Boston Properties LTD Partnership 10-Q 11 May 15 2015 Q1 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	3 Months Ended
	Mar. 31, 2015	4-May-15
Document And Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Entity Registrant Name	BOSTON PROPERTIES LTD PARTNERSHIP
Amendment Flag	FALSE
Entity Central Index Key	1043121
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		0

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
ASSETS
Real estate, at cost	$17,731,971	$17,810,133
Construction in progress	797,148	736,311
Land held for future development	271,327	268,114
Less: accumulated depreciation	-3,573,516	-3,476,321
Total real estate	15,226,930	15,338,237
Cash and cash equivalents	1,064,396	1,763,079
Cash held in escrows	588,218	487,321
Investments in securities	20,736	19,459
Tenant and other receivables (net of allowance for doubtful accounts of $1,099 and $1,142, respectively)	47,768	46,595
Accrued rental income (net of allowance of $1,126 and $1,499, respectively)	713,874	691,999
Deferred charges, net	806,468	831,744
Prepaid expenses and other assets	165,985	164,432
Investments in unconsolidated joint ventures	196,188	193,394
Total assets	18,830,563	19,536,260
Liabilities:
Mortgage notes payable	4,289,120	4,309,484
Unsecured senior notes (net of discount of $11,899 and $12,296, respectively)	5,288,101	5,287,704
Unsecured line of credit	0	0
Mezzanine notes payable	309,475	309,796
Outside member's notes payable	180,000	180,000
Accounts payable and accrued expenses	224,086	243,263
Distributions payable	112,796	882,472
Accrued interest payable	186,630	163,532
Other liabilities	483,762	502,255
Total liabilities	11,073,970	11,878,506
Commitments and contingencies	0	0
Noncontrolling interests:
Redeemable interest in property partnerships	105,520	104,692
Redeemable partnership units—12,667 series four preferred units outstanding at redemption value at March 31, 2015 and December 31, 2014	633	633
Redeemable partnership units—16,242,774 and 16,453,670 common units and 1,845,626 and 1,496,799 long term incentive units outstanding at redemption value at March 31, 2015 and December 31, 2014, respectively	2,541,058	2,310,046
Capital:
5.25% Series B cumulative redeemable preferred units, liquidation preference $2,500 per unit, 80,000 units issued and outstanding at March 31, 2015 and December 31, 2014	193,623	193,623
Boston Properties Limited Partnership partners’ capital—1,714,905 and 1,710,644 general partner units and 151,687,202 and 151,403,301 limited partner units outstanding at March 31, 2015 and December 31, 2014, respectively	3,316,257	3,446,293
Noncontrolling interests in property partnerships	1,599,502	1,602,467
Total capital	5,109,382	5,242,383
Total liabilities and capital	$18,830,563	$19,536,260

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified
Tenant and other receivables, allowance for doubtful accounts	$1,099	$1,142
Accrued rental income, allowance	1,126	1,499
Unsecured senior notes, discount	$11,899	$12,296
Redeemable partnership units, series four preferred units outstanding (in units)	12,667	12,667
Redeemable partnership units, common units (in units)	16,242,774	16,453,670
Redeemable partnership units, long term incentive units outstanding at redemption value (in units)	1,845,626	1,496,799
General Partners' Capital Account, Units Outstanding (in units)	1,714,905	1,710,644
Limited Partners' Capital Account, Units Outstanding (in units)	151,687,202	151,403,301
Series B Cumulative Redeemable Preferred Stock [Member]
Series B Dividend Rate Percentage	5.25%	5.25%
Series B, Liquidation Preference Per Unit (dollars per share)	$2,500	$2,500
Series B, Unitsssued	80,000	80,000
Series B, Units Outstanding (in shares)	80,000	80,000

Consolidated_Statements_Of_Ope

Consolidated Statements Of Operations (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenue
Base rent	$490,682	$455,018
Recoveries from tenants	88,593	81,934
Parking and other	24,788	24,333
Total rental revenue	604,063	561,285
Hotel revenue	9,085	8,193
Development and management services	5,328	5,216
Total revenue	618,476	574,694
Expenses
Rental	221,350	206,388
Hotel	7,576	6,797
General and administrative	28,791	29,905
Transaction costs	327	437
Depreciation and amortization	152,224	152,245
Total expenses	410,268	395,772
Operating income	208,208	178,922
Other income (expense)
Income from unconsolidated joint ventures	14,834	2,816
Interest and other income	1,407	1,311
Gains from investments in securities	393	286
Interest expense	-108,757	-113,554
Income before gains on sales of real estate	116,085	69,781
Gains on sales of real estate	95,084	0
Net income	211,169	69,781
Net income attributable to noncontrolling interests
Noncontrolling interest in property partnerships	-15,208	-4,354
Noncontrolling interest-redeemable preferred units	-3	-619
Net income attributable to Boston Properties Limited Partnership	195,958	64,808
Preferred distributions	-2,589	-2,589
Net income attributable to Boston Properties Limited Partnership common unitholders	$193,369	$62,219
Basic earnings per common unit attributable to Boston Properties Limited Partnership
Net income (in dollars per share)	$1.13	$0.37
Weighted average number of common units outstanding (in shares)	171,084	169,841
Diluted earnings per common unit attributable to Boston Properties Limited Partnership
Diluted Earnings: Net income, Per Unit Amount (in dollars per share)	$1.12	$0.37
Weighted average number of common and common equivalent units outstanding (in shares)	171,727	169,980

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$211,169		$69,781
Other comprehensive income (loss):
Effective portion of interest rate contracts	-3,533		0
Amortization of interest rate contracts (1)	627	[1],[2]	629	[1],[2]
Other comprehensive income (loss)	-2,906		629
Comprehensive income	208,263		70,410
Comprehensive income attributable to noncontrolling interests	-15,211		-4,973
Comprehensive income attributable to Boston Properties Limited Partnership	$193,052		$65,437
[1]	(1) Consists of amounts from previous interest rate hedging programs.
[2]	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 $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning Balance	$3,639,916	$4,187,171
Contributions	3,763	1,535
Net income allocable to general and limited partner units	175,770	58,648
Distributions	-102,300	-102,050
Accumulated other comprehensive loss	-2,603	567
Unearned compensation	-1,608	-474
Conversion of redeemable partnership units	8,689	627
Adjustment to reflect redeemable partnership units at redemption value	-211,747	-261,862
Ending Balance	$3,509,880	$3,884,162

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income	$211,169	$69,781
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	152,224	152,245
Non-cash compensation expense	11,011	10,380
Income from unconsolidated joint ventures	-14,834	-2,816
Distributions of net cash flow from operations of unconsolidated joint ventures	1,350	1,431
Gains from investments in securities	-393	-286
Non-cash portion of interest expense	-10,884	-7,676
Settlement of accreted debt discount on repurchases of unsecured exchangeable senior notes	0	-92,979
Gains on sales of real estate	-95,084	0
Change in assets and liabilities:
Cash held in escrows	1,044	2,961
Tenant and other receivables, net	-1,173	21,652
Accrued rental income, net	-23,250	-10,127
Prepaid expenses and other assets	3,447	5,989
Accounts payable and accrued expenses	-5,535	1,288
Accrued interest payable	23,098	11,128
Other liabilities	-23,136	-22,197
Tenant leasing costs	-27,608	-16,565
Total adjustments	-9,723	54,428
Net cash provided by operating activities	201,446	124,209
Cash flows from investing activities:
Construction in progress	-60,013	-97,025
Building and other capital improvements	-19,391	-17,510
Tenant improvements	-26,950	-31,551
Proceeds from sales of real estate	194,821	0
Proceeds from sales of real estate placed in escrow	-201,857	0
Proceeds from sales of real estate released from escrow	99,916	0
Deposits on real estate	-5,000	0
Capital contributions to unconsolidated joint ventures	-2,444	0
Capital distributions from unconsolidated joint ventures	24,527	113
Investments in securities, net	-884	-1,099
Net cash provided by (used in) investing activities	2,725	-147,072
Cash flows from financing activities:
Repayments of mortgage notes payable	-7,024	-6,630
Redemption/Repurchase of unsecured exchangeable senior notes	0	-654,521
Proceeds from real estate financing transaction	6,000	0
Payments on real estate financing transaction	-636	0
Deferred financing costs	-20	-18
Net proceeds from equity transactions	-145	-527
Distributions	-883,684	-496,330
Proceeds from noncontrolling interest in property partnership	629	468
Distributions to noncontrolling interest in property partnerships	-17,974	-5,143
Net cash used in financing activities	-902,854	-1,162,701
Net decrease in cash and cash equivalents	-698,683	-1,185,564
Cash and cash equivalents, beginning of period	1,763,079	2,365,137
Cash and cash equivalents, end of period	1,064,396	1,179,573
Supplemental disclosures:
Cash paid for interest	104,508	220,790
Interest capitalized	7,965	17,709
Non-cash investing and financing activities:
Additions to real estate included in accounts payable and accrued expenses	9,243	9,393
Distributions declared but not paid	112,796	114,799
Conversions of redeemable partnership units to partners' capital	8,689	627
Issuance of restricted securities to employees and directors	$42,279	$26,534

