View Filing Data

Unsecured exchangeable senior notes

$ 2,813,338

$ 2,643,301

Unsecured senior notes

2,872,058

2,172,389

1,759,490

1,904,081

Net of the adjustment for the equity component allocation

104,419

$ 140,400

Carrying Amount [Member]

Unsecured exchangeable senior notes

2,813,338

Unsecured senior notes

2,872,058

^[1]

1,759,490

Total

7,444,886

Estimate Fair Value [Member]

Unsecured exchangeable senior notes

2,912,476

Unsecured senior notes

3,316,303

1,973,879

Total

$ 8,202,658

[1]	Includes the unamortized net impact of the adjustment for the equity component allocation totaling approximately $104.4 million (See Note 7).

Real Estate Activity During the Nine Months Ended September 30, 2010 (Details) $ in Thousands	3 Months Ended		9 Months Ended		33 Months Ended
	Sep. 30, 2010 USD ($)	Sep. 30, 2009 USD ($)	Sep. 30, 2010 USD ($)	Sep. 30, 2009 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)
Statement [Line Items]
Gain on sale recognized		$ 2,394	$ 2,734	$ 9,682
Acquisition closing costs	1,893		1,893
Mortgage note payable assumed in connection with the acquisition of real estate			202,604
Mortgage loan	$ 2,813,338		$ 2,813,338			$ 2,643,301
250 West 55th Street in New York City [Member]
Statement [Line Items]
Office building, construction suspended, square feet	1,000,000		1,000,000
Costs accrued related to suspension of development			$ 27,800
Settlement of termination of the lease agreement	$ 12,800		12,800
Amount recognized due to termination of the lease agreement			7,200
510 Madison Avenue [Member]
Statement [Line Items]
Acquisition Costs	287,000		287,000
Acquisition closing costs	$ 1,500
Junior mezzanine loan interest acquisition costs			$ 22,500
Net rentable square feet of acquisition	347,000		347,000
Mortgage note payable assumed in connection with the acquisition of real estate			$ 202,600
Mortgage loan	$ 267,500		$ 267,500
Variable interest spread over LIBOR			0.30%
Maturity date			Feb. 24, 2012
Weston Corporate Center in Weston Massachusetts [Member]
Statement [Line Items]
Weston Corporate Center, net rentable square feet	356,000		356,000
Weston Corporate Center, percentage leased			100.00%
Greater Washington, DC [Member]
Statement [Line Items]
Deferred gain on sale of parcel sold			$ 33,700
Net rentable square feet of development			165,000
Gain on sale recognized			$ 1,800		$ 23,400
280 Park Avenue [Member]
Statement [Line Items]
Gain on sale recognized			1,000
Management Fees Revenue			12,200
Reston Virginia [Member]
Statement [Line Items]
Acquisition Costs	$ 20,300		20,300
Bay Colony Corporate Center [Member]
Statement [Line Items]
Acquisition Costs	$ 185,000		$ 185,000
Acquisition date			September 27, 2010
Net rentable square feet of acquisition	1,000,000		1,000,000
Cash portion of purchase price	$ 41,100		$ 41,100
Portion of acquisition included in debt	$ 143,900		$ 143,900
Interest at a fixed rate	6.53%		6.53%
Maturity date			Jun. 11, 2012
Acquisition site, acres			58
Contractual Amount Of Lease Agreement [Member] \| 250 West 55th Street in New York City [Member]
Statement [Line Items]
Costs accrued related to suspension of development			$ 20,000

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures Table) (Details)

9 Months Ended

Sep. 30, 2010

300 Billerica Road One & Two Circle Star Way [Member]

Mountain View Research And Technology Parks [Member]

25.00%

Entity Owning Land And Infrastructure Of Project [Member]

39.50%

Office Joint Venture Entities [Member]

33.33%

Retail Joint Venture Entities [Member]

66.67%

Residential Joint Venture Entities [Member]

5.00%

Square 407 Limited Partnership [Member]

