Boston Properties LTD Partnership 10-Q 7 Nov 14 2014 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2014	Nov. 03, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Entity Registrant Name	'BOSTON PROPERTIES LTD PARTNERSHIP	'
Amendment Flag	'false	'
Entity Central Index Key	'0001043121	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	0

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
ASSETS	'	'
Real estate, at cost	$17,932,669	$16,727,886
Construction in progress	715,609	1,523,179
Land held for future development	276,804	297,376
Less: accumulated depreciation	-3,398,390	-3,096,910
Total real estate	15,526,692	15,451,531
Cash and cash equivalents	846,664	2,365,137
Cash held in escrows	153,161	57,201
Investments in securities	18,834	16,641
Tenant and other receivables (net of allowance for doubtful accounts of $1,080 and $1,636, respectively)	43,210	59,464
Accrued rental income (net of allowance of $7,397 and $3,636, respectively)	689,885	651,603
Deferred charges, net	837,907	884,450
Prepaid expenses and other assets	219,074	184,477
Investments in unconsolidated joint ventures	180,149	126,084
Total assets	18,515,576	19,796,588
Liabilities:	'	'
Mortgage notes payable	4,328,464	4,449,734
Unsecured senior notes (net of discount of $12,828 and $14,146, respectively)	5,837,172	5,835,854
Unsecured exchangeable senior notes (net of discount of $0 and $182, respectively)	0	744,880
Unsecured line of credit	0	0
Mezzanine notes payable	310,114	311,040
Outside members' notes payable	180,000	180,000
Accounts payable and accrued expenses	253,600	202,470
Distributions payable	112,708	497,242
Accrued interest payable	181,954	167,523
Other liabilities	517,428	578,969
Total liabilities	11,721,440	12,967,712
Commitments and contingencies	0	0
Noncontrolling interests:	'	'
Redeemable interest in property partnership	104,105	99,609
Redeemable partnership units— 0 and 666,116 series two preferred units outstanding (0 and 874,168 common units at redemption value, if converted) at September 30, 2014 and December 31, 2013, respectively	0	87,740
Redeemable partnership units—40,440 and 360,126 series four preferred units outstanding at redemption value at September 30, 2014 and December 31, 2013, respectively	2,022	18,006
Redeemable partnership units—16,456,297 and 15,583,370 common units and 1,505,386 and 1,455,761 long term incentive units outstanding at redemption value at September 30, 2014 and December 31, 2013, respectively	2,079,244	1,710,218
Capital:	'	'
5.25% Series B cumulative redeemable preferred units, liquidation preference $2,500 per unit, 80,000 units issued and outstanding at September 30, 2014 and December 31, 2013	193,623	193,623
Boston Properties Limited Partnership partners’ capital—1,710,615 and 1,700,222 general partner units and 151,389,171 and 151,282,879 limited partner units outstanding at September 30, 2014 and December 31, 2013, respectively	3,698,577	3,993,548
Noncontrolling interests in property partnerships	716,565	726,132
Total capital	4,608,765	4,913,303
Total liabilities and capital	$18,515,576	$19,796,588

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Tenant and other receivables, allowance for doubtful accounts	$1,080	$1,636
Accrued rental income, allowance	7,397	3,636
Unsecured senior notes, discount	12,828	14,146
Unsecured exchangeable senior notes, discount	$0	$182
Redeemable partnership units, series two preferred units outstanding (in units)	0	666,116
Redeemable partnership units, common units at redemption value, if converted (in units)	0	874,168
Redeemable partnership units, series four preferred units outstanding (in units)	40,440	360,126
Redeemable partnership units, common units (in units)	16,456,297	15,583,370
Redeemable partnership units, long term incentive units outstanding at redemption value (in units)	1,505,386	1,455,761
General Partners' Capital Account, Units Outstanding (in units)	1,710,615	1,700,222
Limited Partners' Capital Account, Units Outstanding (in units)	151,389,171	151,282,879
Series B Cumulative Redeemable Preferred Stock [Member]	'	'
Series B Dividend Rate Percentage	5.25%	5.25%
Series B, Liquidation Preference Per Unit	$2,500	$2,500
Series B, Unitsssued	80,000	80,000
Series B, Units Outstanding	80,000	80,000

Consolidated_Statements_Of_Ope

Consolidated Statements Of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenue	'	'	'	'
Base rent	$484,071	$449,636	$1,402,328	$1,221,874
Recoveries from tenants	90,103	80,718	253,419	213,358
Parking and other	26,236	25,000	76,869	71,984
Total rental revenue	600,410	555,354	1,732,616	1,507,216
Hotel revenue	11,918	10,652	32,478	30,061
Development and management services	6,475	5,475	18,197	22,063
Total revenue	618,803	571,481	1,783,291	1,559,340
Expenses	'	'	'	'
Rental	215,179	199,288	624,213	544,368
Hotel	7,585	6,580	21,697	20,959
General and administrative	22,589	24,841	75,765	94,673
Transaction costs	1,402	766	2,500	1,744
Impairment loss	0	0	0	4,401
Depreciation and amortization	155,217	151,216	460,064	400,131
Total expenses	401,972	382,691	1,184,239	1,066,276
Operating income	216,831	188,790	599,052	493,064
Other income (expense)	'	'	'	'
Income from unconsolidated joint ventures	4,419	14,736	10,069	72,240
Gains on consolidation of joint ventures	0	-1,810	0	385,991
Interest and other income	3,421	3,879	6,841	6,646
Gains (losses) from investments in securities	-297	956	651	1,872
Gains (losses) from early extinguishments of debt	0	-30	0	122
Interest expense	-113,308	-122,173	-337,839	-325,746
Income from continuing operations	111,066	84,348	278,774	634,189
Discontinued operations	'	'	'	'
Income from discontinued operations	0	1,677	0	7,486
Gain on sale of real estate from discontinued operations	0	88,565	0	88,565
Gain on forgiveness of debt from discontinued operations	0	0	0	20,736
Impairment loss from discontinued operations	0	0	0	-2,852
Income before gains on sales of real estate	111,066	174,590	278,774	748,124
Gains on sales of real estate	41,937	0	41,937	0
Net income	153,003	174,590	320,711	748,124
Net income attributable to noncontrolling interests	'	'	'	'
Noncontrolling interests in property partnerships	-5,566	3,279	-17,473	924
Noncontrolling interest—redeemable preferred units	-2,722	-3,729	-8,868	-8,796
Net income attributable to Boston Properties Limited Partnership	$144,715	$174,140	$294,370	$740,252
Basic earnings per common unit attributable to Boston Properties Limited Partnership	'	'	'	'
Income from continuing operations	$0.85	$0.50	$1.73	$3.69
Discontinued operations	$0	$0.53	$0	$0.67
Net income	$0.85	$1.03	$1.73	$4.36
Weighted average number of common units outstanding	170,785	169,236	170,340	168,975
Diluted earnings per common unit attributable to Boston Properties Limited Partnership	'	'	'	'
Income from continuing operations	$0.85	$0.50	$1.73	$3.69
Discontinued operations	$0	$0.52	$0	$0.66
Net income	$0.85	$1.02	$1.73	$4.35
Weighted average number of common and common equivalent units outstanding	170,938	169,521	170,491	169,356

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Statement of Comprehensive Income [Abstract]	'		'		'		'
Net income	$153,003		$174,590		$320,711		$748,124
Other comprehensive income:	'		'		'		'
Amortization of interest rate contracts (1)	628	[1]	629	[1]	1,881	[1]	1,884	[1]
Other comprehensive income	628		629		1,881		1,884
Comprehensive income	153,631		175,219		322,592		750,008
Comprehensive income attributable to noncontrolling interests	-8,288		-450		-26,341		-7,872
Comprehensive income attributable to Boston Properties Limited Partnership	$145,343		$174,769		$296,251		$742,136
[1]	Amounts reclassified from comprehensive income primarily to interest expense within the Company's Consolidated Statements of Operations.

Consolidated_Statements_Of_Par

Consolidated Statements Of Partners' Capital (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Increase (Decrease) in Partners' Capital [Roll Forward]	'	'
Beginning Balance	$4,187,171	$3,330,605
Contributions	3,892	196,968
Net income allocable to general and limited partner units	272,405	671,268
Distributions	-306,340	-302,081
Accumulated other comprehensive loss	1,690	1,695
Unearned compensation	2,046	3,811
Conversion of redeemable partnership units	2,368	10,406
Adjustment to reflect redeemable partnership units at redemption value	-271,032	50,898
Ending Balance	$3,892,200	$3,963,570

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities:	'	'
Net income	$320,711	$748,124
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	460,064	403,957
Non-cash compensation expense	22,708	39,001
Impairment loss	0	4,401
Income from unconsolidated joint ventures	-10,069	-72,240
Gains on consolidation of joint ventures	0	-385,991
Distributions of net cash flow from operations of unconsolidated joint ventures	3,130	29,607
Gains from investments in securities	-651	-1,872
Non-cash portion of interest expense	-28,753	29,149
Settlement of accreted debt discount on repurchases of unsecured exchangeable senior notes	-92,979	-56,532
Gains from early extinguishments of debt	0	-264
Gains on sales of real estate	-41,937	0
Gain on sale of real estate from discontinued operations	0	-88,565
Gain on forgiveness of debt from discontinued operations	0	-20,736
Impairment loss from discontinued operations	0	2,852
Change in assets and liabilities:	'	'
Cash held in escrows	3,957	4,017
Tenant and other receivables, net	16,254	3,628
Accrued rental income, net	-42,180	-44,636
Prepaid expenses and other assets	-34,804	-41,245
Accounts payable and accrued expenses	4,237	9,179
Accrued interest payable	14,431	35,089
Other liabilities	-60,795	-9,352
Tenant leasing costs	-63,647	-37,150
Total adjustments	148,966	-197,703
Net cash provided by operating activities	469,677	550,421
Cash flows from investing activities:	'	'
Acquisitions of real estate	0	-522,900
Construction in progress	-305,192	-279,786
Building and other capital improvements	-57,329	-46,805
Tenant improvements	-80,692	-78,462
Proceeds from the sales of real estate	103,542	160,815
Proceeds from sales of real estate placed in escrow	-99,917	0
Cash recorded upon consolidation	0	79,468
Repayments of notes receivable, net	0	12,491
Capital contributions to unconsolidated joint ventures	-47,767	0
Capital distributions from unconsolidated joint ventures	641	223,067
Investments in securities, net	-1,542	-1,333
Net cash used in investing activities	-488,256	-453,445
Cash flows from financing activities:	'	'
Repayments of mortgage notes payable	-82,030	-96,750
Proceeds from unsecured senior notes	0	1,194,753
Repayment/redemption of unsecured exchangeable senior notes	-654,521	-393,468
Deferred financing costs	-31	-15,180
Net proceeds from preferred unit issuance	0	193,623
Net proceeds from equity transactions	1,530	-348
Redemption of preferred units	-15,984	-43,070
Distributions	-726,314	-337,440
Contributions from noncontrolling interests in property partnerships	2,980	6,386
Distributions to noncontrolling interests in property partnerships	-25,524	-6,185
Net cash provided by (used in) financing activities	-1,499,894	502,321
Net increase (decrease) in cash and cash equivalents	-1,518,473	599,297
Cash and cash equivalents, beginning of period	2,365,137	1,041,978
Cash and cash equivalents, end of period	846,664	1,641,275
Supplemental disclosures:	'	'
Cash paid for interest	489,949	368,652
Interest capitalized	44,809	50,252
Non-cash investing and financing activities:	'	'
Additions to real estate included in accounts payable and accrued expenses	20,016	6,397
Real estate and related intangibles recorded upon consolidation	0	3,356,000
Debt recorded upon consolidation	0	2,056,000
Working capital recorded upon consolidation	0	170,748
Noncontrolling interests recorded upon consolidation	0	480,861
Investment in unconsolidated joint venture eliminated upon consolidation	0	361,808
Mortgage note payable extinguished through foreclosure	0	25,000
Real estate transferred upon foreclosure	0	6,954
Land improvements contributed by noncontrolling interest in property partnership	0	4,546
Distributions declared but not paid	112,708	112,470
Issuance of common stock in connection with the exchange of exchangeable senior notes	0	43,834
Conversions of redeemable partnership units to partners’ capital	2,368	10,406
Conversions of redeemable preferred units to common units	33,306	0
Issuance of restricted securities to employees	$27,445	$30,077

Organization

Organization	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization	'
	1. Organization
	Boston Properties Limited Partnership (the “Company”), a Delaware limited partnership, is the entity through which Boston Properties, Inc., a self-administered and self-managed real estate investment trust (“REIT”), conducts substantially all of its business and owns (either directly or through subsidiaries) substantially all of its assets. Boston Properties, Inc. is the sole general partner of the Company and at September 30, 2014 owned an approximate 89.5% (89.2% at September 30, 2013) general and limited partnership interest in the Company. Partnership interests in the Company are denominated as “common units of partnership interest” (also referred to as “OP Units”), “long term incentive units of partnership interest” (also referred to as “LTIP Units”) or “preferred units of partnership interest” (also referred to as “Preferred Units”). In addition, in February 2011 and February 2012, the Company issued LTIP Units in connection with the granting to employees of outperformance awards (also referred to as “2011 OPP Units” and “2012 OPP Units,” respectively, and collectively as “OPP Units”). On January 31, 2014, the measurement period for the Company’s 2011 OPP Unit awards expired and the Company’s total return to shareholders (“TRS”) was not sufficient for employees to earn and therefore become eligible to vest in any of the 2011 OPP Unit awards. Accordingly, all 2011 OPP Unit awards were automatically forfeited (See Notes 8 and 11). In February 2013 and February 2014, the Company issued LTIP Units in connection with the granting to employees of multi-year, long-term incentive program ("MYLTIP") awards (also referred to as “2013 MYLTIP Units” and “2014 MYLTIP Units,” respectively, and collectively as "MYLTIP Units"). Because the rights, preferences and privileges of OPP Units and MYLTIP Units differ from other LTIP Units granted to employees as part of the annual compensation process, unless specifically noted otherwise, all references to LTIP Units exclude OPP Units and MYLTIP Units (See Notes 8 and 11).
	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 the Company 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, the Company 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 such 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. An LTIP Unit is generally the economic equivalent of a share of restricted common stock of Boston Properties, Inc. LTIP 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 Note 9).
	At September 30, 2014, there were two series of Preferred Units outstanding (i.e., Series Four Preferred Units and Series B Preferred Units).
	•	The Series Four Preferred Units are not convertible into or exchangeable for any security of the Company or Boston Properties, Inc., have a per unit liquidation preference of $50.00 and are entitled to receive quarterly distributions of $0.25 per unit (or an annual rate of 2.00%) (See Notes 8 and 13).
	•	The Series B Preferred Units were issued to Boston Properties, Inc. on March 27, 2013 in connection with Boston Properties, Inc.'s 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 the Company in exchange for 80,000 Series B Preferred Units having terms and preferences generally mirroring those of the Series B Preferred Stock (See Note 9).
	All references herein to the Company refer to Boston Properties Limited Partnership and its consolidated subsidiaries, collectively, unless the context otherwise requires.
	Properties
	At September 30, 2014, the Company owned or had interests in a portfolio of 172 commercial real estate properties (the “Properties”) aggregating approximately 46.4 million net rentable square feet, including ten properties under construction totaling approximately 3.3 million net rentable square feet. In addition, the Company has structured parking for approximately 45,835 vehicles containing approximately 15.7 million square feet. At September 30, 2014, the Properties consist of:
	•	163 office properties, including 132 Class A office properties (including nine properties under construction) and 31 Office/Technical properties;
	•	one hotel;
	•	five retail properties (including one property under construction); and
	•	three residential properties.
	The Company owns or controls undeveloped land parcels totaling approximately 492.1 acres.
	The Company considers Class A office properties to be centrally 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. The Company considers Office/Technical properties to be properties that support office, research and development, laboratory and other technical uses. The Company’s definitions of Class A Office and Office/Technical properties may be different than those used by other companies.

Basis_Of_Presentation_And_Summ

Basis Of Presentation And Summary Of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2014
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 the Company, nor does it have employees of its own. The Company, 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 ("VIE"s) 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 accounting principles generally accepted in the United States of America 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 accounting principles generally accepted in the United States of America 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 accounting principles generally accepted in the United States of America. 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, 2013. Certain prior year amounts have been reclassified to conform to the current year presentation. Beginning on January 1, 2014, the properties that were historically part of the Company's Princeton region are reflected as the suburban component of the Company's New York region (See Note 12).
	The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. The Company determines the fair value of its unsecured senior notes and unsecured exchangeable senior notes using market prices. The inputs used in determining the fair value of the Company’s unsecured senior notes and unsecured exchangeable senior notes are categorized at a level 1 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) due to the fact that the Company 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 analyses 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.
	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. The following table presents the aggregate carrying value of the Company’s indebtedness and the Company’s corresponding estimate of fair value as of September 30, 2014 and December 31, 2013 (in thousands):
		September 30, 2014				December 31, 2013
		Carrying		Estimated		Carrying			Estimated
		Amount		Fair Value		Amount			Fair Value
	Mortgage notes payable	$	4,328,464	$	4,460,353	$	4,449,734		$	4,545,283
	Mezzanine notes payable	310,114		310,141		311,040			311,064
	Unsecured senior notes	5,837,172		6,173,499		5,835,854			6,050,517
	Unsecured exchangeable senior notes	—		—		744,880		-1	750,266
	Total	$	10,475,750	$	10,943,993	$	11,341,508		$	11,657,130
	_______________
	-1	Includes the net adjustment for the equity component allocation totaling approximately $2.4 million at December 31, 2013.
	Out-of-Period Adjustment
	During the nine months ended September 30, 2014, the Company recorded an allocation of net income to the noncontrolling interest holder in its Fountain Square consolidated joint venture totaling approximately $1.9 million related to the cumulative non-cash adjustment to the accretion of the changes in the redemption value of the noncontrolling interest. This resulted in the overstatement of Noncontrolling Interests in Property Partnerships by approximately $1.9 million during the nine months ended September 30, 2014 and an understatement of Noncontrolling Interests in Property Partnerships in the aggregate amount of approximately $1.9 million in previous periods prior to 2014. Because this adjustment was not material to the prior periods’ consolidated financial statements and the impact of recording the adjustment in 2014 was not material to the Company’s consolidated financial statements, the Company recorded the related adjustment during the nine months ended September 30, 2014. The out of period adjustment was identified and recorded during the second quarter of 2014.
	Recent Accounting Pronouncements
	On April 10, 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") No. 2014-08, "Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity" (“ASU No. 2014-08”). ASU No. 2014-08 clarifies that discontinued operations presentation applies only to disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results (e.g., a disposal of a major geographical area, a major line of business, a major equity method investment or other major parts of an entity). ASU No. 2014-08 is effective prospectively for reporting periods beginning after December 15, 2014. Early adoption is permitted, and the Company early adopted ASU No. 2014-08 during the first quarter of 2014. The Company’s adoption of ASU No. 2014-08 did not have a material impact on its consolidated financial statements.
	In May 2014, the FASB issued ASU 2014-09, "Revenue from Contract 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 and will supersede 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. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB's Accounting Standards Codification ("ASC"). ASU 2014-09 is effective for annual reporting periods (including interim periods within that reporting period) beginning after December 15, 2016 and shall be applied using either a full retrospective or modified retrospective approach. Early adoption is not permitted. The Company is currently assessing the potential impact that the adoption of ASU 2014-09 will have on its consolidated financial statements.
	In June 2014, the FASB issued ASU No. 2014-12, “Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period” (“ASU 2014-12”). The amendments in ASU 2014-12 require that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. A reporting entity should apply existing guidance in ASC Topic No. 718, “Compensation - Stock Compensation” (“ASC 718”), as it relates to awards with performance conditions that affect vesting to account for such awards. The amendments in ASU 2014-12 are effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Early adoption is permitted. Entities may apply the amendments in ASU 2014-12 either: (a) prospectively to all awards granted or modified after the effective date; or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. The Company does not expect the adoption of ASU 2014-12 to have a material impact on its consolidated financial statements.
	In August 2014, the FASB issued ASU No. 2014-15, "Presentation of Financial Statements - Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern" (“ASU 2014-15”). ASU 2014-15 requires an entity to evaluate whether there are conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued (or within one year after the financial statements are available to be issued when applicable) and to provide related footnote disclosures in certain circumstances. ASU 2014-15 is effective for the annual period ending after December 15, 2016, and for annual and interim periods thereafter with early adoption permitted. The Company does not expect the adoption of ASU 2014-15 to have a material impact on its consolidated financial statements.