Organization

Organization	3 Months Ended
	Mar. 31, 2015
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 March 31, 2015 and December 31, 2014 owned an approximate 89.5% 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 2012, the Company issued LTIP Units in connection with the granting to employees of outperformance awards (also referred to as “2012 OPP Units” ). On February 6, 2015, the measurement period for the Company’s 2012 OPP Unit awards expired and the Company’s total return to shareholders (“TRS”) was sufficient for employees to earn and therefore become eligible to vest in a portion of the 2012 OPP Unit awards (See Notes 7 and 10). In February 2013, February 2014 and February 2015, 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,” “2014 MYLTIP Units" and "2015 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 7 and 10).
	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 8).
	At March 31, 2015, there were two series of Preferred Units outstanding (i.e., Series Four Preferred Units and Series B Preferred Units).
	•	The 12,667 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 Note 7).
	•	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 8).
	All references herein to the Company refer to Boston Properties Limited Partnership and its consolidated subsidiaries, collectively, unless the context otherwise requires.
	Properties
	At March 31, 2015, the Company owned or had interests in a portfolio of 168 commercial real estate properties (the “Properties”) aggregating approximately 45.5 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 43,341 vehicles containing approximately 14.7 million square feet. At March 31, 2015, the Properties consisted of:
	•	160 office properties, including 129 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
	•	two residential properties.
	The Company owns or controls undeveloped land parcels totaling approximately 483.1 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	3 Months Ended
	Mar. 31, 2015
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, 2014.
	Fair Value of Financial Instruments
	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 using market prices. The inputs used in determining the fair value of the Company’s unsecured 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 March 31, 2015 and December 31, 2014 (in thousands):
		March 31, 2015				December 31, 2014
		Carrying		Estimated		Carrying		Estimated
		Amount		Fair Value		Amount		Fair Value
	Mortgage notes payable	$	4,289,120	$	4,428,519	$	4,309,484	$	4,449,541
	Mezzanine notes payable	309,475		306,143		309,796		306,156
	Unsecured senior notes	5,288,101		5,749,666		5,287,704		5,645,819
	Total	$	9,886,696	$	10,484,328	$	9,906,984	$	10,401,516
	The Company uses interest rate swap agreements to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves.  The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties.  However, as of March 31, 2015, the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives.  As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.
	Recent Accounting Pronouncements
	On April 10, 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2014-08, "Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity" (“ASU 2014-08”). ASU 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 2014-08 is effective prospectively for reporting periods beginning after December 15, 2014. Early adoption is permitted, and the Company early adopted ASU 2014-08 during the first quarter of 2014. The Company’s adoption of ASU 2014-08 resulted in the operating results and gain on sale of real estate from the operating property sold during the three months ended March 31, 2015 not being reflected as Discontinued Operations in the Company's Consolidated Statements of Operations (See Note 3).
	In February 2015, the FASB issued ASU 2015-02, “Consolidation (Topic 810): Amendments to the Consolidation Analysis” (“ASU 2015-02”). ASU 2015-02 affects reporting entities that are required to evaluate whether they should consolidate certain legal entities. ASU 2015-02 modifies the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities, eliminates the presumption that a general partner should consolidate a limited partnership and affects the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships. ASU 2015-02 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. A reporting entity may apply the amendments in ASU 2015-02 using: (a) a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the fiscal year of adoption; or (b) by applying the amendments retrospectively. The Company is currently assessing the potential impact that the adoption of ASU 2015-02 will have on its consolidated financial statements.
	In April 2015, the FASB issued ASU 2015-03, "Simplifying the Presentation of Debt Issuance Costs" ("ASU 2015-03"), which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs is not affected. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years and shall be applied on a retrospective basis, wherein the balance sheet of each individual period presented should be adjusted to reflect the period-specific effects of applying the new guidance. Early adoption is permitted for financial statements that have not been previously issued. The Company does not expect the adoption of ASU 2015-03 to have a material impact on its consolidated financial statements.

Real_Estate_Activity_During_th

Real Estate Activity During the Three Months Ended March 31, 2015	3 Months Ended
	Mar. 31, 2015
Real Estate [Abstract]
Real Estate Activity During The Six Months Ended June 30, 2014	3. Real Estate Activity During the Three Months Ended March 31, 2015
	Dispositions
	On February 19, 2015, the Company completed the sale of a parcel of land within its Washingtonian North property located in Gaithersburg, Maryland for a gross sale price of $8.7 million. Net cash proceeds totaled approximately $8.3 million, resulting in a gain on sale of real estate totaling approximately $3.7 million. The parcel contains approximately 8.5 acres of the approximately 27 acre property.
	On March 17, 2015, the Company completed the sale of its Residences on The Avenue property located in Washington, DC for a gross sale price of $196.0 million. Net cash proceeds totaled approximately $192.5 million, resulting in a gain on sale of real estate totaling approximately $91.4 million. The Company has agreed to provide net operating income support of up to $6.0 million should the property’s net operating income fail to achieve certain thresholds, which has been recorded as a reduction to the gain on sale. The Residences on The Avenue is comprised of 335 apartment units and approximately 50,000 net rentable square feet of retail space, subject to a ground lease that expires on February 1, 2068. The Residences on The Avenue contributed approximately $1.1 million and $0.8 million of net income to the Company for the period from January 1, 2015 through March 16, 2015 and for the three months ended March 31, 2014, respectively.

Investments_in_Unconsolidated_

Investments in Unconsolidated Joint Ventures	3 Months Ended
	Mar. 31, 2015
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	4. Investments in Unconsolidated Joint Ventures
	The investments in unconsolidated joint ventures consist of the following at March 31, 2015:
	Entity		Properties		Nominal %				Carrying Value of Investment (1)
					Ownership
									(in thousands)
	Square 407 Limited Partnership		Market Square North		50	%			$	(7,345	)
	The Metropolitan Square Associates LLC		Metropolitan Square		51	%			8,850
	BP/CRF 901 New York Avenue LLC		901 New York Avenue		25	%	(2)		(12,907		)
	WP Project Developer LLC		Wisconsin Place Land and Infrastructure		33.3	%	(3)		45,283
	Annapolis Junction NFM, LLC		Annapolis Junction		50	%	(4)		25,935
	540 Madison Venture LLC		540 Madison Avenue		60	%			67,809
	500 North Capitol LLC		500 North Capitol Street, NW		30	%			(2,493		)
	501 K Street LLC		1001 6th Street		50	%	(5)		42,735
	Podium Developer LLC		North Station (Phase I - Air Rights)		50	%			5,576
									$	173,443
	_______________
	-1	Investments with deficit balances aggregating approximately $22.7 million have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.
	-2	The Company’s economic ownership has increased based on the achievement of certain return thresholds.
	-3	The Company’s wholly-owned 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.
	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:
		March 31, 2015				December 31, 2014
		(in thousands)
	ASSETS
	Real estate and development in process, net	$	1,036,221			$	1,034,552
	Other assets	224,398				264,097
	Total assets	$	1,260,619			$	1,298,649
	LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
	Mortgage and notes payable	$	831,039			$	830,075
	Other liabilities	38,500				34,211
	Members’/Partners’ equity	391,080				434,363
	Total liabilities and members’/partners’ equity	$	1,260,619			$	1,298,649
	Company’s share of equity	$	201,037			$	209,828
	Basis differentials (1)	(27,594		)		(27,786		)
	Carrying value of the Company’s investments in unconsolidated joint ventures (2)	$	173,443			$	182,042
	_______________
	-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.
	-2	Investments with deficit balances aggregating approximately $22.7 million and $11.4 million at March 31, 2015 and December 31, 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.
	The combined summarized statements of operations of the Company's unconsolidated joint ventures are as follows:
		For the three months ended March 31,
		2015				2014
		(in thousands)
	Total revenue (1)	$	39,532			$	38,034
	Expenses
	Operating	16,275				15,464
	Depreciation and amortization	9,071				9,092
	Total expenses	25,346				24,556
	Operating income	14,186				13,478
	Other expense
	Interest expense	7,980				8,012
	Net income	$	6,206			$	5,466
	Company’s share of net income (2)	$	14,642			$	2,625
	Basis differential	192				191
	Income from unconsolidated joint ventures	$	14,834			$	2,816
	_______________
	-1	Includes straight-line rent adjustments of $1.6 million and $0.6 million for the three months ended March 31, 2015 and 2014, respectively. Includes net above-/below-market rent adjustments of $(0.1) million and $0.1 million for the three months ended March 31, 2015 and 2014, respectively.
	-2	During the three months ended March 31, 2015, the Company received a distribution of approximately $24.5 million, which was generated from the excess loan proceeds from the refinancing of 901 New York Avenue's mortgage loan to a new 10-year mortgage loan totaling $225.0 million.  The Company’s allocation of income and distributions for the three months ended March 31, 2015 was not proportionate to its nominal ownership interest as a result of the achievement of specified investment return thresholds, as provided for in the joint venture agreement.

Derivative_Instruments_and_Hed

Derivative Instruments and Hedging Activities (Notes)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	5. Derivative Instruments and Hedging Activities
	On February 19, 2015, the Company commenced a planned interest rate hedging program in contemplation of a financing with a target commencement date in September 2016 and maturity in September 2026. The Company entered into five forward-starting interest rate swap contracts during the three months ended March 31, 2015, which fix the 10-year swap rate at a weighted-average rate of approximately 2.492% per annum on notional amounts aggregating $250.0 million (See Note 12). The Company's interest rate swap contracts consisted of the following at March 31, 2015:
	Derivative Instrument	Notional Amount			Effective Date		Maturity Date	Strike Rate		Balance Sheet Location	Fair Value
		(in thousands)									(in thousands)
	Interest Rate Swap	$	50,000		1-Sep-16		1-Sep-26	2.571	%	Other Liabilities	$	(1,062	)
	Interest Rate Swap	75,000			1-Sep-16		1-Sep-26	2.476	%	Other Liabilities	(946		)
	Interest Rate Swap	50,000			1-Sep-16		1-Sep-26	2.523	%	Other Liabilities	(844		)
	Interest Rate Swap	50,000			1-Sep-16		1-Sep-26	2.48	%	Other Liabilities	(654		)
	Interest Rate Swap	25,000			1-Sep-16		1-Sep-26	2.348	%	Other Liabilities	(27		)
		$	250,000								$	(3,533	)
	The Company entered into the interest rate swap contracts designated and qualifying as a cash flow hedges to reduce its exposure to the variability in future cash flows attributable to changes in the 10-year swap rate in contemplation of obtaining 10-year fixed-rate financing in September 2016. The Company has formally documented all of its relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking various hedge transactions. The Company also assesses and documents, both at the hedging instrument’s inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in cash flows associated with the hedged items. All components of the forward-starting interest rate swap contracts were included in the assessment of hedge effectiveness. The Company has agreements with each of its derivative counterparties that contain a provision where the Company could be declared in default on its derivative obligations if repayment of the underlying indebtedness is accelerated by the lender due to the Company's default on the indebtedness. As of March 31, 2015, the fair value of derivatives in a net liability position, which excludes any adjustment for nonperformance risk, related to these agreements was approximately $3.5 million. As of March 31, 2015, the Company has not posted any collateral related to these agreements. If the Company had breached any of these provisions at March 31, 2015, it could have been required to settle its obligations under the agreements at their termination value of approximately $3.5 million. The Company accounts for the effective portion of changes in the fair value of a derivative in accumulated other comprehensive income (loss) and subsequently reclassifies the effective portion to earnings over the term that the hedged transaction affects earnings. The Company accounts for the ineffective portion of changes in the fair value of a derivative directly in earnings. During the three months ended March 31, 2015, the Company has recorded the changes in fair value of the swap contracts related to the effective portion of the interest rate contracts aggregating approximately $3.5 million in Other Liabilities and Accumulated Other Comprehensive Loss within the Company’s Consolidated Balance Sheets. During the three months ended March 31, 2015, the Company did not record any hedge ineffectiveness. The Company does not expect to reclassify into earnings any amounts recorded within Accumulated Other Comprehensive Loss relating to the forward-starting interest rate swap contracts within the next 12 months.
	The following table presents the location in the financial statements of the gains or losses recognized related to the Company's cash flow hedges for the three months ended March 31, 2015 and 2014:
		Three Months Ended March 31,
		2015			2014
		(in thousands)
	Amount of gain (loss) related to the effective portion recognized in other comprehensive income (loss)	$	(3,533	)	$	—
	Amount of gain (loss) related to the effective portion subsequently reclassified to earnings (1)	$	(627	)	$	(629	)
	Amount of gain (loss) related to the ineffective portion and amount excluded from effectiveness testing	$	—		$	—
	__________
	(1) Consists of amounts from previous interest rate hedging programs.
	The following table reflects the changes in accumulated other comprehensive loss for the three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	(12,973	)
	Effective portion of interest rate contracts	(3,533		)
	Amortization of interest rate contracts (1)	627
	Balance at March 31, 2015	$	(15,879	)
	Balance at January 1, 2014	$	(15,481	)
	Amortization of interest rate contracts (1)	629
	Balance at March 31, 2014	$	(14,852	)
	__________
	(1) Consists of amounts from previous interest rate hedging programs.