0.00%

50.00%

The Metropolitan Square Associates LLC [Member]

Market Square North

51.00%

BP/CRF 901 New York Avenue LLC [Member]

Metropolitan Square

25.00%

^[1]

WP Project Developer LLC [Member]

901 New York Avenue

23.90%

^[2]

Wisconsin Place Retail LLC [Member]

Wisconsin Place Land and Infrastructure

5.00%

RBP Joint Venture LLC [Member]

Wisconsin Place Retail

50.00%

^[3]

Boston Properties Office Value Added Fund LP [Member]

Eighth Avenue and 46th Street

36.90%

^[1],[4]

Annapolis Junction NFM LLC [Member]

300 Billerica Road, One Two Circle Star Way and Mountain View Research and Technology Parks

50.00%

^[5]

Parcels of undeveloped land

Annapolis Junction

0.67

767 Venture LLC [Member]

60.00%

2 GCT Venture LLC [Member]

The General Motors Building

60.00%

540 Madison Venture LLC [Member]

Two Grand Central Tower

60.00%

125 West 55th Street Venture LLC [Member]

540 Madison Avenue

60.00%

500 North Capitol LLC [Member]

125 West 55th Street

30.00%

500 North Capitol Street, NW

[1]	The Company's economic ownership can increase based on the achievement of certain return thresholds.
[2]	Represents the Company's effective ownership interest. The Company has a 66.67%, 5% and 0% interest in the office, retail and residential joint venture entities, respectively, each of which owns a 33.33% interest in the entity owning the land and infrastructure of the project.
[3]	This property is not in operation and consists of assembled land.
[4]	Represents the Company's effective ownership interest. The Company has a 25.0% interest in the 300 Billerica Road and One amp; Two Circle Star Way properties and a 39.5% interest in the Mountain View Research and Technology Park properties (See also Note 15).
[5]	Two of the three Annapolis Junction land parcels are undeveloped land.

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

Sep. 30, 2010

Dec. 31, 2009

Real estate and development in process, net

$ 9,529,710

$ 9,065,881

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

2,813,338

2,643,301

Other liabilities

104,914

127,538

792,434

763,636

Unconsolidated Joint Ventures [Member]

Real estate and development in process, net

5,099,521

5,149,868

Other assets

806,595

760,001

Total assets

5,906,116

5,909,869

Members'/Partners' equity

3,257,015

3,217,893

Other liabilities

986,624

1,071,904

1,662,477

1,620,072

Total liabilities and members'/partners' equity

5,906,116

5,909,869

Company's share of equity

948,064

927,184

Basis differentials

^[1]

(155,630)

(163,548)

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

$ 792,434

$ 763,636

[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 occur from impairment of investments 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.

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

3 Months Ended

9 Months Ended

Sep. 30, 2010

Sep. 30, 2009

Sep. 30, 2010

Sep. 30, 2009

Joint ventures total revenue

$ 388,224

$ 377,303

$ 1,163,963

$ 1,144,337

Interest

97,103

77,090

285,887

234,653

Depreciation and amortization

81,133

78,181

245,608

242,556

Total expenses

331,700

308,397

990,554

953,362

Net income

68,089

77,650

203,083

211,753

Income from unconsolidated joint ventures

11,565

6,350

26,940

11,096

Unconsolidated Joint Ventures [Member]

Joint ventures total revenue

^[1]

155,126

148,885

457,217

445,827

Operating

45,546

41,977

130,083

122,614

Interest

59,120

58,975

176,705

173,356

Depreciation and amortization

50,548

57,160

164,763

175,648

Other

3,581

Total expenses

158,795

158,112

475,132

471,618

Net income

(3,669)

(9,227)

(17,915)

(25,791)

Company's share of net loss

(487)

(4,174)

(7,207)

(12,619)

Impairment loss on investments

(7,357)

