Boston Properties (BXP) 8-K 3 Jun 14 2013 FY Other Events Financial data

Document_And_Entity_Informatio

Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 21, 2014	Jun. 30, 2013
Document And Entity Information [Abstract]	'	'	'
Document Type	'8-K	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Entity Registrant Name	'BOSTON PROPERTIES INC	'	'
Amendment Flag	'false	'	'
Entity Central Index Key	'0001037540	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	153,006,302	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Public Float	'	'	$15,937,365,185

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
ASSETS	'	'
Real estate, at cost	$18,978,765	$14,893,328
Less: accumulated depreciation	-3,161,571	-2,934,160
Total real estate	15,817,194	11,959,168
Cash and cash equivalents	2,365,137	1,041,978
Cash held in escrows	57,201	55,181
Investments in securities	16,641	12,172
Tenant and other receivables (net of allowance for doubtful accounts of $1,636 and $1,960, respectively)	59,464	69,555
Related party notes receivable	0	282,491
Interest receivable from related party notes receivable	0	104,816
Accrued rental income (net of allowance of $3,636 and $1,571, respectively)	651,603	598,199
Deferred charges, net	884,450	588,235
Prepaid expenses and other assets	184,477	90,610
Investments in unconsolidated joint ventures	126,084	659,916
Total assets	20,162,251	15,462,321
Liabilities:	'	'
Mortgage notes payable	4,449,734	3,102,485
Unsecured senior notes (net of discount of $14,146 and $10,472, respectively	5,835,854	4,639,528
Unsecured exchangeable senior notes (net of discount of $182 and $1,653, respectively)	744,880	1,170,356
Unsecured line of credit	0	0
Mezzanine notes payable	311,040	0
Outside members' notes payable	180,000	0
Accounts payable and accrued expenses	202,470	199,102
Dividends and distributions payable	497,242	110,488
Accrued interest payable	167,523	72,461
Other liabilities	578,969	324,613
Total liabilities	12,967,712	9,619,033
Commitments and contingencies	0	0
Noncontrolling interest:	'	'
Redeemable preferred units of the Operating Partnership	51,312	110,876
Redeemable interest in property partnerships	99,609	97,558
Equity:	'	'
Excess stock, $.01 par value, 150,000,000 shares authorized, none issued or outstanding	0	0
Preferred stock, $.01 par value, 50,000,000 shares authorized	'	'
5.25% Series B cumulative redeemable preferred stock, $.01 par value, liquidation preference $2,500 per share, 92,000 shares authorized, 80,000 and no shares issued and outstanding at December 31, 2013 and December 31, 2012, respectively	200,000	0
Common stock, $.01 par value, 250,000,000 shares authorized, 153,062,001 and 151,680,109 issued 152,983,101 and 151,601,209 outstanding at December 31, 2013 and December 31, 2012, respectively	1,530	1,516
Additional paid-in capital	5,662,453	5,222,073
Dividends in excess of earnings	-108,552	-109,985
Treasury common stock at cost, 78,900 shares at December 31, 2013 and December 31, 2012	-2,722	-2,722
Accumulated other comprehensive loss	-11,556	-13,817
Total stockholders' equity attributable to Boston Properties, Inc.	5,741,153	5,097,065
Noncontrolling interests:	'	'
Common units of the Operating Partnership	576,333	539,753
Property partnerships	726,132	-1,964
Total equity	7,043,618	5,634,854
Total liabilities and equity	$20,162,251	$15,462,321

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Tenant and other receivables, allowance for doubtful accounts	$1,636	$1,960
Accrued rental income, allowance	3,636	1,571
Unsecured senior notes, discount	14,146	10,472
Unsecured exchangeable senior notes, discount	$182	$1,653
Excess stock, par value	$0.01	$0.01
Excess stock, shares authorized	150,000,000	150,000,000
Excess stock, shares issued	0	0
Excess stock, shares outstanding	0	0
Preferred stock, par value	$0.01	$0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	153,062,001	151,680,109
Common stock, shares outstanding	152,983,101	151,601,209
Treasury common stock at cost, shares	78,900	78,900
Series B Cumulative Redeemable Preferred Stock [Member]	'	'
Preferred stock, par value	$0.01	$0
Preferred stock, shares authorized	92,000	0
Series B Dividend Rate Percentage	5.25%	0.00%
Preferred stock, shares issued	80,000	0
Series B Liquidation Preference Per Share	$2,500	$0
Preferred stock, shares outstanding	80,000	0

Consolidated_Statements_Of_Ope

Consolidated Statements Of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue	'	'	'
Base rent	$1,675,412	$1,457,834	$1,376,278
Recoveries from tenants	292,944	228,170	198,083
Parking and other	97,158	89,207	80,496
Total rental revenue	2,065,514	1,775,211	1,654,857
Hotel revenue	40,330	37,915	34,529
Development and management services	29,695	34,060	33,406
Total revenue	2,135,539	1,847,186	1,722,792
Expenses	'	'	'
Rental	742,956	639,088	572,668
Hotel	28,447	28,120	26,128
General and administrative	115,329	90,129	87,101
Transaction costs	1,744	3,653	1,987
Impairment loss	8,306	0	0
Depreciation and amortization	560,637	445,875	429,742
Total expenses	1,457,419	1,206,865	1,117,626
Operating income	678,120	640,321	605,166
Other income (expense)	'	'	'
Income from unconsolidated joint ventures	75,074	49,078	85,896
Gains on consolidation of joint ventures	385,991	0	0
Interest and other income	8,310	10,091	5,358
Gains (losses) from investments in securities	2,911	1,389	-443
Interest expense	-446,880	-410,970	-391,533
Gains (losses) from early extinguishments of debt	122	-4,453	-1,494
Income (loss) from continuing operations	703,648	285,456	302,950
Discontinued operations	'	'	'
Income from discontinued operations	8,022	9,806	10,876
Gain on sale of real estate from discontinued operations	112,829	36,877	0
Gain on forgiveness of debt from discontinued operations	20,182	0	0
Impairment loss from discontinued operations	-3,241	0	0
Net income (loss)	841,440	332,139	313,826
Net income attributable to noncontrolling interests	'	'	'
Noncontrolling interests in property partnerships	-1,347	-3,792	-1,558
Noncontrolling interest - redeemable preferred units of the Operating Partnership	-6,046	-3,497	-3,339
Noncontrolling interest - common units of the Operating Partnership	-70,085	-30,125	-35,007
Noncontrolling interest in discontinued operations - common units of the Operating Partnership	-14,151	-5,075	-1,243
Net income attributable to Boston Properties, Inc.	749,811	289,650	272,679
Preferred dividends	-8,057	0	0
Net income attributable to Boston Properties, Inc. common shareholders	$741,754	$289,650	$272,679
Basic earnings per common share attributable to Boston Properties, Inc.:	'	'	'
Income from continuing operations (in dollars per share)	$4.06	$1.65	$1.80
Discontinued operations (in dollars per share)	$0.81	$0.28	$0.07
Net income (in dollars per share)	$4.87	$1.93	$1.87
Weighted average number of common shares outstanding (in shares)	152,201	150,120	145,693
Diluted earnings per common share attributable to Boston Properties, Inc.:	'	'	'
Income from continuing operations (in dollars per share)	$4.05	$1.64	$1.80
Discontinued operations (in dollars per share)	$0.81	$0.28	$0.06
Diluted Earnings: Net income, Per Share Amount (in dollars per share)	$4.86	$1.92	$1.86
Weighted average number of common and common equivalent shares outstanding (in shares)	152,521	150,711	146,218

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Statement of Comprehensive Income [Abstract]	'		'		'
Net income	$841,440		$332,139		$313,826
Other comprehensive income:	'		'		'
Amortization of interest rate contracts	2,513	[1]	2,594	[1]	2,595	[1]
Other Comprehensive income	2,513		2,594		2,595
Comprehensive income	843,953		334,733		316,421
Net income attributable to noncontrolling interests	-91,629		-42,489		-41,147
Other comprehensive income attributable to noncontrolling interests	-252		-273		-297
Comprehensive income attributable to Boston Properties, Inc.	$752,072		$291,971		$274,977
[1]	Amounts reclassified from comprehensive income primarily to interest expense within the Company's Consolidated Statements of Operations

Consolidated_Statements_Of_Sto

Consolidated Statements Of Stockholders' Equity (USD $)	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Dividends In Excess Of Earnings [Member]	Treasury Stock, At Cost [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]
In Thousands, except Share data, unless otherwise specified
Equity, value at Dec. 31, 2010	$4,964,193	$1,402	'	$4,417,162	($24,763)	($2,722)	($18,436)	$591,550
Equity, shares at Dec. 31, 2010	'	140,199,000	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'	'
Conversion of operating partnership units to Common Stock, shares	'	2,919,000	'	'	'	'	'	'
Conversion of operating partnership units to Common Stock, value	0	29	'	85,469	'	'	'	-85,498
Allocated net income for the year	310,487	'	'	'	272,679	'	'	37,808
Dividends/distributions declared	-340,128	'	'	'	-300,996	'	'	-39,132
Shares issued in connection with exchange of exchangeable senior notes, value	0	'	'	'	'	'	'	'
Sale of Common Stock, net of offering costs, shares	'	4,660,000	'	'	'	'	'	'
Sale of Common Stock, net of offering costs, value	439,037	47	'	438,990	'	'	'	'
Shares issued pursuant to stock purchase plan, shares	'	6,000	'	'	'	'	'	'
Shares issued pursuant to stock purchase plan, value	620	'	'	620	'	'	'	'
Net activity from stock option and incentive plan, shares	'	324,000	'	'	'	'	'	'
Net activity from stock option and incentive plan, value	38,719	3	'	17,289	'	'	'	21,427
Noncontrolling interest in property partnerships recorded upon consolidation	0	'	'	'	'	'	'	'
Distributions to noncontrolling interests in property partnerships	-2,007	'	'	'	'	'	'	-2,007
Amortization of interest rate contracts	2,595	'	'	'	'	'	2,298	297
Reallocation of noncontrolling interest	0	'	'	-23,073	'	'	'	23,073
Equity, value at Dec. 31, 2011	5,413,516	1,481	'	4,936,457	-53,080	-2,722	-16,138	547,518
Equity, shares at Dec. 31, 2011	'	148,108,000	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'	'
Conversion of operating partnership units to Common Stock, shares	'	1,111,000	'	'	'	'	'	'
Conversion of operating partnership units to Common Stock, value	0	11	'	34,610	'	'	'	-34,621
Conversion of redeemable preferred units to common units	5,852	'	'	'	'	'	'	5,852
Allocated net income for the year	326,839	'	'	'	289,650	'	'	37,189
Dividends/distributions declared	-387,989	'	'	'	-346,555	'	'	-41,434
Shares issued in connection with exchange of exchangeable senior notes, value	0	'	'	'	'	'	'	'
Sale of Common Stock, net of offering costs, shares	'	2,348,000	'	'	'	'	'	'
Sale of Common Stock, net of offering costs, value	247,027	24	'	247,003	'	'	'	'
Shares issued pursuant to stock purchase plan, shares	'	7,000	'	'	'	'	'	'
Shares issued pursuant to stock purchase plan, value	781	'	'	781	'	'	'	'
Net activity from stock option and incentive plan, shares	'	27,000	'	'	'	'	'	'
Net activity from stock option and incentive plan, value	29,124	'	'	5,419	'	'	'	23,705
Noncontrolling interest in property partnerships recorded upon consolidation	0	'	'	'	'	'	'	'
Distributions to noncontrolling interests in property partnerships	-2,890	'	'	'	'	'	'	-2,890
Amortization of interest rate contracts	2,594	'	'	'	'	'	2,321	273
Reallocation of noncontrolling interest	0	'	'	-2,197	'	'	'	2,197
Equity, value at Dec. 31, 2012	5,634,854	1,516	'	5,222,073	-109,985	-2,722	-13,817	537,789
Equity, shares at Dec. 31, 2012	151,601,209	151,601,000	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'	'
Conversion of operating partnership units to Common Stock, shares	'	929,000	'	'	'	'	'	'
Conversion of operating partnership units to Common Stock, value	0	10	'	30,281	'	'	'	-30,291
Conversion of redeemable preferred units to common units	16,494	'	'	'	'	'	'	16,494
Allocated net income for the year	828,757	'	'	'	749,811	'	'	78,946
Dividends/distributions declared	-831,826	'	'	'	-748,378	'	'	-83,448
Issuance of 5.25% Series B cumulative redeemable preferred stock	193,623	'	200,000	-6,377	'	'	'	'
Shares issued in connection with exchange of exchangeable senior notes, value	43,834	4	'	43,830	'	'	'	'
Equity component of exchange of exchangeable senior notes	-43,869	'	'	-43,869	'	'	'	'
shares issued in connection with exchange of exchangeable senior notes, shares	'	419,000	'	'	'	'	'	'
Shares issued pursuant to stock purchase plan, shares	'	6,000	'	'	'	'	'	'
Shares issued pursuant to stock purchase plan, value	681	'	'	681	'	'	'	'
Net activity from stock option and incentive plan, shares	'	28,000	'	'	'	'	'	'
Net activity from stock option and incentive plan, value	35,571	'	'	7,701	'	'	'	27,870
Noncontrolling interest in property partnerships recorded upon consolidation	480,861	'	'	'	'	'	'	480,861
Sale of interest in property partnerships and contributions from noncontrolling interest in property partnerships	687,164	'	'	429,600	'	'	'	257,564
Distributions to noncontrolling interests in property partnerships	-5,039	'	'	'	'	'	'	-5,039
Amortization of interest rate contracts	2,513	'	'	'	'	'	2,261	252
Reallocation of noncontrolling interest	0	'	'	-21,467	'	'	'	21,467
Equity, value at Dec. 31, 2013	$7,043,618	$1,530	$200,000	$5,662,453	($108,552)	($2,722)	($11,556)	$1,302,465
Equity, shares at Dec. 31, 2013	152,983,101	152,983,000	'	'	'	'	'	'