Commitments_And_Contingencies

Commitments And Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	6. Commitments and Contingencies
	General
	In the normal course of business, the Company guarantees its performance of services or indemnifies third parties against its negligence. In addition, in the normal course of business, the Company guarantees to certain tenants the obligations of its subsidiaries for the payment of tenant improvement allowances and brokerage commissions in connection with their leases and limited costs arising from delays in delivery of their premises.
	The Company has letter of credit and performance obligations related to lender and development requirements that total approximately $21.6 million.
	Certain of the Company’s joint venture agreements include provisions whereby, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exception, under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners (See also Note 7). 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 March 31, 2015, the maximum funding obligation under the guarantee was approximately $16.4 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 $25.7 million related to its obligations to provide funds for certain tenant re-leasing costs. The mortgage financing will mature on January 6, 2017.
	In connection with the mortgage financing collateralized by the Company's consolidated joint venture's Fountain Square property located in Reston, Virginia, the Company has agreed to guarantee approximately $0.7 million related to its obligation to provide funds for certain tenant re-leasing costs. The mortgage financing will mature on October 11, 2016.
	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. During 2014, the Company received an initial distribution totaling approximately $7.7 million. On March 11, 2015, the Company received a second interim distribution totaling approximately $4.5 million, which is included in Base Rent in the accompanying Consolidated Statements of Operations for the three months ended March 31, 2015, leaving a remaining claim of approximately $33.0 million. Recently, claims of similar priority to that of the Company's remaining claim were quoted privately reflecting a value for the Company's remaining claim of approximately $5.5 million. The Company will continue to evaluate whether to attempt to sell the remaining claim or wait until the trustee distributes proceeds from the Lehman Brothers estate. Given the inherent uncertainties in bankruptcy proceedings, there can be no assurance as to the timing or amount of proceeds, if any, that the Company may ultimately realize on the remaining claim, whether by sale to a third party or by one or more distributions from the trustee. Accordingly, the Company has not recorded any estimated recoveries associated with this gain contingency within its consolidated financial statements at March 31, 2015.
	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 and further extended to December 31, 2020 by the Terrorism Risk Insurance Program Reauthorization Act of 2015 (“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. 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 is backstopped by the Federal Government if the aggregate industry insured losses resulting from a certified act of terrorism exceed a “program trigger.” In 2015, the program trigger is $100 million and the coinsurance is 15%, however, both will increase in subsequent years pursuant to 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. 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 Salesforce Tower) with a $170 million per occurrence limit (increased on March 1, 2015 from $120 million), and a $170 million annual aggregate limit (increased on March 1, 2015 from $120 million), $20 million of which is provided by IXP, as a direct insurer. 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. 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. Insofar as the Company owns IXP, it is responsible for its liquidity and capital resources, and the accounts of IXP are part of the Company’s consolidated financial statements. In particular, if a loss occurs which is covered by the Company’s NBCR Coverage but is less than the applicable program trigger under TRIA, IXP would be responsible for the full amount of the loss without any backstop by the Federal Government. IXP would also be responsible for any recoupment charges by the Federal Government in the event losses are paid out and its insurance policy is maintained after the payout by the Federal Government. If the Company experiences a loss and IXP is required to pay under its insurance policy, the Company would ultimately record the loss to the extent of the required payment. Therefore, insurance coverage provided by IXP should not be considered as the equivalent of third-party insurance, but rather as a modified form of self-insurance. In addition, the Company 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	3 Months Ended
	Mar. 31, 2015
Noncontrolling Interest [Abstract]
Noncontrolling Interests	7. 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 March 31, 2015, the noncontrolling interests in the Company consisted of 16,242,774 OP Units, 1,845,626 LTIP Units (including 217,688 2012 OPP Units), 309,818 2013 MYLTIP Units, 476,320 2014 MYLTIP Units, 368,415 2015 MYLTIP Units and 12,667 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 accretes 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 records 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 three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	104,692
	Net income	75
	Distributions	(1,400		)
	Adjustment to reflect redeemable interest at redemption value	2,153
	Balance at March 31, 2015	$	105,520
	Balance at January 1, 2014	$	99,609
	Net loss	(106		)
	Distributions	(1,050		)
	Adjustment to reflect redeemable interest at redemption value	1,874
	Balance at March 31, 2014	$	100,327
	Noncontrolling Interest—Redeemable Preferred Units of the Company
	The Preferred Units at March 31, 2015 consisted of 12,667 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 of 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. On October 16, 2014, the Company released to the holders 27,773 Series Four Preferred Units that were previously subject to the security interest under the pledge agreement. 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. 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 17, 2015, 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 three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	633
	Net income	3
	Distributions	(3		)
	Balance at March 31, 2015	$	633
	Balance at January 1, 2014	$	105,746
	Net income	619
	Distributions	(619		)
	Reallocation of partnership interest	12,378
	Balance at March 31, 2014	$	118,124
	Noncontrolling Interest—Common Units of the Company
	During the three months ended March 31, 2015, 258,599 OP Units were presented by the holders for redemption (including 46,992 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 March 31, 2015, the Company had outstanding 309,818 2013 MYLTIP Units, 476,320 2014 MYLTIP Units and 368,415 2015 MYLTIP Units. Prior to the measurement date (February 4, 2016 for 2013 MYLTIP Units, February 3, 2017 for 2014 MYLTIP Units and February 4, 2018 for 2015 MYLTIP Units), holders of MYLTIP Units will be entitled to receive per unit distributions equal to one-tenth (10%) of the regular quarterly distributions payable on an OP Unit, but will not be entitled to receive any special distributions. After the measurement date, the number of MYLTIP Units, both vested and unvested, that MYLTIP award recipients have earned, if any, based on the establishment of a performance pool, will be entitled to receive distributions in an amount per unit equal to distributions, both regular and special, payable on an OP Unit.
	On February 6, 2015, the measurement period for the Company’s 2012 OPP Unit awards ended and Boston Properties, Inc.’s TRS performance was sufficient for employees to earn and therefore become eligible to vest in a portion of the 2012 OPP Unit awards. The final outperformance pool was determined to be approximately $32.1 million, or approximately 80% of the total maximum outperformance pool of $40.0 million. As a result, 174,549 2012 OPP Units were automatically forfeited.
	On January 28, 2015, the Company paid a special cash distribution on the OP Units and LTIP Units in the amount of $4.50 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 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 December 31, 2014. The special cash distribution was in addition to the regular quarterly distribution on the OP Units and LTIP Units. Holders of MYLTIP Units are not entitled to receive any special distributions. On March 18, 2015, 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 2013 MYLTIP Units, 2014 MYLTIP Units and 2015 MYLTIP Units in the amount of $0.065 per unit, in each case payable on April 30, 2015 to holders of record as of the close of business on March 31, 2015.
	The following table reflects the activity of the noncontrolling interests—redeemable common units for the three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	2,310,046
	Contributions	38,371
	Net income	20,188
	Distributions	(11,705		)
	Conversion of redeemable partnership units	(8,689		)
	Unearned compensation	(18,597		)
	Accumulated other comprehensive loss	(303		)
	Adjustment to reflect redeemable partnership units at redemption value	211,747
	Balance at March 31, 2015	$	2,541,058
	Balance at January 1, 2014	$	1,710,218
	Contributions	23,379
	Net income	6,160
	Distributions	(11,218		)
	Conversion of redeemable partnership units	(627		)
	Unearned compensation	(14,619		)
	Accumulated other comprehensive loss	62
	Adjustment to reflect redeemable partnership units at redemption value	249,484
	Balance at March 31, 2014	$	1,962,839
	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 March 31, 2015 was approximately $2.5 billion based on the closing price of Boston Properties, Inc.’s common stock of $140.48 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 $1.6 billion at March 31, 2015 and December 31, 2014, are included in Noncontrolling Interests—Property Partnerships on the accompanying Consolidated Balance Sheets.
	The following table reflects the activity of the noncontrolling interests in property partnerships for the three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	1,602,467
	Capital contributions	629
	Net income	12,980
	Distributions	(16,574		)
	Balance at March 31, 2015	$	1,599,502
	Balance at January 1, 2014	$	726,132
	Capital contributions	468
	Net income	2,586
Distributions	(4,093		)
Balance at March 31, 2014	$	725,093

Partners_Capital

Partners' Capital	3 Months Ended
	Mar. 31, 2015
Partners' Capital [Abstract]
Partners' Capital	8. Partners’ Capital
	As of March 31, 2015, Boston Properties, Inc. owned 1,714,905 general partnership units and 151,687,202 limited partnership units.
	On June 3, 2014, Boston Properties, Inc. established an “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. 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 ATM stock offering program since its inception.
	During the three months ended March 31, 2015, Boston Properties, Inc. acquired 258,599 OP Units in connection with the redemption of an equal number of redeemable OP Units from third parties.
	During the three months ended March 31, 2015, the Company issued 5,909 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 28, 2015, the Company paid a special cash distribution and regular quarterly distribution aggregating $5.15 per OP Unit to unitholders of record as of the close of business on December 31, 2014. On March 18, 2015, Boston Properties, Inc.'s Board of Directors declared a distribution of $0.65 per OP Unit payable on April 30, 2015 to unitholders of record as of the close of business on March 31, 2015.
	As of March 31, 2015, 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 17, 2015, the Company paid a distribution on its outstanding Series B Preferred Units of $32.8125 per unit. On March 18, 2015, Boston Properties, Inc.'s Board of Directors declared a distribution of $32.8125 per Series B Preferred Unit payable on May 15, 2015 to shareholders of record as of the close of business on May 5, 2015.