Real_Estate_Activity_During_th

Real Estate Activity During the Nine Months Ended September 30, 2014	9 Months Ended
	Sep. 30, 2014
Real Estate [Abstract]	'
Real Estate Activity During The Nine Months Ended September 30, 2014	'
	3. Real Estate Activity During the Nine Months Ended September 30, 2014
	Developments
	On February 10, 2014, the Company completed and fully placed in-service The Avant at Reston Town Center development project comprised of 359 apartment units and retail space aggregating approximately 355,000 square feet located in Reston, Virginia.
	On April 1, 2014, the Company commenced construction of its 99 Third Avenue development project totaling approximately 17,000 net rentable square feet of retail space located in Waltham, Massachusetts.
	On April 3, 2014, the Company commenced construction of its 690 Folsom Street development project totaling approximately 26,000 net rentable square feet of office and retail space located in San Francisco, California.
	On April 10, 2014, a consolidated joint venture in which the Company has a 95% interest signed a lease with salesforce.com for 714,000 square feet at the new Salesforce Tower (formerly Transbay Tower), the 1.4 million square foot, 61-story Class A office development project currently under construction at 415 Mission Street in the South Financial District of San Francisco, California. In conjunction with the lease signing, the Company has commenced construction of the building.
	On May 20, 2014, the Company commenced construction of its 888 Boylston Street development project totaling approximately 425,000 net rentable square feet of Class A office space located in Boston, Massachusetts.
	On May 20, 2014, the Company commenced construction of its 10 CityPoint development project totaling approximately 245,000 net rentable square feet of Class A office space located in Waltham, Massachusetts.
	On August 31, 2014, the Company completed and fully placed in-service 250 West 55th Street, a Class A office project with approximately 988,000 net rentable square feet located in New York City.
	On September 17, 2014, the Company completed and fully placed in-service 680 Folsom Street, a Class A office project with approximately 525,000 net rentable square feet located in San Francisco, California.
	Dispositions
	On June 11, 2014, the Company entered into a contract for the sale of its Patriots Park properties located in Reston, Virginia for a sale price of $321.0 million, which exceeds the carrying value at September 30, 2014. Patriots Park consists of three Class A office properties aggregating approximately 706,000 net rentable square feet (See Note 13).
	On July 29, 2014, the Company completed the sale of its Mountain View Technology Park properties and Mountain View Research Park Building Sixteen property located in Mountain View, California for an aggregate sale price of approximately $92.1 million. Net cash proceeds totaled approximately $91.2 million, resulting in a gain on sale of real estate totaling approximately $36.4 million. Mountain View Technology Park is a seven-building complex of Office/Technical properties aggregating approximately 135,000 net rentable square feet. Mountain View Research Park Building Sixteen is an Office/Technical property with approximately 63,000 net rentable square feet.
	On August 20, 2014, a portion of the land parcel at the Company’s One Reston Overlook property located in Reston, Virginia was taken by eminent domain. Net cash proceeds totaled approximately $2.6 million, resulting in a gain on sale of real estate totaling approximately $1.2 million.
	On August 22, 2014, the Company completed the sale of a parcel of land within its Broad Run Business Park property located in Loudoun County, Virginia for a sale price of approximately $9.8 million. Net cash proceeds totaled approximately $9.7 million, resulting in a gain on sale of real estate totaling approximately $4.3 million. The parcel is an approximately 15.5 acre land parcel subject to a ground lease that was scheduled to expire on October 31, 2048 with a tenant that exercised its purchase option under the ground lease.
	On September 16, 2014, the Company entered into a binding purchase and sale agreement to sell a 45% interest in each of 601 Lexington Avenue in New York City and Atlantic Wharf Office Building and 100 Federal Street in Boston for an aggregate gross sales price of approximately $1.827 billion in cash, less the partner’s pro rata share of the indebtedness secured by 601 Lexington Avenue, subject to certain prorations and adjustments. In connection with the sale, the Company will form a joint venture for each property with the buyer and provide customary property management and leasing services to the joint ventures. 601 Lexington Avenue is a 1,669,000 square foot Class A office complex located in Midtown Manhattan. The property consists of a 59-story tower as well as a six-story low-rise office and retail building. The property is subject to existing mortgage indebtedness of approximately $712.9 million. The Atlantic Wharf Office Building is a 791,000 square foot Class A office tower located on Boston's Waterfront. 100 Federal Street is a 1,323,000 square foot Class A office tower located in Boston's Financial District. The transaction will not qualify as a sale of real estate for financial reporting purposes as the Company will continue to control the joint ventures and will therefore continue to account for the properties on a consolidated basis in its financial statements (See Note 13).
	The Company did not have any dispositions during the three and nine months ended September 30, 2014 that qualified for discontinued operations presentation. The following table summarizes the income from discontinued operations for the three and nine months ended September 30, 2013 related to One Preserve Parkway, 10 & 20 Burlington Mall Road, 1301 New York Avenue, Montvale Center and 303 Almaden Boulevard and the related gain on sale of real estate, gain on forgiveness of debt and impairment loss:
		For the three months ended September 30,		For the nine months ended September 30,
		2013		2013
		(in thousands)
	Total revenue	$	4,112	$	17,962
	Expenses
	Operating	1,495		6,290
	Depreciation and amortization	940		3,826
	Total expenses	2,435		10,116
	Operating income	1,677		7,846
	Other expense
	Interest expense	—		360
	Income from discontinued operations	$	1,677	$	7,486
	Gain on sale of real estate from discontinued operations	$	88,565	$	88,565
	Gain on forgiveness of debt from discontinued operations	$	—	$	20,736
	Impairment loss from discontinued operations	$	—	$	(2,852	)

Investments_in_Unconsolidated_

Investments in Unconsolidated Joint Ventures	9 Months Ended
	Sep. 30, 2014
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 September 30, 2014:
	Entity		Properties		Nominal %				Carrying Value of Investment
					Ownership
									(in thousands)
	Square 407 Limited Partnership		Market Square North		50	%			$	(8,540	)
	The Metropolitan Square Associates LLC		Metropolitan Square		51	%			8,343
	BP/CRF 901 New York Avenue LLC		901 New York Avenue		25	%	(1)		(1,436		)
	WP Project Developer LLC		Wisconsin Place Land and Infrastructure		33.3	%	(2)		46,011
	Annapolis Junction NFM, LLC		Annapolis Junction		50	%	(3)		24,484
	2 GCT Venture LLC		N/A		60	%	-4		424
	540 Madison Venture LLC		540 Madison Avenue		60	%			70,418
	500 North Capitol LLC		500 North Capitol Street, NW		30	%			(1,467		)
	501 K Street LLC		501 K Street		50	%	-5		41,912
									$	180,149
	_______________
	-1	The Company’s economic ownership has increased based on the achievement of certain return thresholds.
	-2	The Company’s wholly-owned entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking garage and infrastructure of the project.
	-3	The joint venture owns two in-service buildings, two buildings under construction and two undeveloped land parcels.
	-4	Two Grand Central Tower was sold on October 25, 2011.
	-5	Under the joint venture agreement, the partner will be entitled to up to two additional payments from the venture based on increases in total square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.
	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 at an agreed upon fair value. Under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners.
	The combined summarized balance sheets of the Company's unconsolidated joint ventures are as follows:
		September 30, 2014				31-Dec-13
		(in thousands)
	ASSETS
	Real estate and development in process, net	$	1,014,663			$	924,297
	Other assets	182,905				163,149
	Total assets	$	1,197,568			$	1,087,446
	LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
	Mortgage and notes payable	$	753,692			$	749,732
	Other liabilities	23,180				28,830
	Members’/Partners’ equity	420,696				308,884
	Total liabilities and members’/partners’ equity	$	1,197,568			$	1,087,446
	Company’s share of equity	$	208,125			$	154,726
	Basis differentials (1)	(27,976		)		(28,642		)
	Carrying value of the Company’s investments in unconsolidated joint ventures	$	180,149			$	126,084
	_______________
	-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.
	The combined summarized statements of operations of the Company's unconsolidated joint ventures are as follows:
		For the three months ended September 30,								For the nine months ended September 30,
		2014				2013				2014		2013
		(in thousands)
	Total revenue (1)	$	41,958			$	37,983			$	118,429	$	273,464
	Expenses
	Operating	15,516				14,963				46,441		89,826
	Depreciation and amortization	9,429				9,784				27,688		76,202
	Total expenses	24,945				24,747				74,129		166,028
	Operating income	17,013				13,236				44,300		107,436
	Other expense
	Interest expense	7,950				8,148				23,946		104,436
	Losses from early extinguishment of debt	—				—				—		1,677
	Income from continuing operations	9,063				5,088				20,354		1,323
	Gains on sales of real estate	—				12,441				—		14,207
	Net income	$	9,063			$	17,529			$	20,354	$	15,530
	Company’s share of net income	$	4,200			$	3,149			$	9,403	$	1,974
	Gains on sales of real estate	—				11,174				—		54,501
	Basis differential	219				413				666		(1,213		)
	Elimination of inter-entity interest on partner loan	—				—				—		16,978
	Income from unconsolidated joint ventures	$	4,419			$	14,736			$	10,069	$	72,240
	Gains on consolidation of joint ventures	$	—			$	(1,810	)		$	—	$	385,991
	_______________
	-1	Includes straight-line rent adjustments of $0.2 million and $0.6 million for the three months ended September 30, 2014 and 2013, respectively, and $1.1 million and $7.6 million for the nine months ended September 30, 2014 and 2013, respectively. Includes net below-market rent adjustments of $(0.1) million and $(0.1) million for the three months ended September 30, 2014 and 2013, respectively, and $(0.1) million and $33.9 million for the nine months ended September 30, 2014 and 2013, respectively.
On April 10, 2014, the Company entered into a joint venture with an unrelated third party to acquire a parcel of land located at 501 K Street in Washington, DC. The Company anticipates the land parcel will accommodate an approximate 520,000 square foot Class A office property to be developed in the future. The joint venture partner contributed the land for a 50% interest in the joint venture and the Company contributed cash of approximately $39.0 million for its 50% interest. Under the joint venture agreement, the partner will be entitled to up to two additional payments from the venture based on increases in total square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.
On April 30, 2014, the Company's partner in its Annapolis Junction joint venture contributed a parcel of land and improvements and the Company contributed cash of approximately $5.4 million to the joint venture. The Company has a 50% interest in this joint venture. The joint venture has commenced construction of Annapolis Junction Building Eight, which when completed will consist of a Class A office property with approximately 125,000 net rentable square feet located in Annapolis, Maryland. In addition, on June 23, 2014, the joint venture obtained construction financing collateralized by the development project totaling $26.0 million. The construction financing bears interest at a variable rate equal to LIBOR plus 1.50% per annum and matures on June 23, 2017, with two, one-year extension options, subject to certain conditions.

Mortgage_Notes_Payable_Notes

Mortgage Notes Payable (Notes)	9 Months Ended
	Sep. 30, 2014
Mortgage Notes Payable [Abstract]	'
Mortgage Notes Payable Disclosure [Text Block]	'
	5. Mortgage Notes Payable
	On July 1, 2014, the Company used available cash to repay the mortgage loan collateralized by its New Dominion Technology Park Building Two property located in Herndon, Virginia totaling $63.0 million. The mortgage loan bore interest at a fixed rate of 5.55% per annum and was scheduled to mature on October 1, 2014. There was no prepayment penalty.

Unsecured_Exchangeable_Senior_

Unsecured Exchangeable Senior Notes Unsecured Exchangeable Senior Notes	9 Months Ended
	Sep. 30, 2014
Unsecured Exchangeable Senior Notes [Abstract]	'
Unsecured Exchangeable Senior Notes	'
	6. Unsecured Exchangeable Senior Notes
	On February 18, 2014, the Company repaid at maturity the $747.5 million aggregate principal amount of its 3.625% exchangeable senior notes due 2014 plus accrued and unpaid interest thereon.

Commitments_And_Contingencies

Commitments And Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments And Contingencies	'
	7. 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 of approximately $19.1 million related to lender and development requirements.
	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 (See also Note 8). 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.
	In connection with the assumption of 767 Fifth Avenue's (the General Motors Building) secured loan by the Company’s consolidated joint venture, 767 Venture, LLC, the Company guaranteed the consolidated joint venture’s obligation to fund various escrows, including tenant improvements, taxes and insurance in lieu of cash deposits. As of September 30, 2014, the maximum funding obligation under the guarantee was approximately $14.8 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.
	In connection with the mortgage financing collateralized by the Company's John Hancock Tower property located in Boston, Massachusetts, the Company has agreed to guarantee approximately $28.8 million related to its obligations to provide funds for certain tenant re-leasing costs. The mortgage financing matures on January 6, 2017.
	From time to time, the Company (or the applicable joint venture) has also agreed to guarantee portions of the principal, interest or other amounts in connection with other unconsolidated joint venture borrowings. In addition to the financial guarantees referenced above, the Company has agreed to customary environmental indemnifications and nonrecourse carve-outs (e.g., guarantees against fraud, misrepresentation and bankruptcy) on certain of its unconsolidated joint venture loans.
	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. On September 18, 2014, the Company received an initial distribution totaling approximately $7.7 million, which is included in Base Rent in the accompanying Consolidated Statements of Operations for the three and nine months ended September 30, 2014, leaving a remaining claim of approximately $37.5 million. Recently, claims of similar priority to that of the Company's remaining claim were quoted privately within a range of $0.25 to $0.26 per $1.00. The Company will continue to evaluate whether to attempt to sell the remaining claim or wait until the trustee distributes proceeds from the Lehman estate. Given the inherent uncertainties in bankruptcy proceedings, there can be no assurance as to the timing or amount of 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 September 30, 2014.
	Insurance
	The Company carries insurance coverage on its properties of types and in amounts and with deductibles that it believes are in line with coverage customarily obtained by owners of similar properties. In response to the uncertainty in the insurance market following the terrorist attacks of September 11, 2001, the Federal Terrorism Risk Insurance Act (as amended, “TRIA”) was enacted in November 2002 to require regulated insurers to make available coverage for “certified” acts of terrorism (as defined by the statute). The expiration date of TRIA was extended to December 31, 2014 by the Terrorism Risk Insurance Program Reauthorization Act of 2007 (“TRIPRA”) and the Company can provide no assurance that it will be extended further. Currently, 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. Through June 9, 2014, $1.375 billion of the Terrorism Coverage for 767 Fifth Avenue in excess of $250 million was provided by NYXP, LLC (“NYXP”), as a direct insurer. After June 9, 2014, all of the Terrorism Coverage for 767 Fifth Avenue has been provided by third party insurers. The Company also currently carries nuclear, biological, chemical and radiological terrorism insurance coverage for acts of terrorism certified under TRIA (“NBCR Coverage”), which is provided by IXP as a direct insurer, for the properties in our 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 and the Terrorism Coverage provided by NYXP are backstopped by the Federal Government if the aggregate industry insured losses resulting from a certified act of terrorism exceed a “program trigger.” The program trigger is $100.0 million and the coinsurance is 15%. Under TRIPRA, 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 TRIPRA. The Company may elect to terminate the NBCR Coverage if the Federal Government seeks recoupment for losses paid under TRIA, if there is a change in its portfolio or for any other reason. In the event TRIPRA is not extended beyond December 31, 2014, (i) the Company's $1.0 billion portfolio property insurance program and the $250 million of additional Terrorism Coverage for 601 Lexington Avenue will continue to provide Terrorism Coverage through the expiration of the program on March 1, 2015, (ii) the $1.625 billion property insurance program for 767 Fifth Avenue will continue to provide Terrorism Coverage through the expiration of the program on June 9, 2015, (iii) the Company will evaluate alternative approaches to secure coverage for acts of terrorism thereby potentially increasing our overall cost of insurance, (iv) if such insurance is not available at commercially reasonable rates with limits equal to our current coverage or at all, the Company may not continue to have full occurrence limit coverage for acts of terrorism, (v) the Company may not satisfy the insurance requirements under existing or future debt financings secured by individual properties, (vi) the Company may not be able to obtain future debt financings secured by individual properties and (vii) the Company may cancel the insurance policies issued by IXP for the NBCR Coverage. The Company intends to continue to monitor the scope, nature and cost of available terrorism insurance and maintain terrorism insurance in amounts and on terms that are commercially reasonable.
	The Company also currently carries earthquake insurance on its properties located in areas known to be subject to earthquakes in an amount and subject to self-insurance that the Company believes is commercially reasonable. In addition, this insurance is subject to a deductible in the amount of 5% of the value of the affected property. Specifically, the Company currently carries earthquake insurance which covers its San Francisco region (excluding 535 Mission Street and Salesforce Tower (formerly Transbay Tower)) with a $120 million per occurrence limit and a $120 million annual aggregate limit, $20 million of which is provided by IXP, as a direct insurer. The builders risk policy maintained for the development of 535 Mission Street in San Francisco includes a $15 million per occurrence and annual aggregate limit of earthquake coverage. In addition, the builders risk policy maintained for the development of Salesforce Tower in San Francisco includes a $60 million per occurrence and annual aggregate limit of earthquake coverage (increased from $15 million on July 29, 2014). 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 properties and the Company’s NBCR Coverage. NYXP, a captive insurance company which is a wholly-owned subsidiary of the Company, acted as a direct insurer with respect to a portion of the Company’s Terrorism Coverage for 767 Fifth Avenue through June 9, 2014. NYXP only insured losses which exceeded the program trigger under TRIA and NYXP reinsured with a third-party insurance company any coinsurance payable under TRIA. Insofar as the Company owns IXP and NYXP, it is responsible for their liquidity and capital resources, and the accounts of IXP and NYXP 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 and NYXP would also be responsible for any recoupment charges by the Federal Government in the event losses are paid out and their insurance policies are maintained after the payout by the Federal Government. If the Company experiences a loss and IXP or NYXP are required to pay under their insurance policies, the Company would ultimately record the loss to the extent of the required payment. Therefore, insurance coverage provided by IXP and NYXP should not be considered as the equivalent of third-party insurance, but rather as a modified form of self-insurance. In addition, the Company 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

