy Text Block]	Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). The objective of ASU 2014-09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers, which supersedes most of the existing revenue recognition guidance, including industry-specific guidance. The core principle is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying ASU 2014-09, companies will perform a five-step analysis of transactions to determine when and how revenue is recognized. The five-step analysis consists of the following: (i) identifying the contract with a customer, (ii) identifying the performance obligations in the contract, (iii) determining the transaction price, (iv) allocating the transaction price to the performance obligations in the contract and (v) recognizing revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB’s ASC. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date” (“ASU 2015-14”), which delayed the effective date of ASU 2014-09 by one year making it effective for the first interim period within annual reporting periods beginning after December 15, 2017. Early adoption was permitted as of the original effective date. In May 2016, the FASB issued ASU No. 2016-12, “Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients” (“ASU 2016-12”). ASU 2016-12 is intended to clarify and provide practical expedients for certain aspects of ASU 2014-09 and notes that lease contracts with customers are a scope exception. ASU 2014-09 was effective for the Company for reporting periods beginning after December 15, 2017. The Company adopted ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The adoption of ASU 2014-09 did not have a material impact on the Company’s consolidated financial statements. The Company applied the guidance only to contracts that were not completed as of January 1, 2018. The Company does not have material contract assets and liabilities within the scope of ASC 606. The adoption of ASU 2014-09 resulted in a change to the timing pattern of revenue recognized, but not the total revenue recognized over time for certain of the Company’s development services contracts. As a result, the modified retrospective approach resulted in the Company recognizing on January 1, 2018 the cumulative effect of adopting ASU 2014-09 aggregating approximately $4.9 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners’ Capital of Boston Properties Limited Partnership and approximately $0.6 million to Noncontrolling Interests - Common Units of Boston Properties, Inc. and Noncontrolling Interests - Redeemable Partnership Units of Boston Properties Limited Partnership on the corresponding Consolidated Balance Sheets. The Company disaggregates its revenue by source within its Consolidated Statements of Operations. As an owner and operator of real estate, the Company derives the majority of its revenue from leasing space to tenants at its properties. As a result, the majority of the Company’s revenue is accounted for pursuant to ASC 840 “Leases” (“ASC 840”) and is reflected within Base Rent in the Consolidated Statements of Operations. In addition, the Company earns revenue from recoveries from tenants, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs. Revenue from recoveries from tenants is recognized under the guidance within ASC 840 until the adoption of ASC 842 "Leases" in 2019 at which time it may fall within the guidance under ASC 606 pending a final determination from the FASB. The Company also earns revenue from the following sources; parking and other revenue, hotel revenue and development and management services revenue. Parking and other revenue is derived primarily from monthly and transient daily parking. In addition, the Company has certain lease arrangements for parking accounted for under the guidance in ASC 840. The monthly and transient daily parking revenue falls within the scope of ASC 606 and is accounted for at the point in time when control of the goods or services transfers to the customer and the Company’s performance obligation is satisfied, consistent with the Company’s previous accounting. Hotel revenue is derived from room rentals and other sources such as charges to guests for telephone service, movie and vending commissions, meeting and banquet room revenue and laundry services. Hotel revenue also falls within the scope of ASC 606 and is accounted for at the point in time when control of the goods or services transfers to the customer and the Company’s performance obligation is satisfied, consistent with the Company’s previous accounting. Development and management services revenue is earned from unconsolidated joint venture entities and third party property owners. The Company determined that the performance obligations associated with its development services contracts are satisfied over time and that the Company would recognize its development services revenue under the output method evenly over time from the development commencement date through the substantial completion date of the development management services project due to the stand-ready nature of the contracts. Significant judgments impacting the amount and timing of revenue recognized from the Company's development services contracts include estimates of total development project costs from which the fees are typically derived and estimates of the period of time until substantial completion of the development project, the period of time over which the development services are required to be performed. As a result, the pattern of revenue recognized over time under ASC 606 differs from the Company’s previous accounting. The Company recognizes development fees earned from unconsolidated joint venture projects equal to its cost plus profit to the extent of the third party partners’ ownership interest. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis, because such fees are contingent upon the collection of rents. The revenue recognized under property management services contracts is recognized consistent with the Company's previous accounting. ASU 2014-09 also updates the principal versus agent considerations and as a result the Company determined that amounts reimbursed for payroll and related costs received from unconsolidated joint venture entities and third party property owners in connection with management services contracts should be reflected on a gross basis instead of on a net basis as the Company has determined that it is the principal under these arrangements. During the three months ended March 31, 2018, the Company recognized approximately $2.9 million of expenses consisting of payroll and related costs from management services contracts and recognized corresponding revenue of approximately $2.9 million reflecting the direct reimbursements of such costs from the unconsolidated joint venture entities and third party property owners.
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2016-18”). ASU 2016-18 requires companies to include restricted cash and restricted cash equivalents with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 also requires a disclosure of a reconciliation between the statement of financial position and the statement of cash flows when the statement of financial position includes more than one line item for cash, cash equivalents, restricted cash and restricted cash equivalents. Entities with material restricted cash and restricted cash equivalents balances are required to disclose the nature of the restrictions. ASU 2016-18 was effective for reporting periods beginning after December 15, 2017, with early adoption permitted, and is required to be applied retrospectively to all periods presented. The Company adopted ASU 2016-18 effective January 1, 2018. The adoption of ASU 2016-18 did not have a material impact on the Company’s consolidated financial statements. The retrospective adoption of ASU 2016-18 resulted in a decrease to net cash provided by operating activities totaling approximately $6.7 million, an increase to net cash used in investing activities totaling approximately $5.2 million and a corresponding increase to the net decrease in cash and cash equivalents and cash held in escrows totaling approximately $11.9 million from amounts previously reported for the three months ended March 31, 2017. Cash held in escrows include amounts established pursuant to various agreements for security deposits, property taxes, insurance and other costs. Cash held in escrows also include cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties.