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:	'	'	'
Net income	$841,440	$332,139	$313,826
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'
Depreciation and amortization	565,397	454,044	439,184
Non-cash compensation expense	45,155	29,679	29,672
Impairment loss	8,306	0	0
Income from unconsolidated joint ventures	-75,074	-49,078	-85,896
Gains on consolidation of joint ventures	385,991	0	0
Distributions of net cash flow from operations of unconsolidated joint ventures	32,600	47,002	39,851
Losses (gains) on investments in securities	-2,911	-1,389	443
Non-cash portion of interest expense	2,649	43,131	54,962
Settlement of accreted debt discount on repurchases of senior notes	-56,532	-69,499	-5,601
Losses (gains) from early extinguishments of debt	-264	-1,000	1,494
Gain on sale of real estate from discontinued operations	-112,829	-36,877	0
Gain on forgiveness of debt from discontinued operations	-20,182	0	0
Impairment loss from discontinued operations	3,241	0	0
Change in assets and liabilities:	'	'	'
Cash held in escrows	315	10,272	-9,801
Tenant and other receivables, net	-443	23,155	-19,396
Accrued rental income, net	-59,972	-77,363	-79,992
Prepaid expenses and other assets	12,966	6,990	-39,213
Accounts payable and accrued expenses	13,108	3,854	6,660
Accrued interest payable	21,302	3,356	6,778
Other liabilities	2,073	1,354	6,569
Tenant leasing costs	-56,428	-76,821	-53,212
Total adjustments	-63,514	310,810	292,502
Net cash provided by operating activities	777,926	642,949	606,328
Cash flows from investing activities:	'	'	'
Acquisitions of real estate	-522,900	-788,052	-112,180
Construction in progress	-396,835	-356,397	-271,856
Building and other capital improvements	-73,821	-49,943	-61,961
Tenant improvements	-105,425	-139,662	-76,320
Proceeds from the sale of real estate	250,078	61,963	0
Cash recorded upon consolidation	79,468	0	0
Proceeds from land transaction	0	0	43,887
Proceeds from mortgage loan released from (placed in) escrow	0	0	267,500
Deposit on real estate	0	0	10,000
Issuance of notes receivable,net	12,491	-2,049	-10,442
Capital contributions to unconsolidated joint ventures	0	-6,214	-17,970
Capital distributions from unconsolidated joint ventures	225,862	3,557	140,505
Investments in securities, net	-1,558	-1,235	-1,259
Net cash used in investing activities	-532,640	-1,278,032	-90,096
Cash flows from financing activities:	'	'	'
Proceeds from mortgage notes payable	0	0	1,178,306
Repayments of mortgage notes payable	-80,311	-253,877	-1,251,841
Proceeds from unsecured senior notes	1,194,753	997,790	848,019
Redemption/repurchase of unsecured senior notes	0	-224,261	0
Redemption/repurchase/exchange of unsecured exchangeable senior notes	-393,468	-507,434	-44,586
Deferred financing costs	-15,195	-8,468	-15,970
Net proceeds from preferred stock issuance	193,623	0	0
Deposit on mortgage loan financing	0	0	-14,500
Returned deposit on mortgage loan financing	0	0	14,500
Net proceeds from ATM stock issuances	0	247,027	439,037
Net proceeds from equity transactions	-334	226	9,667
Redemption of preferred units	-43,070	-18,329	0
Dividends and distributions	-451,118	-372,899	-332,597
Proceeds from sale of ownership interest and contributions from noncontrolling interest in property partnerships	682,617	0	0
Distributions to noncontrolling interest in property partnerships	-9,624	-5,922	-2,007
Net cash provided by (used in) financing activities	1,077,873	-146,147	828,028
Net increase (decrease) in cash and cash equivalents	1,323,159	-781,230	1,344,260
Cash and cash equivalents, beginning of year	1,041,978	1,823,208	'
Cash and cash equivalents, end of year	2,365,137	1,041,978	1,823,208
Supplemental disclosures:	'	'	'
Cash paid for interest	547,973	480,866	386,170
Interest capitalized	68,152	44,278	48,178
Non-cash investing and financing activities:	'	'	'
Additions to real estate included in accounts payable and accrued expenses	19,824	14,059	10,767
Real estate and related intangibles recorded upon consolidation	3,356,000	0	0
Debt recorded upon consolidation	2,056,000	0	0
Working capital recorded upon consolidation	177,315	0	0
Noncontrolling Interests recorded upon consolidation	480,861	0	0
investment in unconsolidated joint venture elminated upon consolidation	361,808	0	0
Mortgage note extinguished through foreclosure	25,000	0	0
Real estate transferred upon foreclosure	7,508	0	0
Land improvements contributed by noncontrolling interests in property partnership	4,546	0	0
Mortgage note payable assumed in connection with the acquisition of real estate	0	211,250	143,900
Redeemable noncontrolling Interest in property partnerships	0	98,787	0
Preferred units issued iIn connection with acquisition of real estate	0	79,405	0
Dividends and distributions declared but not paid	497,242	110,488	91,901
Issuance of common stock in connection with the exchange of exchangeable senior notes	43,834	0	0
Conversions of noncontrolling interests to stockholders' equity	30,291	34,621	85,498
Conversion of redeemable preferred units to common units	16,494	5,852	0
Issuance of restricted securities to employees and directors	$30,077	$26,198	$25,087

Organization

Organization	12 Months Ended
	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization	'
	Organization
	Boston Properties, Inc. (the “Company”), a Delaware corporation, is a self-administered and self-managed real estate investment trust (“REIT”). The Company is the sole general partner of Boston Properties Limited Partnership (the “Operating Partnership”) and at December 31, 2013 owned an approximate 89.5% (89.0% at December 31, 2012) general and limited partnership interest in the Operating Partnership. Partnership interests in the Operating Partnership are denominated as “common units of partnership interest” (also referred to as “OP Units”), “long term incentive units of partnership interest” (also referred to as “LTIP Units”) or “preferred units of partnership interest” (also referred to as “Preferred Units”). In addition, in February 2011 and February 2012, the Company issued LTIP Units in connection with the granting to employees of outperformance awards (also referred to as “2011 OPP Units” and “2012 OPP Units,” respectively, and collectively as “OPP Units”). In February 2013, the Company issued LTIP Units in connection with the granting to employees of 2013 MYLTIP Units (“2013 MYLTIP Units”). Because the rights, preferences and privileges of OPP Units and 2013 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 2013 MYLTIP Units (See Notes 11 and 17).
	Unless specifically noted otherwise, all references to OP Units exclude units held by the Company. A holder of an OP Unit may present such OP Unit to the Operating Partnership for redemption at any time (subject to restrictions agreed upon at the time of issuance of OP Units to particular holders that may restrict such redemption right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, the Operating Partnership is obligated to redeem such OP Unit for cash equal to the value of a share of common stock of the Company (“Common Stock”) at such time. In lieu of a cash redemption, the Company 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 the Company 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 the Company. 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 12).
	At December 31, 2013, there were three series of Preferred Units outstanding (i.e., Series Two Preferred Units, Series Four Preferred Units and Series B Preferred Units).
	•	The Series Two Preferred Units bear a distribution that is set in accordance with an amendment to the partnership agreement of the Operating Partnership. Each Series Two Preferred Unit may also be converted into approximately 1.312336 OP Units or redeemed for $50.00 of cash at the election of the holder thereof or the Operating Partnership in accordance with the terms and conditions set forth in the applicable amendment to the partnership agreement (See Note 11).
	•	The Series Four Preferred Units are not convertible into or exchangeable for any common equity of the Operating Partnership or the Company, 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 11).
	•	The Series B Preferred Units were issued to the Company on March 27, 2013 in connection with the Company'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"). The Company contributed the net proceeds from the offering to the Operating Partnership in exchange for 80,000 Series B Preferred Units having terms and preferences generally mirroring those of the Series B Preferred Stock (See Note 12).
	All references herein to the Company refer to Boston Properties, Inc. and its consolidated subsidiaries, including the Operating Partnership, collectively, unless the context otherwise requires.
	Properties
	At December 31, 2013, the Company owned or had interests in a portfolio of 175 commercial real estate properties (the “Properties”) aggregating approximately 44.4 million net rentable square feet, including nine properties under construction totaling approximately 2.9 million net rentable square feet. In addition, the Company has structured parking for approximately 45,234 vehicles containing approximately 15.4 million square feet. At December 31, 2013, the Properties consist of:
	•	167 office properties, including 128 Class A office properties (including eight properties under construction) and 39 Office/Technical properties;
	•	one hotel;
	•	four retail properties; and
	•	three residential properties (including one property under construction).
	The Company owns or controls undeveloped land parcels totaling approximately 503.6 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. Net rentable square feet amounts are unaudited.
	Basis of Presentation
	Boston Properties, Inc. does not have any other significant assets, liabilities or operations, other than its investment in the Operating Partnership, nor does it have employees of its own. The Operating Partnership, not Boston Properties, Inc., executes all significant business relationships. 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.