Noncontrolling Interests	9 Months Ended
	Sep. 30, 2014
Noncontrolling Interest [Abstract]	'
Noncontrolling Interests	'
	8. Noncontrolling Interests
	Noncontrolling interests relate to the interests in the Company not owned by Boston Properties, Inc. and interests in consolidated property partnerships not wholly-owned by the Company. As of September 30, 2014, the noncontrolling interests in the Company consisted of 16,456,297 OP Units, 1,505,386 LTIP Units, 394,590 2012 OPP Units, 314,974 2013 MYLTIP Units, 483,555 2014 MYLTIP Units and 40,440 Series Four Preferred Units (none of which are convertible into OP Units) held by parties other than Boston Properties, Inc.
	Noncontrolling Interest—Redeemable Interest in Property Partnership
	On October 4, 2012, the Company completed the formation of a joint venture that owns and operates Fountain Square located in Reston, Virginia. The joint venture partner contributed the property valued at approximately $385.0 million and related mortgage indebtedness totaling approximately $211.3 million for a nominal 50% interest in the joint venture. The Company contributed cash totaling approximately $87.0 million for its nominal 50% interest, which cash was distributed to the joint venture partner. Pursuant to the joint venture agreement (i) the Company has rights to acquire the partner's nominal 50% interest and (ii) the partner has the right to cause the Company to acquire the partner's interest on January 4, 2016, in each case at a fixed price totaling approximately $102.0 million in cash. The fixed price option rights expire on January 31, 2016. The Company is consolidating this joint venture due to the Company's right to acquire the partner's nominal 50% interest. The Company initially recorded the noncontrolling interest at its acquisition-date fair value as temporary equity, due to the redemption option existing outside the control of the Company. The Company will accrete the changes in the redemption value quarterly over the period from the acquisition date to the earliest redemption date using the effective interest method.  The Company will record the accretion after the allocation of net income and distributions of cash flow to the noncontrolling interest account balance.
	The following table reflects the activity of the noncontrolling interest—redeemable interest in property partnership in the Company's Fountain Square consolidated joint venture for the nine months ended September 30, 2014 and 2013 (in thousands):
	Balance at January 1, 2014	$	99,609
	Net loss	(519		)
	Distributions	(4,300		)
	Adjustment to reflect redeemable interest at redemption value	9,315			-1
	Balance at September 30, 2014	$	104,105
	Balance at January 1, 2013	$	97,558
	Net loss	(1,523		)
	Distributions	(3,935		)
	Adjustment to reflect redeemable interest at redemption value	6,549
	Balance at September 30, 2013	$	98,649
	_______________
	(1) Includes an out-of-period adjustment totaling approximately $1.9 million (See Note 2).
	Noncontrolling Interest—Redeemable Preferred Units of the Company
	On March 11, 2014, the Company’s general partner notified the holders of the outstanding Series Two Preferred Units that it had elected to redeem all of such Series Two Preferred Units on May 12, 2014. As a result of the Company's election to redeem the units, all of the holders of the Series Two Preferred Units elected to convert such units into 1.312336 OP Units, or an aggregate of 874,168 OP Units, on or before May 12, 2014. As of May 12, 2014, the holders of all remaining 666,116 Series Two Preferred Units of partnership interest in the Company converted such units into an aggregate of 874,168 OP Units. The Series Two Preferred Units bore a preferred distribution equal to the greater of (1) the distribution which would have been paid in respect of the Series Two Preferred Unit had such Series Two Preferred Unit been converted into an OP Unit (including both regular and special distributions) or (2) 6.00% per annum on a liquidation preference of $50.00 per unit, and were convertible into OP Units at a rate of $38.10 per Preferred Unit (1.312336 OP Units for each Preferred Unit). In connection with the conversion of the remaining Series Two Preferred Units in May 2014, the Company paid accrued and unpaid distributions which included the special cash distribution on an as-converted basis. On February 18, 2014, the Company paid a distribution on its outstanding Series Two Preferred Units of $0.85302 per unit. Due to the holders' redemption option existing outside the control of the Company’s general partner, the Series Two Preferred Units were presented outside of permanent equity in the Company's Consolidated Balance Sheets.
	The Preferred Units at September 30, 2014 consisted of 40,440 Series Four Preferred Units, which bear a preferred distribution equal to 2.00% per annum on a liquidation preference of $50.00 per unit and are not convertible into OP Units. The holders of Series Four Preferred Units have the right, at certain times and subject to certain conditions set forth in the Certificate of Designations establishing the rights, limitations and preferences of the Series Four Preferred Units, to require the Company to redeem all their units for cash at the redemption price of $50.00 per unit. The Company also has the right, at certain times and subject to certain conditions, to redeem all of the Series Four Preferred Units for cash at the redemption price of $50.00 per unit. In order to secure the performance of certain post-issuance obligations by the holders, all of such outstanding Series Four Preferred Units were subject to forfeiture pursuant to the terms of a pledge agreement and not eligible for redemption until and unless such security interest is released. On May 19, 2014, the Company released to the holders 319,687 Series Four Preferred Units that were previously subject to the security interest. On July 3, 2014, the Company redeemed such units for cash totaling approximately $16.0 million, plus accrued and unpaid distributions. An aggregate of 40,440 Series Four Preferred Units remain outstanding and subject to the security interest under the pledge agreement (See Note 13). Due to the holders' redemption option existing outside the control of the Company, the Series Four Preferred Units are not included in Partners' Capital in the Company's Consolidated Balance Sheets.
	On February 18, 2014, the Company paid a distribution on its outstanding Series Four Preferred Units of $0.25 per unit. On May 15, 2014, the Company paid a distribution on its outstanding Series Four Preferred Units of $0.25 per unit. On August 15, 2014, the Company paid a distribution on its outstanding Series Four Preferred Units of $0.25 per unit.
	The following table reflects the activity of the noncontrolling interests—redeemable preferred units of the Company for the nine months ended September 30, 2014 and 2013 (in thousands):
	Balance at January 1, 2014	$	105,746
	Net income	1,014
	Distributions	(1,014		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(15,984		)
	Reallocation of partnership interest (1)	(87,740		)
	Balance at September 30, 2014	$	2,022
	Balance at January 1, 2013	$	199,378
	Net income	3,385
	Distributions	(3,385		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(43,070		)
	Reallocation of partnership interest	1,425
	Balance at September 30, 2013	$	157,733
	_______________
	(1) Includes the conversion of the remaining 666,116 Series Two Preferred Units into 874,168 OP Units during the nine months ended September 30, 2014.
	Noncontrolling Interest—Common Units of the Company
	During the nine months ended September 30, 2014, 70,422 OP Units were presented by the holders for redemption (including 67,368 OP Units issued upon conversion of LTIP Units) and were redeemed by Boston Properties, Inc. in exchange for an equal number of shares of Common Stock.
	At September 30, 2014, the Company had outstanding 394,590 2012 OPP Units, 314,974 2013 MYLTIP Units and 483,555 2014 MYLTIP Units. Prior to the measurement date (February 6, 2015 for 2012 OPP Units, February 4, 2016 for 2013 MYLTIP Units and February 3, 2017 for 2014 MYLTIP Units), holders of OPP Units and 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 OPP Units and MYLTIP Units, both vested and unvested, that OPP and 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 January 31, 2014, the measurement period for the Company’s 2011 OPP Unit awards expired and Boston Properties, Inc.'s TRS was not sufficient for employees to earn and therefore become eligible to vest in any of the 2011 OPP Unit awards. As a result, the Company accelerated the then remaining unrecognized compensation expense totaling approximately $1.2 million during the nine months ended September 30, 2014. Accordingly, all 2011 OPP Unit awards were automatically forfeited.
	On January 29, 2014, the Company paid a special cash distribution on the OP Units and LTIP Units in the amount of $2.25 per unit, a regular quarterly cash distribution on the OP Units and LTIP Units in the amount of $0.65 per unit, and a regular quarterly distribution on the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units in the amount of $0.065 per unit, to holders of record as of the close of business on December 31, 2013. The special cash distribution was in addition to the regular quarterly distribution on the OP Units and LTIP Units. Holders of the 2011 OPP Units, 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units are not entitled to receive any special distributions. On April 30, 2014, the Company paid a distribution on the OP Units and LTIP Units in the amount of $0.65 per unit, and a distribution on the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units in the amount of $0.065 per unit, to holders of record as of the close of business on March 31, 2014. On July 31, 2014, the Company paid a distribution on the OP Units and LTIP Units in the amount of $0.65 per unit, and a distribution on the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units in the amount of $0.065 per unit, to holders of record as of the close of business on June 30, 2014. On September 11, 2014, Boston Properties, Inc., as general partner of the Company, declared a distribution on the OP Units and LTIP Units in the amount of $0.65 per unit and a distribution on the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units in the amount of $0.065 per unit, in each case payable on October 31, 2014 to holders of record as of the close of business on September 30, 2014.
	The following table reflects the activity of the noncontrolling interests—redeemable common units for the nine months ended September 30, 2014 and 2013 (in thousands):
	Balance at January 1, 2014	$	1,710,218
	Contributions	23,990
	Net income	29,819
	Distributions	(34,426		)
	Conversion of redeemable partnership units	(2,368		)
	Unearned compensation	(6,952		)
	Accumulated other comprehensive loss	191
	Adjustment to reflect redeemable partnership units at redemption value	358,772
	Balance at September 30, 2014	$	2,079,244
	Balance at January 1, 2013	$	1,836,522
	Contributions	26,384
	Net income	74,395
	Distributions	(33,956		)
	Conversion of redeemable partnership units	(10,406		)
	Unearned compensation	(2,262		)
	Accumulated other comprehensive loss	189
	Adjustment to reflect redeemable partnership units at redemption value	(52,323		)
	Balance at September 30, 2013	$	1,838,543
	Pursuant to the Company’s partnership agreement, certain limited partners in the Company have the right to redeem all or any portion of their interest for cash from the Company. However, Boston Properties, Inc. may elect to acquire the limited partner’s interest by issuing its Common Stock in exchange for the interest. The amount of cash to be paid to the limited partner if the redemption right is exercised and Boston Properties, Inc. does not elect to issue its Common Stock is based on the trading price of Boston Properties, Inc.’s common stock at that time. Due to the redemption option existing outside the control of the Company, such limited partners’ units are not included in Partners’ Capital. The value of the OP Units not owned by Boston Properties, Inc. (including LTIP Units assuming that all conditions had been met for the conversion thereof), assuming all of such units had been redeemed at September 30, 2014 was approximately $2.1 billion based on the closing price of Boston Properties, Inc.’s common stock of $115.76 per share.
	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 $716.6 million at September 30, 2014 and approximately $726.1 million at December 31, 2013, are included in Noncontrolling Interests—Property Partnerships on the accompanying Consolidated Balance Sheets.
On February 7, 2013, the partner in the Company's Salesforce Tower (formerly Transbay Tower) joint venture issued a notice that it was electing under the joint venture agreement to reduce its nominal ownership interest in the venture from 50% to 5%. On February 26, 2013, the Company issued a notice to the partner electing to proceed with the venture on that basis. As a result, the Company has a 95% nominal interest in and is consolidating the joint venture. Under the joint venture agreement, if certain return thresholds are achieved the partner will be entitled to an additional promoted interest. In addition, 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), then the partner has the option to require the Company to fund up to 2.5% of the total project costs (i.e., of 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 construction loan interest rates. Also, under the agreement, (1) the partner has the right to cause the Company to purchase the partner's interest after the defined stabilization date and (2) the Company has the right to acquire the partner's interest on the third anniversary of the stabilization date, in each case at an agreed upon purchase price or appraised value.
On May 31, 2013, the Company's two joint venture partners in 767 Venture, LLC (the entity that owns 767 Fifth Avenue(the General Motors Building) in New York City) transferred all of their interests in the joint venture to third parties. In connection with the transfer, the Company and its new joint venture partners modified the Company's relative decision making authority and consent rights with respect to the joint venture's assets and operations. These changes resulted in the Company having sufficient financial and operating control over 767 Venture, LLC such that the Company now accounts for the assets, liabilities and operations of 767 Venture, LLC on a consolidated basis in its financial statements instead of under the equity method of accounting. Upon consolidation, the Company recognized the new joint venture partners' aggregate 40% equity interest at its aggregate fair value of approximately $480.9 million within Noncontrolling Interests—Property Partnerships on the accompanying Consolidated Balance Sheets.
On October 9, 2013, the Company completed the sale of a 45% ownership interest in its Times Square Tower property for a gross sale price of $684.0 million in cash. Net cash proceeds totaled approximately $673.1 million, after the payment of transaction costs. In connection with the sale, the Company formed a joint venture with the buyer and will provide customary property management and leasing services to the joint venture. Times Square Tower is an approximately 1,246,000 net rentable square foot Class A office tower located in New York City. The transaction did not qualify as a sale of real estate for financial reporting purposes because the Company continues to control the joint venture and will therefore continue to account for the entity on a consolidated basis in its financial statements. The Company has accounted for the transaction as an equity transaction and has recognized noncontrolling interest in its Consolidated Balance Sheets totaling approximately $243.5 million, which is equal to 45% of the carrying value of the total equity of the property immediately prior to the transaction.
The following table reflects the activity of the noncontrolling interests in property partnerships for the nine months ended September 30, 2014 and 2013 (in thousands):
Balance at January 1, 2014	$	726,132
Capital contributions	2,980
Net income	8,677
Distributions	(21,224		)
Balance at September 30, 2014	$	716,565
Balance at January 1, 2013	$	(1,964	)
Fair value of capital recorded upon consolidation	480,861
Capital contributions	10,932
Net income (loss)	(5,950		)
Distributions	(2,250		)
Balance at September 30, 2013	$	481,629

Partners_Capital

Partners' Capital	9 Months Ended
	Sep. 30, 2014
Partners' Capital [Abstract]	'
Partners' Capital	'
	9. Partners’ Capital
	As of September 30, 2014, Boston Properties, Inc. owned 1,710,615 general partnership units and 151,389,171 limited partnership units.
	On June 3, 2014, Boston Properties, Inc. established a new “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 Boston Properties, Inc.'s prior $600.0 million ATM stock offering program that expired on June 2, 2014 with approximately $305.3 million of unsold common stock. Boston Properties, Inc. intends to use the net proceeds from any offering for general business purposes, which may include investment opportunities and debt reduction. Boston Properties, Inc. contributes the net proceeds from any such sales to the Company in exchange for a number of OP Units equal to the number of shares issued. No shares of common stock have been issued under this new ATM stock offering program.
	During the nine months ended September 30, 2014, Boston Properties, Inc. acquired 70,422 OP Units in connection with the redemption of an equal number of redeemable OP Units from third parties.
	During the nine months ended September 30, 2014, the Company issued 17,124 OP Units to Boston Properties, Inc. in connection with the exercise by certain employees of options to purchase Common Stock of Boston Properties, Inc.
	On January 29, 2014, the Company paid a special cash distribution and regular quarterly distribution aggregating $2.90 per OP Unit to unitholders of record as of the close of business on December 31, 2013. On April 30, 2014, the Company paid a distribution of $0.65 per OP Unit to unitholders of record as of the close of business on March 31, 2014. On July 31, 2014, the Company paid a distribution of $0.65 per OP Unit to unitholders of record as of the close of business on June 30, 2014. On September 11, 2014, Boston Properties, Inc.'s Board of Directors declared a distribution of $0.65 per OP Unit payable on October 31, 2014 to unitholders of record as of the close of business on September 30, 2014.
	As of September 30, 2014, 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. contributed the net proceeds of the offering to the Company in exchange for 80,000 Series B Preferred Units having terms and preferences generally mirroring those of the Series B Preferred Stock. 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. may not 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 or 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., the Company or its affiliates.
	On February 18, 2014, the Company paid a distribution on its outstanding Series B Preferred Units of $32.8125 per unit. On May 15, 2014, the Company paid a distribution on its outstanding Series B Preferred Units of $32.8125 per unit. On August 15, 2014, the Company paid a distribution on its outstanding Series B Preferred Units of $32.8125 per unit. On September 11, 2014, Boston Properties, Inc.'s Board of Directors declared a distribution of $32.8125 per Series B Preferred Unit payable on November 17, 2014 to shareholders of record as of the close of business on November 5, 2014.