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

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value

The following table presents the aggregate carrying value of the Company’s mortgage notes payable, net, unsecured line of credit and unsecured senior notes, net and the Company’s corresponding estimate of fair value as of March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018				December 31, 2017
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Mortgage notes payable, net	$	2,974,930	$	2,957,054	$	2,979,281	$	3,042,920
Unsecured senior notes, net	7,249,383		7,262,443		7,247,330		7,461,615
Unsecured line of credit	115,000		115,000		45,000		45,000
Total	$	10,339,313	$	10,334,497	$	10,271,611	$	10,549,535

Real Estate Real Estate (Tables)

3 Months Ended

Mar. 31, 2018

Schedule of Real Estate Properties [Table Text Block]

Boston Properties, Inc.

Real estate consisted of the following at March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Land	$	5,105,376		$	5,080,679
Land held for future development (1)	204,506			204,925
Buildings and improvements	12,435,573			12,284,164
Tenant improvements	2,266,796			2,219,608
Furniture, fixtures and equipment	41,507			37,928
Construction in progress	1,262,886			1,269,338
Total	21,316,644			21,096,642
Less: Accumulated depreciation	(4,674,838		)	(4,589,634		)
	$	16,641,806		$	16,507,008

_______________


(1)	Includes pre-development costs.

Schedule of Real Estate Properties [Table Text Block]

Boston Properties Limited Partnership

Real estate consisted of the following at March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Land	$	5,001,810		$	4,976,303
Land held for future development (1)	204,506			204,925
Buildings and improvements	12,130,901			11,977,062
Tenant improvements	2,266,796			2,219,608
Furniture, fixtures and equipment	41,507			37,928
Construction in progress	1,262,886			1,269,338
Total	20,908,406			20,685,164
Less: Accumulated depreciation	(4,580,949		)	(4,496,959		)
	$	16,327,457		$	16,188,205

_______________


(1)	Includes pre-development costs.

Investments in Unconsolidated Joint Ventures (Tables)

3 Months Ended

Mar. 31, 2018

Investments In Unconsolidated Joint Ventures [Abstract]

Investments In Unconsolidated Joint Ventures

The investments in unconsolidated joint ventures consist of the following at March 31, 2018 and December 31, 2017:



		Nominal % Ownership			Carrying Value of Investment (1)
Entity	Properties	Nominal % Ownership			March 31, 2018			December 31, 2017
					(in thousands)
Square 407 Limited Partnership	Market Square North	50.0	%		$	(7,811	)	$	(8,258	)
The Metropolitan Square Associates LLC	Metropolitan Square	20.0	%		3,372			3,339
BP/CRF 901 New York Avenue LLC	901 New York Avenue	25.0	%	(2)	(13,262		)	(13,811		)
WP Project Developer LLC	Wisconsin Place Land and Infrastructure	33.3	%	(3)	39,340			39,710
Annapolis Junction NFM, LLC	Annapolis Junction	50.0	%	(4)	17,974			18,381
540 Madison Venture LLC	540 Madison Avenue	60.0	%		66,259			66,179
500 North Capitol Venture LLC	500 North Capitol Street, NW	30.0	%		(4,129		)	(3,876		)
501 K Street LLC	1001 6th Street	50.0	%	(5)	42,636			42,657
Podium Developer LLC	The Hub on Causeway	50.0	%		67,883			67,120
Residential Tower Developer LLC	The Hub on Causeway - Residential	50.0	%	(6)	29,752			28,212
Hotel Tower Developer LLC	The Hub on Causeway - Hotel Air Rights	50.0	%		1,751			1,690
1265 Main Office JV LLC	1265 Main Street	50.0	%		4,539			4,641
BNY Tower Holdings LLC	Dock 72 at the Brooklyn Navy Yard	50.0	%		71,582			72,104
CA-Colorado Center Limited Partnership	Colorado Center	50.0	%		254,226			254,440
7750 Wisconsin Avenue LLC	7750 Wisconsin Avenue	50.0	%	(6)	67,404			21,452
					$	641,516		$	593,980

_______________


(1)	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, 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 four 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, 2018		December 31, 2017
	(in thousands)
ASSETS
Real estate and development in process, net	$	1,844,695	$	1,768,996
Other assets	376,127		367,743
Total assets	$	2,220,822	$	2,136,739
LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
Mortgage and notes payable, net	$	1,471,762	$	1,437,440
Other liabilities	95,597		99,215
Members’/Partners’ equity	653,463		600,084
Total liabilities and members’/partners’ equity	$	2,220,822	$	2,136,739
Company’s share of equity	$	335,580	$	286,495
Basis differentials (1)	305,936		307,485
Carrying value of the Company’s investments in unconsolidated joint ventures (2)	$	641,516	$	593,980

_______________

(1)


(2)	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, 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,
	2018			2017
	(in thousands)
Total revenue (1)	$	56,486		$	54,761
Expenses
Operating	22,849			22,079
Depreciation and amortization	14,725			14,309
Total expenses	37,574			36,388
Operating income	18,912			18,373
Other expense
Interest expense	14,424			9,300
Net income	$	4,488		$	9,073

Company’s share of net income	$	1,826		$	4,323
Basis differential (2)	(1,365		)	(1,239		)
Income from unconsolidated joint ventures	$	461		$	3,084

_______________


(1)	Includes straight-line rent adjustments of approximately $1.8 million and $7.0 million for the three months ended March 31, 2018 and 2017, respectively.


(2)	Includes straight-line rent adjustments of approximately $0.7 million and $0.7 million for the three months ended March 31, 2018 and 2017, 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, 2018 and 2017, respectively.

Noncontrolling Interests (Tables)

3 Months Ended

Mar. 31, 2018

Noncontrolling Interest [Line Items]

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

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 2018:



Record Date	Payment Date	Dividend (Per Share)		Distribution (Per Unit)
March 29, 2018	April 30, 2018		$0.80		$0.80
December 29, 2017	January 30, 2018		$0.80		$0.80

Schedule Of Noncontrolling Interest Common Units [Table Text Block]



Balance at December 31, 2017	$	2,292,263
Contributions	34,258
Net income	20,432
Distributions	(14,351		)
Conversion of redeemable partnership units	(832		)
Unearned compensation	(20,453		)
Cumulative effect of a change in accounting principle	563
Other comprehensive income	155
Adjustment to reflect redeemable partnership units at redemption value	(115,432		)
Balance at March 31, 2018	$	2,196,603

Balance at December 31, 2016	$	2,262,040
Contributions	29,918
Net income	11,432
Distributions	(13,653		)
Conversion of redeemable partnership units	(793		)
Unearned compensation	(18,633		)
Cumulative effect of a change in accounting principle	(1,763		)
Other comprehensive income	146
Adjustment to reflect redeemable partnership units at redemption value	126,416
Balance at March 31, 2017	$	2,395,110

Schedule Of Noncontrolling Interest Property Partnerships [Table Text Block]

The following table reflects the activity of the noncontrolling interests—property partnerships for the three months ended March 31, 2018 and 2017 (in thousands):



Balance at December 31, 2017	$	1,683,760
Capital contributions	15,267
Net income	17,234
Accumulated other comprehensive income	144
Distributions	(30,690		)
Balance at March 31, 2018	$	1,685,715