Earnings_Per_Common_Unit

Earnings Per Common Unit	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Common Unit	9. Earnings Per Common Unit
	The following table provides a reconciliation of both the net income attributable to Boston Properties Limited Partnership common unitholders and the number of common units used in the computation of basic earnings per common unit, which is calculated by dividing net income attributable to Boston Properties Limited Partnership common unitholders by the weighted-average number of common units outstanding during the period. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are also participating securities. As such, unvested restricted common stock of Boston Properties, Inc. and the Company’s LTIP 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 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 17,854,000 and 16,811,000 redeemable common units for the three months ended March 31, 2015 and 2014, respectively.
		For the three months ended March 31, 2015
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,369		171,084	$	1.13
	Allocation of undistributed earnings to participating securities	(210		)	—	—
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,159		171,084	$	1.13
	Effect of Dilutive Securities:
	Stock Based Compensation	—			643	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,159		171,727	$	1.12
		For the three months ended March 31, 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 common unitholders	$	62,219		169,841	$	0.37
	Effect of Dilutive Securities:
	Stock Based Compensation	—			139	—
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	62,219		169,980	$	0.37

Stock_Option_and_Incentive_Pla

Stock Option and Incentive Plan	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	10. Stock Option and Incentive Plan
	On January 21, 2015, Boston Properties, Inc.'s Compensation Committee approved the 2015 Multi-Year, Long-Term Incentive Program awards under Boston Properties, Inc.'s 2012 Plan to certain officers and employees of Boston Properties, Inc. The 2015 MYLTIP awards utilize TRS over a three-year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will be based on Boston Properties, Inc.'s 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 $40.8 million depending on Boston Properties, Inc.'s TRS relative to the two indices, with three tiers (threshold: approximately $8.2 million; target: approximately $16.3 million; high: approximately $40.8 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 4, 2018 and 50% on February 4, 2019, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by Boston Properties, Inc. without cause, or termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 4, 2018, earned awards will be calculated based on TRS performance up to the date of the change of control. The 2015 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 Accounting Standards Codification (“ASC”) 718 “Compensation-Stock Compensation,” the 2015 MYLTIP awards have an aggregate value of approximately $15.7 million, which amount will generally be amortized into earnings over the four-year plan period under the graded vesting method.
	On February 6, 2015, the measurement period for the Company’s 2012 OPP Unit awards ended and Boston Properties, Inc.’s TRS performance was sufficient for employees to earn and therefore become eligible to vest in a portion of the 2012 OPP Unit awards. The final outperformance pool was determined to be approximately $32.1 million, or approximately 80% of the total maximum outperformance pool of $40.0 million. As a result, 174,549 2012 OPP Units were automatically forfeited.
	During the three months ended March 31, 2015, Boston Properties, Inc. issued 30,965 shares of restricted common stock and the Company issued 183,789 LTIP Units (including 85,962 LTIP Units issued on January 1, 2015 to Mortimer B. Zuckerman, non-executive Chairman of the Board of Boston Properties, Inc., pursuant to the Transition Benefits Agreement dated March 10, 2013) and 375,000 2015 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 2015 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 three months ended March 31, 2015 were valued at approximately $4.4 million ($141.81 per share). The LTIP Units granted (excluding the number issued to Mr. Zuckerman, as discussed above) were valued at approximately $12.7 million ($129.75 per unit weighted-average fair value) using a Monte Carlo simulation method model. The per unit fair values of the LTIP Units granted were estimated on the dates of grant and for a substantial majority of such units were valued using the following assumptions: an expected life of 5.7 years, a risk-free interest rate of 1.47% and an expected price volatility of 26%. The value of the LTIP Units issued to Mr. Zuckerman was expensed between March 2013 and July 2014, in accordance with the vesting schedule set forth in the Transition Benefits Agreement. As the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and 2015 MYLTIP Units are subject to both a service condition and a market condition, the Company recognizes the compensation expense related to the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and 2015 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, 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and 2015 MYLTIP Units was approximately $10.1 million and $9.9 million for the three months ended March 31, 2015 and 2014, respectively. At March 31, 2015, there was $26.2 million of unrecognized compensation expense related to unvested restricted stock and LTIP Units and $27.2 million of unrecognized compensation expense related to unvested 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and 2015 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 3.1 years.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	11. 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. 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, interest expense, depreciation and amortization expense, gains from investments in securities, income from unconsolidated joint ventures, gains on sales of real estate, noncontrolling interests and preferred distributions 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 common unitholders.
	Information by geographic area and property type (dollars in thousands):
	For the three months ended March 31, 2015:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	169,907		$	253,098		$	66,252		$	93,131		$	582,388
	Office/Technical	6,120			—			5,659			3,042			14,821
	Residential	1,178			—			—			5,676			6,854
	Hotel	9,085			—			—			—			9,085
	Total	186,290			253,098			71,911			101,849			613,148
	% of Grand Totals	30.38		%	41.28		%	11.73		%	16.61		%	100		%
	Rental Expenses:
	Class A Office	74,465			85,061			21,909			32,280			213,715
	Office/Technical	1,986			—			912			1,191			4,089
	Residential	509			—			—			3,037			3,546
	Hotel	7,576			—			—			—			7,576
	Total	84,536			85,061			22,821			36,508			228,926
	% of Grand Totals	36.92		%	37.16		%	9.97		%	15.95		%	100		%
	Net operating income	$	101,754		$	168,037		$	49,090		$	65,341		$	384,222
	% of Grand Totals	26.48		%	43.73		%	12.78		%	17.01		%	100		%
	For the three months ended March 31, 2014:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	170,942		$	217,308		$	54,608		$	97,048		$	539,906
	Office/Technical	5,820			—			6,217			3,660			15,697
	Residential	1,163			—			—			4,519			5,682
	Hotel	8,193			—			—			—			8,193
	Total	186,118			217,308			60,825			105,227			569,478
	% of Grand Totals	32.68		%	38.16		%	10.68		%	18.48		%	100		%
	Rental Expenses:
	Class A Office	71,398			74,371			19,313			33,439			198,521
	Office/Technical	1,689			—			1,214			1,202			4,105
	Residential	448			—			—			3,314			3,762
	Hotel	6,797			—			—			—			6,797
	Total	80,332			74,371			20,527			37,955			213,185
	% of Grand Totals	37.68		%	34.89		%	9.63		%	17.8		%	100		%
	Net operating income	$	105,786		$	142,937		$	40,298		$	67,272		$	356,293
	% of Grand Totals	29.69		%	40.12		%	11.31		%	18.88		%	100		%
	The following is a reconciliation of Net Operating Income to net income attributable to Boston Properties Limited Partnership common unitholders:
		Three months ended
		March 31,
		2015			2014
		(in thousands)
	Net Operating Income	$	384,222		$	356,293
	Add:
	Development and management services income	5,328			5,216
	Income from unconsolidated joint ventures	14,834			2,816
	Interest and other income	1,407			1,311
	Gains from investments in securities	393			286
	Gains on sales of real estate	95,084			—
	Less:
	General and administrative expense	28,791			29,905
	Transaction costs	327			437
	Depreciation and amortization expense	152,224			152,245
	Interest expense	108,757			113,554
	Noncontrolling interests in property partnerships	15,208			4,354
	Noncontrolling interest—redeemable preferred units	3			619
	Preferred distributions	2,589			2,589
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,369		$	62,219

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events
	From April 1, 2015 through May 8, 2015, the Company entered into three forward-starting interest rate swap contracts which fix the ten-year swap rate at a weighted-average rate of 2.344% per annum on notional amounts aggregating $75.0 million. The interest rate swap contracts were entered into in advance of a financing with a target commencement date in September 2016 and maturity in September 2026 (See Note 5).
	On May 8, 2015, the Company entered into a joint venture with an unrelated third party to redevelop an existing building into a Class A office building totaling approximately 120,000 net rentable square feet at 1265 Main Street in Waltham, Massachusetts.  The joint venture partner contributed real estate and improvements, with an aggregate fair value of approximately $9.4 million, for its initial 50% interest in the joint venture. For its initial 50% interest, the Company will contribute cash totaling approximately $9.4 million as the joint venture incurs costs. The joint venture has entered into a fifteen-year lease with a tenant to occupy 100% of the building.

Basis_Of_Presentation_And_Summ1

Basis Of Presentation And Summary Of Significant Accounting Policies Recent Accounting Pronouncement (Policies)	3 Months Ended
	Mar. 31, 2015
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") 2014-08, "Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity" (“ASU 2014-08”). ASU 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 2014-08 is effective prospectively for reporting periods beginning after December 15, 2014. Early adoption is permitted, and the Company early adopted ASU 2014-08 during the first quarter of 2014. The Company’s adoption of ASU 2014-08 resulted in the operating results and gain on sale of real estate from the operating property sold during the three months ended March 31, 2015 not being reflected as Discontinued Operations in the Company's Consolidated Statements of Operations (See Note 3).
	In February 2015, the FASB issued ASU 2015-02, “Consolidation (Topic 810): Amendments to the Consolidation Analysis” (“ASU 2015-02”). ASU 2015-02 affects reporting entities that are required to evaluate whether they should consolidate certain legal entities. ASU 2015-02 modifies the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities, eliminates the presumption that a general partner should consolidate a limited partnership and affects the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships. ASU 2015-02 is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. A reporting entity may apply the amendments in ASU 2015-02 using: (a) a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the fiscal year of adoption; or (b) by applying the amendments retrospectively. The Company is currently assessing the potential impact that the adoption of ASU 2015-02 will have on its consolidated financial statements.
	In April 2015, the FASB issued ASU 2015-03, "Simplifying the Presentation of Debt Issuance Costs" ("ASU 2015-03"), which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs is not affected. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years and shall be applied on a retrospective basis, wherein the balance sheet of each individual period presented should be adjusted to reflect the period-specific effects of applying the new guidance. Early adoption is permitted for financial statements that have not been previously issued. The Company does not expect the adoption of ASU 2015-03 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)	3 Months Ended
	Mar. 31, 2015
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 March 31, 2015 and December 31, 2014 (in thousands):
		March 31, 2015				December 31, 2014
		Carrying		Estimated		Carrying		Estimated
		Amount		Fair Value		Amount		Fair Value
	Mortgage notes payable	$	4,289,120	$	4,428,519	$	4,309,484	$	4,449,541
	Mezzanine notes payable	309,475		306,143		309,796		306,156
	Unsecured senior notes	5,288,101		5,749,666		5,287,704		5,645,819
	Total	$	9,886,696	$	10,484,328	$	9,906,984	$	10,401,516