Basis differential

3,125

2,319

7,918

7,099

Elimination of inter-entity interest on partner loan

8,927

8,205

26,229

23,973

Income from unconsolidated joint ventures

$ 11,565

$ 6,350

$ 26,940

$ 11,096

[1]

Includes straight-line rent adjustments of $5.9 million and $6.7 million for the three months ended September 30, 2010 and 2009, respectively, and $19.8 million and $20.3 million for the nine months ended September 30, 2010 and 2009, respectively. Includes net "above-" and "below-market" rent adjustments of $30.5 million and $37.8 million for the three months ended September 30, 2010 and 2009, respectively, and $97.6 million and $115.1 million for the nine months ended September 30, 2010 and 2009, respectively.

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2010	Sep. 30, 2009	Sep. 30, 2010	Sep. 30, 2009
Statement [Line Items]
Straight-line rent adjustments	$ 5.9	$ 6.7	$ 19.8	$ 20.3
Above and below market rent adjustments, net	$ 30.5	$ 37.8	$ 97.6	$ 115.1

Investments in Unconsolidated Joint Ventures (Details)
$ in Thousands

9 Months Ended

Sep. 30, 2010

USD ($)

The Metropolitan Square Associates LLC [Member]

The Metropolitan Square Associates LLC [Member] | Previous mortgage loan [Member]

51.00%

Mortgage loans, carrying amount

$ 123,600

8.23%

The Metropolitan Square Associates LLC [Member] | New Mortgage Loan [Member]

May 01, 2010

5.75%

$ 175,000

2 GCT Venture LLC [Member]

May 05, 2020

2 GCT Venture LLC [Member] | Previous mortgage loan [Member]

60.00%

$ 190,000

5.10%

Repayment of previous mortgage by investor

Jul. 11, 2010

$ 10,000

2 GCT Venture LLC [Member] | New Mortgage Loan [Member]

$ 180,000

6.00%

125 West 55th Street Venture LLC [Member]

Apr. 10, 2015

Guarantee maximum funding obligation, 125 West 55th Street

60.00%

$ 21,300

Cash deposit into the escrow account

10,000

Escrow account remaining funding obligation

11,300

Maximum funding obligation

$ 8,600

125 West 55th Street Venture LLC [Member] | Mezzanine Loans [Member]

Repayment outstanding mezzanine loans

7.81%

$ 63,500

500 North Capitol LLC [Member]

Mar. 01, 2010

North Capital Street net rentable square feet

30.00%

176,000

Investment in joint venture, total cost

$ 1,900

Investment in joint venture, cash contributions

$ 1,400

Investment in joint venture, common units issued | shares

5,906

500 North Capitol LLC [Member] | Previous mortgage loan [Member]

500 North Capitol LLC [Member] | New Mortgage Loan [Member]

$ 26,800

Variable interest rate at period end

5.75%

$ 22,000

Eighth Avenue and 46th Street New York [Member]

Mar. 31, 2013

Land parcels and development rights received in exchange

50.00%

$ 6,400

Land parcels and development rights relinquished in exchange

5,400

Payment from land parcels and development rights

$ 1,000

Mortgage Repayment Date

Jun. 15, 2010

Market Square North [Member]

Market Square North [Member] | Previous mortgage loan [Member]

50.00%

Mortgage loans, carrying amount

$ 81,100

7.70%

Market Square North [Member] | New Mortgage Loan [Member]

Dec. 19, 2010

4.85%

$ 130,000

Annapolis Junction NFM LLC [Member]

Oct. 01, 2020

Mortgage loan extension option, years

50.00%

^[1]

Mortgage loans, carrying amount

$ 42,700

Variable interest spread over LIBOR

1.00%

Joint Venture Which Refinanced Mortgage [Member] | 125 West 55th Street Venture LLC [Member] | Previous mortgage loan [Member]

Sep. 12, 2011

$ 200,000

5.75%

Joint Venture Which Refinanced Mortgage [Member] | 125 West 55th Street Venture LLC [Member] | New Mortgage Loan [Member]

Mar. 01, 2010

6.09%

Guarantee maximum funding obligation, 125 West 55th Street

$ 207,000

21,300

Cash deposit into the escrow account

10,000

Escrow account remaining funding obligation

$ 11,300

Joint Venture Which Modified Mortgage [Member] | 125 West 55th Street Venture LLC [Member] | New Mortgage Loan [Member]

Mar. 10, 2015

Mar. 10, 2020

[1]	Two of the three Annapolis Junction land parcels are undeveloped land.