Balance at December 31, 2016	$	1,530,647
Capital contributions	8,145
Net income	4,424
Accumulated other comprehensive income	72
Distributions	(13,635		)
Balance at March 31, 2017	$	1,529,653

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, 2018	April 30, 2018		$0.80		$0.080
December 29, 2017	January 30, 2018		$0.80		$0.080

Stockholders' Equity / Partners' Capital Tables (Tables)

3 Months Ended

Mar. 31, 2018

Class of Stock [Line Items]

Dividends Declared [Table Text Block]

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 2018:



Record Date	Payment Date	Dividend (Per Share)		Distribution (Per Unit)
March 29, 2018	April 30, 2018		$0.80		$0.80
December 29, 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 2018:

Earnings Per Share / Common Unit (Tables)

3 Months Ended

Mar. 31, 2018

Computation Of Basic And Diluted Earnings Per Share



	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



	Three months ended March 31, 2017
	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	$	97,083	153,860	$	0.63
Effect of Dilutive Securities:
Stock Based Compensation	—		354	—
Diluted Earnings:
Net income attributable to Boston Properties, Inc. common shareholders	$	97,083	154,214	$	0.63

Computation Of Basic And Diluted Earnings Per Share



	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



	Three months ended March 31, 2017
	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	$	110,662	171,581	$	0.64
Effect of Dilutive Securities:
Stock Based Compensation	—		354	—
Diluted Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$	110,662	171,935	$	0.64

Segment Information (Tables)

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Schedule Of Reconciliation Of Net Operating Income To Net Income

Boston Properties, Inc.



	Three months ended March 31,
	2018		2017
	(in thousands)
Net income attributable to Boston Properties, Inc. common shareholders	$	176,021	$	97,083
Add:
Preferred dividends	2,625		2,625
Noncontrolling interest—common units of Boston Properties Limited Partnership	20,432		11,432
Noncontrolling interests in property partnerships	17,234		4,424
Interest expense	90,220		95,534
Losses (gains) from investments in securities	126		(1,042		)
Depreciation and amortization expense	165,797		159,205
Transaction costs	21		34
Payroll and related costs from management services contracts	2,885		—
General and administrative expense	35,894		31,386
Less:
Gains on sales of real estate	96,397		133
Interest and other income	1,648		614
Income from unconsolidated joint ventures	461		3,084
Direct reimbursements of payroll and related costs from management services contracts	2,885		—
Development and management services revenue	8,405		6,472
Net Operating Income	$	401,459	$	390,378

Boston Properties Limited Partnership



	Three months ended March 31,
	2018		2017
	(in thousands)
Net income attributable to Boston Properties Limited Partnership common unitholders	$	200,907	$	110,662
Add:
Preferred distributions	2,625		2,625
Noncontrolling interests in property partnerships	17,234		4,424
Interest expense	90,220		95,534
Losses (gains) from investments in securities	126		(1,042		)
Depreciation and amortization expense	163,853		157,058
Transaction costs	21		34
Payroll and related costs from management services contracts	2,885		—
General and administrative expense	35,894		31,386
Less:
Gains on sales of real estate	98,907		133
Interest and other income	1,648		614
Income from unconsolidated joint ventures	461		3,084
Direct reimbursements of payroll and related costs from management services contracts	2,885		—
Development and management services revenue	8,405		6,472
Net Operating Income	$	401,459	$	390,378

Schedule Of Segment Information By Geographic Area And Property Type

Information by geographic area and property type (dollars in thousands):

For the three months ended March 31, 2018:



	Boston			New York			San Francisco			Washington, DC			Total
Rental Revenue:
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		%

For the three months ended March 31, 2017:



	Boston			New York			San Francisco			Washington, DC			Total
Rental Revenue:
Office	$	185,436		$	241,570		$	84,641		$	102,733		$	614,380
Residential	1,139			—			—			2,817			3,956
Hotel	7,420			—			—			—			7,420
Total	193,995			241,570			84,641			105,550			625,756
% of Grand Totals	31.00		%	38.60		%	13.53		%	16.87		%	100.00		%
Rental Expenses:
Office	75,256			91,684			24,474			35,322			226,736
Residential	495			—			—			1,056			1,551
Hotel	7,091			—			—			—			7,091
Total	82,842			91,684			24,474			36,378			235,378
% of Grand Totals	35.19		%	38.95		%	10.40		%	15.46		%	100.00		%
Net operating income	$	111,153		$	149,886		$	60,167		$	69,172		$	390,378
% of Grand Totals	28.47		%	38.40		%	15.41		%	17.72		%	100.00		%