Earnings_Per_Common_Unit

Earnings Per Common Unit	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Earnings Per Common Unit	'
	10. Earnings Per Common Unit
	The following table provides a reconciliation of both the net income attributable to Boston Properties Limited Partnership 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 by the weighted-average number of common units outstanding during the period. The terms of the Series Two Preferred Units enable the holders to obtain OP Units of the Company and as a result these are considered participating securities. 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 the Company’s LTIP Units, 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 OPP Units and 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, the Company 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 17,665,000 and 16,829,000 redeemable common units for the three months ended September 30, 2014 and 2013, respectively, and approximately 17,263,000 and 16,975,000 redeemable common units for the nine months ended September 30, 2014 and 2013, respectively.
		For the three months ended September 30, 2014
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties Limited Partnership	$	144,715		170,785	$	0.85
	Allocation of undistributed earnings to participating securities	(70		)	—	—
	Net income attributable to Boston Properties Limited Partnership	$	144,645		170,785	$	0.85
	Effect of Dilutive Securities:
	Stock Based Compensation	—			153	—
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	144,645		170,938	$	0.85
		For the three months ended September 30, 2013
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties Limited Partnership	$	83,898		169,236	$	0.5
	Discontinued operations attributable to Boston Properties Limited Partnership	90,242			—	0.53
	Allocation of undistributed earnings to participating securities	(651		)	—	—
	Net income attributable to Boston Properties Limited Partnership	$	173,489		169,236	$	1.03
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			285	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	173,489		169,521	$	1.02
		For the nine months ended September 30, 2014
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	294,370		170,340	$	1.73
	Effect of Dilutive Securities:
	Stock Based Compensation	—			151	—
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	294,370		170,491	$	1.73
		For the nine months ended September 30, 2013
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties Limited Partnership	$	626,317		168,975	$	3.71
	Discontinued operations attributable to Boston Properties Limited Partnership	113,935			—	0.67
	Allocation of undistributed earnings to participating securities	(4,183		)	—	(0.02		)
	Net income attributable to Boston Properties Limited Partnership	$	736,069		168,975	$	4.36
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			381	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	736,069		169,356	$	4.35

Stock_Option_and_Incentive_Pla

Stock Option and Incentive Plan	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock Option and Incentive Plan	'
	11. Stock Option and Incentive Plan
	On January 27, 2014, Boston Properties, Inc.'s Compensation Committee approved the 2014 MYLTIP awards under Boston Properties, Inc.'s 2012 Plan to certain officers and employees of Boston Properties, Inc. The 2014 MYLTIP awards utilize TRS over a three-year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards, if any, will be based on Boston Properties, Inc.'s TRS relative to (i) the Cohen & Steers Realty Majors Portfolio Index (50% weight) and (ii) the NAREIT Office Index adjusted to exclude Boston Properties, Inc. (50% weight). Earned awards will range from $0 to a maximum of approximately $40.2 million depending on the Boston Properties, Inc.'s TRS relative to the two indices, with four tiers (threshold: approximately $6.7 million; target: approximately $13.4 million; high: approximately $26.8 million; and exceptional: approximately $40.2 million) and linear interpolation between tiers. Earned awards measured on the basis of relative TRS performance are subject to an absolute TRS component in the form of relatively simple modifiers that (A) reduce the level of earned awards in the event Boston Properties, Inc.'s annualized TRS is less than 0% and (B) cause some awards to be earned in the event Boston Properties, Inc.'s annualized TRS is more than 12% even though on a relative basis alone Boston Properties, Inc.'s TRS would not result in any earned awards.
	Earned awards (if any) will vest 50% on February 3, 2017 and 50% on February 3, 2018, 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, termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 3, 2017, earned awards will be calculated as of the date of the change of control based upon performance through such date as measured against performance hurdles (without proration). The 2014 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 the FASB's ASC 718 “Compensation-Stock Compensation” the 2014 MYLTIP awards have an aggregate value of approximately $12.7 million, which amount will generally be amortized into earnings over the four-year plan period under the graded vesting method.
	On January 31, 2014, the measurement period for the Company’s 2011 OPP Unit awards expired and Boston Properties, Inc.'s TRS was not sufficient for employees to earn and therefore become eligible to vest in any of the 2011 OPP Unit awards. As a result, the Company accelerated the then remaining unrecognized compensation expense totaling approximately $1.2 million during the nine months ended September 30, 2014. Accordingly, all 2011 OPP Unit awards were automatically forfeited.
	During the nine months ended September 30, 2014, Boston Properties, Inc. issued 23,968 shares of restricted common stock, no non-qualified stock options and the Company issued 127,094 LTIP Units and 485,459 2014 MYLTIP Units to employees and non-employee directors under the 2012 Plan. Employees and non-employee directors paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit and 2014 MYLTIP Unit. An LTIP Unit is generally the economic equivalent of a share of restricted stock in Boston Properties, Inc. 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, as adjusted for forfeitures, 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 nine months ended September 30, 2014 were valued at approximately $2.6 million ($109.27 per share weighted-average). The LTIP Units granted were valued at approximately $12.8 million ($100.61 per unit weighted-average fair value) using a Monte Carlo simulation method model. The per unit fair value of each LTIP Unit granted was estimated on the date of grant using the following assumptions: an expected life of 5.7 years, a risk-free interest rate of 1.84% and an expected price volatility of 27%. As the 2011 OPP Units, 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units are subject to both a service condition and a market condition, the Company recognizes the compensation expense related to the 2011 OPP Units, 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units 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. Dividends paid on both vested and unvested shares of restricted stock are charged directly to Partners’ Capital in the Consolidated Balance Sheets. Aggregate stock-based compensation expense associated with restricted stock, non-qualified stock options, LTIP Units, 2011 OPP Units, 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units was approximately $5.0 million and $6.2 million for the three months ended September 30, 2014 and 2013, respectively, and approximately $21.0 million and $38.1 million for the nine months ended September 30, 2014 and 2013, respectively. On January 31, 2014, the measurement period for the Company’s 2011 OPP Awards expired and Boston Properties, Inc.'s TRS was not sufficient for employees to earn and therefore become eligible to vest in any of the 2011 OPP Awards. As a result, the Company accelerated the then remaining unrecognized compensation expense totaling approximately $1.2 million. For the three and nine months ended September 30, 2013, stock-based compensation expense includes approximately $1.6 million and $20.2 million, respectively, consisting of the acceleration of the expense of Boston Properties, Inc.’s Executive Chairman’s stock-based compensation awards and the stock-based compensation awards associated with his transition benefits agreement related to Boston Properties, Inc.'s succession planning. At September 30, 2014, there was $19.7 million of unrecognized compensation expense related to unvested restricted stock and LTIP Units and $16.5 million of unrecognized compensation expense related to unvested 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 2.9 years.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	12. Segment Information
	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. Beginning on January 1, 2014, the properties that were historically part of the Princeton region are reflected as the suburban component of the New York region. Therefore, the operations for the Princeton region have been included in the New York region. Accordingly, amounts reflected below for the New York region have been adjusted to reflect the Company's retrospective inclusion of the Princeton region in the New York region. The Company’s segments by geographic area are Boston, New York, San Francisco and Washington, DC. Segments by property type include: Class A Office, Office/Technical, Residential and Hotel.
	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. Interest and other income, development and management services income, general and administrative expenses, transaction costs, impairment loss, interest expense, depreciation and amortization expense, gains (losses) from investments in securities, gains (losses) from early extinguishments of debt, income from unconsolidated joint ventures, gains on consolidation of joint ventures, discontinued operations, gains on sales of real estate and noncontrolling interests are not included in Net Operating Income as internal reporting addresses these items on a corporate level.
	Net Operating Income is not a measure of operating results or cash flows from operating activities as measured by accounting principles generally accepted in the United States of America, and it is not indicative of cash available to fund cash needs and should not be considered an alternative to cash flows as a measure of liquidity. All companies may not calculate Net Operating Income in the same manner. The Company considers Net Operating Income to be an appropriate supplemental measure to net income because it helps both investors and management to understand the core operations of the Company’s properties. The Company's management also uses Net Operating Income to evaluate regional property level performance and to make decisions about resource allocations. Further, the Company believes Net Operating Income is useful to investors as a performance measure because, when compared across periods, Net Operating Income reflects the impact on operations from trends in occupancy rates, rental rates, operating costs and acquisition and development activity on an unleveraged basis, providing perspectives not immediately apparent from net income attributable to Boston Properties Limited Partnership.
	On May 31, 2013, the Company's two joint venture partners in 767 Venture, LLC (the entity that owns 767 Fifth Avenue (the General Motors Building) located in New York City) transferred all of their interests in the joint venture to third parties. Effective as of May 31, 2013, the Company accounts for the assets, liabilities and operations of 767 Venture, LLC on a consolidated basis in its financial statements instead of under the equity method of accounting. Upon consolidation, the operations for this building are included in the New York region.
	Information by geographic area and property type (dollars in thousands):
	For the three months ended September 30, 2014:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	176,788		$	243,033		$	61,691		$	96,219		$	577,731
	Office/Technical	6,056			—			5,892			3,713			15,661
	Residential	1,137			—			—			5,881			7,018
	Hotel	11,918			—			—			—			11,918
	Total	195,899			243,033			67,583			105,813			612,328
	% of Grand Totals	31.99		%	39.69		%	11.04		%	17.28		%	100		%
	Rental Expenses:
	Class A Office	69,026			82,335			22,484			32,898			206,743
	Office/Technical	1,901			—			1,363			1,009			4,273
	Residential	509			—			—			3,654			4,163
	Hotel	7,585			—			—			—			7,585
	Total	79,021			82,335			23,847			37,561			222,764
	% of Grand Totals	35.47		%	36.96		%	10.71		%	16.86		%	100		%
	Net operating income	$	116,878		$	160,698		$	43,736		$	68,252		$	389,564
	% of Grand Totals	30		%	41.25		%	11.23		%	17.52		%	100		%
	For the three months ended September 30, 2013:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	170,415		$	214,086		$	53,841		$	96,141		$	534,483
	Office/Technical	5,662			—			5,839			3,877			15,378
	Residential	1,125			—			—			4,368			5,493
	Hotel	10,652			—			—			—			10,652
	Total	187,854			214,086			59,680			104,386			566,006
	% of Grand Totals	33.19		%	37.83		%	10.54		%	18.44		%	100		%
	Rental Expenses:
	Class A Office	67,228			73,355			20,006			31,678			192,267
	Office/Technical	1,763			—			1,287			1,064			4,114
	Residential	466			—			—			2,441			2,907
	Hotel	6,580			—			—			—			6,580
	Total	76,037			73,355			21,293			35,183			205,868
	% of Grand Totals	36.94		%	35.63		%	10.34		%	17.09		%	100		%
	Net operating income	$	111,817		$	140,731		$	38,387		$	69,203		$	360,138
	% of Grand Totals	31.05		%	39.08		%	10.66		%	19.21		%	100		%
	For the nine months ended September 30, 2014:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	520,857		$	684,240		$	173,749		$	287,489		$	1,666,335
	Office/Technical	17,788			—			18,451			11,044			47,283
	Residential	3,389			—			—			15,609			18,998
	Hotel	32,478			—			—			—			32,478
	Total	574,512			684,240			192,200			314,142			1,765,094
	% of Grand Totals	32.55		%	38.76		%	10.89		%	17.8		%	100		%
	Rental Expenses:
	Class A Office	206,242			231,668			63,078			98,818			599,806
	Office/Technical	5,326			—			3,885			3,335			12,546
	Residential	1,501			—			—			10,360			11,861
	Hotel	21,697			—			—			—			21,697
	Total	234,766			231,668			66,963			112,513			645,910
	% of Grand Totals	36.35		%	35.86		%	10.37		%	17.42		%	100		%
	Net operating income	$	339,746		$	452,572		$	125,237		$	201,629		$	1,119,184
	% of Grand Totals	30.36		%	40.43		%	11.19		%	18.02		%	100		%
For the nine months ended September 30, 2013:
	Boston			New York			San			Washington,			Total
							Francisco			DC
Rental Revenue:
Class A Office	$	495,376		$	510,767		$	159,843		$	284,554		$	1,450,540
Office/Technical	16,853			—			11,317			11,951			40,121
Residential	3,257			—			—			13,298			16,555
Hotel	30,061			—			—			—			30,061
Total	545,547			510,767			171,160			309,803			1,537,277
% of Grand Totals	35.49		%	33.23		%	11.13		%	20.15		%	100		%
Rental Expenses:
Class A Office	195,206			177,800			58,036			94,145			525,187
Office/Technical	5,177			—			2,439			3,095			10,711
Residential	1,316			—			—			7,154			8,470
Hotel	20,959			—			—			—			20,959
Total	222,658			177,800			60,475			104,394			565,327
% of Grand Totals	39.38		%	31.45		%	10.7		%	18.47		%	100		%
Net operating income	$	322,889		$	332,967		$	110,685		$	205,409		$	971,950
% of Grand Totals	33.22		%	34.26		%	11.39		%	21.13		%	100		%
The following is a reconciliation of Net Operating Income to net income attributable to Boston Properties Limited Partnership:
	Three months ended						Nine months ended September 30,
	September 30,
	2014			2013			2014			2013
	(in thousands)
Net Operating Income	$	389,564		$	360,138		$	1,119,184		$	971,950
Add:
Development and management services income	6,475			5,475			18,197			22,063
Income from unconsolidated joint ventures	4,419			14,736			10,069			72,240
Gains on consolidation of joint ventures	—			(1,810		)	—			385,991
Interest and other income	3,421			3,879			6,841			6,646
Gains (losses) from investments in securities	(297		)	956			651			1,872
Gains (losses) from early extinguishments of debt	—			(30		)	—			122
Income from discontinued operations	—			1,677			—			7,486
Gain on sale of real estate from discontinued operations	—			88,565			—			88,565
Gain on forgiveness of debt from discontinued operations	—			—			—			20,736
Gains on sales of real estate	41,937			—			41,937			—
Less:
General and administrative expense	22,589			24,841			75,765			94,673
Transaction costs	1,402			766			2,500			1,744
Depreciation and amortization expense	155,217			151,216			460,064			400,131
Interest expense	113,308			122,173			337,839			325,746
Impairment loss	—			—			—			4,401
Impairment loss from discontinued operations	—			—			—			2,852
Noncontrolling interest in property partnerships	5,566			(3,279		)	17,473			(924		)
Noncontrolling interest—redeemable preferred units	2,722			3,729			8,868			8,796
Net income attributable to Boston Properties Limited Partnership	$	144,715		$	174,140		$	294,370		$	740,252

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	13. Subsequent Events
	On October 2, 2014, the Company completed the sale of its Patriots Park properties located in Reston, Virginia for a gross sale price of $321.0 million, which exceeded the carrying value of the properties. Patriots Park consists of three Class A office properties aggregating approximately 706,000 net rentable square feet.
	On October 16, 2014, the Company released to the holders 27,773 Series Four Preferred Units that were previously subject to a security interest under a pledge agreement (See Note 8). On November 5, 2014, the Company redeemed such units for cash totaling approximately $1.4 million. An aggregate of 12,667 Series Four Preferred Units remain outstanding and subject to the security interest under the pledge agreement.
	On October 22, 2014, MIT exercised its right to purchase the Company’s 415 Main Street property (formerly Seven Cambridge Center) located in Cambridge, Massachusetts on February 1, 2016 for approximately $106 million.  As part of its lease signed on July 14, 2004, MIT was granted a fixed price option to purchase the building at the beginning of the 11th lease year. 415 Main Street is an Office/Technical property with approximately 231,000 net rentable square feet occupied by the Broad Institute.  The sale is subject to the satisfaction of customary closing conditions and there can be no assurance that the sale will be consummated on the terms currently contemplated or at all.
	On October 24, 2014, the Company completed the sale of a parcel of land at 130 Third Avenue in Waltham, Massachusetts that is permitted for 129,000 square feet for a sale price of approximately $14.3 million, which exceeded the carrying value of the property.
	On October 24, 2014, a joint venture in which the Company has a 50% interest extended the loan collateralized by its Annapolis Junction Building Six property. At the time of the extension, the outstanding balance of the construction loan totaled approximately $13.9 million and bore interest at a variable rate equal to LIBOR plus 1.65% per annum and was scheduled to mature on November 17, 2014. The extended loan has a total commitment amount of $16.4 million, bears interest at a variable rate equal to LIBOR plus 2.25% per annum and matures on November 17, 2015. Annapolis Junction Building Six is a Class A office property with approximately 119,000 net rentable square feet located in Annapolis, Maryland.
	On October 30, 2014, the Company completed the sale of a 45% interest in each of 601 Lexington Avenue in New York City and Atlantic Wharf Office Building and 100 Federal Street in Boston for an aggregate gross sales price of approximately $1.827 billion in cash, less the partner’s pro rata share of the indebtedness secured by 601 Lexington Avenue, subject to certain prorations and adjustments. In connection with the sale, the Company formed a joint venture for each property with the buyer and will provide customary property management and leasing services to the joint ventures. 601 Lexington Avenue is a 1,669,000 square foot Class A office complex located in Midtown Manhattan. The property consists of a 59-story tower as well as a six-story low-rise office and retail building. The property is subject to existing mortgage indebtedness of approximately $712.9 million. The Atlantic Wharf Office Building is a 791,000 square foot Class A office tower located on Boston's Waterfront. 100 Federal Street is a 1,323,000 square foot Class A office tower located in Boston's Financial District. The transaction did not qualify as a sale of real estate for financial reporting purposes as the Company continues to control the joint ventures and will therefore continue to account for the properties on a consolidated basis in its financial statements.
	On November 1, 2014, the Company partially placed in-service 535 Mission Street, a Class A office project with approximately 307,000 net rentable square feet located in San Francisco, California.
	On November 3, 2014, the Company issued notices to redeem on December 15, 2014 (i) $300.0 million in aggregate principal amount of its 5.625% senior notes due 2015, which were scheduled to mature on April 15, 2015 (the “5.625% Notes”), and (ii) $250.0 million in aggregate principal amount of its 5.000% senior notes due 2015, which were scheduled to mature on June 1, 2015 (the “5.000% Notes”). The redemption price for each of the notes will equal the sum of (a) the present values as of the redemption date of the remaining scheduled payments of principal and interest from the redemption date to maturity (excluding any accrued and unpaid interest) discounted on a semi-annual basis at a rate equal to the yield to maturity of a comparable United States Treasury security plus (i) in the case of the 5.625% Notes, 0.35%, or (ii) in the case of the 5.000% Notes, 0.25%, plus (b) accrued interest to, but excluding, December 15, 2014, as provided in the applicable indenture. The redemption price for each series of notes will be calculated three business days prior to the redemption date and will be payable on December 15, 2014 in accordance with the terms of the applicable indentures.
	On November 6, 2014, the Company entered into an option agreement pursuant to which the Company has been granted an option to purchase real property located at 425 Fourth Street in San Francisco, California.  In connection with the execution of the agreement, the Company paid a non-refundable option payment to the current owner of $1.0 million.   The Company intends to pursue the entitlements necessary to develop the property.  The purchase price has not been determined and is dependent on the entitlements obtained.   There can be no assurance that the Company will be successful in obtaining the desired entitlements or that it will ultimately determine to exercise the option.