Mortgage Notes Payable (Narratives) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2010	Sep. 30, 2009	Dec. 31, 2009
Statement [Line Items]
Amount of loan that was repaid	$ 301,531	$ 119,268
Mortgage note payable assumed in connection with the acquisition of real estate	202,604
Mortgage loan	$ 2,813,338		$ 2,643,301
510 Madison Avenue [Member]
Statement [Line Items]
Maturity date	Feb. 24, 2012
Mortgage note payable assumed in connection with the acquisition of real estate	$ 202,600
Mortgage loan	$ 267,500
Variable interest spread over LIBOR	0.30%
Cambridge Center [Member]
Statement [Line Items]
Amount of loan that was repaid	$ 22,600
Interest at a fixed rate	7.73%
Maturity date	Jul. 15, 2010
Pre-payment penalty	$ 0
Carnegie Center 202 206 & 214 [Member]
Statement [Line Items]
Amount of loan that was repaid	$ 55,800
Interest at a fixed rate	8.13%
Maturity date	Oct. 01, 2010
Pre-payment penalty	$ 0
Reservoir Place [Member]
Statement [Line Items]
Mortgage loans, carrying amount	$ 50,000
Maturity date	Jul. 30, 2014
Variable interest spread over LIBOR	3.85%
Variable interest spread over Eurodollar	2.20%

Unsecured Senior Notes (Narratives) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2010	Sep. 30, 2009
Statement [Line Items]
Net proceed of senior note after offering expense	$ 699,237
Treasury rate lock agreement rate basis, treasury term	10
Treasury rate lock agreements	2
Fixed treasury interest rate ten year	3.873%
Notional amount of treasury rate lock	$ 350,000
Cash settled treasury rate lock agreements	400
Senior Notes 5.625% Due 2020 [Member]
Statement [Line Items]
Net proceed of senior note after offering expense	$ 693,500
Long-term Debt, percentage bearing fixed interest rate	5.625%
Public offering date	April 19, 2010
Aggregate principal amount	$ 700,000
Maturity date	Nov. 15, 2020
Note price, percentage of principal amount	99.891%
Yield	5.708%

Unsecured Senior Notes (Unsecured Senior Notes Outstanding Table) (Details) - USD ($)

9 Months Ended

Sep. 30, 2010

Dec. 31, 2009

Amount due prior to maturity

$ 1,873,694,000

Net discount

(2,942,000)

$ (2,611,000)

Senior Notes, Total

2,872,058,000

$ 2,172,389,000

Senior Notes [Member]

10 Year Unsecured Senior Notes 6.381% [Member]

2,875,000,000

Net discount

$ (2,942,000)

6.25%

^[1]

6.381%

^[2]

Jan. 15, 2013

10 Year Unsecured Senior Notes 6.291% [Member]

$ 750,000,000

6.25%

6.291%

^[2]

Jan. 15, 2013

12 Year Unsecured Senior Notes 5.693% [Member]

$ 175,000,000

5.625%

5.693%

^[2]

Apr. 15, 2015

12 Year Unsecured Senior Notes 5.194% [Member]

$ 300,000,000

5.00%

5.194%

^[2]

Jun. 01, 2015

10 Year Unsecured Senior Notes 5.967% [Member]

$ 250,000,000

5.875%

5.967%

^[2]

Oct. 15, 2019

Year 10 Unsecured Senior Notes 5.708% [Member]

$ 700,000,000

5.625%

5.708%

^[2]

Nov. 15, 2020

$ 700,000,000

[1]	Yield on issuance date including the effects of discounts on the notes.
[2]	No principal amounts are due prior to maturity.