Summary_Of_Significant_Account

Summary Of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Basis Of Presentation And Summary Of Significant Accounting Policies	'
	Summary of Significant Accounting Policies
	Real Estate
	Upon acquisitions of real estate that constitutes a business, which includes the consolidation of previously unconsolidated joint ventures, the Company assesses the fair value of acquired tangible and intangible assets (including land, buildings, tenant improvements, “above-” and “below-market” leases, leasing and assumed financing origination costs, acquired in-place leases, other identified intangible assets and assumed liabilities, and allocates the purchase price to the acquired assets and assumed liabilities, including land and buildings as if vacant. The Company assesses and considers fair value based on estimated cash flow projections that utilize discount and/or capitalization rates that it deems appropriate, as well as available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known and anticipated trends, and market and economic conditions. The fair value of the tangible assets of an acquired property considers the value of the property as if it were vacant. The Company also considers an allocation of purchase price of other acquired intangibles, including acquired in-place leases that may have a customer relationship intangible value, including (but not limited to) the nature and extent of the existing relationship with the tenants, the tenant's credit quality and expectations of lease renewals. Based on its acquisitions to date, the Company's allocation to customer relationship intangible assets has been immaterial.
	The Company records acquired “above-” and “below-market” leases at their fair values (using a discount rate which reflects the risks associated with the leases acquired) equal to the difference between (1) the contractual amounts to be paid pursuant to each in-place lease and (2) management's estimate of fair market lease rates for each corresponding in-place lease, measured over a period equal to the remaining term of the lease for above-market leases and the initial term plus the term of any below-market fixed rate renewal options for below- market leases. Acquired “above-” and “below-market” lease values have been reflected within Prepaid Expenses and Other Assets and Other Liabilities, respectively, in the Company's Consolidated Balance Sheets. Other intangible assets acquired include amounts for in-place lease values that are based on the Company's evaluation of the specific characteristics of each tenant's lease. Factors to be considered include estimates of carrying costs during hypothetical expected lease-up periods considering current market conditions, and costs to execute similar leases. In estimating carrying costs, the Company includes real estate taxes, insurance and other operating expenses and estimates of lost rentals at market rates during the expected lease-up periods, depending on local market conditions. In estimating costs to execute similar leases, the Company considers leasing commissions, legal and other related expenses.
	Management reviews its long-lived assets for impairment following the end of each quarter and when there is an event or change in circumstances that indicates an impairment in value. An impairment loss is recognized if the carrying amount of its assets is not recoverable and exceeds its fair value. If such criteria are present, an impairment loss is recognized based on the excess of the carrying amount of the asset over its fair value. The evaluation of anticipated cash flows is highly subjective and is based in part on assumptions regarding future occupancy, rental rates and capital requirements that could differ materially from actual results in future periods. Since cash flows on properties considered to be “long-lived assets to be held and used” are considered on an undiscounted basis to determine whether an asset has been impaired, the Company's established strategy of holding properties over the long term directly decreases the likelihood of recording an impairment loss. If the Company's strategy changes or market conditions otherwise dictate an earlier sale date, an impairment loss may be recognized and such loss could be material. If the Company determines that impairment has occurred, the affected assets must be reduced to their fair value, less cost to sell.
	Accounting Standards Codification (“ASC”) ASC 360 "Property Plant and Equipment" requires that qualifying assets and liabilities and the results of operations that have been sold, or otherwise qualify as “held for sale,” be presented as discontinued operations in all periods presented if the property operations are expected to be eliminated and the Company will not have significant continuing involvement following the sale. The components of the property’s net income that is reflected as discontinued operations include the net gain (or loss) upon the disposition of the property held for sale, operating results, depreciation and interest expense (if the property is subject to a secured loan). The Company generally considers assets to be “held for sale” when the transaction has been approved by the Board of Directors, or a committee thereof, and there are no known significant contingencies relating to the sale, such that the property sale within one year is considered probable. Following the classification of a property as “held for sale,” no further depreciation is recorded on the assets, and the asset is written down to the lower of carrying value or fair market value, less cost to sell.
	Real estate is stated at depreciated cost. A variety of costs are incurred in the acquisition, development and leasing of properties. The cost of buildings and improvements includes the purchase price of property, legal fees and other acquisition costs. The Company expenses costs that it incurs to effect a business combination such as legal, due diligence and other closing related costs. Costs directly related to the development of properties are capitalized. Capitalized development costs include interest, internal wages, property taxes, insurance, and other project costs incurred during the period of development. After the determination is made to capitalize a cost, it is allocated to the specific component of a project that is benefited. Determinations of when a development project commences and capitalization begins, and when a development project is substantially complete and held available for occupancy and capitalization must cease, involve a degree of judgment. The Company’s capitalization policy on development properties is guided by guidance in ASC 835-20 “Capitalization of Interest” and ASC 970 “Real Estate – General.” The costs of land and buildings under development include specifically identifiable costs. The capitalized costs include pre-construction costs necessary to the development of the property, development costs, construction costs, interest costs, real estate taxes, salaries and related costs and other costs incurred during the period of development. The Company begins the capitalization of costs during the pre-construction period, which it defines as activities that are necessary to the development of the property. The Company considers a construction project as substantially completed and held available for occupancy upon the completion of tenant improvements, but no later than one year from cessation of major construction activity. The Company ceases capitalization on the portion (1) substantially completed and (2) occupied or held available for occupancy, and capitalizes only those costs associated with the portion under construction, or if activities necessary for the development of the property have been suspended. Interest costs capitalized for the years ended December 31, 2013, 2012 and 2011 were $68.2 million, $44.3 million and $48.2 million, respectively. Salaries and related costs capitalized for the years ended December 31, 2013, 2012 and 2011 were $7.7 million, $7.1 million and $6.5 million, respectively.
	Expenditures for repairs and maintenance are charged to operations as incurred. Significant betterments are capitalized. When assets are sold or retired, their costs and related accumulated depreciation are removed from the accounts with the resulting gains or losses reflected in net income or loss for the period.
	The Company computes depreciation and amortization on properties using the straight-line method based on estimated useful asset lives. In accordance with ASC 805, the Company allocates the acquisition cost of real estate to its components and depreciates or amortizes these assets (or liabilities) over their useful lives. The amortization of acquired “above-” and “below-market” leases and acquired in-place leases is recorded as an adjustment to revenue and depreciation and amortization, respectively, in the Consolidated Statements of Operations.
	Depreciation is computed on a straight-line basis over the estimated useful lives of the assets as follows:
	Land improvements		25 to 40 years
	Buildings and improvements		10 to 40 years
	Tenant improvements		Shorter of useful life or terms of related lease
	Furniture, fixtures, and equipment		3 to 7 years
	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash on hand and investments with maturities of three months or less from the date of purchase. The majority of the Company’s cash and cash equivalents are held at major commercial banks which may at times exceed the Federal Deposit Insurance Corporation limit of $250,000. The Company has not experienced any losses to date on its invested cash.
	Cash Held in Escrows
	Escrows include amounts established pursuant to various agreements for security deposits, property taxes, insurance and other costs.
	Investments in Securities
	The Company accounts for investments in trading securities at fair value, with gains or losses resulting from changes in fair value recognized currently in earnings. The designation of trading securities is generally determined at acquisition. The Company maintains a deferred compensation plan that is designed to allow officers of the Company to defer a portion of their current income on a pre-tax basis and receive a tax-deferred return on these deferrals. The Company’s obligation under the plan is that of an unsecured promise to pay the deferred compensation to the plan participants in the future. At December 31, 2013 and 2012, the Company had maintained approximately $16.6 million and $12.2 million, respectively, in a separate account, which is not restricted as to its use. The Company recognized gains (losses) of approximately $2.9 million, $1.4 million and $(0.4) million on its investments in the account associated with the Company’s deferred compensation plan during the years ended December 31, 2013, 2012 and 2011, respectively.
	Tenant and Other Receivables
	Tenant and other accounts receivable, other than accrued rents receivable, are expected to be collected within one year.
	Deferred Charges
	Deferred charges include leasing costs and financing fees. Leasing costs include an allocation for acquired intangible in-place lease values and direct and incremental fees and costs incurred in the successful negotiation of leases, including brokerage, legal, internal leasing employee salaries and other costs which have been deferred and are being amortized on a straight-line basis over the terms of the respective leases. Internal leasing salaries and related costs capitalized for the years ended December 31, 2013, 2012 and 2011 were $5.1 million, $5.6 million and $4.4 million, respectively. External fees and costs incurred to obtain long-term financing have been deferred and are being amortized over the terms of the respective loans and are included within interest expense. Unamortized financing and leasing costs are charged to expense upon the early repayment or significant modification of the financing or upon the early termination of the lease, respectively. Fully amortized deferred charges are removed from the books upon the expiration of the lease or maturity of the debt.
	Investments in Unconsolidated Joint Ventures
	The Company consolidates variable interest entities (VIEs) in which it is considered to be the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. The primary beneficiary is defined by the entity having both of the following characteristics: (1) the power to direct the activities that, when taken together, most significantly impact the variable interest entity's performance, and (2) the obligation to absorb losses and right to receive the returns from the variable interest entity that would be significant to the variable interest entity. For ventures that are not VIEs the Company consolidates entities for which it has significant decision making control over the ventures' operations. The Company's judgment with respect to its level of influence or control of an entity involves the consideration of various factors including the form of the Company's ownership interest, its representation in the entity's governance, the size of its investment (including loans), estimates of future cash flows, its ability to participate in policy making decisions and the rights of the other investors to participate in the decision making process and to replace the Company as manager and/or liquidate the venture, if applicable. The Company's assessment of its influence or control over an entity affects the presentation of these investments in the Company's consolidated financial statements. In addition to evaluating control rights, the Company consolidates entities in which the outside partner has no substantive kick-out rights to remove the Company as the managing member.
	Accounts of the consolidated entity are included in the accounts of the Company and the non-controlling interest is reflected on the Consolidated Balance Sheets as a component of equity or in temporary equity between liabilities and equity. Investments in unconsolidated joint ventures are recorded initially at cost, and subsequently adjusted for equity in earnings and cash contributions and distributions. Any difference between the carrying amount of these investments on the balance sheet and the underlying equity in net assets is amortized as an adjustment to equity in earnings of unconsolidated joint ventures over the life of the related asset. Under the equity method of accounting, the net equity investment of the Company is reflected within the Consolidated Balance Sheets, and the Company's share of net income or loss from the joint ventures is included within the Consolidated Statements of Operations. The joint venture agreements may designate different percentage allocations among investors for profits and losses; however, the Company's recognition of joint venture income or loss generally follows the joint venture's distribution priorities, which may change upon the achievement of certain investment return thresholds. The Company may account for cash distributions in excess of its investment in an unconsolidated joint venture as income when the Company is not the general partner in a limited partnership and when the Company has neither the requirement nor the intent to provide financial support to the joint venture. The Company's investments in unconsolidated joint ventures are reviewed for impairment periodically and the Company records impairment charges when events or circumstances change indicating that a decline in the fair values below the carrying values has occurred and such decline is other-than-temporary, which is dependent on a number of factors, including the performance of each investment and market conditions.