Basis_Of_Presentation_And_Summ1

Basis Of Presentation And Summary Of Significant Accounting Policies Recent Accounting Pronouncement (Policies)	9 Months Ended
	Sep. 30, 2014
Recent Accounting Pronouncement [Abstract]	'
Recent Accounting Pronouncement [Policy Text Block]	'
	Recent Accounting Pronouncements
	On April 10, 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") No. 2014-08, "Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity" (“ASU No. 2014-08”). ASU No. 2014-08 clarifies that discontinued operations presentation applies only to disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results (e.g., a disposal of a major geographical area, a major line of business, a major equity method investment or other major parts of an entity). ASU No. 2014-08 is effective prospectively for reporting periods beginning after December 15, 2014. Early adoption is permitted, and the Company early adopted ASU No. 2014-08 during the first quarter of 2014. The Company’s adoption of ASU No. 2014-08 did not have a material impact on its consolidated financial statements.
	In May 2014, the FASB issued ASU 2014-09, "Revenue from Contract 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 and will supersede 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. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB's Accounting Standards Codification ("ASC"). ASU 2014-09 is effective for annual reporting periods (including interim periods within that reporting period) beginning after December 15, 2016 and shall be applied using either a full retrospective or modified retrospective approach. Early adoption is not permitted. The Company is currently assessing the potential impact that the adoption of ASU 2014-09 will have on its consolidated financial statements.
	In June 2014, the FASB issued ASU No. 2014-12, “Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period” (“ASU 2014-12”). The amendments in ASU 2014-12 require that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. A reporting entity should apply existing guidance in ASC Topic No. 718, “Compensation - Stock Compensation” (“ASC 718”), as it relates to awards with performance conditions that affect vesting to account for such awards. The amendments in ASU 2014-12 are effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Early adoption is permitted. Entities may apply the amendments in ASU 2014-12 either: (a) prospectively to all awards granted or modified after the effective date; or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. The Company does not expect the adoption of ASU 2014-12 to have a material impact on its consolidated financial statements.
	In August 2014, the FASB issued ASU No. 2014-15, "Presentation of Financial Statements - Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern" (“ASU 2014-15”). ASU 2014-15 requires an entity to evaluate whether there are conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued (or within one year after the financial statements are available to be issued when applicable) and to provide related footnote disclosures in certain circumstances. ASU 2014-15 is effective for the annual period ending after December 15, 2016, and for annual and interim periods thereafter with early adoption permitted. The Company does not expect the adoption of ASU 2014-15 to have a material impact on its consolidated financial statements.

Basis_Of_Presentation_And_Summ2

Basis Of Presentation And Summary Of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2014
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 indebtedness and the Company’s corresponding estimate of fair value as of September 30, 2014 and December 31, 2013 (in thousands):
		September 30, 2014				December 31, 2013
		Carrying		Estimated		Carrying			Estimated
		Amount		Fair Value		Amount			Fair Value
	Mortgage notes payable	$	4,328,464	$	4,460,353	$	4,449,734		$	4,545,283
	Mezzanine notes payable	310,114		310,141		311,040			311,064
	Unsecured senior notes	5,837,172		6,173,499		5,835,854			6,050,517
	Unsecured exchangeable senior notes	—		—		744,880		-1	750,266
	Total	$	10,475,750	$	10,943,993	$	11,341,508		$	11,657,130
	_______________
	-1	Includes the net adjustment for the equity component allocation totaling approximately $2.4 million at December 31, 2013.

Real_Estate_Activity_During_th1

Real Estate Activity During the Nine Months Ended September 30, 2014 (Tables)	9 Months Ended
	Sep. 30, 2014
Real Estate [Abstract]	'
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	'
	The Company did not have any dispositions during the three and nine months ended September 30, 2014 that qualified for discontinued operations presentation. The following table summarizes the income from discontinued operations for the three and nine months ended September 30, 2013 related to One Preserve Parkway, 10 & 20 Burlington Mall Road, 1301 New York Avenue, Montvale Center and 303 Almaden Boulevard and the related gain on sale of real estate, gain on forgiveness of debt and impairment loss:
		For the three months ended September 30,		For the nine months ended September 30,
		2013		2013
		(in thousands)
	Total revenue	$	4,112	$	17,962
	Expenses
	Operating	1,495		6,290
	Depreciation and amortization	940		3,826
	Total expenses	2,435		10,116
	Operating income	1,677		7,846
	Other expense
	Interest expense	—		360
	Income from discontinued operations	$	1,677	$	7,486
	Gain on sale of real estate from discontinued operations	$	88,565	$	88,565
	Gain on forgiveness of debt from discontinued operations	$	—	$	20,736
	Impairment loss from discontinued operations	$	—	$	(2,852	)

Investments_in_Unconsolidated_1

Investments in Unconsolidated Joint Ventures (Tables)	9 Months Ended
	Sep. 30, 2014
Investments In Unconsolidated Joint Ventures [Abstract]	'
Investments In Unconsolidated Joint Ventures	'
	The investments in unconsolidated joint ventures consist of the following at September 30, 2014:
	Entity		Properties		Nominal %				Carrying Value of Investment
					Ownership
									(in thousands)
	Square 407 Limited Partnership		Market Square North		50	%			$	(8,540	)
	The Metropolitan Square Associates LLC		Metropolitan Square		51	%			8,343
	BP/CRF 901 New York Avenue LLC		901 New York Avenue		25	%	(1)		(1,436		)
	WP Project Developer LLC		Wisconsin Place Land and Infrastructure		33.3	%	(2)		46,011
	Annapolis Junction NFM, LLC		Annapolis Junction		50	%	(3)		24,484
	2 GCT Venture LLC		N/A		60	%	-4		424
	540 Madison Venture LLC		540 Madison Avenue		60	%			70,418
	500 North Capitol LLC		500 North Capitol Street, NW		30	%			(1,467		)
	501 K Street LLC		501 K Street		50	%	-5		41,912
									$	180,149
	_______________
	-1	The Company’s economic ownership has increased based on the achievement of certain return thresholds.
	-2	The Company’s wholly-owned entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking garage and infrastructure of the project.
	-3	The joint venture owns two in-service buildings, two buildings under construction and two undeveloped land parcels.
	-4	Two Grand Central Tower was sold on October 25, 2011.
	-5	Under the joint venture agreement, the partner will be entitled to up to two additional payments from the venture based on increases in total square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.
Balance Sheets Of The Unconsolidated Joint Ventures	'
	The combined summarized balance sheets of the Company's unconsolidated joint ventures are as follows:
		September 30, 2014				31-Dec-13
		(in thousands)
	ASSETS
	Real estate and development in process, net	$	1,014,663			$	924,297
	Other assets	182,905				163,149
	Total assets	$	1,197,568			$	1,087,446
	LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
	Mortgage and notes payable	$	753,692			$	749,732
	Other liabilities	23,180				28,830
	Members’/Partners’ equity	420,696				308,884
	Total liabilities and members’/partners’ equity	$	1,197,568			$	1,087,446
	Company’s share of equity	$	208,125			$	154,726
	Basis differentials (1)	(27,976		)		(28,642		)
	Carrying value of the Company’s investments in unconsolidated joint ventures	$	180,149			$	126,084
	_______________
	-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.
Statements Of Operations Of The Joint Ventures	'
	The combined summarized statements of operations of the Company's unconsolidated joint ventures are as follows:
		For the three months ended September 30,								For the nine months ended September 30,
		2014				2013				2014		2013
		(in thousands)
	Total revenue (1)	$	41,958			$	37,983			$	118,429	$	273,464
	Expenses
	Operating	15,516				14,963				46,441		89,826
	Depreciation and amortization	9,429				9,784				27,688		76,202
	Total expenses	24,945				24,747				74,129		166,028
	Operating income	17,013				13,236				44,300		107,436
	Other expense
	Interest expense	7,950				8,148				23,946		104,436
	Losses from early extinguishment of debt	—				—				—		1,677
	Income from continuing operations	9,063				5,088				20,354		1,323
	Gains on sales of real estate	—				12,441				—		14,207
	Net income	$	9,063			$	17,529			$	20,354	$	15,530
	Company’s share of net income	$	4,200			$	3,149			$	9,403	$	1,974
	Gains on sales of real estate	—				11,174				—		54,501
	Basis differential	219				413				666		(1,213		)
	Elimination of inter-entity interest on partner loan	—				—				—		16,978
	Income from unconsolidated joint ventures	$	4,419			$	14,736			$	10,069	$	72,240
	Gains on consolidation of joint ventures	$	—			$	(1,810	)		$	—	$	385,991
	_______________
	-1	Includes straight-line rent adjustments of $0.2 million and $0.6 million for the three months ended September 30, 2014 and 2013, respectively, and $1.1 million and $7.6 million for the nine months ended September 30, 2014 and 2013, respectively. Includes net below-market rent adjustments of $(0.1) million and $(0.1) million for the three months ended September 30, 2014 and 2013, respectively, and $(0.1) million and $33.9 million for the nine months ended September 30, 2014 and 2013, respectively.

Noncontrolling_Interests_Table

Noncontrolling Interests (Tables)	9 Months Ended
	Sep. 30, 2014
Noncontrolling Interest [Abstract]	'
Schedule of Redeemable Interest in Property Partnerships [Table Text Block]	'
	he following table reflects the activity of the noncontrolling interest—redeemable interest in property partnership in the Company's Fountain Square consolidated joint venture for the nine months ended September 30, 2014 and 2013 (in thousands):
	Balance at January 1, 2014	$	99,609
	Net loss	(519		)
	Distributions	(4,300		)
	Adjustment to reflect redeemable interest at redemption value	9,315			-1
	Balance at September 30, 2014	$	104,105
	Balance at January 1, 2013	$	97,558
	Net loss	(1,523		)
	Distributions	(3,935		)
	Adjustment to reflect redeemable interest at redemption value	6,549
	Balance at September 30, 2013	$	98,649
	_______________
	(1) Includes an out-of-period adjustment totaling approximately $1.9 million (See Note 2).
Schedule Of Series Two Preferred Units	'
	The following table reflects the activity of the noncontrolling interests—redeemable preferred units of the Company for the nine months ended September 30, 2014 and 2013 (in thousands):
	Balance at January 1, 2014	$	105,746
	Net income	1,014
	Distributions	(1,014		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(15,984		)
	Reallocation of partnership interest (1)	(87,740		)
	Balance at September 30, 2014	$	2,022
	Balance at January 1, 2013	$	199,378
	Net income	3,385
	Distributions	(3,385		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(43,070		)
	Reallocation of partnership interest	1,425
	Balance at September 30, 2013	$	157,733
	_______________
	(1) Includes the conversion of the remaining 666,116 Series Two Preferred Units into 874,168 OP Units during the nine months ended September 30, 2014
Noncontrolling Interests-Redeemable Common Units	'
	The following table reflects the activity of the noncontrolling interests—redeemable common units for the nine months ended September 30, 2014 and 2013 (in thousands):
	Balance at January 1, 2014	$	1,710,218
	Contributions	23,990
	Net income	29,819
	Distributions	(34,426		)
	Conversion of redeemable partnership units	(2,368		)
	Unearned compensation	(6,952		)
	Accumulated other comprehensive loss	191
	Adjustment to reflect redeemable partnership units at redemption value	358,772
	Balance at September 30, 2014	$	2,079,244
	Balance at January 1, 2013	$	1,836,522
	Contributions	26,384
	Net income	74,395
	Distributions	(33,956		)
	Conversion of redeemable partnership units	(10,406		)
	Unearned compensation	(2,262		)
	Accumulated other comprehensive loss	189
	Adjustment to reflect redeemable partnership units at redemption value	(52,323		)
	Balance at September 30, 2013	$	1,838,543
Noncontrolling Interests-Property Partnerships	'
	The following table reflects the activity of the noncontrolling interests in property partnerships for the nine months ended September 30, 2014 and 2013 (in thousands):
	Balance at January 1, 2014	$	726,132
	Capital contributions	2,980
	Net income	8,677
	Distributions	(21,224		)
	Balance at September 30, 2014	$	716,565
	Balance at January 1, 2013	$	(1,964	)
	Fair value of capital recorded upon consolidation	480,861
	Capital contributions	10,932
	Net income (loss)	(5,950		)
	Distributions	(2,250		)
	Balance at September 30, 2013	$	481,629

Earnings_Per_Common_Unit_Table

Earnings Per Common Unit (Tables)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Computation Of Basic And Diluted Earnings Per Unit	'
	approximately 17,665,000 and 16,829,000 redeemable common units for the three months ended September 30, 2014 and 2013, respectively, and approximately 17,263,000 and 16,975,000 redeemable common units for the nine months ended September 30, 2014 and 2013, respectively.
		For the three months ended September 30, 2014
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties Limited Partnership	$	144,715		170,785	$	0.85
	Allocation of undistributed earnings to participating securities	(70		)	—	—
	Net income attributable to Boston Properties Limited Partnership	$	144,645		170,785	$	0.85
	Effect of Dilutive Securities:
	Stock Based Compensation	—			153	—
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	144,645		170,938	$	0.85
		For the three months ended September 30, 2013
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties Limited Partnership	$	83,898		169,236	$	0.5
	Discontinued operations attributable to Boston Properties Limited Partnership	90,242			—	0.53
	Allocation of undistributed earnings to participating securities	(651		)	—	—
	Net income attributable to Boston Properties Limited Partnership	$	173,489		169,236	$	1.03
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			285	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	173,489		169,521	$	1.02
		For the nine months ended September 30, 2014
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	294,370		170,340	$	1.73
	Effect of Dilutive Securities:
	Stock Based Compensation	—			151	—
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	294,370		170,491	$	1.73
		For the nine months ended September 30, 2013
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties Limited Partnership	$	626,317		168,975	$	3.71
	Discontinued operations attributable to Boston Properties Limited Partnership	113,935			—	0.67
	Allocation of undistributed earnings to participating securities	(4,183		)	—	(0.02		)
	Net income attributable to Boston Properties Limited Partnership	$	736,069		168,975	$	4.36
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			381	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership	$	736,069		169,356	$	4.35

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
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 September 30, 2014:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	176,788		$	243,033		$	61,691		$	96,219		$	577,731
	Office/Technical	6,056			—			5,892			3,713			15,661
	Residential	1,137			—			—			5,881			7,018
	Hotel	11,918			—			—			—			11,918
	Total	195,899			243,033			67,583			105,813			612,328
	% of Grand Totals	31.99		%	39.69		%	11.04		%	17.28		%	100		%
	Rental Expenses:
	Class A Office	69,026			82,335			22,484			32,898			206,743
	Office/Technical	1,901			—			1,363			1,009			4,273
	Residential	509			—			—			3,654			4,163
	Hotel	7,585			—			—			—			7,585
	Total	79,021			82,335			23,847			37,561			222,764
	% of Grand Totals	35.47		%	36.96		%	10.71		%	16.86		%	100		%
	Net operating income	$	116,878		$	160,698		$	43,736		$	68,252		$	389,564
	% of Grand Totals	30		%	41.25		%	11.23		%	17.52		%	100		%
	For the three months ended September 30, 2013:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	170,415		$	214,086		$	53,841		$	96,141		$	534,483
	Office/Technical	5,662			—			5,839			3,877			15,378
	Residential	1,125			—			—			4,368			5,493
	Hotel	10,652			—			—			—			10,652
	Total	187,854			214,086			59,680			104,386			566,006
	% of Grand Totals	33.19		%	37.83		%	10.54		%	18.44		%	100		%
	Rental Expenses:
	Class A Office	67,228			73,355			20,006			31,678			192,267
	Office/Technical	1,763			—			1,287			1,064			4,114
	Residential	466			—			—			2,441			2,907
	Hotel	6,580			—			—			—			6,580
	Total	76,037			73,355			21,293			35,183			205,868
	% of Grand Totals	36.94		%	35.63		%	10.34		%	17.09		%	100		%
	Net operating income	$	111,817		$	140,731		$	38,387		$	69,203		$	360,138
	% of Grand Totals	31.05		%	39.08		%	10.66		%	19.21		%	100		%
	For the nine months ended September 30, 2014:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	520,857		$	684,240		$	173,749		$	287,489		$	1,666,335
	Office/Technical	17,788			—			18,451			11,044			47,283
	Residential	3,389			—			—			15,609			18,998
	Hotel	32,478			—			—			—			32,478
	Total	574,512			684,240			192,200			314,142			1,765,094
	% of Grand Totals	32.55		%	38.76		%	10.89		%	17.8		%	100		%
	Rental Expenses:
	Class A Office	206,242			231,668			63,078			98,818			599,806
	Office/Technical	5,326			—			3,885			3,335			12,546
	Residential	1,501			—			—			10,360			11,861
	Hotel	21,697			—			—			—			21,697
	Total	234,766			231,668			66,963			112,513			645,910
	% of Grand Totals	36.35		%	35.86		%	10.37		%	17.42		%	100		%
	Net operating income	$	339,746		$	452,572		$	125,237		$	201,629		$	1,119,184
	% of Grand Totals	30.36		%	40.43		%	11.19		%	18.02		%	100		%
	For the nine months ended September 30, 2013:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	495,376		$	510,767		$	159,843		$	284,554		$	1,450,540
Office/Technical	16,853			—			11,317			11,951			40,121
Residential	3,257			—			—			13,298			16,555
Hotel	30,061			—			—			—			30,061
Total	545,547			510,767			171,160			309,803			1,537,277
% of Grand Totals	35.49		%	33.23		%	11.13		%	20.15		%	100		%
Rental Expenses:
Class A Office	195,206			177,800			58,036			94,145			525,187
Office/Technical	5,177			—			2,439			3,095			10,711
Residential	1,316			—			—			7,154			8,470
Hotel	20,959			—			—			—			20,959
Total	222,658			177,800			60,475			104,394			565,327
% of Grand Totals	39.38		%	31.45		%	10.7		%	18.47		%	100		%
Net operating income	$	322,889		$	332,967		$	110,685		$	205,409		$	971,950
% of Grand Totals	33.22		%	34.26		%	11.39		%	21.13		%	100		%
Schedule Of Reconciliation Of Net Operating Income To Net Income	'
	The following is a reconciliation of Net Operating Income to net income attributable to Boston Properties Limited Partnership:
		Three months ended						Nine months ended September 30,
		September 30,
		2014			2013			2014			2013
		(in thousands)
	Net Operating Income	$	389,564		$	360,138		$	1,119,184		$	971,950
	Add:
	Development and management services income	6,475			5,475			18,197			22,063
	Income from unconsolidated joint ventures	4,419			14,736			10,069			72,240
	Gains on consolidation of joint ventures	—			(1,810		)	—			385,991
	Interest and other income	3,421			3,879			6,841			6,646
	Gains (losses) from investments in securities	(297		)	956			651			1,872
	Gains (losses) from early extinguishments of debt	—			(30		)	—			122
	Income from discontinued operations	—			1,677			—			7,486
	Gain on sale of real estate from discontinued operations	—			88,565			—			88,565
	Gain on forgiveness of debt from discontinued operations	—			—			—			20,736
	Gains on sales of real estate	41,937			—			41,937			—
	Less:
	General and administrative expense	22,589			24,841			75,765			94,673
	Transaction costs	1,402			766			2,500			1,744
	Depreciation and amortization expense	155,217			151,216			460,064			400,131
	Interest expense	113,308			122,173			337,839			325,746
	Impairment loss	—			—			—			4,401
	Impairment loss from discontinued operations	—			—			—			2,852
	Noncontrolling interest in property partnerships	5,566			(3,279		)	17,473			(924		)
	Noncontrolling interest—redeemable preferred units	2,722			3,729			8,868			8,796
	Net income attributable to Boston Properties Limited Partnership	$	144,715		$	174,140		$	294,370		$	740,252