Organization (Details) ft² in Millions	3 Months Ended	12 Months Ended
Organization (Details) ft² in Millions	Mar. 31, 2018 ft² series Real_Estate_Properties yr shares	Dec. 31, 2017 shares
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.60%	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	179
Net Rentable Area (in sf) \| ft²	50.3
Total Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	13
Net Rentable Area (in sf) \| ft²	6.5
Total Office Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	167
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	4
Retail Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	5
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 (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Entity Information [Line Items]
Payroll and related costs from management services contracts	$ 2,885	$ 0
Direct reimbursements of payroll and related costs from management services contracts	2,885	0
Net Cash Provided by (Used in) Operating Activities	(225,778)	(239,852)
Cumulative effect of a change in accounting principle	(5,496)	2,035
Net Cash Provided by (Used in) Investing Activities	183,788	267,823
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	50,240	65,905
Interest Expense	90,220	95,534
Boston Properties Limited Partnership
Entity Information [Line Items]
Payroll and related costs from management services contracts	2,885	0
Direct reimbursements of payroll and related costs from management services contracts	2,885	0
Net Cash Provided by (Used in) Operating Activities	(225,778)	(239,852)
Cumulative effect of a change in accounting principle	(4,933)	272
Net Cash Provided by (Used in) Investing Activities	183,788	267,823
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	50,240	65,905
Interest Expense	90,220	95,534
Dividends In Excess Of Earnings [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	(4,933)	272
Noncontrolling Interests [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	(563)	1,763
Noncontrolling Interests [Member] \| Boston Properties Limited Partnership
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	(563)	1,763
Accounting Standards Update 2014-09 [Member]
Entity Information [Line Items]
Payroll and related costs from management services contracts	2,900
Direct reimbursements of payroll and related costs from management services contracts	2,900
Cumulative effect of a change in accounting principle	(4,900)
Accounting Standards Update 2014-09 [Member] \| Noncontrolling Interests [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	(600)
Accounting Standards Update 2016-18 [Member]
Entity Information [Line Items]
Net Cash Provided by (Used in) Operating Activities		6,700
Net Cash Provided by (Used in) Investing Activities		5,200
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		$ 11,900
Accounting Standards Update 2017-12 [Member]
Entity Information [Line Items]
Interest Expense	$ 1,700

Basis Of Presentation And Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	$ 2,974,930	$ 2,979,281
Unsecured senior notes, net	7,249,383	7,247,330
Unsecured line of credit	115,000	45,000
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	2,974,930	2,979,281
Unsecured senior notes, net	7,249,383	7,247,330
Unsecured line of credit	115,000	45,000
Total	10,339,313	10,271,611
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	2,957,054	3,042,920
Unsecured senior notes, net	7,262,443	7,461,615
Unsecured line of credit	115,000	45,000
Total	$ 10,334,497	$ 10,549,535

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

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

Mar. 31, 2018

Dec. 31, 2017

SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]

Land

$ 5,105,376

$ 5,080,679

Land held for future development

^[1]

204,506

204,925

Buildings and improvements

12,435,573

12,284,164

Tenant improvements

2,266,796

2,219,608

Furniture, fixtures and equipment

41,507

37,928

Construction in Progress

1,262,886

1,269,338

Total

21,316,644

21,096,642

Accumulated depreciation

(4,674,838)

(4,589,634)

Total real estate

16,641,806

16,507,008

SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]

Land

5,001,810

4,976,303

Land held for future development

^[1]

204,506

204,925

Buildings and improvements

12,130,901

11,977,062

Tenant improvements

2,266,796

2,219,608

Furniture, fixtures and equipment

41,507

37,928

Construction in Progress

1,262,886

1,269,338

Total

20,908,406

20,685,164

Accumulated depreciation

(4,580,949)

(4,496,959)

Total real estate

$ 16,327,457

$ 16,188,205

[1]	Includes pre-development costs.