	To the extent that the Company contributes assets to a joint venture, the Company’s investment in the joint venture is recorded at the Company’s cost basis in the assets that were contributed to the joint venture. To the extent that the Company’s cost basis is different than the basis reflected at the joint venture level, the basis difference is amortized over the life of the related asset and included in the Company’s share of equity in net income of the joint venture. In accordance with the provisions of ASC 970-323 “Investments—Equity Method and Joint Ventures” (“ASC 970-323”), the Company will recognize gains on the contribution of real estate to joint ventures, relating solely to the outside partner’s interest, to the extent the economic substance of the transaction is a sale.
	Equity Offering Costs
	Underwriting commissions and offering costs have been reflected as a reduction of additional paid-in capital.
	Treasury Stock
	The Company’s share repurchases are reflected as treasury stock utilizing the cost method of accounting and are presented as a reduction to consolidated stockholders’ equity.
	Dividends
	Earnings and profits, which determine the taxability of dividends to stockholders, will differ from income reported for financial reporting purposes due to the differences for federal income tax purposes in the treatment of gains/losses on the sale of real property, revenue and expense recognition, compensation expense, and in the estimated useful lives and basis used to compute depreciation.
	The tax treatment of common dividends per share for federal income tax purposes is as follows:
			For the year ended December 31,
			2013							2012								2011
			Per Share				%			Per Share				%				Per Share			%
	Ordinary income		$	2.31			48.71	%		$	2.29		0.5839	96.45	%	0.9093		$	2.06	0.9093	97.39	%
	Capital gain income		2.44				51.29	%		0.08			—	3.55	%	—		0.05		—	2.61	%
	Total		$	4.75		-1	100	%		$	2.37			100	%			$	2.11	1	100	%
	(1) The fourth quarter 2013 dividend of $2.90 per common share consists of a $2.25 per common share special dividend and a $0.65 per common share regular quarterly dividend of which approximately $2.44 per common share was allocable to 2013 and approximately $0.46 per common share is allocable to 2014.
	Revenue Recognition
	Contractual rental revenue is reported on a straight-line basis over the terms of the respective leases. The impact of the straight-line rent adjustment increased revenue by approximately $65.8 million, $77.6 million and $77.0 million for the years ended December 31, 2013, 2012 and 2011, respectively, as the revenue recorded exceeded amounts billed. Accrued rental income, as reported on the Consolidated Balance Sheets, represents cumulative rental income earned in excess of rent payments received pursuant to the terms of the individual lease agreements. The Company maintains an allowance against accrued rental income for future potential tenant credit losses. The credit assessment is based on the estimated accrued rental income that is recoverable over the term of the lease. The Company also maintains an allowance for doubtful accounts for estimated losses resulting from the inability of tenants to make required rent payments. The computation of this allowance is based on the tenants’ payment history and current credit status, as well as certain industry or geographic specific credit considerations. If the Company’s estimates of collectability differ from the cash received, then the timing and amount of the Company’s reported revenue could be impacted. The credit risk is mitigated by the high quality of the Company’s existing tenant base, reviews of prospective tenants’ risk profiles prior to lease execution and consistent monitoring of the Company’s portfolio to identify potential problem tenants.
	In accordance with ASC 805, the Company recognizes rental revenue of acquired in-place “above-” and “below-market” leases at their fair values over the terms of the respective leases. The impact of the acquired in-place “above-” and “below-market” leases increased revenue by approximately $28.0 million, $14.6 million and $10.8 million for the years ended December 31, 2013, 2012 and 2011, respectively. The following table summarizes the scheduled amortization of the Company's acquired “above-” and “below-market” lease intangibles for each of the five succeeding years (in thousands).
			Acquired Above-Market Lease Intangibles				Acquired Below-Market Lease Intangibles
	2014		$	23,669			$	61,700
	2015		22,758				55,207
	2016		20,576				52,461
	2017		12,279				40,346
	2018		8,637				37,774
	Recoveries from tenants, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs are recognized as revenue in the period during which the expenses are incurred. Tenant reimbursements are recognized and presented in accordance with guidance in ASC 605-45 “Principal Agent Considerations” (“ASC 605-45”). ASC 605-45 requires that these reimbursements be recorded on a gross basis, as the Company is generally the primary obligor with respect to purchasing goods and services from third-party suppliers, has discretion in selecting the supplier and has credit risk. The Company also receives reimbursement of payroll and payroll related costs from third parties which the Company reflects on a net basis in accordance with ASC 605-45.
	The Company's parking revenues are derived from leases, monthly parking and transient parking. The Company recognizes parking revenue as earned.
	The Company’s hotel revenues are derived from room rentals and other sources such as charges to guests for telephone service, movie and vending commissions, meeting and banquet room revenue and laundry services. Hotel revenues are recognized as earned.
	The Company receives management and development fees from third parties. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis, because such fees are contingent upon the collection of rents. The Company reviews each development agreement and records development fees as earned depending on the risk associated with each project. Profit on development fees earned from joint venture projects is recognized as revenue to the extent of the third party partners’ ownership interest.
	Gains on sales of real estate are recognized pursuant to the provisions included in ASC 360-20 “Real Estate Sales” (“ASC 360-20”). The specific timing of a sale is measured against various criteria in ASC 360-20 related to the terms of the transaction and any continuing involvement in the form of management or financial assistance associated with the properties. If the sales criteria for the full accrual method are not met, the Company defers some or all of the gain recognition and accounts for the continued operations of the property by applying the finance, leasing, profit sharing, deposit, installment or cost recovery methods, as appropriate, until the sales criteria are met.
	Ground Leases
	The Company has non-cancelable ground lease obligations with various initial term expiration dates through 2068. The Company recognizes ground rent expense on a straight-line basis over the terms of the respective ground lease agreements. The future contractual minimum lease payments to be made by the Company as of December 31, 2013, under non-cancelable ground leases which expire on various dates through 2068, are as follows:
	Years Ending December 31,	(in thousands)
	2014	$	13,184
	2015	13,507
	2016	13,732
	2017	13,963
2018	14,198
Thereafter	899,187
Earnings Per Share
Basic earnings per share (“EPS”) is computed by dividing net income available to common shareholders, as adjusted for unallocated earnings (if any) of certain securities issued by the Operating Partnership, by the weighted average number of shares of Common Stock outstanding during the year. Diluted EPS reflects the potential dilution that could occur from shares issuable in connection with awards under stock-based compensation plans, including upon the exercise of stock options, and securities of the Operating Partnership that are exchangeable for Common Stock.
Fair Value of Financial Instruments
The carrying values of cash and cash equivalents, marketable securities, escrows, receivables, accounts payable, accrued expenses and other assets and liabilities are reasonable estimates of their fair values because of the short maturities of these 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 and unsecured exchangeable senior notes using market prices. The inputs used in determining the fair value of the Company’s unsecured senior notes and unsecured exchangeable senior notes is 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 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 December 31, 2013 and December 31, 2012 (in thousands):
	December 31, 2013										December 31, 2012
	Carrying						Estimated				Carrying					Estimated
	Amount						Fair Value				Amount					Fair Value
Mortgage notes payable	$	4,449,734					$	4,545,283			$	3,102,485				$	3,256,940
Mezzanine notes payable	311,040						311,064				—					—
Unsecured senior notes	5,835,854						6,050,517				4,639,528					5,162,486
Unsecured exchangeable senior notes	744,880				-1		750,266				1,170,356			-1		1,278,554
Total	$	11,341,508					$	11,657,130			$	8,912,369				$	9,697,980
_______________
-1	Includes the net adjustment for the equity component allocation totaling approximately $2.4 million and $25.5 million at December 31, 2013 and December 31, 2012, respectively.
Derivative Instruments and Hedging Activities
Derivative instruments and hedging activities require management to make judgments on the nature of its derivatives and their effectiveness as hedges. These judgments determine if the changes in fair value of the derivative instruments are reported in the Consolidated Statements of Operations as a component of net income or as a component of comprehensive income and as a component of equity on the consolidated balance sheets. While management believes its judgments are reasonable, a change in a derivative’s effectiveness as a hedge could materially affect expenses, net income and equity. The Company accounts for the effective portion of changes in the fair value of a derivative in 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.
Income Taxes
The Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the “Code”), commencing with its taxable year ended December 31, 1997. As a result, the Company generally will not be subject to federal corporate income tax on its taxable income that is distributed to its stockholders. A REIT is subject to a number of organizational and operational requirements, including a requirement that it currently distribute at least 90% of its annual taxable income. The Company’s policy is to distribute at least 100% of its taxable income. Accordingly, the only provision for federal income taxes in the accompanying consolidated financial statements relates to the Company’s consolidated taxable REIT subsidiaries. The Company’s taxable REIT subsidiaries did not have significant tax provisions or deferred income tax items. The Company has no uncertain tax positions recognized as of December 31, 2013 and 2012.
The Company owns a hotel property which is managed through a taxable REIT subsidiary. The hotel taxable REIT subsidiary, a wholly owned subsidiary of the Operating Partnership, is the lessee pursuant to the lease for the hotel property. As lessor, the Operating Partnership is entitled to a percentage of gross receipts from the hotel property. Marriott International, Inc. continues to manage the hotel property under the Marriott name and under terms of the existing management agreement. The hotel taxable REIT subsidiary is subject to tax at the federal and state level and, accordingly, the Company has recorded a tax provision in the Company’s Consolidated Statements of Operations for the years ended December 31, 2013, 2012 and 2011.
The net difference between the tax basis and the reported amounts of the Company’s assets and liabilities is approximately $1.7 billion and $0.8 billion as of December 31, 2013 and 2012, respectively, which is primarily related to the difference in basis of contributed property and accrued rental income.
Certain entities included in the Company’s consolidated financial statements are subject to certain state and local taxes. These taxes are recorded as operating expenses in the accompanying consolidated financial statements.
The following table reconciles GAAP net income attributable to Boston Properties, Inc. to taxable income:
		For the year ended December 31,
		2013				2012				2011
		(in thousands)
Net income attributable to Boston Properties, Inc.		$	749,811			$	289,650			$	272,679
Straight-line rent adjustments		(74,445		)		(80,281		)		(77,422		)
Book/Tax differences from depreciation and amortization		170,370				105,599				117,675
Book/Tax differences on gains/losses from capital transactions		(124,413		)		(22,408		)		(38,443		)
Book/Tax differences from stock-based compensation		42,146				19,660				827
Other book/tax differences, net		(12,797		)		35,461				29,389
Taxable income		$	750,672			$	347,681			$	304,705
Stock-Based Employee Compensation Plans
At December 31, 2013, the Company has a stock-based employee compensation plan. Effective January 1, 2005, the Company adopted early ASC 718 “Compensation – Stock Compensation” (“ASC 718”), which revised the fair value based method of accounting for share-based payment liabilities, forfeitures and modifications of stock-based awards and clarified previous guidance in several areas, including measuring fair value, classifying an award as equity or as a liability and attributing compensation cost to reporting periods.
Use of Estimates in the Preparation of Financial Statements
The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. These estimates include such items as depreciation and allowances for doubtful accounts. Actual results could differ from those estimates.
Out-of-Period Adjustment
During the year ended December 31, 2012, the Company recorded additional real estate operating expenses totaling approximately $3.2 million related to the cumulative non-cash straight-line adjustment to the ground rent expense of certain ground leases that were not previously recognized on a straight-line basis. This resulted in the overstatement of real estate operating expenses by approximately $3.2 million during the year ended December 31, 2012 and in the understatement of real estate operating expenses in the aggregate amount of approximately $3.2 million in previous periods. Because this adjustment was not material to the prior years’ consolidated financial statements and the impact of recording the adjustment in the current period is not material to the Company’s consolidated financial statements, the Company recorded the related adjustment during the year ended December 31, 2012.
Reclassifications
The Company has modified the presentation of expenses to operate its San Francisco and Princeton regional offices to reflect the growing activity in its San Francisco region and to have a consistent presentation across the Company. These expenses, which totaled approximately $8.1 million, $7.7 million and $7.5 million for the years ended December 31, 2013, 2012 and 2011, respectively, were previously included in Rental Operating Expenses and are now included in General and Administrative Expenses for all periods presented.
Recent Accounting Pronouncements
In February 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2013-02, "Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income" (“ASU No. 2013-02”). ASU No. 2013-02 requires an entity to provide information about the amounts reclassified out of accumulated other comprehensive income by component. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income, but only if the amount reclassified is required to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures that provide additional detail about those amounts. ASU No. 2013-02 is effective prospectively for reporting periods beginning after December 15, 2012. The Company’s adoption of ASU No. 2013-02 did not have a material impact on its consolidated financial statements.