Organization_Details

Organization (Details) (USD $)

9 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

sqft

Commercial Real Estate Properties [Member]

Total Properties Under Construction [Member]

Total Office Properties [Member]

Class A Office Properties [Member]

Office Properties Under Construction [Member]

Office/Technical Properties [Member]

Hotel Properties [Member]

Retail Properties [Member]

Retail Properties Under Construction [Member]

Residential Properties [Member]

series four preferred units [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Depository shares of Series B Cumulative Redeemable Preferred [Member]

Series B Preferred Units [Member]

Vehicles

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

acre

sqft

sqft

Y

Real Estate Properties [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

General and limited partnership interest in the operating partnership (percent)

89.50%

89.20%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Restriction on redemption of OP units from date of issuance (years)

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

One OP unit is equivalent to one share of Common Stock (in shares)

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OP unit conversion rate (in shares)

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Series B, Units Outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

80,000

80,000

8,000,000

80,000

Ratio of depository shares to shares of Series B Preferred Stock

'

'

'

'

'

'

'

'

'

'

'

'

'

0.01

'

'

'

Series B, Dividend Rate, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

5.25%

'

'

'

Preferred Units Liquidation Preference

'

'

'

'

'

'

'

'

'

'

'

'

$50

'

'

'

'

Number of series of preferred units outstanding

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of real estate properties

'

'

172

10

163

132

9

31

1

5

1

3

'

'

'

'

'

Net Rentable Area (in sf)

'

'

46,400,000

3,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of vehicles in structured parking

45,835

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Area of parking structures (in square feet)

15,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Area of undeveloped land parcels owned (in acres)

492.1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred Stock Dividend Payable Per Share

'

'

'

'

'

'

'

'

'

'

'

'

$0.25

'

'

'

'

Series Four Preferred Units Annual Dividend Payable Rate

'

'

'

'

'

'

'

'

'

'

'

'

2.00%

'

'

'

'

Basis_Of_Presentation_And_Summ3

Basis Of Presentation And Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Accounting Policies [Abstract]	'
Cumulative non-cash adjustment to the accretion of the changes in the redemption value of the noncontrolling interest	$1.90

Basis_Of_Presentation_And_Summ4

Basis Of Presentation And Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]	'	'
Mortgage notes payable	$4,328,464,000	$4,449,734,000
Mezzanine notes payable	310,114,000	311,040,000
Unsecured senior notes	5,837,172,000	5,835,854,000
Unsecured exchangeable senior notes	0	744,880,000
Carrying Amount [Member]	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'
Mortgage notes payable	4,328,464,000	4,449,734,000
Mezzanine notes payable	310,114,000	311,040,000
Unsecured senior notes	5,837,172,000	5,835,854,000
Unsecured exchangeable senior notes	0	744,880,000	[1]
Total	10,475,750,000	11,341,508,000
Estimated Fair Value [Member]	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'
Mortgage notes payable	4,460,353,000	4,545,283,000
Mezzanine notes payable	310,141,000	311,064,000
Unsecured senior notes	6,173,499,000	6,050,517,000
Unsecured exchangeable senior notes	0	750,266,000
Total	10,943,993,000	11,657,130,000
ASC 470-20 Adjustment [Member]	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'
Impact of accounting pronouncement	'	$2,400,000
[1]	Includes the net adjustment for the equity component allocation totaling approximately $2.4 million at December 31, 2013.

Real_Estate_Activity_During_th2

Real Estate Activity During the Nine Months Ended September 30, 2014 (Narrative) (Details) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Jul. 29, 2014

Jun. 11, 2014

Aug. 20, 2014

Aug. 22, 2014

Aug. 22, 2014

Feb. 10, 2014

Apr. 01, 2014

20-May-14

20-May-14

Aug. 31, 2014

Sep. 17, 2014

Apr. 03, 2014

Jul. 29, 2014

Jul. 29, 2014

Sep. 16, 2014

Apr. 10, 2014

Sep. 16, 2014

Sep. 16, 2014

Sep. 16, 2014

Sep. 16, 2014

Sep. 16, 2014

Oct. 02, 2014

Oct. 30, 2014

Oct. 30, 2014

Oct. 30, 2014

Oct. 30, 2014

Oct. 30, 2014

Oct. 30, 2014

Mountain View Technology Park and Mountain View Research Building Sixteen [Member]

Patriots park [Member]

Land at One Reston Overlook [Member]

Land Parcel Within Broad Run Business Park [Member]

Land Parcel Within Broad Run Business Park [Member]

The Avant at Reston Town Center Residential [Member]

99 Third Avenue [Member]

888 Boylston Street [Member]

10 CityPoint [Member]

250 West 55th Street [Member]

680 Folsom Street [Member]

690 Folsom Street [Member]

Mountain View Technology [Member]

Mountain View Research Building Sixteen [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

sqft

acre

sqft

sqft

sqft

sqft

sqft

sqft

sqft

Mountain View Technology Park and Mountain View Research Building Sixteen [Member]

Mountain View Technology Park and Mountain View Research Building Sixteen [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

Salesforece Tower (formerly Transbay Tower) [Member]

601 Lexington Avenue [Member]

Atlantic Wharf Office [Member]

100 Federal Street [Member]

Office Tower [Member]

Low Rise [Member]

Patriots park [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Buildings

apartments

Buildings

sqft

floor

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue [Member]

601 Lexington Avenue [Member]

sqft

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue [Member]

Atlantic Wharf Office [Member]

100 Federal Street [Member]

Office Tower [Member]

Low Rise [Member]

sqft

sqft

sqft

sqft

sqft

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

Buildings

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue [Member]

601 Lexington Avenue [Member]

floor

floor

sqft

sqft

sqft

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

floor

floor

Real Estate Properties [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gross sales Price Before Deducting Indebtedness

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$1,827,000,000

'

'

'

'

'

'

'

$1,827,000,000

'

'

'

'

'

Proceeds from the sales of real estate

'

'

103,542,000

160,815,000

91,200,000

'

2,600,000

9,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gains on sales of real estate

41,937,000

0

41,937,000

0

36,400,000

'

1,200,000

4,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Area of Land

'

'

'

'

'

'

'

'

15.5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Sales price

'

'

'

'

92,100,000

321,000,000

'

'

9,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

321,000,000

'

'

'

'

'

'

Number of real estate properties

'

'

'

'

'

3

'

'

'

'

'

'

'

'

'

'

7

'

'

'

'

'

'

'

'

3

'

'

'

'

'

'

Number of apartment units

'

'

'

'

'

'

'

'

'

359

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ownership Percentage of Partner

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

45.00%

'

'

'

'

'

'

'

45.00%

'

'

'

'

'

Square Footage Of Signed Lease

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

714,000

'

'

'

'

'

'

'

'

'

'

'

'

Number of floors real estate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

61

'

'

'

59

6

'

'

'

'

'

59

6

Secured Debt Carrying Amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$712,900,000

'

'

'

'

'

'

'

$712,900,000

'

'

'

'

'

Area of Real Estate Property

'

'

'

'

'

706,000

'

'

'

355,000

17,000

425,000

245,000

988,000

525,000

26,000

135,000

63,000

'

1,400,000

1,669,000

791,000

1,323,000

'

'

706,000

'

1,669,000

791,000

1,323,000

'

'

Ownership Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

95.00%

'

'

'

'

'

'

'

'

'

'

'

'

Real_Estate_Activity_During_th3

Real Estate Activity During the Nine Months Ended September 30, 2014 (Summary Of The Discontinued Operations Related to Montvale Center, 303 Almaden Blvd, 1301 New York Avenue, One Preserve Parkway, and 10 & 20 Burlington Mall Road) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Total revenue	$618,803	$571,481	$1,783,291	$1,559,340
Expenses	'	'	'	'
Depreciation and amortization	155,217	151,216	460,064	400,131
Total expenses	401,972	382,691	1,184,239	1,066,276
Operating income	216,831	188,790	599,052	493,064
Other expense	'	'	'	'
Interest expense	113,308	122,173	337,839	325,746
Income from discontinued operations	'	90,242	'	113,935
Gain on sale of real estate from discontinued operations	0	88,565	0	88,565
Gain on forgiveness of debt from discontinued operations attributable to Boston Properties LImited Partnership	0	0	0	20,736
Impairment loss from discontinued operations attributable to Boston Properties Limited Partnership	0	0	0	-2,852
Montvale Center, 303 Almaden Blvd, 1301 New York Avenue, One Preserve Parkway and 10 & 20 Burlington Mall Road [Member]	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Total revenue	'	'	'	17,962
Expenses	'	'	'	'
Operating	'	'	'	6,290
Depreciation and amortization	'	'	'	3,826
Total expenses	'	'	'	10,116
Operating income	'	'	'	7,846
Other expense	'	'	'	'
Interest expense	'	'	'	360
Income from discontinued operations	'	'	'	7,486
Gain on sale of real estate from discontinued operations	'	'	'	88,565
Gain on forgiveness of debt from discontinued operations attributable to Boston Properties LImited Partnership	'	'	'	20,736
Impairment loss from discontinued operations attributable to Boston Properties Limited Partnership	'	'	'	-2,852
One Three Zero One New York Avenue, One Preserve Parkway and ten & twenty Burlington Mall Road [Member]	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Total revenue	'	4,112	'	'
Expenses	'	'	'	'
Operating	'	1,495	'	'
Depreciation and amortization	'	940	'	'
Total expenses	'	2,435	'	'
Operating income	'	1,677	'	'
Other expense	'	'	'	'
Interest expense	'	0	'	'
Income from discontinued operations	'	1,677	'	'
Gain on sale of real estate from discontinued operations	'	88,565	'	'
Gain on forgiveness of debt from discontinued operations attributable to Boston Properties LImited Partnership	'	0	'	'
Impairment loss from discontinued operations attributable to Boston Properties Limited Partnership	'	$0	'	'

Investments_in_Unconsolidated_2

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

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

In Thousands, unless otherwise specified

Square 407 Limited Partnership [Member]

The Metropolitan Square Associates LLC [Member]

BP/CRF 901 New York Avenue LLC [Member]

WP Project Developer LLC [Member]

Annapolis Junction NFM, LLC [Member]

2 GCT Venture LLC [Member]

540 Madison Venture LLC [Member]

500 North Capitol LLC [Member]

Entity Owning Land And Infrastructure Of Project [Member]

501 K Street [Member]

Land_Parcels

payments

Buildings

sqft

Schedule of Equity Method Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Properties

'

'

'Market Square North

'Metropolitan Square

'901 New York Avenue

'Wisconsin Place Land and Infrastructure

'Annapolis Junction

'N/A

[1]

'540 Madison Avenue

'500 North Capitol Street, NW

'

'501 K Street

Ownership Percentage

'

'

50.00%

51.00%

25.00%

[2]

33.30%

[3]

50.00%

[4]

60.00%

[1]

60.00%

30.00%

33.30%

50.00%

[5]

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

$180,149

$126,084

($8,540)

$8,343

($1,436)

$46,011

$24,484

$424

$70,418

($1,467)

'

$41,912

Number of real estate properties

'

'

'

'

'

'

2

'

'

'

'

'

Number of buildings under construction

'

'

'

'

'

'

2

'

'

'

'

'

Parcels of undeveloped land

'

'

'

'

'

'

2

'

'

'

'

'

Potential additonal payments to joint venture partner

'

'

'

'

'

'

'

'

'

'

'

2

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

'

'

'

'

'

'

'

'

'

'

'

520,000

[1]

Two Grand Central Tower was sold on October 25, 2011.

[2]

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

[3]

The Company’s wholly-owned entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking garage and infrastructure of the project.

[4]

The joint venture owns two in-service buildings, two buildings under construction and two undeveloped land parcels.

[5]

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

Investments_in_Unconsolidated_3

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
ASSETS	'		'
Real estate and development in process, net	$15,526,692		$15,451,531
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY	'		'
Mortgage and notes payable	4,328,464		4,449,734
Other liabilities	517,428		578,969
Total liabilities and capital	18,515,576		19,796,588
Carrying value of the Company's investments in unconsolidated joint ventures	180,149		126,084
Unconsolidated Joint Ventures [Member]	'		'
ASSETS	'		'
Real estate and development in process, net	1,014,663		924,297
Other assets	182,905		163,149
Total assets	1,197,568		1,087,446
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY	'		'
Mortgage and notes payable	753,692		749,732
Other liabilities	23,180		28,830
Members'/Partners' equity	420,696		308,884
Total liabilities and capital	1,197,568		1,087,446
Company's share of equity	208,125		154,726
Basis differentials	-27,976	[1]	-28,642	[1]
Carrying value of the Company's investments in unconsolidated joint ventures	$180,149		$126,084
[1]	unt 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_4

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Total revenue	$618,803,000	$571,481,000	$1,783,291,000	$1,559,340,000
Expenses	'	'	'	'
Depreciation and amortization	155,217,000	151,216,000	460,064,000	400,131,000
Total expenses	401,972,000	382,691,000	1,184,239,000	1,066,276,000
Operating income	216,831,000	188,790,000	599,052,000	493,064,000
Other expense	'	'	'	'
Interest expense	113,308,000	122,173,000	337,839,000	325,746,000
Losses from Early Extinguishment of Debt	0	30,000	0	-122,000
Income from continuing operations	111,066,000	84,348,000	278,774,000	634,189,000
Net income	153,003,000	174,590,000	320,711,000	748,124,000
Income from unconsolidated joint ventures	4,419,000	14,736,000	10,069,000	72,240,000
Gains on consolidation of joint ventures	0	-1,810,000	0	385,991,000
Unconsolidated Joint Ventures [Member]	'	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Total revenue	41,958,000	37,983,000	118,429,000	273,464,000
Expenses	'	'	'	'
Operating	15,516,000	14,963,000	46,441,000	89,826,000
Depreciation and amortization	9,429,000	9,784,000	27,688,000	76,202,000
Total expenses	24,945,000	24,747,000	74,129,000	166,028,000
Operating income	17,013,000	13,236,000	44,300,000	107,436,000
Other expense	'	'	'	'
Interest expense	7,950,000	8,148,000	23,946,000	104,436,000
Losses from Early Extinguishment of Debt	0	0	0	1,677,000
Income from continuing operations	9,063,000	5,088,000	20,354,000	1,323,000
Gain on sale of real estate	0	12,441,000	0	14,207,000
Net income	9,063,000	17,529,000	20,354,000	15,530,000
Company's share of net income (loss)	4,200,000	3,149,000	9,403,000	1,974,000
Gain on sale of real estate	0	11,174,000	0	54,501,000
Basis differential	219,000	413,000	666,000	-1,213,000
Elimination of inter-entity interest on partner loan	0	0	0	16,978,000
Income from unconsolidated joint ventures	4,419,000	14,736,000	10,069,000	72,240,000
Gains on consolidation of joint ventures	0	-1,810,000	0	385,991,000
Straight Line Rent Adjustments	200,000	600,000	1,100,000	7,600,000
Below market rent adjustments, net	($100,000)	($100,000)	($100,000)	$33,900,000

Investments_in_Unconsolidated_5

Investments in Unconsolidated Joint Ventures Investment in Unconsolidated Joint ventures (Narrative) (Details) (USD $)	9 Months Ended		0 Months Ended			0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Apr. 10, 2014	Sep. 30, 2014		Jun. 23, 2014	Apr. 30, 2014	Apr. 10, 2014	Apr. 10, 2014	Apr. 30, 2014
			501 K Street [Member]	501 K Street [Member]		Annapolis Junction Building Eight [Member]	Annapolis Junction Building Eight [Member]	joint venture partner [Member]	Company [Member]	Company [Member]
			sqft	payments		Y	sqft	501 K Street [Member]	501 K Street [Member]	Annapolis Junction Building Eight [Member]
				sqft
Schedule of Equity Method Investments [Line Items]	'	'	'	'		'	'	'	'	'
Debt Instrument, Description of Variable Rate Basis	'	'	'	'		' LIBOR plus 1.50%	'	'	'	'
Capital contributions to unconsolidated joint ventures	$47,767,000	$0	$39,000,000	'		'	$5,400,000	'	'	'
Ownership Percentage	'	'	'	50.00%	[1]	'	'	50.00%	50.00%	50.00%
Net Rentable Area (in sf)	'	'	520,000	'		'	125,000	'	'	'
Construction Loan Facility Borrowing Capacity	'	'	'	'		$26,000,000	'	'	'	'
Debt Instrument, Basis Spread on Variable Rate	'	'	'	'		1.50%	'	'	'	'
Maturity Date	'	'	'	'		23-Jun-17	'	'	'	'
Number of extensions	'	'	'	'		2	'	'	'	'
Extension Option (in years)	'	'	'	'		1	'	'	'	'
Potential additonal payments to joint venture partner	'	'	'	2		'	'	'	'	'
Minimum square footage to make a potential additional payment to joint venture partner (in sqft)	'	'	'	520,000		'	'	'	'	'
[1]	Under the joint venture agreement, the partner will be entitled to up to two additional payments from the venture based on increases in total square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.