Investments_in_Unconsolidated_1

Investments in Unconsolidated Joint Ventures (Tables)	3 Months Ended
	Mar. 31, 2015
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	The investments in unconsolidated joint ventures consist of the following at March 31, 2015:
	Entity		Properties		Nominal %				Carrying Value of Investment (1)
					Ownership
									(in thousands)
	Square 407 Limited Partnership		Market Square North		50	%			$	(7,345	)
	The Metropolitan Square Associates LLC		Metropolitan Square		51	%			8,850
	BP/CRF 901 New York Avenue LLC		901 New York Avenue		25	%	(2)		(12,907		)
	WP Project Developer LLC		Wisconsin Place Land and Infrastructure		33.3	%	(3)		45,283
	Annapolis Junction NFM, LLC		Annapolis Junction		50	%	(4)		25,935
	540 Madison Venture LLC		540 Madison Avenue		60	%			67,809
	500 North Capitol LLC		500 North Capitol Street, NW		30	%			(2,493		)
	501 K Street LLC		1001 6th Street		50	%	(5)		42,735
	Podium Developer LLC		North Station (Phase I - Air Rights)		50	%			5,576
									$	173,443
	_______________
	-1	Investments with deficit balances aggregating approximately $22.7 million have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.
	-2	The Company’s economic ownership has increased based on the achievement of certain return thresholds.
	-3	The Company’s wholly-owned 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.
Balance Sheets Of The Unconsolidated Joint Ventures	The combined summarized balance sheets of the Company's unconsolidated joint ventures are as follows:
		March 31, 2015				December 31, 2014
		(in thousands)
	ASSETS
	Real estate and development in process, net	$	1,036,221			$	1,034,552
	Other assets	224,398				264,097
	Total assets	$	1,260,619			$	1,298,649
	LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
	Mortgage and notes payable	$	831,039			$	830,075
	Other liabilities	38,500				34,211
	Members’/Partners’ equity	391,080				434,363
	Total liabilities and members’/partners’ equity	$	1,260,619			$	1,298,649
	Company’s share of equity	$	201,037			$	209,828
	Basis differentials (1)	(27,594		)		(27,786		)
	Carrying value of the Company’s investments in unconsolidated joint ventures (2)	$	173,443			$	182,042
	_______________
	-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.
	-2	Investments with deficit balances aggregating approximately $22.7 million and $11.4 million at March 31, 2015 and December 31, 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.
Statements Of Operations Of The Joint Ventures	The combined summarized statements of operations of the Company's unconsolidated joint ventures are as follows:
		For the three months ended March 31,
		2015				2014
		(in thousands)
	Total revenue (1)	$	39,532			$	38,034
	Expenses
	Operating	16,275				15,464
	Depreciation and amortization	9,071				9,092
	Total expenses	25,346				24,556
	Operating income	14,186				13,478
	Other expense
	Interest expense	7,980				8,012
	Net income	$	6,206			$	5,466
	Company’s share of net income (2)	$	14,642			$	2,625
	Basis differential	192				191
	Income from unconsolidated joint ventures	$	14,834			$	2,816
	_______________
	-1	Includes straight-line rent adjustments of $1.6 million and $0.6 million for the three months ended March 31, 2015 and 2014, respectively. Includes net above-/below-market rent adjustments of $(0.1) million and $0.1 million for the three months ended March 31, 2015 and 2014, respectively.
	-2	During the three months ended March 31, 2015, the Company received a distribution of approximately $24.5 million, which was generated from the excess loan proceeds from the refinancing of 901 New York Avenue's mortgage loan to a new 10-year mortgage loan totaling $225.0 million.  The Company’s allocation of income and distributions for the three months ended March 31, 2015 was not proportionate to its nominal ownership interest as a result of the achievement of specified investment return thresholds, as provided for in the joint venture agreement.

Derivative_Instruments_and_Hed1

Derivative Instruments and Hedging Activities Derivative Instruments and hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]
	Derivative Instrument	Notional Amount			Effective Date		Maturity Date	Strike Rate		Balance Sheet Location	Fair Value
		(in thousands)									(in thousands)
	Interest Rate Swap	$	50,000		1-Sep-16		1-Sep-26	2.571	%	Other Liabilities	$	(1,062	)
	Interest Rate Swap	75,000			1-Sep-16		1-Sep-26	2.476	%	Other Liabilities	(946		)
	Interest Rate Swap	50,000			1-Sep-16		1-Sep-26	2.523	%	Other Liabilities	(844		)
	Interest Rate Swap	50,000			1-Sep-16		1-Sep-26	2.48	%	Other Liabilities	(654		)
	Interest Rate Swap	25,000			1-Sep-16		1-Sep-26	2.348	%	Other Liabilities	(27		)
		$	250,000								$	(3,533	)
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block]
		Three Months Ended March 31,
		2015			2014
		(in thousands)
	Amount of gain (loss) related to the effective portion recognized in other comprehensive income (loss)	$	(3,533	)	$	—
	Amount of gain (loss) related to the effective portion subsequently reclassified to earnings (1)	$	(627	)	$	(629	)
	Amount of gain (loss) related to the ineffective portion and amount excluded from effectiveness testing	$	—		$	—
	__________
	(1) Consists of amounts from previous interest rate hedging programs.
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
	Balance at January 1, 2015	$	(12,973	)
	Effective portion of interest rate contracts	(3,533		)
	Amortization of interest rate contracts (1)	627
	Balance at March 31, 2015	$	(15,879	)
	Balance at January 1, 2014	$	(15,481	)
	Amortization of interest rate contracts (1)	629
	Balance at March 31, 2014	$	(14,852	)
	__________
	(1) Consists of amounts from previous interest rate hedging programs.

Noncontrolling_Interests_Table

Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 2015
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 three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	104,692
	Net income	75
	Distributions	(1,400		)
	Adjustment to reflect redeemable interest at redemption value	2,153
	Balance at March 31, 2015	$	105,520
	Balance at January 1, 2014	$	99,609
	Net loss	(106		)
	Distributions	(1,050		)
	Adjustment to reflect redeemable interest at redemption value	1,874
	Balance at March 31, 2014	$	100,327
Schedule Of Series Two Preferred Units	The following table reflects the activity of the noncontrolling interests—redeemable preferred units of the Company for the three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	633
	Net income	3
	Distributions	(3		)
	Balance at March 31, 2015	$	633
	Balance at January 1, 2014	$	105,746
	Net income	619
	Distributions	(619		)
	Reallocation of partnership interest	12,378
	Balance at March 31, 2014	$	118,124
Noncontrolling Interests-Redeemable Common Units	The following table reflects the activity of the noncontrolling interests—redeemable common units for the three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	2,310,046
	Contributions	38,371
	Net income	20,188
	Distributions	(11,705		)
	Conversion of redeemable partnership units	(8,689		)
	Unearned compensation	(18,597		)
	Accumulated other comprehensive loss	(303		)
	Adjustment to reflect redeemable partnership units at redemption value	211,747
	Balance at March 31, 2015	$	2,541,058
	Balance at January 1, 2014	$	1,710,218
	Contributions	23,379
	Net income	6,160
	Distributions	(11,218		)
	Conversion of redeemable partnership units	(627		)
	Unearned compensation	(14,619		)
	Accumulated other comprehensive loss	62
	Adjustment to reflect redeemable partnership units at redemption value	249,484
	Balance at March 31, 2014	$	1,962,839
Noncontrolling Interests-Property Partnerships	The following table reflects the activity of the noncontrolling interests in property partnerships for the three months ended March 31, 2015 and 2014 (in thousands):
	Balance at January 1, 2015	$	1,602,467
	Capital contributions	629
	Net income	12,980
	Distributions	(16,574		)
	Balance at March 31, 2015	$	1,599,502
	Balance at January 1, 2014	$	726,132
	Capital contributions	468
	Net income	2,586
	Distributions	(4,093		)
	Balance at March 31, 2014	$	725,093

Earnings_Per_Common_Unit_Table

Earnings Per Common Unit (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Computation Of Basic And Diluted Earnings Per Unit
		For the three months ended March 31, 2015
		Income			Units	Per Unit
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per unit amounts)
	Basic Earnings:
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,369		171,084	$	1.13
	Allocation of undistributed earnings to participating securities	(210		)	—	—
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,159		171,084	$	1.13
	Effect of Dilutive Securities:
	Stock Based Compensation	—			643	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,159		171,727	$	1.12
		For the three months ended March 31, 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 common unitholders	$	62,219		169,841	$	0.37
	Effect of Dilutive Securities:
	Stock Based Compensation	—			139	—
	Diluted Earnings:
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	62,219		169,980	$	0.37

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
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 March 31, 2015:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	169,907		$	253,098		$	66,252		$	93,131		$	582,388
	Office/Technical	6,120			—			5,659			3,042			14,821
	Residential	1,178			—			—			5,676			6,854
	Hotel	9,085			—			—			—			9,085
	Total	186,290			253,098			71,911			101,849			613,148
	% of Grand Totals	30.38		%	41.28		%	11.73		%	16.61		%	100		%
	Rental Expenses:
	Class A Office	74,465			85,061			21,909			32,280			213,715
	Office/Technical	1,986			—			912			1,191			4,089
	Residential	509			—			—			3,037			3,546
	Hotel	7,576			—			—			—			7,576
	Total	84,536			85,061			22,821			36,508			228,926
	% of Grand Totals	36.92		%	37.16		%	9.97		%	15.95		%	100		%
	Net operating income	$	101,754		$	168,037		$	49,090		$	65,341		$	384,222
	% of Grand Totals	26.48		%	43.73		%	12.78		%	17.01		%	100		%
	For the three months ended March 31, 2014:
		Boston			New York			San			Washington,			Total
								Francisco			DC
	Rental Revenue:
	Class A Office	$	170,942		$	217,308		$	54,608		$	97,048		$	539,906
	Office/Technical	5,820			—			6,217			3,660			15,697
	Residential	1,163			—			—			4,519			5,682
	Hotel	8,193			—			—			—			8,193
	Total	186,118			217,308			60,825			105,227			569,478
	% of Grand Totals	32.68		%	38.16		%	10.68		%	18.48		%	100		%
	Rental Expenses:
	Class A Office	71,398			74,371			19,313			33,439			198,521
	Office/Technical	1,689			—			1,214			1,202			4,105
	Residential	448			—			—			3,314			3,762
	Hotel	6,797			—			—			—			6,797
	Total	80,332			74,371			20,527			37,955			213,185
	% of Grand Totals	37.68		%	34.89		%	9.63		%	17.8		%	100		%
	Net operating income	$	105,786		$	142,937		$	40,298		$	67,272		$	356,293
	% of Grand Totals	29.69		%	40.12		%	11.31		%	18.88		%	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 common unitholders:
		Three months ended
		March 31,
		2015			2014
		(in thousands)
	Net Operating Income	$	384,222		$	356,293
	Add:
	Development and management services income	5,328			5,216
	Income from unconsolidated joint ventures	14,834			2,816
	Interest and other income	1,407			1,311
	Gains from investments in securities	393			286
	Gains on sales of real estate	95,084			—
	Less:
	General and administrative expense	28,791			29,905
	Transaction costs	327			437
	Depreciation and amortization expense	152,224			152,245
	Interest expense	108,757			113,554
	Noncontrolling interests in property partnerships	15,208			4,354
	Noncontrolling interest—redeemable preferred units	3			619
	Preferred distributions	2,589			2,589
	Net income attributable to Boston Properties Limited Partnership common unitholders	$	193,369		$	62,219