Real_Estate

Real Estate	12 Months Ended
	Dec. 31, 2013
Real Estate [Abstract]	'
Real Estate	'
	Real Estate
	Real estate consisted of the following at December 31 (in thousands):
			2013				2012
	Land		$	4,450,532			$	2,605,162
	Land held for future development		297,376				275,094
	Buildings and improvements		11,065,113				9,517,343
	Tenant improvements		1,617,401				1,435,508
	Furniture, fixtures and equipment		25,164				23,441
	Construction in progress		1,523,179				1,036,780
	Total		18,978,765				14,893,328
	Less: Accumulated depreciation		(3,161,571		)		(2,934,160		)
			$	15,817,194			$	11,959,168
	Acquisitions
	On February 6, 2013, the Company completed the acquisition of 535 Mission Street, a development site, in San Francisco, California for an aggregate purchase price of approximately $71.0 million in cash, including work completed and materials purchased to date. When completed, 535 Mission Street will consist of a 27-story, Class A office tower with approximately 307,000 net rentable square feet of office and retail space. The property is currently under development.
	On March 26, 2013, a consolidated joint venture in which the Company has a 95% interest completed the acquisition of a land parcel in San Francisco, California that will support a 60-story, 1.4 million square foot office tower known as Transbay Tower. The purchase price for the land was approximately $192.0 million. On February 7, 2013, the partner in the joint venture issued a notice that it was electing under the joint venture agreement to reduce its nominal ownership interest in the venture from 50% to 5%. On February 26, 2013, the Company issued a notice to the partner electing to proceed with the venture on that basis. As a result, the Company has a 95% nominal interest in and is consolidating the joint venture (See Note 11). The initial phase of the development consisting of building the project to grade is currently under development.
	On March 29, 2013, the Company completed the acquisition of a parcel of land located in Reston, Virginia for a purchase price of approximately $27.0 million. The land parcel is commercially zoned for 250,000 square feet of office space.
	On April 10, 2013, the Company acquired the Mountain View Research Park and Mountain View Technology Park properties from Boston Properties Office Value-Added Fund, L.P. (the "Value-Added Fund") for an aggregate net purchase price of approximately $233.1 million. Mountain View Research Park is a 16-building complex of Office/Technical properties aggregating approximately 604,000 net rentable square feet. Mountain View Technology Park is a seven-building complex of Office/Technical properties aggregating approximately 135,000 net rentable square feet. The following table summarizes the allocation of the aggregate purchase price of Mountain View Research Park and Mountain View Technology Park at the date of acquisition (in thousands) in accordance with the guidance in ASC 805 "Business Combinations."
	Land	$	126,521
	Building and improvements	82,451
	Tenant improvements	7,326
	In-place lease intangibles	23,279
	Above-market rents	843
	Below-market rents	(7,336		)
	Net assets acquired	$	233,084
	On May 31, 2013, the Company's two joint venture partners in 767 Venture, LLC (the entity that owns 767 Fifth Avenue (the General Motors Building) located in New York City) transferred all of their interests in the joint venture to third parties. 767 Fifth Avenue (the General Motors Building) is a Class A office property totaling approximately 1.8 million net rentable square feet. In connection with the transfer, the Company and its new joint venture partners modified the Company's relative decision making authority and consent rights with respect to the joint venture's assets and operations. These changes resulted in the Company having sufficient financial and operating control over 767 Venture, LLC such that, effective as of May 31, 2013, the Company accounts for the assets, liabilities and operations of 767 Venture, LLC on a consolidated basis in its financial statements instead of under the equity method of accounting (See Notes 5 and 11). The following table summarizes the allocation of the aggregate purchase price of 767 Fifth Avenue (the General Motors Building) at the date of consolidation on May 31, 2013 (in thousands) in accordance with the guidance in ASC 805 "Business Combinations."
	.
	Real estate and related intangibles recorded upon consolidation
	Land	$	1,796,252
	Building and improvements	1,447,446
	Tenant improvements	85,208
	In-place lease intangibles	357,781
	Above market rents	101,897
	Below market rents	(239,641		)
	Above market assumed debt adjustments	(192,943		)
		$	3,356,000
	Debt recorded upon consolidation
	Mortgage notes payable	$	(1,300,000	)
	Mezzanine notes payable	(306,000		)
	Members' notes payable	(450,000		)	-1
		$	(2,056,000	)
	Working capital recorded upon consolidation
	Cash and cash equivalents	$	79,468
	Cash held in escrows	2,403
	Tenant and other receivables	7,104
	Prepaid expenses and other assets	4,269
	Accounts payable and accrued expenses	(2,418		)
	Accrued interest payable	(182,369		)	-2
	Other liabilities	(6,304		)
		$	(97,847	)
	Noncontrolling interest recorded upon consolidation
	Noncontrolling interests	$	(520,000	)
	Noncontrolling interests - working capital	39,139
		$	(480,861	)
	Net assets recorded upon consolidation	$	721,292
	_______________
	(1) The Company's member loan totaling $270.0 million eliminates in consolidation.
	(2) The Company's share of the accrued interest payable on the members' loans totaling approximately $105.5 million eliminates in consolidation.
	Mountain View Research Park and Mountain View Technology Park contributed approximately $16.7 million of revenue and approximately $0.4 million of earnings to the Company for the period from April 10, 2013 through December 31, 2013. 767 Fifth Avenue (the General Motors Building) contributed approximately $168.4 million of revenue and approximately $8.4 million of earnings to the Company for the period from May 31, 2013 through December 31, 2013.
	The accompanying unaudited pro forma information for the years ended December 31, 2013 and 2012 is presented as if the operating property acquisitions of (1) Mountain View Research Park and Mountain View Technology Park on April 10, 2013 and the approximately $26.5 million gain on consolidation and (2) 767 Fifth Avenue (the General Motors Building) on May 31, 2013 and the approximately $359.5 million gain on consolidation, had occurred on January 1, 2012. This unaudited pro forma information is based upon the historical consolidated financial statements of the Company and should be read in conjunction with the consolidated financial statements and notes thereto. This pro forma information does not purport to represent what the actual results of operations of the Company would have been had the above occurred, nor do they purport to predict the results of operations of future periods.
	Pro Forma (Unaudited)	Year ended December 31,
	(in thousands, except per share data)	2013				2012
	Total revenue	$	2,257,098			$	2,149,391
	Income from continuing operations	$	302,354			$	634,457
Net income attributable to Boston Properties, Inc.	$	400,017			$	626,174
Basic earnings per share:
Net income per share attributable to Boston Properties, Inc.	$	2.58			$	4.15
Diluted earnings per share:
Net income per share attributable to Boston Properties, Inc.	$	2.57			$	4.13
Developments
On March 22, 2013, the Company completed and fully placed in-service Two Patriots Park, a Class A office redevelopment project with approximately 256,000 net rentable square feet located in Reston, Virginia.
On April 25, 2013, the Company commenced construction of its 601 Massachusetts Avenue, a Class A office development project totaling approximately 478,000 net rentable square feet located in Washington, DC.
On June 14, 2013, the Company completed and fully placed in-service Seventeen Cambridge Center, a Class A office project with approximately 195,000 net rentable square feet located in Cambridge, Massachusetts.
On July 1, 2013, the Company completed and fully placed in-service its Cambridge Center Connector, a Class A office project with approximately 43,000 net rentable square feet located in Cambridge, Massachusetts.
On October 29, 2013, the Company entered into a lease agreement as landlord with a third-party tenant for a build-to-suit project with approximately 130,000 net rentable square feet of Class A office space located in Princeton, New Jersey.
As of December 31, 2013, the Company has placed in-service approximately 63% of The Avant at Reston Town Center development project comprised of 359 apartment units and retail space aggregating approximately 355,000 square feet located in Reston, Virginia (See Note 20).
As of December 31, 2013, the Company has placed in-service approximately 6% of its 250 West 55th Street development project. When completed, this project will consist of approximately 989,000 net rentable square feet of Class A office space located in New York City.
As of December 31, 2013, the Company has placed in-service approximately 1% of its 680 Folsom Street development project. When completed, this project will consist of approximately 525,000 net rentable square feet of Class A office space located in San Francisco, California.
Dispositions
On February 20, 2013, the foreclosure sale of the Company's Montvale Center property was ratified by the court. As a result of the ratification, the mortgage loan totaling $25.0 million was extinguished and the related obligations were satisfied with the transfer of the real estate resulting in the recognition of a gain on forgiveness of debt totaling approximately $20.2 million. The operating results of the property through the date of ratification have been classified as discontinued operations on a historical basis for all periods presented.
On June 28, 2013, the Company completed the sale of its 303 Almaden Boulevard property located in San Jose, California for a sale price of $40.0 million. Net cash proceeds totaled approximately $39.3 million. 303 Almaden Boulevard is a Class A office property totaling approximately 158,000 net rentable square feet. Because the Company entered into the related purchase and sale agreement on March 28, 2013 and the carrying value of the property exceeded its net sale price, the Company recognized an impairment loss totaling approximately $3.2 million during the three months ended March 31, 2013. As a result, there was no loss on sale of real estate recognized during the year ended December 31, 2013. The impairment loss and operating results of this property have been classified as discontinued operations on a historical basis for all periods presented. The sale of this asset caused the Company to reevaluate its strategy for development of its adjacent Almaden land parcel, which can accommodate an approximately 840,000 square feet office complex.  Based on a shorter than expected hold period, the Company reduced the carrying value of the land parcel to its estimated fair market value and recognized an impairment loss of approximately $8.3 million during the three months ended March 31, 2013. The Company's estimated fair value, as measured on a non-recurring basis, was based on comparable land sales. The Company has determined that its valuation of the land falls within Level 3 of the fair value hierarchy, as it has utilized significant unobservable inputs in its assessment.
On August 22, 2013, the Company completed the sale of its 1301 New York Avenue property located in Washington, DC for a net contract sale price of approximately $121.7 million. After adjusting for outstanding lease and other transaction costs assumed by the buyer, the gross sale price was approximately $135.0 million. Net cash proceeds totaled approximately $121.5 million, resulting in a gain on sale of approximately $86.4 million. 1301 New York Avenue is a Class A office property totaling approximately 201,000 net rentable square feet. The operating results of the property through the date of sale have been classified as discontinued operations on a historical basis for all periods presented.
On October 9, 2013, the Company completed the sale of a 45% ownership interest in its Times Square Tower property for a gross sale price of $684.0 million in cash. Net cash proceeds totaled approximately $673.1 million, after the payment of transaction costs. In connection with the sale, the Company formed a joint venture with the buyer and will provide customary property management and leasing services to the joint venture. Times Square Tower is an approximately 1,246,000 net rentable square foot Class A office tower located in New York City. The transaction did not qualify as a sale of real estate for financial reporting purposes because the Company continues to control the joint venture and will therefore continue to account for the entity on a consolidated basis in its financial statements. The Company has accounted for the transaction as an equity transaction and has recognized noncontrolling interest in its consolidated balance sheets totaling approximately $243.5 million, which is equal to 45% of the carrying value of the total equity of the property immediately prior to the transaction. The difference between the net cash proceeds received and the noncontrolling interest recognized, which difference totals approximately $429.6 million, has not been reflected as a gain on sale of real estate in the Company’s consolidated statements of operations and has instead been reflected as an increase to additional paid-in capital in the Company’s consolidated balance sheets.
On December 20, 2013, the Company completed the sale of its 10 & 20 Burlington Mall Road property located in Burlington, Massachusetts for a sale price of approximately $30.0 million. Net cash proceeds totaled approximately $29.4 million, resulting in a gain on sale of approximately $20.5 million. 10 & 20 Burlington Mall Road consists of two Class A office properties aggregating approximately 152,000 net rentable square feet. The operating results of the properties through the date of sale have been classified as discontinued operations on a historical basis for all periods presented.
On December 20, 2013, the Company completed the sale of its One Preserve Parkway property located in Rockville, Maryland for a sale price of approximately $61.3 million. Net cash proceeds totaled approximately $59.9 million, resulting in a gain on sale of approximately $5.9 million. One Preserve Parkway is a Class A office property totaling approximately 184,000 net rentable square feet. The operating results of the property through the date of sale have been classified as discontinued operations on a historical basis for all periods presented.
The following table summarizes the income from discontinued operations related to One Preserve Parkway, 10 & 20 Burlington Mall Road, 1301 New York Avenue, 303 Almaden Boulevard, Montvale Center and Bedford Business Park and the related gains on sales of real estate, gain on forgiveness of debt and impairment loss for the years ended December 31, 2013, 2012 and 2011:
	For the year ended December 31,
	2013				2012				2011
	(in thousands)
Total revenue	$	20,138			$	32,607			$	36,734
Expenses
Operating	6,996				12,038				13,818
Depreciation and amortization	4,760				8,169				9,442
Total expenses	11,756				20,207				23,260
Operating income	8,382				12,400				13,474
Other expense
Interest expense	360				2,594				2,598
Income from discontinued operations	$	8,022			$	9,806			$	10,876
Noncontrolling interest in income from discontinued operations – common units of the Operating Partnership	(803		)		(1,031		)		(1,243		)
Income from discontinued operations attributable to Boston Properties, Inc.	$	7,219			$	8,775			$	9,633
Gains on sales of real estate from discontinued operations	$	112,829			$	36,877			$	—
Gain on forgiveness of debt from discontinued operations	20,182				—				—
Impairment loss from discontinued operations	(3,241		)		—				—
Noncontrolling interest in gains on sales of real estate, gain on forgiveness of debt and impairment loss from discontinued operations – common units of the Operating Partnership	(13,348		)		(4,044		)		—
Gains on sales of real estate, gain on forgiveness of debt and impairment loss from discontinued operations attributable to Boston Properties, Inc.	$	116,422			$	32,833			$	—