Real Estate Narrative (Details) $ in Thousands				3 Months Ended
Real Estate Narrative (Details) $ in Thousands	Feb. 23, 2018 ft²	Jan. 09, 2018 USD ($) ft²	Jan. 08, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Jan. 31, 2018 ft² apartments	Jan. 24, 2018 ft²
Real Estate [Line Items]
Proceeds from sales of real estate				$ 116,120	$ 133
Gains on sales of real estate				96,397	133
17Fifty Presidents Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²							276,000
Signature at Reston [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²						515,000
Number of apartment units \| apartments						508
Reston Gateway [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²	1,100,000.0
Square Footage Of Signed Lease \| ft²	850,000
Boston Properties Limited Partnership
Real Estate [Line Items]
Proceeds from sales of real estate				116,120	133
Gains on sales of real estate				$ 98,907	133
500 E Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) \| ft²		262,000
Net Contractual Sales Price		$ 118,600
Net income (loss)			$ 100		$ 1,600
Proceeds from sales of real estate		116,100
Gains on sales of real estate		96,400
500 E Street [Member] \| Boston Properties Limited Partnership
Real Estate [Line Items]
Gains on sales of real estate		$ 98,900

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

3 Months Ended

Mar. 31, 2018

USD ($)

ft²

Land_Parcels

Buildings

payments

Dec. 31, 2017

USD ($)

Schedule of Equity Method Investments [Line Items]

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

$ (470,140)

$ (443,980)

$ 666,718

619,925

Square 407 Limited Partnership [Member]

Schedule of Equity Method Investments [Line Items]

Market Square North

50.00%

The Metropolitan Square Associates LLC [Member]

^[1]

$ (7,811)

(8,258)

Schedule of Equity Method Investments [Line Items]

Metropolitan Square

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

20.00%

^[1]

$ 3,372

3,339

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]

$ (13,262)

(13,811)

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]

$ 39,340

39,710

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]

$ 17,974

18,381

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]

$ 66,259

66,179

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]

$ (4,129)

(3,876)

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]

$ 42,636

42,657

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

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

50.00%

^[1]

$ 67,883

67,120

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

^[6]

50.00%

^[1]

$ 29,752

28,212

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]

$ 1,751

1,690

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]

$ 4,539

4,641

BNY Tower Holdings LLC [Member]

Schedule of Equity Method Investments [Line Items]

Dock 72 at the Brooklyn Navy Yard

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

50.00%

^[1]

$ 71,582

72,104

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]

$ 254,226

254,440

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]

$ 67,404

21,452

Schedule of Equity Method Investments [Line Items]

25,200

25,900

Schedule of Equity Method Investments [Line Items]

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

(95,597)

(99,215)

^[1],[7]

$ 641,516

$ 593,980

[1]	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, 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 four 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]	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

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

Mar. 31, 2018

Dec. 31, 2017

ASSETS

Real estate and development in process, net

$ 16,641,806

$ 16,507,008

Liabilities and Members'/Partners' Equity [Abstract]

Mortgage notes payable, net

2,974,930

2,979,281

Other Liabilities

470,140

443,980

Total liabilities and equity / capital

19,583,939

19,372,233

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

666,718

619,925

Real estate and development in process, net

ASSETS

1,844,695

1,768,996

Other assets

376,127

367,743

Total assets

2,220,822

2,136,739

Liabilities and Members'/Partners' Equity [Abstract]

Mortgage notes payable, net

1,471,762

1,437,440

Other Liabilities

95,597

99,215

Members'/Partners' equity

653,463

600,084

Total liabilities and equity / capital

2,220,822

2,136,739

Company's share of equity

335,580

286,495

Basis differentials

^[1]

305,936

307,485

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

^[2],[3]

641,516

593,980

Liabilities and Members'/Partners' Equity [Abstract]

Other Liabilities

(25,200)

(25,900)

Basis differentials

$ 321,100

$ 322,500

[1]	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, 2018 and December 31, 2017, there was an aggregate basis differential of approximately $321.1 million and $322.5 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.
[2]	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[3]	Investments with deficit balances aggregating approximately $25.2 million and $25.9 million at March 31, 2018 and December 31, 2017, 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, 2018

Mar. 31, 2017

Schedule of Equity Method Investments [Line Items]

Total revenue

$ 661,151

$ 632,228

Expenses

Depreciation and amortization

165,797

159,205

Total expenses

452,999

426,003

Operating income

208,152

206,225

Other expense

Interest expense

90,220

95,534

Income from unconsolidated joint ventures

216,312

115,564

461

3,084

Schedule of Equity Method Investments [Line Items]

Total revenue

^[1]

56,486

54,761

Expenses

Operating

22,849

22,079

Depreciation and amortization

14,725

14,309

Total expenses

37,574

36,388

Operating income

18,912

18,373

Other expense

Interest expense

14,424

9,300