Unsecured Exchangeable Senior Notes (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2010	Sep. 30, 2009	Sep. 30, 2010	Sep. 30, 2009	Dec. 31, 2009
Statement [Line Items]
Net Of Adjustment For Equity Component Allocation	$ 104,419		$ 104,419		$ 140,400
Proceeds attributable to equity component of the notes	230,300		230,300
Deferred financing Costs attributable to equity component	1,000		1,000
Interest expense	17,100	$ 18,600	52,300	$ 55,800
Non cash interest expense	9,500	9,800	28,800	28,700
Carrying amount of equity component	229,300		229,300		229,300
Losses from early extinguishments of debt		$ 16	8,221	510
Unsecured exchangeable senior notes	1,759,490		1,759,490		$ 1,904,081
Amount paid for repurchase			172,294
3.625% Exchangeable Senior Notes [Member]
Statement [Line Items]
Value of exchangeable senior notes	$ 747,500		$ 747,500
Coupon/Stated Rate	3.625%		3.625%
Debt instrument effective interest rate			6.555%
Maturity date			Feb. 15, 2014
2.875% Exchangeable Senior Notes [Member]
Statement [Line Items]
Value of exchangeable senior notes	$ 862,500		$ 862,500
Coupon/Stated Rate	2.875%		2.875%
Debt instrument effective interest rate			5.63%
Maturity date			Feb. 15, 2037
Losses from early extinguishments of debt			$ 8,200
Value of repurchase of senior notes due in 2037			186,300
Amount paid for repurchase			185,500
Carrying value of repurchased notes	$ 177,300		177,300
3.750% Exchangeable Senior Notes [Member]
Statement [Line Items]
Value of exchangeable senior notes	$ 450,000		$ 450,000
Coupon/Stated Rate	3.75%		3.75%
Debt instrument effective interest rate			5.958%
Maturity date			May 15, 2036

Unsecured Exchangeable Senior Notes (Unsecured Exchangeable Senior Notes Outstanding) (Details)

9 Months Ended

12 Months Ended

Sep. 30, 2010

USD ($)

$ / shares

Dec. 31, 2007

USD ($)

$ / shares

Dec. 17, 2007

$ / shares

Aug. 13, 2010

USD ($)

Dec. 31, 2009

USD ($)

Adjustment for the equity component allocation, net of accumulated amortization

$ 1,873,694,000

Net Discount

(9,785,000)

$ (15,529,000)

(104,419,000)

(140,400,000)

Unsecured exchangeable senior notes - Total

$ 1,759,490,000

$ 1,904,081,000

Revised exchange price due to capped call transaction | $ / shares

136.13

3.625% Exchangeable Senior Notes [Member]

3.625%

^[1]

4.037%

Exchange Rate

^[2]

8.5051

First optional redemption date

$ 747,500,000

N/A

Initial exchange per share

Feb. 15, 2014

Initial exchange price

$ 1,000

$ 117.58

Revised exchange price due to capped call transaction

137.17

Premium over closing price

40.00%

Closing price per share of common stock

$ 97.98

Net cost of capped call transaction

$ 44,400,000

2.875% Exchangeable Senior Notes [Member]

2.875%

^[1]

3.462%

Exchange Rate

^[3]

7.0430

First optional redemption date

$ 676,194,000

^[4]

February 20, 2012

Special distribution per share common stock | $ / shares

Feb. 15, 2037

Initial exchange price

$ 1,000

$ 5.98

Initial exchange rate

6.6090

Revised exchange rate

7.0430

Revised exchange price resulting from special distribution | $ / shares

$ 141.98

Repurchase price for the notes

100.00%

3.750% Exchangeable Senior Notes [Member]

3.75%

^[1]

3.787%

Exchange Rate

^[5]

10.0066

First optional redemption date

$ 450,000,000

^[6]

May 18, 2013