Organization_Details

Organization (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Jul. 03, 2014
	sqft
	Vehicles
	acre
	Y
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.50%	89.50%
Restriction on redemption of OP units from date of issuance (years)	1
in lieu of a cash redemption OP unit to Common Stock conversion (in shares)	1
One OP unit is equivalent to one share of Common Stock (in shares)	1
OP unit conversion rate (in shares)	1
Number of series of preferred units outstanding	2
Number of vehicles in structured parking	43,341
Area of parking structures (in square feet)	14,700,000
Area of undeveloped land parcels owned (in acres)	483.1
Commercial Real Estate Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	168
Net Rentable Area (in sf)	45,500,000
Total Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	10
Net Rentable Area (in sf)	3,300,000
Total Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	160
Class A Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	129
Office Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	9
Office/Technical Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	31
Hotel Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	1
Retail Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	5
Retail Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	1
Residential Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	2
Series B Cumulative Redeemable Preferred Stock [Member]
Real Estate Properties [Line Items]
Series B, Units Outstanding (in shares)	80,000	80,000
Ratio of depository shares to shares of Series B Preferred Stock	0.01
Series B, Dividend Rate, Percentage	5.25%
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Real Estate Properties [Line Items]
Series B, Units Outstanding (in shares)	8,000,000
Series B Preferred Units [Member]
Real Estate Properties [Line Items]
Series B, Units Outstanding (in shares)	80,000
Noncontrolling Interests [Member]
Real Estate Properties [Line Items]
Series Four Preferred Units (in shares)	12,667
Noncontrolling Interests [Member] | series four preferred units [Member]
Real Estate Properties [Line Items]
Preferred Units Liquidation Preference	50
Series Four Preferred Units (in shares)	12,667		12,667
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 (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	$4,289,120	$4,309,484
Mezzanine notes payable	309,475	309,796
Unsecured senior notes	5,288,101	5,287,704
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	4,289,120	4,309,484
Mezzanine notes payable	309,475	309,796
Unsecured senior notes	5,288,101	5,287,704
Total	9,886,696	9,906,984
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable	4,428,519	4,449,541
Mezzanine notes payable	306,143	306,156
Unsecured senior notes	5,749,666	5,645,819
Total	$10,484,328	$10,401,516

Real_Estate_Activity_During_th1

Real Estate Activity During the Three Months Ended March 31, 2015 (Narrative) (Details) (USD $)	3 Months Ended		0 Months Ended		3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Feb. 19, 2015	Mar. 17, 2015	Mar. 16, 2015
Real Estate Properties [Line Items]
Proceeds from sales of real estate	$194,821,000	$0
Gains on sales of real estate	95,084,000	0
Operating income	208,208,000	178,922,000
Washingtonian North land parcel [Member]
Real Estate Properties [Line Items]
Sale Price Of Sold Property			8,700,000
Proceeds from sales of real estate			8,300,000
Gains on sales of real estate			3,700,000
Land sold (in acres)			8.5
Area of Land (in acres)			27
Residences on The Avenue [Member]
Real Estate Properties [Line Items]
Sale Price Of Sold Property				196,000,000
Number of apartment units (apartment units)				335
Net Rentable Area (retail space) (in sf)				50,000
Proceeds from sales of real estate				192,500,000
Gains on sales of real estate				91,400,000
Rental revenue supoprt payments to buyer maximum				6,000,000
Operating income		$800,000			$1,100,000

Investments_in_Unconsolidated_2

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Carrying value of the Company's investments in unconsolidated joint ventures	$196,188		$193,394
Square 407 Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Market Square North
Ownership Percentage	50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	-7,345	[1]
The Metropolitan Square Associates LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Metropolitan Square
Ownership Percentage	51.00%
Carrying value of the Company's investments in unconsolidated joint ventures	8,850	[1]
BP/CRF 901 New York Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	901 New York Avenue
Ownership Percentage	25.00%	[2]
Carrying value of the Company's investments in unconsolidated joint ventures	-12,907	[1]
WP Project Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Wisconsin Place Land and Infrastructure
Ownership Percentage	33.30%	[3]
Carrying value of the Company's investments in unconsolidated joint ventures	45,283	[1]
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Annapolis Junction
Ownership Percentage	50.00%	[4]
Carrying value of the Company's investments in unconsolidated joint ventures	25,935	[1]
Number of real estate properties	2
Number of buildings under construction	2
Parcels of undeveloped land	2
540 Madison Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	540 Madison Avenue
Ownership Percentage	60.00%
Carrying value of the Company's investments in unconsolidated joint ventures	67,809	[1]
500 North Capitol LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	500 North Capitol Street, NW
Ownership Percentage	30.00%
Carrying value of the Company's investments in unconsolidated joint ventures	-2,493	[1]
Entity Owning Land And Infrastructure Of Project [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	33.30%
501 K Street [Member]
Schedule of Equity Method Investments [Line Items]
Properties	1001 6th Street
Ownership Percentage	50.00%	[5]
Carrying value of the Company's investments in unconsolidated joint ventures	42,735	[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
Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	North Station (Phase I - Air Rights)
Ownership Percentage	50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	5,576	[1]
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value of the Company's investments in unconsolidated joint ventures	-22,700		-11,400
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value of the Company's investments in unconsolidated joint ventures	$173,443	[1],[6]	$182,042	[6]
[1]	(1)Investments with deficit balances aggregating approximately $22.7 million have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.
[2]	(2)The Company’s economic ownership has increased based on the achievement of certain return thresholds.
[3]	(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]	(4)The joint venture owns two in-service buildings, two buildings under construction and two undeveloped land parcels.
[5]	(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.
[6]	(2)Investments with deficit balances aggregating approximately $22.7 million and $11.4 million at March 31, 2015 and December 31, 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.

Investments_in_Unconsolidated_3

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
ASSETS
Real estate and development in process, net	$15,226,930		$15,338,237
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage notes payable	4,289,120		4,309,484
Other liabilities	483,762		502,255
Total liabilities and capital	18,830,563		19,536,260
Carrying value of the Company's investments in unconsolidated joint ventures	196,188		193,394
Unconsolidated Joint Ventures [Member]
ASSETS
Real estate and development in process, net	1,036,221		1,034,552
Other assets	224,398		264,097
Total assets	1,260,619		1,298,649
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage notes payable	831,039		830,075
Other liabilities	38,500		34,211
Members'/Partners' equity	391,080		434,363
Total liabilities and capital	1,260,619		1,298,649
Company's share of equity	201,037		209,828
Basis differentials	-27,594	[1]	-27,786	[1]
Carrying value of the Company's investments in unconsolidated joint ventures	173,443	[2],[3]	182,042	[2]
Unconsolidated Joint Ventures [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Carrying value of the Company's investments in unconsolidated joint ventures	($22,700)		($11,400)
[1]	(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.
[2]	(2)Investments with deficit balances aggregating approximately $22.7 million and $11.4 million at March 31, 2015 and December 31, 2014, respectively, have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.
[3]	(1)Investments with deficit balances aggregating approximately $22.7 million have been reflected within Other Liabilities on the Company's Consolidated Balance Sheets.

Investments_in_Unconsolidated_4

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Total revenue	$618,476,000		$574,694,000
Expenses
Depreciation and amortization	152,224,000		152,245,000
Total expenses	410,268,000		395,772,000
Operating income	208,208,000		178,922,000
Other expense
Interest expense	108,757,000		113,554,000
Net income	211,169,000		69,781,000
Income from unconsolidated joint ventures	14,834,000		2,816,000
Distributions from excess loan proceeds	24,527,000		113,000
Mortgage loan	4,289,120,000				4,309,484,000
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	39,532,000	[1]	38,034,000	[1]
Expenses
Operating	16,275,000		15,464,000
Depreciation and amortization	9,071,000		9,092,000
Total expenses	25,346,000		24,556,000
Operating income	14,186,000		13,478,000
Other expense
Interest expense	7,980,000		8,012,000
Net income	6,206,000		5,466,000
Company's share of net income (loss)	14,642,000	[2]	2,625,000
Basis differential	192,000		191,000
Income from unconsolidated joint ventures	14,834,000		2,816,000
Straight Line Rent Adjustments	1,600,000		600,000
Below market rent adjustments, net	-100,000		100,000
Mortgage loan	831,039,000				830,075,000
BP/CRF 901 New York Avenue LLC [Member]
Other expense
Distributions from excess loan proceeds	24,500,000
Mortgage loan	$225,000,000
Mortgage loan term (in years)	10
[1]	(1)Includes straight-line rent adjustments of $1.6 million and $0.6 million for the three months ended March 31, 2015 and 2014, respectively. Includes net above-/below-market rent adjustments of $(0.1) million and $0.1 million for the three months ended March 31, 2015 and 2014, respectively.
[2]	(2)During the three months ended March 31, 2015, the Company received a distribution of approximately $24.5 million, which was generated from the excess loan proceeds from the refinancing of 901 New York Avenue's mortgage loan to a new 10-year mortgage loan totaling $225.0 million. The Company’s allocation of income and distributions for the three months ended March 31, 2015 was not proportionate to its nominal ownership interest as a result of the achievement of specified investment return thresholds, as provided for in the joint venture agreement.

Derivative_Instruments_and_Hed2

Derivative Instruments and Hedging Activities (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Debt Instrument [Line Items]
Repayments of Secured Debt	$7,024,000	$6,630,000
Amount of gain (loss) related to the effective portion recognized in other comprehensive income (loss)	-3,533,000	0
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Number of interest rate swap agreements entered into (swap contracts)	5
Maximum period of hedging exposure to the variability in future cash flows for forecasted transactions (in years)	10
Derivative, Average Fixed Interest Rate	2.49%
Notional Amount	250,000,000
Amount of gain (loss) related to the effective portion recognized in other comprehensive income (loss)	-3,500,000
Time period when the effects of the swaps may be reclassified into earnings (in months)	12
Derivative, Net Liability Position, Aggregate Fair Value	3,500,000
Assets Needed for Immediate Settlement, Aggregate Fair Value	($3,500,000)

Derivative_Instruments_and_Hed3

Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Notional Information (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Fair value	($3,533)	$0
Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	250,000
Interest Rate Swap [Member] | Interest Rate Sawp 2.571%t [Member]
Derivative [Line Items]
Notional Amount	50,000
Strike Price	2.57%
Fair value	-1,062
Interest Rate Swap [Member] | Interest Rate Swap 2.476%[Member]
Derivative [Line Items]
Notional Amount	75,000
Strike Price	2.48%
Fair value	-946
Interest Rate Swap [Member] | Interest Rate Swap 2.523% [Member]
Derivative [Line Items]
Notional Amount	50,000
Strike Price	2.52%
Fair value	-844
Interest Rate Swap [Member] | Interest Rate Swap 2.480% [Member]
Derivative [Line Items]
Notional Amount	50,000
Strike Price	2.48%
Fair value	-654
Interest Rate Swap [Member] | Interest Rate Swap 2.348% [Member]
Derivative [Line Items]
Notional Amount	25,000
Strike Price	2.35%
Fair value	($27)

Derivative_Instruments_and_Hed4

Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Gain or Loss Recognized Related to Cash Flow hedges (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Derivative [Line Items]
Amount of gain (loss) related to the effective portion recognized in other comprehensive income (loss)	($3,533)		$0
Amount of gain (loss) related to the effective portion subsequently reclassified to earnings (1)	-627	[1]	-629	[1]
Amount of gain (loss) related to the ineffective portion and amount excluded from effectiveness testing	$0		$0
[1]	(1) Consists of amounts from previous interest rate hedging programs.