Mortgage_Notes_Payable_Details

Mortgage Notes Payable (Details) (USD $)	9 Months Ended		3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Jul. 01, 2014
			Mortgages [Member]	Mortgages [Member]
			New Dominion Technology Park, Bldg. Two [Member]	New Dominion Technology Park, Bldg. Two [Member]
Debt Instrument [Line Items]	'	'	'	'
Repayments of Secured Debt	$82,030,000	$96,750,000	$63,000,000	'
Coupon/Stated Rate (percent)	'	'	'	5.55%
Maturity Date	'	'	1-Oct-14	'
Penalty For Early Repayment Of Debt	'	'	$0	'

Unsecured_Exchangeable_Senior_1

Unsecured Exchangeable Senior Notes Unsecured exchangeable Senior Notes (Narrative) (details) (Unsecured Debt [Member], Three point six two five percent exchangeable senior notes [Member], USD $)	0 Months Ended
In Millions, unless otherwise specified	Feb. 18, 2014
Unsecured Debt [Member] | Three point six two five percent exchangeable senior notes [Member]	'
Debt Instrument [Line Items]	'
Coupon/Stated Rate (percent)	3.63%
Redemption of unsecured senior notes	$747.50

Commitments_And_Contingencies_

Commitments And Contingencies (Details) (USD $)

2 Months Ended

7 Months Ended

9 Months Ended

5 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2014

Jul. 28, 2014

Sep. 30, 2014

Sep. 18, 2014

Jun. 09, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2009

Jan. 10, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

767 Venture, LLC [Member]

767 Venture, LLC [Member]

Lehman [Member]

Lehman [Member]

Lehman [Member]

Lehman [Member]

Lehman [Member]

601 Lexington Avenue [Member]

John Hancock Tower [Member]

Minimum [Member]

Maximum [Member]

Commitments And Contingencies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Letter of credit and performance obligations

$19,100,000

'

$19,100,000

'

'

'

'

'

'

'

'

'

'

Maximum funding obligation

'

'

'

'

'

14,800,000

'

'

'

'

'

'

'

Guarantee Obligation Related To Tenant Re-Leasing Costs

'

'

'

'

'

'

'

'

'

'

'

'

28,800,000

Property insurance program per occurrence limits

1,000,000,000

'

1,000,000,000

'

'

1,625,000,000

'

'

'

'

'

'

'

Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP

'

'

'

'

'

'

'

'

'

'

'

250,000,000

'

Coverage for acts of Terrorism certified under TRIA in excess of amount provided by NYIXP, LLC, as a direct insurer

'

'

'

'

1,375,000,000

'

'

'

'

'

'

'

'

Coverage for acts of terrorism certified under TRIA in excess

'

'

'

'

250,000,000

'

'

'

'

'

'

'

'

Per occurrence limit for NBCR Coverage

'

'

1,000,000,000

'

'

'

'

'

'

'

'

'

'

Value of program trigger

100,000,000

'

100,000,000

'

'

'

'

'

'

'

'

'

'

Coinsurance of program trigger (percent)

'

'

15.00%

'

'

'

'

'

'

'

'

'

'

Deductible in insurance as a percentage of the value of the affected property, San Francisco (percent)

'

'

5.00%

'

'

'

'

'

'

'

'

'

'

Per occurrence limit of the earthquake insurance which covers San Francisco region

'

'

120,000,000

'

'

'

'

'

'

'

'

'

'

Annual aggregate limit of the earthquake insurance which covers San Francisco region

'

'

120,000,000

'

'

'

'

'

'

'

'

'

'

Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco

'

'

20,000,000

'

'

'

'

'

'

'

'

'

'

Earthquake Coverage Included In Builders Risk Policy For 535 Mission

'

'

15,000,000

'

'

'

'

'

'

'

'

'

'

Earthquake Coverage Included In Builders Risk Policy For SalesforceTower

60,000,000

15,000,000

'

'

'

'

'

'

'

'

'

'

'

Operating partnership guarantee to cover liabilities of IXP

20,000,000

'

20,000,000

'

'

'

'

'

'

'

'

'

'

Maturity Date

'

'

'

'

'

'

'

'

'

'

'

'

6-Jan-17

Bankruptcy claim, amount filed by general creditor

'

'

'

'

'

'

'

45,300,000

'

'

'

'

'

Bankruptcy claim amount allowed by court to creditor

'

'

'

'

'

'

37,500,000

'

45,200,000

'

'

'

'

Bankruptcy Claims, Amount of Claims Settled

'

'

'

$7,700,000

'

'

'

'

'

'

'

'

'

Bankruptcy claim, price on the private market

'

'

'

'

'

'

'

'

'

0.25

0.26

'

'

Bankruptcy claim, denominator used to evaluate claim price amount

'

'

'

'

'

'

1

'

'

'

'

'

'

Noncontrolling_Interests_Narra

Noncontrolling Interests (Narrative) (Details)	Sep. 30, 2014
Noncontrolling Interests [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Operating Partnership (OP) Units (in shares)	16,456,297
Long-Term Incentive Plan (LTIP) Units (in shares)	1,505,386
Series Four Preferred Units (in shares)	40,440
2012 OPP Units [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Outperformance awards in LTIP Units (in shares)	394,590
MYLTIP [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
2013 MYLTIP	314,974
2014 MYLTIP Units [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
2014 MYLTIP	483,555

Noncontrolling_Interests_Redee

Noncontrolling Interests (Redeemable Preferred Units) (Narrative) (Details) (USD $)

Sep. 30, 2014

Mar. 11, 2014

12-May-14

Sep. 30, 2014

Feb. 18, 2014

Sep. 30, 2014

Sep. 30, 2014

Aug. 15, 2014

Jul. 03, 2014

19-May-14

15-May-14

Feb. 18, 2014

In Millions, except Share data, unless otherwise specified

Noncontrolling Interests [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

series four preferred units [Member]

series four preferred units [Member]

series four preferred units [Member]

series four preferred units [Member]

series four preferred units [Member]

series four preferred units [Member]

series four preferred units [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Series Two Preferred Units (in shares)

'

'

666,116

666,116

'

'

'

'

'

'

'

'

Liquidation preference percentage

'

'

6.00%

'

'

'

'

'

'

'

'

'

Operating Units liquidation preference (in dollars per share)

'

'

$38.10

'

'

'

'

'

'

'

'

'

OP Units for each Preferred Unit (in shares)

'

1.312336

'

'

'

'

'

'

'

'

'

'

Series Two Preferred Units On Converted Basis

'

874,168

874,168

874,168

'

'

'

'

'

'

'

'

Distributions to Series Two Preferred Units (in dollars per share)

'

'

'

'

$0.85

'

'

$0.25

'

'

$0.25

$0.25

Series Four Preferred Units (in shares)

40,440

'

'

'

'

'

40,440

'

40,440

'

'

'

Series Four Preferred Units Annual Dividend Payable Rate

'

'

'

'

'

2.00%

2.00%

'

'

'

'

'

Preferred Units Liquidation Preference

'

'

$50

'

'

$50

$50

'

'

'

'

'

Series Four Preferred Units Released from Escrow

'

'

'

'

'

'

'

'

'

319,687

'

'

Redemption of Series Four Preferred Units

'

'

'

'

'

'

'

'

$16

'

'

'

Noncontrolling_Interests_Commo

Noncontrolling Interests (Common Units) (Narrative) (Details) (USD $)	0 Months Ended			9 Months Ended
	Jul. 31, 2014	Apr. 30, 2014	Jan. 29, 2014	Sep. 30, 2014	Sep. 11, 2014
OP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
OP Units for redemption (in shares)	'	'	'	70,422	'
Redemption of OP units issued on conversion of LTIP Units (in shares)	'	'	'	67,368	'
OPP and MYLTIP Units distribution as percentage of OP Unit distribution prior to measurement date	'	'	'	10.00%	'
Distributions made to OP and LTIP units per unit (in dollars per share)	$0.65	$0.65	$0.65	'	'
Distribution paid to outperformance awards, OPP Units (in dollars per share)	$0.07	$0.07	$0.07	'	'
Distribution declared to OP and LTIP units by Boston Properties, Inc. (in dollars per share)	'	'	'	'	$0.65
Distribution declared to outperformance awards OPP Units by Boston Properties, Inc. (in dollars per share)	'	'	'	'	$0.07
Common units of operating partnership if converted value	'	'	'	$2,100,000,000	'
Closing price of common stock (in dollars per share)	'	'	'	$115.76	'
2012 OPP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Outperformance awards in LTIP Units (in shares)	'	'	'	394,590	'
MYLTIP [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
2013 MYLTIP	'	'	'	314,974	'
2014 MYLTIP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
2014 MYLTIP	'	'	'	483,555	'
Quarter 4 2013 [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividend shareholder of record date	'	'	'	31-Dec-13	'
Dividend payable date	'	'	'	29-Jan-14	'
Quarter 4 2013 [Member] | OP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividend payable date	'	'	'	29-Jan-14	'
Holders of record date	'	'	'	31-Dec-13	'
Quarter 1 2014 [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividend shareholder of record date	'	'	'	31-Mar-14	'
Dividend payable date	'	'	'	30-Apr-14	'
Quarter 1 2014 [Member] | OP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividend payable date	'	'	'	30-Apr-14	'
Holders of record date	'	'	'	31-Mar-14	'
Quarter 2 2014 [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividend shareholder of record date	'	'	'	30-Jun-14	'
Dividend payable date	'	'	'	31-Jul-14	'
Quarter 2 2014 [Member] | OP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividend payable date	'	'	'	31-Jul-14	'
Holders of record date	'	'	'	30-Jun-14	'
Quarter 3 2014 [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividend shareholder of record date	'	'	'	30-Sep-14	'
Dividends declared date	'	'	'	11-Sep-14	'
Dividend payable date	'	'	'	31-Oct-14	'
Quarter 3 2014 [Member] | OP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Dividends declared date	'	'	'	11-Sep-14	'
Dividend payable date	'	'	'	31-Oct-14	'
Holders of record date	'	'	'	30-Sep-14	'
special dividend [Member] | OP Units [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Distributions made to OP and LTIP units per unit (in dollars per share)	'	'	$2.25	'	'
2011 OPP Unitsn [Member]	'	'	'	'	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'
Accelerated compensation expenses related to 2011 OPP Units	'	'	'	$1,200,000	'

Noncontrolling_Interests_Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) (USD $)	9 Months Ended			0 Months Ended				0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	31-May-13	31-May-13	Oct. 09, 2013	Apr. 10, 2014	Feb. 26, 2013	Feb. 07, 2014
				767 Fifth Avenue (The GM Building) [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member]	Salesforece Tower (formerly Transbay Tower) [Member]	Salesforece Tower (formerly Transbay Tower) [Member]	Salesforece Tower (formerly Transbay Tower) [Member]
				Consolidated Properties [Member]	Consolidated Properties [Member]	Time Square Tower [Member]	Consolidated Properties [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member]
					partners	Consolidated Properties [Member]	sqft	Consolidated Properties [Member]	Consolidated Properties [Member]
						sqft
Noncontrolling Interest [Line Items]	'	'	'	'	'	'	'	'	'
Partners Joint Venture Ownership Percentage	'	'	'	40.00%	'	'	'	'	'
Number of Joint Venture Partners	'	'	'	'	2	'	'	'	'
Ownership Percentage of Partner	'	'	'	'	'	45.00%	'	5.00%	50.00%
Sales price	'	'	'	'	'	$684,000,000	'	'	'
Ownership Percentage	'	'	'	'	'	'	95.00%	95.00%	'
maximum percentage of construction costs to allow partner to have a loan	'	'	'	'	'	'	'	50.00%	'
Portion of total costs partner can require the company to fund	'	'	'	'	'	'	'	2.50%	'
portion of partners equity that can be funded by the company	'	'	'	'	'	'	'	50.00%	'
Portion allocation to noncontrolling interest based on carrying value of the total equity of the property prior to the sale	'	'	'	'	'	243,500,000	'	'	'
Fair value of capital recorded upon consolidation	0	480,861,000	'	480,900,000	'	'	'	'	'
Proceeds from sale of an interest in a real estate asset	'	'	'	'	'	673,100,000	'	'	'
Area of Real Estate Property	'	'	'	'	'	1,246,000	1,400,000	'	'
Noncontrolling interests in property partnerships	$716,565,000	'	$726,132,000	'	'	'	'	'	'

Noncontrolling_Interests_Redee1

Noncontrolling Interests (Redeemable Preferred Units) (Details) (USD $)

3 Months Ended

9 Months Ended

In Thousands, except Share data, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

12-May-14

Mar. 11, 2014

Redeemable Preferred Units [Member]

Redeemable Preferred Units [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Noncontrolling Interest [Line Items]

'

'

'

'

'

'

'

'

'

'

'

Series Two Preferred Units (in shares)

'

'

'

'

'

'

'

'

666,116

666,116

'

Series Two Preferred Units On Converted Basis

'

'

'

'

'

'

'

'

874,168

874,168

874,168

Activity of noncontrolling interests

'

'

'

'

'

'

'

'

'

'

'

Beginning Balance

'

'

'

'

$105,746

$199,378

'

'

'

'

'

Net income

2,722

3,729

8,868

8,796

1,014

3,385

'

'

'

'

'

Distributions

'

'

'

'

-1,014

-3,385

'

'

'

'

'

Redemption of redeemable preferred units (Series Four Preferred Units)

'

'

15,984

43,070

-15,984

-43,070

'

'

'

'

'

Reallocation of partnership interest

'

'

'

'

-87,740

[1]

1,425

-2,368

-10,406

'

'

'

Ending Balance

'

'

'

'

$2,022

$157,733

'

'

'

'

'

[1]

Includes the conversion of the remaining 666,116 Series Two Preferred Units into 874,168 OP Units during the nine months ended September 30, 2014.

Noncontrolling_Interests_Nonco

Noncontrolling Interests (Noncontrolling Interests-Redeemable Common Units) (Details) (Noncontrolling Interests [Member], USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Noncontrolling Interests [Member]	'	'
Activity of noncontrolling interests	'	'
Beginning Balance	$1,710,218	$1,836,522
Contributions	23,990	26,384
Net income	29,819	74,395
Distributions	-34,426	-33,956
Conversion of redeemable partnership units	-2,368	-10,406
Unearned compensation	-6,952	-2,262
Accumulated other comprehensive loss	191	189
Adjustments to reflect redeemable partnership units at redemption value	358,772	-52,323
Ending Balance	$2,079,244	$1,838,543

Noncontrolling_Interests_Nonco1

Noncontrolling Interests (Noncontrolling Interests-Property Partnerships) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Activity of noncontrolling interests	'	'	'	'
Beginning balance	'	'	$726,132	'
Fair value of capital recorded upon consolidation	'	'	0	480,861
Capital contributions	'	'	2,980	6,386
Net Income (loss)	5,566	-3,279	17,473	-924
Ending balance	716,565	'	716,565	'
Property Partnerships Member	'	'	'	'
Activity of noncontrolling interests	'	'	'	'
Beginning balance	'	'	726,132	-1,964
Fair value of capital recorded upon consolidation	'	'	'	480,861
Capital contributions	'	'	2,980	10,932
Net Income (loss)	'	'	8,677	-5,950
Distributions	'	'	-21,224	-2,250
Ending balance	$716,565	$481,629	$716,565	$481,629

Noncontrolling_Interests_Redee2

Noncontrolling Interests Redeemable Interest in Property Partnerships (Details) (USD $)	9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013
Redeemable Interest in Property Partnership [Abstract]	'		'
Quantifying Misstatement in Current Year Financial Statements, Amount	($1,900,000)		'
Beginning Balance	99,609,000		97,558,000
Net loss	-519,000		-1,523,000
Distributions	-4,300,000		-3,935,000
Adjustment to reflect redeemable interest at redemption value	9,315,000	[1]	6,549,000
Ending Balance	$104,105,000		$98,649,000
[1]	Includes an out-of-period adjustment totaling approximately $1.9 million (See Note 2).

Noncontrolling_Interests_Nonco2

Noncontrolling Interests Noncontrolling interest - Reddemable interest in Property Partnerships (Details) (Consolidated Properties [Member], Fountain Square [Member], Noncontrolling Interests [Member], USD $)	0 Months Ended
In Millions, unless otherwise specified	Oct. 04, 2012
Consolidated Properties [Member] | Fountain Square [Member] | Noncontrolling Interests [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Aggregate purchase price	$385
Indebtedness assumed	211.3
Ownership Percentage of Partner	50.00%
Payments to Acquire Businesses, Gross	87
Ownership Percentage	50.00%
Future Fixed Price to Acquire Remaining Portion of Joint venture	$102
Fixed Price Option Expiration Date	31-Jan-16

Partners_Capital_Details

Partners' Capital (Details) (USD $)

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

9 Months Ended

Apr. 30, 2014

Jan. 29, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 11, 2014

Dec. 31, 2013

Jun. 03, 2014

Sep. 30, 2014

Jun. 02, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Aug. 15, 2014

15-May-14

Feb. 18, 2014

Sep. 30, 2014

Sep. 11, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Mar. 27, 2018

Sep. 30, 2014

Sep. 30, 2014

Mar. 27, 2018

New ATM program [Member]

New ATM program [Member]

ATM Program [Member]

Quarter 4 2013 [Member]

Quarter 1 2014 [Member]

Quarter 2 2014 [Member]

Quarter 3 2014 [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Depository shares of Series B Cumulative Redeemable Preferred [Member]

Depository shares of Series B Cumulative Redeemable Preferred [Member]

Series B Preferred Units [Member]

Subsequent Event [Member]

Y

Quarter 1 2014 [Member]

Quarter 2 2014 [Member]

Quarter 3 2014 [Member]

Quarter 4 2014 [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Class of Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

General partnership units (in units)

'

'

1,710,615

'

'

1,700,222

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Limited partnership units (in units)

'

'

151,389,171

'

'

151,282,879

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

At the market stock offering program, aggregate value of common stock

'

'

'

'

'

'

$600,000,000

'

$600,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

At Market Stock Offering Program Maximum Length Of Sale In Years

'

'

'

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

At the market stock offering program remaining amount available for issuance

'

'

'

'

'

'

'

'

305,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares of its Common Stock in connection with the redemption of an equal number of OP Units (in shares)

'

'

70,422

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OP Units to Boston Properties, Inc. in connection with the exercise by certain employees of options to purchase Common Stock of Boston Properties, Inc

'

'

17,124

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Dividend payable date

'

'

'

'

'

'

'

'

'

29-Jan-14

30-Apr-14

31-Jul-14

31-Oct-14

'

'

'

'

'

'

18-Feb-14

15-May-14

15-Aug-14

17-Nov-14

'

'

'

'

Dividend paid on common stock (in dollars per share)

$0.65

$2.90

'

'

'

'

'

'

'

'

'

'

'

$32.81

$32.81

$32.81

'

'

'

'

'

'

'

'

'

'

'

Dividend shareholder of record date

'

'

'

'

'

'

'

'

'

31-Dec-13

31-Mar-14

30-Jun-14

30-Sep-14

'

'

'

'

'

'

'

'

'

5-Nov-14

'

'

'

'

Dividends payable, date declared

'

'

'

'

'

'

'

'

'

'

'

'

11-Sep-14

'

'

'

'

'

'

'

'

'

11-Sep-14

'

'

'

'

Dividends payable (in dollars per share)

'

'

'

'

$0.65

'

'

'

'

'

'

'

'

'

'

'

'

$32.81

'

'

'

'

'

'

'

'

'

Series B, Units Outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

80,000

'

80,000

'