Deferred_Charges

Deferred Charges	12 Months Ended
	Dec. 31, 2013
Deferred Charges [Abstract]	'
Deferred Charges	'
	4.     Deferred Charges
	Deferred charges consisted of the following at December 31, (in thousands):
		2013			2012
	Leasing costs, including lease related intangibles	$	1,183,204		$	790,740
	Financing costs	76,798			90,682
		1,260,002			881,422
	Less: Accumulated amortization	(375,552		)	(293,187		)
		$	884,450		$	588,235
	The following table summarizes the scheduled amortization of the Company's acquired in-place lease intangibles for each of the five succeeding years (in thousands).
		Acquired In-Place Lease Intangibles
	2014	$	91,903
	2015	66,716
	2016	55,083
	2017	41,106
	2018	36,306

Investments_in_Unconsolidated_

Investments in Unconsolidated Joint Ventures	12 Months Ended
	Dec. 31, 2013
Investments In Unconsolidated Joint Ventures [Abstract]	'
Investments In Unconsolidated Joint Ventures	'
	Investments in Unconsolidated Joint Ventures
	The investments in unconsolidated joint ventures consist of the following at December 31, 2013:
	Entity	Properties	Nominal %
			Ownership
	Square 407 Limited Partnership	Market Square North	50	%
	The Metropolitan Square Associates LLC	Metropolitan Square	51	%
	BP/CRF 901 New York Avenue LLC	901 New York Avenue	25	%	(1)
	WP Project Developer LLC	Wisconsin Place Land and Infrastructure	33.3	%	(2)
	RBP Joint Venture LLC	N/A	50	%	(3)
	Boston Properties Office Value-Added Fund, L.P.	N/A	39.5	%	-4
	Annapolis Junction NFM, LLC	Annapolis Junction	50	%	-5
	2 GCT Venture LLC	N/A	60	%	(6)
	540 Madison Venture LLC	540 Madison Avenue	60	%
	125 West 55th Street Venture LLC	N/A	60	%	-7
	500 North Capitol LLC	500 North Capitol Street, NW	30	%
	_______________
	-1	The Company’s economic ownership can increase based on the achievement of certain return thresholds.
	-2	The Company’s wholly-owned entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking and infrastructure of the project.
	-3	Eighth Avenue and 46th Street was sold on July 19, 2013.
	-4	The Company acquired Mountain View Research Park and Mountain View Technology Park from the Value-Added Fund on April 10, 2013 (See Note 3). As of December 31, 2013, the investment is comprised of undistributed cash.
	-5	Comprised of two buildings, one building under construction and two undeveloped land parcels.
	-6	Two Grand Central Tower was sold on October 25, 2011. As of December 31, 2013, the investment is comprised of undistributed cash.
	-7	125 West 55th Street was sold on May 30, 2013. As of December 31, 2013, the investment is comprised of undistributed cash.
	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 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 unconsolidated joint ventures are as follows:
		December 31,			December 31,
		2013			2012
		(in thousands)
	ASSETS
	Real estate and development in process, net	$	924,297		$	4,494,971
	Other assets	163,149			673,716
	Total assets	$	1,087,446		$	5,168,687
	LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
	Mortgage and notes payable	$	749,732		$	3,039,922
	Other liabilities	28,830			792,888
	Members’/Partners’ equity	308,884			1,335,877
	Total liabilities and members’/partners’ equity	$	1,087,446		$	5,168,687
	Company’s share of equity	$	154,726		$	787,941
	Basis differentials (1)	(28,642		)	(128,025		)
	Carrying value of the Company’s investments in unconsolidated joint ventures	$	126,084		$	659,916
	_______________
	-1	This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from impairment of investments and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level.
	The combined summarized statements of operations of the joint ventures are as follows:
		For the year ended December 31,
		2013			2012			2011
		(in thousands)
	Total revenue (1)	$	311,548		$	564,205		$	589,294
	Expenses
	Operating	105,319			162,665			170,404
	Depreciation and amortization	86,088			163,134			190,437
	Impairment losses	—			—			40,468
	Total expenses	191,407			325,799			401,309
	Operating income	120,141			238,406			187,985
	Other income (expense)
	Interest expense	(112,535		)	(224,645		)	(228,494		)
	Losses from early extinguishments of debt	(1,677		)	—			—
	Income (loss) from continuing operations	5,929			13,761			(40,509		)
	Gains on sales of real estate	14,207			990			—
	Net income (loss)	$	20,136		$	14,751		$	(40,509	)
	Company’s share of net income (loss)	$	4,612		$	6,863		$	(25,374	)
	Gains on sales of real estate	54,501			—			46,166
	Basis differential	(1,017		)	1,732			27,226
	Elimination of inter-entity interest on partner loan	16,978			40,483			37,878
Income from unconsolidated joint ventures	$	75,074		$	49,078		$	85,896
Gains on consolidation of joint ventures	$	385,991		$	—		$	—
_______________
-1	Includes straight-line rent adjustments of $7.8 million, $12.0 million and $21.9 million for the years ended December 31, 2013, 2012 and 2011, respectively. Includes net below-market rent adjustments of $33.7 million, $91.1 million and $120.3 million for the years ended December 31, 2013, 2012 and 2011, respectively. Total revenue for the year ended December 31, 2012 includes termination income totaling approximately $19.6 million (of which the Company's share is approximately $11.8 million) related to a lease termination with a tenant at 767 Fifth Avenue (The General Motors Building).
On February 28, 2013, a joint venture in which the Company has a 50% interest completed and fully placed in-service Annapolis Junction Building Six, a Class A office property with approximately 119,000 net rentable square feet located in Annapolis, Maryland.
On March 31, 2013, a joint venture in which the Company has a 30% interest completed and fully placed in-service 500 North Capitol Street, NW, a Class A office redevelopment project with approximately 231,000 net rentable square feet located in Washington, DC.
On April 4, 2013, a joint venture in which the Company has a 50% interest obtained construction financing collateralized by its Annapolis Junction Building Seven development project located in Annapolis, Maryland totaling $22.0 million. The construction financing bears interest at a variable rate equal to LIBOR plus 1.65% per annum and matures on April 4, 2016, with two, one-year extension options, subject to certain conditions.
On April 10, 2013, the Company acquired the Mountain View Research Park and Mountain View Technology Park properties from its Value-Added Fund for an aggregate net purchase price of approximately $233.1 million. In conjunction with the acquisition, the Value-Added Fund repaid the mortgage loans collateralized by the Mountain View Research Park and Mountain View Technology Park properties totaling approximately $90.0 million and $20.0 million, respectively, as well as the outstanding loans payable to the Company's Operating Partnership totaling approximately $8.6 million and $3.7 million, respectively. The Mountain View Research Park and Mountain View Technology Park mortgage loans bore interest at variable rates equal to LIBOR plus 2.00% per annum and LIBOR plus 2.50% per annum, respectively, and were scheduled to mature on May 31, 2014 and November 22, 2014, respectively. The joint venture recognized a loss on early extinguishment of debt totaling approximately $0.4 million, of which the Company's share was approximately $0.2 million, consisting of the write-off of unamortized deferred financing costs. Prior to the acquisition, the Company's ownership interest in the properties was approximately 39.5%. As a result of the acquisition, the Company owns 100% of the properties and is accounting for them on a consolidated basis (See Note 3). The Company had previously recognized an impairment loss on its investment in the unconsolidated joint venture. As a result, the Company recognized a gain on its investment of approximately $26.5 million, which is included within gains on consolidation of joint ventures in the Company's consolidated statements of operations.
On May 30, 2013, a joint venture in which the Company has a 60% interest completed the sale of its 125 West 55th Street property located in New York City for a sale price of $470.0 million, including the assumption by the buyer of the mortgage loan collateralized by the property totaling approximately $198.6 million. The mortgage loan bore interest at a fixed rate of 6.09% per annum and was scheduled to mature on March 10, 2020. Net cash proceeds totaled approximately $253.7 million, of which the Company's share was approximately $152.2 million, after the payment of transaction costs. 125 West 55th Street is a Class A office property totaling approximately 588,000 net rentable square feet. The Company had previously recognized an impairment loss on its investment in the unconsolidated joint venture. As a result, the Company recognized a gain on sale of real estate totaling approximately $43.2 million, which is included within income from unconsolidated joint ventures in the Company's consolidated statements of operations.
On May 31, 2013, the Company's two joint venture partners in 767 Venture, LLC (the entity that owns 767 Fifth Avenue (the General Motors Building) located in New York City) transferred all of their interests in the joint venture to third parties. In connection with the transfer, the Company and its new joint venture partners modified the Company's relative decision making authority and consent rights with respect to the joint venture's assets and operations. These changes resulted in the Company having sufficient financial and operating control over 767 Venture, LLC such that the Company now accounts for the assets, liabilities and operations of 767 Venture, LLC on a consolidated basis in its financial statements instead of under the equity method of accounting (See Note 3). Upon consolidation, the Company recognized a non-cash gain on its investment of approximately $359.5 million, which is included within gains on consolidation of joint ventures in the Company's consolidated statements of operations.
On May 31, 2013, a joint venture in which the Company has a 30% interest refinanced its construction loan collateralized by 500 North Capitol Street, NW located in Washington, DC. The construction loan totaling approximately $90.6 million bore interest at a variable rate equal to LIBOR plus 1.65% per annum and was scheduled to mature on October 14, 2014. The joint venture recognized a loss on early extinguishment of debt totaling approximately $1.0 million, of which the Company's share was approximately $0.3 million, consisting of the write-off of unamortized deferred financing costs. The new mortgage loan totaling $105.0 million requires interest only payments at a fixed interest rate of 4.15% per annum and matures on June 6, 2023.
On June 5, 2013, a joint venture in which the Company has a 60% interest refinanced its mortgage loans collateralized by 540 Madison Avenue located in New York City. The mortgage loans aggregating approximately $118.0 million bore interest at a weighted-average fixed rate of 5.20% per annum and were scheduled to mature on July 11, 2013. The joint venture recognized a loss on early extinguishment of debt totaling approximately $0.3 million, of which the Company's share was approximately $0.2 million, related to the acceleration of the remaining balance of the historical fair value debt adjustment, which was the result of purchase accounting. The new mortgage loan totaling $120.0 million requires interest only payments at a variable rate equal to LIBOR plus 1.50% per annum and matures on June 5, 2018.
On July 19, 2013, a joint venture in which the Company has a 50% interest completed the sale of its Eighth Avenue and 46th Street project located in New York City for an imputed sale price of $45.0 million. The Eighth Avenue and 46th Street project is comprised of an assemblage of land parcels and air-rights. Net cash proceeds to the Company totaled approximately $21.8 million, after the payment of transaction costs. The joint venture had previously recognized an impairment loss on the property. As a result, the joint venture recognized a gain on sale of real estate totaling approximately $12.6 million, of which the Company's share was approximately $11.3 million. The Company's share of the gain on sale of real estate is reflective of the Company's share of the net proceeds from the imputed sale price and is included within income from unconsolidated joint ventures in the Company's consolidated statements of operations.
On September 26, 2013, a joint venture in which the Company has a 50% interest entered into a lease agreement for its Annapolis Junction Building Seven development project. Annapolis Junction Building Seven when completed will consist of a Class A office property with approximately 125,000 net rentable square feet located in Annapolis, Maryland.
On October 29, 2013, a joint venture in which the Company has a 50% interest exercised an option to extend the maturity date to November 17, 2014 of the construction financing collateralized by its Annapolis Junction Building Six property. The construction financing totaling approximately $14.0 million bears interest at a variable rate equal to LIBOR plus 1.65% per annum and was scheduled to mature on November 17, 2013. Annapolis Junction Building Six is a Class A office property with approximately 119,000 net rentable square feet located in Annapolis, Maryland.