Derivative_Instruments_and_Hed5

Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Changes in Accumulated Other Comprehensive Loss (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income or Loss [Roll Forward]
Beginning Balance	($12,973)		($15,481)
Effective portion of interest rate contracts	-3,533		0
Amortization of interest rate contracts (1)	627	[1],[2]	629	[1],[2]
Ending Balance	($15,879)		($14,852)
[1]	(1) Consists of amounts from previous interest rate hedging programs.
[2]	Amounts reclassified from comprehensive income primarily to interest expense within the Company's Consolidated Statements of Operations.

Commitments_And_Contingencies_

Commitments And Contingencies (Details) (USD $)	1 Months Ended	2 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Feb. 28, 2015	Mar. 31, 2015	Dec. 31, 2009	Mar. 11, 2015	Dec. 31, 2014	Jan. 10, 2014
Commitments And Contingencies [Line Items]
Letter of credit and performance obligations	$21,600,000		$21,600,000
Property insurance program per occurrence limits	1,000,000,000		1,000,000,000
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	170,000,000	120,000,000
Annual aggregate limit of the earthquake insurance which covers San Francisco region	170,000,000	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 SalesforceTower			60,000,000
Guarantee to cover liabilities of IXP	20,000,000		20,000,000
767 Venture, LLC [Member]
Commitments And Contingencies [Line Items]
Maximum funding obligation	16,400,000		16,400,000
Property insurance program per occurrence limits	1,625,000,000		1,625,000,000
Lehman [Member]
Commitments And Contingencies [Line Items]
Bankruptcy claim, amount filed by general creditor				45,300,000
Bankruptcy claim amount allowed by court to creditor							45,200,000
Bankruptcy Claims, Amount of Claims Settled					4,500,000	7,700,000
Bankruptcy remaining claim amount allowed by court to creditor	33,000,000		33,000,000
Bankruptcy remaining claim amount based on a privately quoted value	5,500,000		5,500,000
601 Lexington Avenue [Member]
Commitments And Contingencies [Line Items]
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP			250,000,000
John Hancock Tower [Member]
Commitments And Contingencies [Line Items]
Guarantee Obligation Related To Tenant Re-Leasing Costs			25,700,000
Fountain Square [Member]
Commitments And Contingencies [Line Items]
Guarantee Obligation Related To Tenant Re-Leasing Costs			$700,000

Noncontrolling_Interests_Narra

Noncontrolling Interests (Narrative) (Details)	Mar. 31, 2015
Noncontrolling Interests [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operating Partnership (OP) Units (in shares)	16,242,774
Long-Term Incentive Plan (LTIP) Units (in shares)	1,845,626
Series Four Preferred Units (in shares)	12,667
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)	217,688
2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP (in shares)	309,818
2014 MYLTIP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP (in shares)	476,320
2015 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIP (in shares)	368,415

Noncontrolling_Interests_Redee

Noncontrolling Interests (Redeemable Preferred Units) (Narrative) (Details) (Noncontrolling Interests [Member], USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Feb. 17, 2015	Nov. 05, 2014	Oct. 16, 2014	Jul. 03, 2014	19-May-14
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Series Four Preferred Units (in shares)	12,667
series four preferred units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distributions to Series Two Preferred Units (in dollars per share)		$0.25
Series Four Preferred Units (in shares)	12,667				12,667
Series Four Preferred Units Annual Dividend Payable Rate	2.00%
Preferred Units Liquidation Preference	$50
Series Four Preferred Units Released from Escrow (in shares)				27,773		319,687
Redemption of Series Four Preferred Units			$1.40		$16

Noncontrolling_Interests_Commo

Noncontrolling Interests (Common Units) (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended	0 Months Ended
	Jan. 28, 2015	Mar. 31, 2015	Feb. 06, 2015	Mar. 18, 2015
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)		258,599
Redemption of OP units issued on conversion of LTIP Units (in shares)		46,992
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
Distribution paid to outperformance awards, OPP Units (in dollars per share)	$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		$2,500,000,000
Closing price of common stock (in dollars per share)		$140.48
2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP (in shares)		309,818
2014 MYLTIP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP (in shares)		476,320
2015 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIP (in shares)		368,415
Quarter 4 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend shareholder of record date		31-Dec-14
Dividend payable date		28-Jan-15
Quarter 4 2014 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date		28-Jan-15
Holders of record date		31-Dec-14
Quarter 1 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend shareholder of record date		31-Mar-15
Dividends declared date		18-Mar-15
Dividend payable date		30-Apr-15
Quarter 1 2015 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividends declared date		18-Mar-15
Dividend payable date		30-Apr-15
Holders of record date		31-Mar-15
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)	$4.50
Opp Units Two Thousand And Twelve [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards earned			32,100,000
Potential maximum amount of Outperformance Awards earned (percent)			80.00%
Potential Awards Earned			$40,000,000
2012 OPP Units Forfeited (in shares)			174,549

Noncontrolling_Interests_Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Noncontrolling Interest [Abstract]
Noncontrolling interests in property partnerships	$1,599,502	$1,602,467

Noncontrolling_Interests_Redee1

Noncontrolling Interests (Redeemable Preferred Units) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Activity of noncontrolling interests
Net income	$3	$619
Redeemable Preferred Units [Member]
Activity of noncontrolling interests
Beginning Balance	633	105,746
Net income	3	619
Distributions	-3	-619
Reallocation of partnership interest		12,378
Ending Balance	633	118,124
Noncontrolling Interests [Member]
Activity of noncontrolling interests
Reallocation of partnership interest	($8,689)	($627)

Noncontrolling_Interests_Nonco

Noncontrolling Interests (Noncontrolling Interests-Redeemable Common Units) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Activity of noncontrolling interests
Accumulated other comprehensive loss	($15,879)	($14,852)	($12,973)	($15,481)
Noncontrolling Interests [Member]
Activity of noncontrolling interests
Beginning Balance	2,310,046	1,710,218
Contributions	38,371	23,379
Net income	20,188	6,160
Distributions	-11,705	-11,218
Conversion of redeemable partnership units	-8,689	-627
Unearned compensation	-18,597	-14,619
Accumulated other comprehensive loss	-303	62
Adjustments to reflect redeemable partnership units at redemption value	211,747	249,484
Ending Balance	$2,541,058	$1,962,839

Noncontrolling_Interests_Nonco1

Noncontrolling Interests (Noncontrolling Interests-Property Partnerships) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Activity of noncontrolling interests
Beginning balance	$1,602,467
Capital contributions	629	468
Net Income	15,208	4,354
Ending balance	1,599,502
Property Partnerships [Member]
Activity of noncontrolling interests
Beginning balance	1,602,467	726,132
Capital contributions	629	468
Net Income	12,980	2,586
Distributions	-16,574	-4,093
Ending balance	$1,599,502	$725,093

Noncontrolling_Interests_Nonco2

Noncontrolling Interests Noncontrolling interest - Reddemable interest in Property Partnerships (Details) (Fountain Square [Member], USD $)	0 Months Ended
In Millions, unless otherwise specified	Oct. 04, 2012
Fountain Square [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	50.00%
Payments to Acquire Businesses, Gross	87
Noncontrolling Interest, Ownership Percentage by Parent	50.00%
Future Fixed Price to Acquire Remaining Portion of Joint venture	$102
Fixed Price Option Expiration Date	31-Jan-16

Noncontrolling_Interests_Redee2

Noncontrolling Interests Redeemable Interest in Property Partnerships (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Redeemable Interest in Property Partnership [Abstract]
Beginning Balance	$104,692	$99,609
Net income (loss)	75	-106
Distributions	-1,400	-1,050
Adjustment to reflect redeemable interest at redemption value	2,153	1,874
Ending Balance	$105,520	$100,327

Partners_Capital_Details

Partners' Capital (Details) (USD $)	0 Months Ended	3 Months Ended	0 Months Ended
	Jan. 28, 2015	Mar. 31, 2015	Jun. 03, 2014	Feb. 17, 2015	Mar. 18, 2015	Dec. 31, 2014	Mar. 27, 2018
			Y
Class of Stock [Line Items]
General partnership units (in units)		1,714,905				1,710,644
Limited partnership units (in units)		151,687,202				151,403,301
Shares of its Common Stock in connection with the redemption of an equal number of OP Units (in shares)		258,599
OP Units to Boston Properties, Inc. in connection with the exercise by certain employees of options to purchase Common Stock of Boston Properties, Inc (in shares)		5,909
Dividend paid on common stock (in dollars per share)	$5.15
Dividends payable (in dollars per share)					$0.65
New ATM program [Member]
Class of Stock [Line Items]
At the market stock offering program, aggregate value of common stock			$600,000,000
At Market Stock Offering Program Maximum Length Of Sale In Years			3
Common Stock, Value, Issued		0
Quarter 4 2014 [Member]
Class of Stock [Line Items]
Dividend payable date		28-Jan-15
Dividend shareholder of record date		31-Dec-14
Quarter 1 2015 [Member]
Class of Stock [Line Items]
Dividend payable date		30-Apr-15
Dividend shareholder of record date		31-Mar-15
Dividends payable, date declared		18-Mar-15
Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Dividend paid on common stock (in dollars per share)				$32.81
Dividends payable (in dollars per share)					$32.81
Series B, Units Outstanding (in shares)		80,000				80,000
Series B, Liquidation Preference Per Unit (dollars per share)		2,500				2,500
Ratio of depository shares to shares of Series B Preferred Stock		0.01
Series B, Dividend Rate, Percentage		5.25%
Series B Cumulative Redeemable Preferred Stock [Member] | Quarter 1 2015 [Member]
Class of Stock [Line Items]
Dividend payable date		17-Feb-15
Series B Cumulative Redeemable Preferred Stock [Member] | Quarter 2 2015 [Member]
Class of Stock [Line Items]
Dividend payable date		15-May-15
Dividend shareholder of record date		5-May-15
Dividends payable, date declared		18-Mar-15
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Class of Stock [Line Items]
Series B, Units Outstanding (in shares)		8,000,000
Series B, Liquidation Preference Per Unit (dollars per share)		25					$25
Series B Preferred Units [Member]
Class of Stock [Line Items]
Series B, Units Outstanding (in shares)		80,000
Subsequent Event [Member] | Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Liquidation Preference Per Unit (dollars per share)							$2,500