'

'

'

'

8,000,000

80,000

'

Series B, Liquidation Preference Per Unit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$2,500

'

$2,500

'

'

'

'

$25

$25

'

$2,500

Proceeds from Issuance of Series B Preferred Stock

'

'

0

193,623,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ratio of depository shares to shares of Series B Preferred Stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.01

'

'

'

'

'

'

'

'

'

'

Series B, Dividend Rate, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.25%

'

'

'

'

'

'

'

'

'

'

Common Stock, Value, Issued

'

'

'

'

'

'

'

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Earnings_Per_Common_Unit_Detai

Earnings Per Common Unit (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Redeemable common units (in shares)	17,665,000	16,829,000	17,263,000	16,975,000
Basic Earnings:	'	'	'	'
Income from continuing operations attributable to Boston Properties Limited Partnership	$144,715	$83,898	$294,370	$626,317
Net income attributable to Boston Properties Limited Partnership, Units (Denominator) (in shares)	170,785,000	169,236,000	170,340,000	168,975,000
Inceom (loss) from continuing operations before discontinued operations and allocation of undistributed earnings (dollars per share)	'	$0.50	'	$3.71
Discontinued operations attributable to Boston Properties Limited Partnership, Income (Numerator)	'	90,242	'	113,935
Discontinued Operations (in shares)	'	0	'	0
Discontinued operations attributable to Boston Properties Limited Partnership, Per Unit Amount (in dollars per share)	$0	$0.53	$0	$0.67
Allocation of undistributed earnings to participating securities	-70	-651	'	-4,183
Allocation of undistributed earnings to participating securities (in shares)	0	0	'	0
Allocation of undistributed earnings to participating securities (per shares)	$0	$0	'	($0.02)
Net income attributable to Boston Properties Limited Partnership	144,645	173,489	'	736,069
Net income	$0.85	$1.03	$1.73	$4.36
Effect of Dilutive Securities:	'	'	'	'
Stock Based Compensation and Exchangeable Senior Notes, Income (Numerator)	0	0	0	0
Stock Based Compensation and Exchangeable Senior Notes, Units (Denominator) (in shares)	153,000	285,000	151,000	381,000
Stock Based Compensation and Exchangeable Senior Notes, Per Unit Amount (in dollars per share)	$0	($0.01)	$0	($0.01)
Diluted Earnings:	'	'	'	'
Diluted Earnings: Net income attributable to Boston Properties Limited Partnership	$144,645	$173,489	$294,370	$736,069
Diluted Earnings: Net income, Units (Denominator) (in shares)	170,938,000	169,521,000	170,491,000	169,356,000
Net income	$0.85	$1.02	$1.73	$4.35

Stock_Option_and_Incentive_Pla1

Stock Option and Incentive Plan (Restricted Stock) (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
stock based compensation expense	$5,000,000	$6,200,000	$21,000,000	$38,100,000
Restricted Stock [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
Shares issued (in shares)	23,968	'	23,968	'
Employee and director payment per share (in dollars per share)	'	'	$0.01	'
Common Stock, Value, Issued	2,600,000	'	2,600,000	'
Employee's weighted average cost per share (in dollars per share)	$109.27	'	$109.27	'
LTIP Units [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
LTIP units issued (in shares)	127,094	'	127,094	'
Expected life assumed to calculate per unit fair value per LTIP unit (in years)	'	'	'5 years 8 months 12 days	'
Risk-free rate	'	'	1.84%	'
Expected price volatility	'	'	27.00%	'
Value of LTIP units issued	'	'	12,800,000	'
Per unit fair value weighted-average (in dollars per share)	$100.61	'	$100.61	'
2011 OPP Unitsn [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
Accelerated compensation expenses related to 2011 OPP Units	'	'	1,200,000	'
MYLTIP [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
MYLTIP units issued (in shares)	485,459	'	485,459	'
LTIPs And Restricted Stock [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
Vesting annual installments	'	'	4	'
Unrecognized compensation expenses	19,700,000	'	19,700,000	'
LTIPs and OPP Awards [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
Employee and director payment per share (in dollars per share)	'	'	$0.25	'
Unvested 2012 OPP Units and 2013 and 2014 MYLTIP Units [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
Unrecognized compensation expenses	16,500,000	'	16,500,000	'
Weighted-average period (in years)	'2 years 10 months 24 days	'	'	'
Board of Directors Chairman [Member]	'	'	'	'
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]	'	'	'	'
stock based compensation expense	'	$1,600,000	'	$20,200,000

Stock_Option_and_Incentive_Pla2

Stock Option and Incentive Plan Stock option and incentive plan (Narrative) (Details) (2014 MYLTIP Units [Member], USD $)	0 Months Ended
	Jan. 27, 2014
	indices
	tiers
	Y
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
TRS Measurement, Years	3
Indices Used to Compare TRS	2
Number of Tiers	4
Percentage of annualized TRS for Reduction of Earned Awards	0.00%
Percentage to Cause Some Awards to be Earned Even if on a Relative Basis it Would Not Result in any Earned Awards	12.00%
Distributions Percent Before Measurement Date	10.00%
Value of MYLTIP Awards	$12,700,000
MYLTIP Value Amortized Into Earnings, Years	4
Cohen & Steers Realty Majors Portfolio Index [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Weighted Percentage of Index Used to Compare to TRS	50.00%
NAREIT Office Index adjusted [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Weighted Percentage of Index Used to Compare to TRS	50.00%
Minimum [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Potential Awards Earned	0
Maximum [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Potential Awards Earned	40,200,000
Threshold [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Amount of Each Tier	6,700,000
Target [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Amount of Each Tier	13,400,000
Exceptional [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Amount of Each Tier	40,200,000
High [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Amount of Each Tier	$26,800,000
MYLTIP Vesting 2017 [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Vesting Percentage	50.00%
Vesting Date	3-Feb-17
MYLTIP vesting two thousand eighteen [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Vesting Percentage	50.00%
Vesting Date	3-Feb-18

Segment_Information_Schedule_O

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]	'	'	'	'
Rental Revenue: Class A Office	$577,731	$534,483	$1,666,335	$1,450,540
Rental Revenue: Office/Technical	15,661	15,378	47,283	40,121
Rental Revenue: Residential	7,018	5,493	18,998	16,555
Rental Revenue: Hotel	11,918	10,652	32,478	30,061
Rental Revenue Total	612,328	566,006	1,765,094	1,537,277
Total revenue	618,803	571,481	1,783,291	1,559,340
Rental Revenue: % of Grand Totals	100.00%	100.00%	100.00%	100.00%
Rental Expenses: Class A Office	206,743	192,267	599,806	525,187
Rental Expenses: Office/Technical	4,273	4,114	12,546	10,711
Rental Expenses: Residential	4,163	2,907	11,861	8,470
Rental Expenses: Hotel	7,585	6,580	21,697	20,959
Rental Expenses: Total	222,764	205,868	645,910	565,327
Rental Expenses: % Of Grand Totals	100.00%	100.00%	100.00%	100.00%
Net operating income	389,564	360,138	1,119,184	971,950
Percentage Of Total Net Operating Income	100.00%	100.00%	100.00%	100.00%
Boston [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Rental Revenue: Class A Office	176,788	170,415	520,857	495,376
Rental Revenue: Office/Technical	6,056	5,662	17,788	16,853
Rental Revenue: Residential	1,137	1,125	3,389	3,257
Rental Revenue: Hotel	11,918	10,652	32,478	30,061
Rental Revenue Total	195,899	187,854	574,512	545,547
Rental Revenue: % of Grand Totals	31.99%	33.19%	32.55%	35.49%
Rental Expenses: Class A Office	69,026	67,228	206,242	195,206
Rental Expenses: Office/Technical	1,901	1,763	5,326	5,177
Rental Expenses: Residential	509	466	1,501	1,316
Rental Expenses: Hotel	7,585	6,580	21,697	20,959
Rental Expenses: Total	79,021	76,037	234,766	222,658
Rental Expenses: % Of Grand Totals	35.47%	36.94%	36.35%	39.38%
Net operating income	116,878	111,817	339,746	322,889
Percentage Of Total Net Operating Income	30.00%	31.05%	30.36%	33.22%
New York	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Rental Revenue: Class A Office	243,033	214,086	684,240	510,767
Rental Revenue: Office/Technical	0	0	0	0
Rental Revenue: Residential	0	0	0	0
Rental Revenue: Hotel	0	0	0	0
Rental Revenue Total	243,033	214,086	684,240	510,767
Rental Revenue: % of Grand Totals	39.69%	37.83%	38.76%	33.23%
Rental Expenses: Class A Office	82,335	73,355	231,668	177,800
Rental Expenses: Office/Technical	0	0	0	0
Rental Expenses: Residential	0	0	0	0
Rental Expenses: Hotel	0	0	0	0
Rental Expenses: Total	82,335	73,355	231,668	177,800
Rental Expenses: % Of Grand Totals	36.96%	35.63%	35.86%	31.45%
Net operating income	160,698	140,731	452,572	332,967
Percentage Of Total Net Operating Income	41.25%	39.08%	40.43%	34.26%
San Francisco [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Rental Revenue: Class A Office	61,691	53,841	173,749	159,843
Rental Revenue: Office/Technical	5,892	5,839	18,451	11,317
Rental Revenue: Residential	0	0	0	0
Rental Revenue: Hotel	0	0	0	0
Rental Revenue Total	67,583	59,680	192,200	171,160
Rental Revenue: % of Grand Totals	11.04%	10.54%	10.89%	11.13%
Rental Expenses: Class A Office	22,484	20,006	63,078	58,036
Rental Expenses: Office/Technical	1,363	1,287	3,885	2,439
Rental Expenses: Residential	0	0	0	0
Rental Expenses: Hotel	0	0	0	0
Rental Expenses: Total	23,847	21,293	66,963	60,475
Rental Expenses: % Of Grand Totals	10.71%	10.34%	10.37%	10.70%
Net operating income	43,736	38,387	125,237	110,685
Percentage Of Total Net Operating Income	11.23%	10.66%	11.19%	11.39%
Washington DC	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Rental Revenue: Class A Office	96,219	96,141	287,489	284,554
Rental Revenue: Office/Technical	3,713	3,877	11,044	11,951
Rental Revenue: Residential	5,881	4,368	15,609	13,298
Rental Revenue: Hotel	0	0	0	0
Rental Revenue Total	105,813	104,386	314,142	309,803
Rental Revenue: % of Grand Totals	17.28%	18.44%	17.80%	20.15%
Rental Expenses: Class A Office	32,898	31,678	98,818	94,145
Rental Expenses: Office/Technical	1,009	1,064	3,335	3,095
Rental Expenses: Residential	3,654	2,441	10,360	7,154
Rental Expenses: Hotel	0	0	0	0
Rental Expenses: Total	37,561	35,183	112,513	104,394
Rental Expenses: % Of Grand Totals	16.86%	17.09%	17.42%	18.47%
Net operating income	$68,252	$69,203	$201,629	$205,409
Percentage Of Total Net Operating Income	17.52%	19.21%	18.02%	21.13%

Segment_Information_Schedule_O1

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Reconciliation of Net Operating Income to net income attributable to Boston Properties Limited Partnership	'	'	'	'
Net Operating Income	$216,831	$188,790	$599,052	$493,064
Development and management services income	6,475	5,475	18,197	22,063
Income from unconsolidated joint ventures	4,419	14,736	10,069	72,240
Gains on consolidation of joint ventures	0	-1,810	0	385,991
Interest and other income	3,421	3,879	6,841	6,646
Gains (losses) from investments in securities	-297	956	651	1,872
Gains (losses) from early extinguishments of debt	0	-30	0	122
Gain on sale of real estate from discontinued operations	0	88,565	0	88,565
Gain on forgiveness of debt from discontinued operations	0	0	0	20,736
Gains on sales of real estate	41,937	0	41,937	0
General and administrative expense	22,589	24,841	75,765	94,673
Transaction costs	1,402	766	2,500	1,744
Depreciation and amortization expense	155,217	151,216	460,064	400,131
Interest expense	113,308	122,173	337,839	325,746
Impairment loss	0	0	0	4,401
Impairment loss from discontinued operations	0	0	0	2,852
Noncontrolling interest in property partnerships	5,566	-3,279	17,473	-924
Noncontrolling interest-redeemable preferred units	2,722	3,729	8,868	8,796
Net income attributable to Boston Properties Limited Partnership	144,715	174,140	294,370	740,252
Intersegment Eliminations [Member]	'	'	'	'
Reconciliation of Net Operating Income to net income attributable to Boston Properties Limited Partnership	'	'	'	'
Net Operating Income	389,564	360,138	1,119,184	971,950
Development and management services income	6,475	5,475	18,197	22,063
Income from unconsolidated joint ventures	4,419	14,736	10,069	72,240
Gains on consolidation of joint ventures	0	-1,810	0	385,991
Interest and other income	3,421	3,879	6,841	6,646
Gains (losses) from investments in securities	-297	956	651	1,872
Gains (losses) from early extinguishments of debt	0	-30	0	122
Income from discontinued operations	0	1,677	0	7,486
Gain on sale of real estate from discontinued operations	0	88,565	0	88,565
Gain on forgiveness of debt from discontinued operations	0	0	0	20,736
Gains on sales of real estate	41,937	0	41,937	0
General and administrative expense	22,589	24,841	75,765	94,673
Transaction costs	1,402	766	2,500	1,744
Depreciation and amortization expense	155,217	151,216	460,064	400,131
Interest expense	113,308	122,173	337,839	325,746
Impairment loss	0	0	0	4,401
Impairment loss from discontinued operations	0	0	0	2,852
Noncontrolling interest in property partnerships	5,566	-3,279	17,473	-924
Noncontrolling interest-redeemable preferred units	2,722	3,729	8,868	8,796
Net income attributable to Boston Properties Limited Partnership	$144,715	$174,140	$294,370	$740,252

Segment_Information_Segment_In

Segment Information Segment Information (narrative) (Details) (767 Fifth Avenue (The GM Building) [Member], Consolidated Properties [Member])	0 Months Ended
	31-May-13
	partners
767 Fifth Avenue (The GM Building) [Member] | Consolidated Properties [Member]	'
Segment Reporting Information [Line Items]	'
Number of Joint Venture Partners	2

Subsequent_Events_Subsequent_E

Subsequent Events Subsequent Events (Details) (USD $)

9 Months Ended

0 Months Ended

0 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Jul. 03, 2014

19-May-14

Nov. 05, 2014

Oct. 16, 2014

Oct. 22, 2014

Nov. 01, 2014

Nov. 06, 2014

Jun. 11, 2014

Oct. 02, 2014

Oct. 24, 2014

Oct. 24, 2014

Oct. 24, 2014

Oct. 23, 2014

Oct. 24, 2014

Sep. 16, 2014

Oct. 30, 2014

Sep. 16, 2014

Oct. 30, 2014

Sep. 16, 2014

Oct. 30, 2014

Sep. 16, 2014

Oct. 30, 2014

Sep. 16, 2014

Oct. 30, 2014

Sep. 16, 2014

Oct. 30, 2014

Nov. 03, 2014

Nov. 03, 2014

Noncontrolling Interests [Member]

series four preferred units [Member]

series four preferred units [Member]

series four preferred units [Member]

Subsequent Event [Member]

Subsequent Event [Member]

415 Main Street (formerly Seven Cambridge Center) [Member]

535 Mission Street [Member]

425 Main Street [Member]

Patriots park [Member]

Patriots park [Member]

One Thirty Third Avenue [Member]

Annapolis Junction Building Six [Member]

Construction Loans [Member]

Construction Loans [Member]

Construction Loans [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Low Rise [Member]

Low Rise [Member]

Office Tower [Member]

Office Tower [Member]

Unsecured Debt [Member]

Unsecured Debt [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

series four preferred units [Member]

series four preferred units [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Buildings

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Annapolis Junction Building Six [Member]

Annapolis Junction Building Six [Member]

Annapolis Junction Building Six [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Consolidated Properties [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

leaseyear

sqft

sqft

Buildings

sqft

sqft

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

601 Lexington Avenue [Member]

601 Lexington Avenue [Member]

Atlantic Wharf Office [Member]

Atlantic Wharf Office [Member]

100 Federal Street [Member]

100 Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

601 Lexington Avenue, Atlantic Wharf Office Building and 100 Hundred Federal Street [Member]

5.625% Unsecured Senior Notes [Member]

5% Unsecured Senior Notes [Member]

sqft

sqft

sqft

Subsequent Event [Member]

sqft

Subsequent Event [Member]

sqft

Subsequent Event [Member]

601 Lexington Avenue [Member]

601 Lexington Avenue [Member]

601 Lexington Avenue [Member]

601 Lexington Avenue [Member]

sqft

sqft

sqft

floor

Subsequent Event [Member]

floor

Subsequent Event [Member]

floor

floor

Subsequent Event [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Sales price

'

'

'

'

'

'

'

'

'

'

'

$321,000,000

$321,000,000

$14,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Repayments of Secured Debt

82,030,000

96,750,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Coupon/Stated Rate (percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.63%

5.00%

Redemption of Series Four Preferred Units

'

'

'

'

16,000,000

'

1,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Series Four Preferred Units (in shares)

'

'

40,440

40,440

40,440

'

12,667

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of real estate properties

'

'

'

'

'

'

'

'

'

'

'

3

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Area of Real Estate Property

'

'

'

'

'

'

'

'

231,000

307,000

'

706,000

706,000

129,000

119,000

'

'

'

'

'

1,669,000

1,669,000

791,000

791,000

1,323,000

1,323,000

'

'

'

'

'

'

Debt Instrument, Repurchased Face Amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

300,000,000

250,000,000

Series Four Preferred Units Released from Escrow

'

'

'

'

'

319,687

'

27,773

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Purchase Option Price for Real Estate Property

'

'

'

'

'

'

'

'

106,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Purchase option date (lease year)

'

'

'

'

'

'

'

'

11

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ownership Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Construction Loan

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

13,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Description of Variable Rate Basis

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'LIBOR

'LIBOR

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Basis Spread on Variable Rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.25%

1.65%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Construction Loan Facility Borrowing Capacity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

16,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ownership Percentage of Partner

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

45.00%

45.00%

'

'

'

'

'

'

'

'

'

'

'

'

Gross sales Price Before Deducting Indebtedness

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,827,000,000

1,827,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Number of floors real estate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6

6

59

59

'

'

Secured Debt Carrying Amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

712,900,000

712,900,000

'

'

'

'

'

'

'

'

'

'

'

'

Basis Points Added to US Treasury Security Used in Redemption Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.35%

0.25%

Non-refundable option payment

'

'

'

'

'

'

'

'

'

'

$1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'