Mortgage_Notes_Payable

Mortgage Notes Payable	12 Months Ended
	Dec. 31, 2013
Loans Payable [Abstract]	'
Mortgage Notes Payable	'
	Mortgage Notes Payable
	The Company had outstanding mortgage notes payable totaling approximately $4.4 billion and $3.1 billion as of December 31, 2013 and 2012, respectively, each collateralized by one or more buildings and related land included in real estate assets. The mortgage notes payable are generally due in monthly installments and mature at various dates through April 10, 2022.
	Fixed rate mortgage notes payable totaled approximately $4.4 billion and $3.1 billion at December 31, 2013 and 2012, respectively, with contractual interest rates ranging from 4.75% to 7.69% per annum at December 31, 2013 and 4.75% to 9.93% per annum at December 31, 2012 (with weighted-averages of 5.70% (excluding the mezzanine notes payable) and 5.65% at December 31, 2013 and 2012, respectively).
	There were no variable rate mortgage loans at December 31, 2013 and December 31, 2012. As of December 31, 2013 and 2012, the LIBOR rate was 0.17% and 0.21%, respectively.
	On February 5, 2013, the Company used available cash to repay the mortgage loan collateralized by its Kingstowne One property located in Alexandria, Virginia totaling approximately $17.0 million. The mortgage loan bore interest at a fixed rate of 5.96% per annum and was scheduled to mature on May 5, 2013. There was no prepayment penalty.
	On February 20, 2013, the foreclosure sale of the Company's Montvale Center property was ratified by the court. As a result of the ratification, the mortgage loan totaling $25.0 million was extinguished and the related obligations were satisfied with the transfer of the real estate resulting in the recognition of a gain on forgiveness of debt totaling approximately $20.2 million. The operating results of the property through the date of ratification have been classified as discontinued operations on a historical basis for all periods (See Note 3).
	On April 1, 2013, the Company used available cash to repay the mortgage loan collateralized by its 140 Kendrick Street property located in Needham, Massachusetts totaling approximately $47.6 million. The mortgage loan bore interest at a fixed rate of 7.51% per annum and was scheduled to mature on July 1, 2013. There was no prepayment penalty. The Company recognized a gain on early extinguishment of debt totaling approximately $0.3 million related to the acceleration of the remaining balance of the historical fair value debt adjustment, which was the result of purchase accounting.
	On May 31, 2013, in conjunction with the consolidation of the Company's 767 Venture, LLC joint venture (the entity that owns 767 Fifth Avenue (the General Motors Building), the Company recorded mortgage loans collateralized by the property aggregating $1.3 billion and mezzanine loans aggregating $306.0 million. The mortgage loans require interest-only payments at a weighted-average fixed interest rate of 5.95% per annum and mature on October 7, 2017. The mezzanine loans require interest-only payments at a weighted-average fixed interest rate of 6.02% per annum and mature on October 7, 2017. The mortgage loans and mezzanine loans were recorded at their fair values aggregating approximately $1.5 billion and $311.7 million, respectively, using weighted-average effective interest rates of approximately 2.44% and 5.53% per annum, respectively. In addition, in conjunction with the consolidation, the Company recorded loans payable to the joint venture's partners totaling $450.0 million and related accrued interest payable totaling approximately $175.8 million. The member loans bear interest at a fixed rate of 11.0% per annum and mature on June 9, 2017. The member loans consist of the portion of the original purchase price for the property that was financed with loans from the joint venture's partners on a pro rata basis. The Company has eliminated in consolidation its member loan totaling $270.0 million and its share of the related accrued interest payable of approximately $114.5 million at December 31, 2013. The remaining notes payable to the outside joint venture partners and related accrued interest payable totaling $180.0 million and approximately $76.4 million as of December 31, 2013 have been reflected as Outside Members' Notes Payable and within Accrued Interest Payable, respectively, on the Consolidated Balance Sheets (See Note 3). The related interest expense from the Outside Members' Notes Payable totaling approximately $16.0 million for the period from May 31, 2013 through December 31, 2013 is fully allocated to the outside joint venture partners as an adjustment to Noncontrolling Interests in Property Partnerships in the Company's Consolidated Statements of Operations.
	Four mortgage loans totaling approximately $2.2 billion at December 31, 2013 and five mortgage loans totaling approximately $951.5 million at December 31, 2012 have been accounted for at their fair values on the dates the mortgage loans were assumed. The impact of recording the mortgage loans at fair value resulted in a decrease to interest expense of approximately $34.4 million, $7.0 million and $9.2 million for the years ended December 31, 2013, 2012 and 2011, respectively. The cumulative liability related to the fair value adjustments was $191.2 million and $38.6 million at December 31, 2013 and 2012, respectively, and is included in mortgage notes payable in the Consolidated Balance Sheets.
	Contractual aggregate principal payments of mortgage notes payable at December 31, 2013 are as follows:
		Principal Payments
		(in thousands)
	2014	$	87,759
	2015	26,182
	2016	608,879
	2017	2,821,750
	2018	18,633
	Thereafter	695,327
	Total aggregate principal payments	4,258,530
	Unamortized balance of historical fair value adjustments	191,204
	Total carrying value of mortgage notes payable	$	4,449,734

Unsecured_Senior_Notes

Unsecured Senior Notes	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Unsecured Senior Notes	'
	Unsecured Senior Notes
	The following summarizes the unsecured senior notes outstanding as of December 31, 2013 (dollars in thousands):
		Coupon/		Effective		Principal			Maturity Date(2)
		Stated Rate		Rate(1)		Amount
	12 Year Unsecured Senior Notes	5.625	%	5.693	%	$	300,000		April 15, 2015
	12 Year Unsecured Senior Notes	5	%	5.194	%	250,000			June 1, 2015
	10 Year Unsecured Senior Notes	5.875	%	5.967	%	700,000			October 15, 2019
	10 Year Unsecured Senior Notes	5.625	%	5.708	%	700,000			November 15, 2020
	10 Year Unsecured Senior Notes	4.125	%	4.289	%	850,000			May 15, 2021
	7 Year Unsecured Senior Notes	3.7	%	3.853	%	850,000			November 15, 2018
	11 Year Unsecured Senior Notes	3.85	%	3.954	%	1,000,000			February 1, 2023
	10.5 Year Unsecured Senior Notes	3.125	%	3.279	%	500,000			September 1, 2023
	10.5 Year Unsecured Senior Notes	3.8	%	3.916	%	700,000			February 1, 2024
	Total principal					5,850,000
	Net unamortized discount					(14,146		)
	Total					$	5,835,854
	_______________
	-1	Yield on issuance date including the effects of discounts on the notes and the amortization of financing costs.
	-2	No principal amounts are due prior to maturity.
	The indenture relating to the unsecured senior notes contains certain financial restrictions and requirements, including (1) a leverage ratio not to exceed 60%, (2) a secured debt leverage ratio not to exceed 50%, (3) an interest coverage ratio of greater than 1.50, and (4) an unencumbered asset value of not less than 150% of unsecured debt. At December 31, 2013, the Company was in compliance with each of these financial restrictions and requirements.
	On April 11, 2013, the Company's Operating Partnership completed a public offering of $500.0 million in aggregate principal amount of its 3.125% senior unsecured notes due 2023. The notes were priced at 99.379% of the principal amount to yield an effective rate (including financing fees) of 3.279% to maturity. The notes will mature on September 1, 2023, unless earlier redeemed. The aggregate net proceeds from the offering were approximately $492.5 million after deducting underwriting discounts and transaction expenses.
	On June 27, 2013, the Company's Operating Partnership completed a public offering of $700.0 million in aggregate principal amount of its 3.800% senior unsecured notes due 2024. The notes were priced at 99.694% of the principal amount to yield an effective rate (including financing fees) of 3.916% to maturity. The notes will mature on February 1, 2024, unless earlier redeemed. The aggregate net proceeds from the offering were approximately $691.9 million after deducting the underwriting discount and transaction expenses.

Unsecured_Exchangeable_Senior_

Unsecured Exchangeable Senior Notes

12 Months Ended

Dec. 31, 2013

Debt Disclosure [Abstract]

'

Unsecured Exchangeable Senior Notes

'

Unsecured Exchangeable Senior Notes

The following summarizes the unsecured exchangeable senior notes outstanding as of December 31, 2013 (dollars in thousands):

Coupon/

Effective

Exchange

Principal

First Optional

Maturity Date

Stated Rate

Rate (1)

Rate

Amount

Redemption Date by the

Company

3.625% Exchangeable Senior Notes

3.625

%

4.037

%

8.6974

-2

$

747,500

N/A

February 15, 2014

Net unamortized discount

(182

)

Adjustment for the equity component allocation, net of accumulated amortization

(2,438

)

Total

$

744,880

_______________

-1

Yield on issuance date including the effects of discounts on the notes but excluding the effects of the adjustment for the equity component allocation.

-2

The initial exchange rate is 8.5051 shares per $1,000 principal amount of the notes (or an initial exchange price of approximately $117.58 per share of Boston Properties, Inc.’s common stock). In addition, the Company entered into capped call transactions with affiliates of certain of the initial purchasers, which are intended to reduce the potential dilution upon future exchange of the notes. The capped call transactions were intended to increase the effective exchange price to the Company of the notes from $117.58 to approximately $137.17 per share (subject to adjustments), representing an overall effective premium of approximately 40% over the closing price on August 13, 2008 of $97.98 per share of Boston Properties, Inc.’s common stock. The net cost of the capped call transactions was approximately $44.4 million. In connection with the special dividend declared on November 27, 2013, the exchange rate of 8.5051 was adjusted to 8.6974 shares per $1,000 principal amount of notes effective as of December 31, 2013, resulting in an exchange price of approximately $114.98 per share of Boston Properties, Inc.'s common stock. As of December 31, 2013, the effective exchange price was $130.21 per share. The Operating Partnership repaid the notes on February 18, 2014 (See Note 20).