Earnings_Per_Common_Unit_Detai

Earnings Per Common Unit (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Redeemable common units (in shares)	17,854,000	16,811,000
Basic Earnings:
Net income attributable to Boston Properties Limited Partnership common unitholders	$193,369	$62,219
Net income attributable to Boston Properties Limited Partnership common unitholders, Units (Denominator) (in shares)	171,084,000	169,841,000
Net income (in dollars per share)	$1.13	$0.37
Allocation of undistrubted earnings to participating securities	-210
Allocation of undistributed earnings to participating securities (in shares)	0
Allocation of undistributed earnings to participating securities (per share)	$0
Net income attributable to Boston Properties Limited Partnership common unitholders	193,159
Weighted Average Number Of Shares Outstanding After Allocation of Undistributed Earnings to Participating Securities Basic (in shares)	171,084,000
Earnings Per Share After Allocation of Undistributed Earnings to Particiapting Securities Basic (dollars per share)	$1.13
Effect of Dilutive Securities:
Stock Based Compensation, Income (Numerator)	0	0
Stock Based Compensation, Units (Denominator) (in shares)	643,000	139,000
Stock Based Compensation, Per Unit Amount (in dollars per share)	($0.01)	$0
Diluted Earnings:
Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders	$193,159	$62,219
Diluted Earnings: Net income, Units (Denominator) (in shares)	171,727,000	169,980,000
Diluted Earnings: Net income, Per Unit Amount (in dollars per share)	$1.12	$0.37

Stock_Option_and_Incentive_Pla1

Stock Option and Incentive Plan (Restricted Stock) (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
stock based compensation expense	$10,100,000	$9,900,000
Restricted Stock [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
Shares issued (in shares)	30,965
Employee and director payment per share (in dollars per share)	$0.01
Common Stock, Value, Issued	4,400,000
Employee's weighted average cost per share (in dollars per share)	$141.81
LTIP Units [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
LTIP units issued (in shares)	183,789
Expected life assumed to calculate per unit fair value per LTIP unit (in years)	5 years 8 months 12 days
Risk-free rate	1.47%
Expected price volatility	26.00%
Value of LTIP units issued	12,700,000
Per unit fair value weighted-average (in dollars per share)	$129.75
2015 MYLTIP [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
MYLTIP units issued (in shares)	375,000
LTIPs And Restricted Stock [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
Vesting annual installments	4
Unrecognized compensation expenses	26,200,000
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, 2014 and 2015 MYLTIP Units [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
Unrecognized compensation expenses	$27,200,000
Weighted-average period (in years)	3 years 1 month 6 days
Non-executive Chairman of the Board of Directors [Member] | LTIP Units [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
LTIP units issued (in shares)	85,962

Stock_Option_and_Incentive_Pla2

Stock Option and Incentive Plan Stock option and incentive plan (Narrative) (Details) (USD $)	0 Months Ended
	Jan. 21, 2015	Feb. 06, 2015
	tiers
	indices
	Y
2015 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TRS Measurement, Years	3
Indices Used to Compare TRS	2
Number of Tiers	3
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	$15,700,000
MYLTIP Value Amortized Into Earnings, Years	4
2015 MYLTIP [Member] | 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%
2015 MYLTIP [Member] | 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%
2015 MYLTIP [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned	0
2015 MYLTIP [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned	40,800,000
2015 MYLTIP [Member] | Threshold [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier	8,200,000
2015 MYLTIP [Member] | Target [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier	16,300,000
2015 MYLTIP [Member] | High [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier	40,800,000
2012 OPP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		40,000,000
Outperformance awards earned		$32,100,000
Potential maximum amount of Outperformance Awards earned (percent)		80.00%
2012 OPP Units Forfeited (in shares)		174,549
MYLTIP Vesting 2018 [Member] | 2015 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage	50.00%
Vesting Date	4-Feb-18
MYLTIP vesting 2019 [Member] | 2015 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage	50.00%
Vesting Date	4-Feb-19

Segment_Information_Schedule_O

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	$582,388	$539,906
Rental Revenue: Office/Technical	14,821	15,697
Rental Revenue: Residential	6,854	5,682
Rental Revenue: Hotel	9,085	8,193
Rental Revenue Total	613,148	569,478
Total revenue	618,476	574,694
Rental Revenue: % of Grand Totals	100.00%	100.00%
Rental Expenses: Class A Office	213,715	198,521
Rental Expenses: Office/Technical	4,089	4,105
Rental Expenses: Residential	3,546	3,762
Rental Expenses: Hotel	7,576	6,797
Rental Expenses: Total	228,926	213,185
Rental Expenses: % Of Grand Totals	100.00%	100.00%
Net operating income	384,222	356,293
Percentage Of Total Net Operating Income	100.00%	100.00%
Boston [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	169,907	170,942
Rental Revenue: Office/Technical	6,120	5,820
Rental Revenue: Residential	1,178	1,163
Rental Revenue: Hotel	9,085	8,193
Rental Revenue Total	186,290	186,118
Rental Revenue: % of Grand Totals	30.38%	32.68%
Rental Expenses: Class A Office	74,465	71,398
Rental Expenses: Office/Technical	1,986	1,689
Rental Expenses: Residential	509	448
Rental Expenses: Hotel	7,576	6,797
Rental Expenses: Total	84,536	80,332
Rental Expenses: % Of Grand Totals	36.92%	37.68%
Net operating income	101,754	105,786
Percentage Of Total Net Operating Income	26.48%	29.69%
New York [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	253,098	217,308
Rental Revenue: Office/Technical	0	0
Rental Revenue: Residential	0	0
Rental Revenue: Hotel	0	0
Rental Revenue Total	253,098	217,308
Rental Revenue: % of Grand Totals	41.28%	38.16%
Rental Expenses: Class A Office	85,061	74,371
Rental Expenses: Office/Technical	0	0
Rental Expenses: Residential	0	0
Rental Expenses: Hotel	0	0
Rental Expenses: Total	85,061	74,371
Rental Expenses: % Of Grand Totals	37.16%	34.89%
Net operating income	168,037	142,937
Percentage Of Total Net Operating Income	43.73%	40.12%
San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	66,252	54,608
Rental Revenue: Office/Technical	5,659	6,217
Rental Revenue: Residential	0	0
Rental Revenue: Hotel	0	0
Rental Revenue Total	71,911	60,825
Rental Revenue: % of Grand Totals	11.73%	10.68%
Rental Expenses: Class A Office	21,909	19,313
Rental Expenses: Office/Technical	912	1,214
Rental Expenses: Residential	0	0
Rental Expenses: Hotel	0	0
Rental Expenses: Total	22,821	20,527
Rental Expenses: % Of Grand Totals	9.97%	9.63%
Net operating income	49,090	40,298
Percentage Of Total Net Operating Income	12.78%	11.31%
Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	93,131	97,048
Rental Revenue: Office/Technical	3,042	3,660
Rental Revenue: Residential	5,676	4,519
Rental Revenue: Hotel	0	0
Rental Revenue Total	101,849	105,227
Rental Revenue: % of Grand Totals	16.61%	18.48%
Rental Expenses: Class A Office	32,280	33,439
Rental Expenses: Office/Technical	1,191	1,202
Rental Expenses: Residential	3,037	3,314
Rental Expenses: Hotel	0	0
Rental Expenses: Total	36,508	37,955
Rental Expenses: % Of Grand Totals	15.95%	17.80%
Net operating income	$65,341	$67,272
Percentage Of Total Net Operating Income	17.01%	18.88%

Segment_Information_Schedule_O1

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Reconciliation of Net Operating Income to net income attributable to Boston Properties Limited Partnership
Net Operating Income	$208,208	$178,922
Development and management services income	5,328	5,216
Income from unconsolidated joint ventures	14,834	2,816
Interest and other income	1,407	1,311
Gains from investments in securities	393	286
General and administrative expense	28,791	29,905
Transaction costs	327	437
Depreciation and amortization expense	152,224	152,245
Interest expense	108,757	113,554
Noncontrolling interest in property partnerships	15,208	4,354
Noncontrolling interest-redeemable preferred units	3	619
Preferred distributions	2,589	2,589
Net income attributable to Boston Properties Limited Partnership common unitholders	193,369	62,219
Net income attributable to Boston Properties Limited Partnership	195,958	64,808
Intersegment Eliminations [Member]
Reconciliation of Net Operating Income to net income attributable to Boston Properties Limited Partnership
Net Operating Income	384,222	356,293
Development and management services income	5,328	5,216
Income from unconsolidated joint ventures	14,834	2,816
Interest and other income	1,407	1,311
Gains from investments in securities	393	286
Gain on sales of real estate	95,084	0
General and administrative expense	28,791	29,905
Transaction costs	327	437
Depreciation and amortization expense	152,224	152,245
Interest expense	108,757	113,554
Noncontrolling interest in property partnerships	15,208	4,354
Noncontrolling interest-redeemable preferred units	3	619
Preferred distributions	2,589	2,589
Net income attributable to Boston Properties Limited Partnership common unitholders	$193,369	$62,219

Subsequent_Events_Subsequent_E

Subsequent Events Subsequent Events (Details) (USD $)	3 Months Ended		1 Months Ended	0 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	8-May-15	8-May-15
			Y
			swaps
Subsequent Event [Line Items]
Payments to enter into a joint venture agreement	$2,444	$0
Interest Rate Swap [Member]
Subsequent Event [Line Items]
Number of interest rate swap agreements entered into (swap contracts)	5
Maximum period of hedging exposure to the variability in future cash flows for forecasted transactions (in years)	10
Derivative, Average Fixed Interest Rate	2.49%
Notional Amount	250,000
Interest Rate Swap [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of interest rate swap agreements entered into (swap contracts)			3
Maximum period of hedging exposure to the variability in future cash flows for forecasted transactions (in years)			10
Derivative, Average Fixed Interest Rate			2.34%	2.34%
Notional Amount			75,000	75,000
1265 Main Street [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Net Rentable Area (in sf)			120,000	120,000
Term of Lease Signed (in years)			15	15
Portion of Building Leased (percentage)			100.00%	100.00%
1265 Main Street [Member] | Subsequent Event [Member] | joint venture partner [Member]
Subsequent Event [Line Items]
Payments to enter into a joint venture agreement				9,400
Ownership Percentage			50.00%	50.00%
1265 Main Street [Member] | Subsequent Event [Member] | Company [Member]
Subsequent Event [Line Items]
Ownership Percentage			50.00%	50.00%
Maximum [Member] | 1265 Main Street [Member] | Subsequent Event [Member] | Company [Member]
Subsequent Event [Line Items]
Payments to enter into a joint venture agreement				$9,400