ASC 470-20 requires the liability and equity components of convertible debt instruments that may be settled in cash upon conversion (including partial cash settlement) to be separately accounted for in a manner that reflects the issuer’s nonconvertible debt borrowing rate. ASC 470-20 requires that the initial proceeds from the sale of the Operating Partnership’s $862.5 million of 2.875% exchangeable senior notes due 2037 (all of which had been redeemed/repurchased as of December 31, 2012), $450.0 million of 3.75% exchangeable senior notes due 2036 (all of which have been redeemed/repurchased as of December 31, 2013) and $747.5 million of 3.625% exchangeable senior notes due 2014 (see Note 20) be allocated between a liability component and an equity component in a manner that reflects interest expense at the interest rate of similar nonconvertible debt that could have been issued by the Operating Partnership at such time. The Company measured the fair value of the debt components of the 2.875%, 3.75% and 3.625% exchangeable senior notes for the periods presented based on effective interest rates of 5.630%, 5.958% and 6.555%, respectively. The aggregate carrying amount of the debt component was approximately $744.9 million and $1.17 billion (net of equity component allocation adjustment of approximately $2.4 million and $25.5 million) at December 31, 2013 and December 31, 2012, respectively. As a result, the Company attributed an aggregate of approximately $230.3 million of the proceeds to the equity component of the notes, which represents the excess proceeds received over the fair value of the notes at the date of issuance. The equity component of the notes has been reflected within Additional Paid-in Capital in the Consolidated Balance Sheets. The Company reclassified approximately $1.0 million of deferred financing costs to Additional Paid-in Capital, which represented the costs attributable to the equity components of the notes. The carrying amount of the equity component was approximately $91.9 million and $148.5 million at December 31, 2013 and December 31, 2012, respectively. The resulting debt discount has been amortized over the period during which the debt was expected to be outstanding (i.e., through the first optional redemption dates or, in the case of the 2014 notes, the maturity date) as additional non-cash interest expense. The aggregate contractual interest expense was approximately $34.8 million, $48.4 million and $66.3 million for the years ended December 31, 2013, 2012 and 2011, respectively. As a result, the Company reported additional non-cash interest expense of approximately $23.1 million, $29.1 million and $38.8 million for the years ended December 31, 2013, 2012 and 2011, respectively.

On April 15, 2013, the Company announced that holders of its Operating Partnership's 3.75% Exchangeable Senior Notes due 2036 (the “Notes”) had the right to surrender their Notes for purchase by the Operating Partnership (the “Put Right”) on May 18, 2013. On April 15, 2013, the Company also announced that the Operating Partnership issued a notice of redemption to the holders of the Notes to redeem, on May 18, 2013 (the “Redemption Date”), all of the Notes outstanding on the Redemption Date. In connection with the notice of redemption, holders of the Notes had the right to exchange their Notes on or prior to May 16, 2013. Notes with respect to which the Put Right was not exercised and that were not surrendered for exchange on or prior to May 16, 2013, were redeemed by the Operating Partnership at a redemption price equal to 100% of the principal amount of the Notes plus accrued and unpaid interest thereon to, but excluding, the Redemption Date. Based on final information provided to the Operating Partnership by the trustee for the Notes, no Notes were validly tendered and accepted for purchase in the Put Right. Pursuant to the notice of redemption, an aggregate principal amount of $990,000 of the Notes was redeemed on May 18, 2013. The remaining aggregate principal amount of $449,010,000 of the Notes was surrendered for exchange and, in addition to the repayment of the principal in cash, the Company issued an aggregate of 419,116 shares of its common stock in exchange for the Notes (See Note 12). The Company recognized a loss on early extinguishment of debt totaling approximately $0.1 million consisting of transaction costs.

Unsecured_Line_of_Credit

Unsecured Line of Credit	12 Months Ended
	Dec. 31, 2013
Unsecured Line of Credit [Abstract]	'
Unsecured Line of Credit [Text Block]	'
	9.    Unsecured Line of Credit
	On July 26, 2013, the Company's Operating Partnership amended and restated the revolving credit agreement governing the Company's Unsecured Line of Credit, which, among other things, (1) increased the total commitment from $750.0 million to $1.0 billion, (2) extended the maturity date from June 24, 2014 to July 26, 2018 and (3) reduced the per annum variable interest rates and other fees. The Operating Partnership may increase the total commitment to $1.5 billion, subject to syndication of the increase and other conditions. At the Operating Partnership’s option, loans outstanding under the Unsecured Line of Credit will bear interest at a rate per annum equal to (1), in the case of loans denominated in Dollars, Euro or Sterling, LIBOR or, in the case of loans denominated in Canadian Dollars, CDOR, in each case, plus a margin ranging from 0.925% to 1.70% based on the Operating Partnership’s credit rating or (2) an alternate base rate equal to the greatest of (a) the Administrative Agent’s prime rate, (b) the Federal Funds rate plus 0.5% or (c) LIBOR for a one month period plus 1.00%, in each case, plus a margin ranging from 0.0% to 0.70% based on the Operating Partnership’s credit rating. The Unsecured Line of Credit also contains a competitive bid option that allows banks that are part of the lender consortium to bid to make loan advances to the Operating Partnership at a reduced interest rate. In addition, the Operating Partnership is also obligated to pay (1) in quarterly installments a facility fee on the total commitment at a rate per annum ranging from 0.125% to 0.35% based on the Operating Partnership’s credit rating and (2) an annual fee on the undrawn amount of each letter of credit equal to the LIBOR margin. Based on the Operating Partnership’s current credit rating, the LIBOR and CDOR margin is 1.00%, the alternate base rate margin is 0.0% and the facility fee is 0.15%. At December 31, 2013 and 2012, there were no amounts outstanding on the Unsecured Line of Credit.
	The terms of the Unsecured Line of Credit require that the Company maintain a number of customary financial and other covenants on an ongoing basis, including: (1) a leverage ratio not to exceed 60%, however, the leverage ratio may increase to no greater than 65% provided that it is reduced back to 60% within one year, (2) a secured debt leverage ratio not to exceed 55%, (3) a fixed charge coverage ratio of at least 1.40, (4) an unsecured debt leverage ratio not to exceed 60%, however, the unsecured debt leverage ratio may increase to no greater than 65% provided that it is reduced back to 60% within one year, (5) an unsecured debt interest coverage ratio of at least 1.75 and (6) limitations on permitted investments. At December 31, 2013, the Company was in compliance with each of these financial and other covenant requirements.

Commitments_And_Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments And Contingencies	'
	Commitments and Contingencies
	General
	In the normal course of business, the Company guarantees its performance of services or indemnifies third parties against its negligence. In addition, in the normal course of business, the Company guarantees to certain tenants the obligations of its subsidiaries for the payment of tenant improvement allowances and brokerage commissions in connection with their leases and limited costs arising from delays in delivery of their premises.
	The Company has letter of credit and performance obligations of approximately $13.9 million related to lender and development requirements.
	Certain of the Company’s joint venture agreements include provisions whereby, at certain specified times, each partner has the right to initiate a purchase or sale of the property or its interest in the joint ventures. Under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. See also Noncontrolling Interest—Redeemable Interest in Property Partnership in Note 11.
	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 December 31, 2013, the maximum funding obligation under the guarantee was approximately $24.1 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 $15.9 million related to its obligation to provide funds for certain tenant re-leasing costs. The mortgage financing matures on January 6, 2017.
	From time to time, the Company (or the applicable joint venture) has also agreed to guarantee portions of the principal, interest or other amounts in connection with other unconsolidated joint venture borrowings. In addition to the financial guarantees referenced above, the Company has agreed to customary environmental indemnifications and nonrecourse carve-outs (e.g., guarantees against fraud, misrepresentation and bankruptcy) on certain of its unconsolidated joint venture loans.
	Concentrations of Credit Risk
	Management of the Company performs ongoing credit evaluations of tenants and may require tenants to provide some form of credit support such as corporate guarantees and/or other financial guarantees. Although the Company’s properties are geographically diverse and the tenants operate in a variety of industries, to the extent the Company has a significant concentration of rental revenue from any single tenant, the inability of that tenant to make its lease payments could have an adverse effect on the Company.
	Some potential losses are not covered by insurance.
	The Company carries insurance coverage on its properties of types and in amounts and with deductibles that it believes are in line with coverage customarily obtained by owners of similar properties. In response to the uncertainty in the insurance market following the terrorist attacks of September 11, 2001, the Federal Terrorism Risk Insurance Act (as amended, “TRIA”) was enacted in November 2002 to require regulated insurers to make available coverage for “certified” acts of terrorism (as defined by the statute). The expiration date of TRIA was extended to December 31, 2014 by the Terrorism Risk Insurance Program Reauthorization Act of 2007 (“TRIPRA”) and the Company can provide no assurance that it will be extended further. Currently, the Company’s property insurance program per occurrence limits are $1.0 billion for its portfolio insurance program, including coverage for acts of terrorism certified under TRIA 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 which is provided by IXP, LLC (“IXP”) as a direct insurer. 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, with $1.375 billion of Terrorism Coverage in excess of $250 million being provided by NYXP, LLC (“NYXP”), as a direct insurer. 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 additional Terrorism Coverage provided by IXP for 601 Lexington Avenue, the NBCR Coverage provided by IXP and the Terrorism Coverage provided by NYXP are backstopped by the Federal Government if the aggregate industry insured losses resulting from a certified act of terrorism exceed a “program trigger.” The program trigger is $100.0 million and the coinsurance is 15%. Under TRIPRA, if the Federal Government pays out for a loss under TRIA, it is mandatory that the Federal Government recoup the full amount of the loss from insurers offering TRIA coverage after the payment of the loss pursuant to a formula in TRIPRA. The Company may elect to terminate the NBCR Coverage if the Federal Government seeks recoupment for losses paid under TRIA, if there is a change in its portfolio or for any other reason. In the event TRIPRA is not extended beyond December 31, 2014, (i) the Company will evaluate alternative approaches to secure coverage for acts of terrorism thereby potentially increasing its overall cost of insurance, (ii) if such insurance is not available at commercially reasonable rates with limits equal to its current coverage or at all, the Company may not continue to have full occurrence limit coverage for acts of terrorism, (iii) the Company may not satisfy the insurance requirements under existing or future debt financings secured by individual properties, (iv) the Company may not be able to obtain future debt financings secured by individual properties and (v) the Company may cancel the insurance policies issued by IXP for the NBCR Coverage and the additional Terrorism Coverage for 601 Lexington Avenue and by NYXP for the Terrorism Coverage for 767 Fifth Avenue. 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 are commercially reasonable. In addition, this insurance is subject to a deductible in the amount of 5% of the value of the affected property. Specifically, the Company currently carries earthquake insurance which covers its San Francisco region (excluding 535 Mission Street and the below grade improvements for Transbay Tower) with a $120 million per occurrence limit and a $120 million annual aggregate limit, $20 million of which is provided by IXP, as a direct insurer. The builders risk policy maintained for the development of 535 Mission Street in San Francisco includes a $15 million per occurrence and annual aggregate limit of earthquake coverage. In addition, the builders risk policy maintained for the development of the below grade improvements of the Transbay Tower in San Francisco includes a $15 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, the additional Terrorism Coverage for 601 Lexington Avenue and the Company’s NBCR Coverage. The additional Terrorism Coverage provided by IXP for 601 Lexington Avenue only applies to losses which exceed the program trigger under TRIA. NYXP, 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 Terrorism Coverage for 767 Fifth Avenue. Currently, NYXP only insures losses which exceed the program trigger under TRIA and NYXP reinsures with a third-party insurance company any coinsurance payable under TRIA. Insofar as the Company owns IXP and NYXP, it is responsible for their liquidity and capital resources, and the accounts of IXP and NYXP are part of the Company’s consolidated financial statements. In particular, if a loss occurs which is covered by the Company’s NBCR Coverage but is less than the applicable program trigger under TRIA, IXP would be responsible for the full amount of the loss without any backstop by the Federal Government. IXP and NYXP would also be responsible for any recoupment charges by the Federal Government in the event losses are paid out and their insurance policies are maintained after the payout by the Federal Government. If the Company experiences a loss and IXP or NYXP are required to pay under their insurance policies, the Company would ultimately record the loss to the extent of the required payment. Therefore, insurance coverage provided by IXP and NYXP should not be considered as the equivalent of third-party insurance, but rather as a modified form of self-insurance. In addition, the Operating Partnership has issued a guarantee to cover liabilities of IXP in the amount of $20.0 million.
	The mortgages on the Company's properties typically contain requirements concerning the financial ratings of the insurers who provide policies covering the property. The Company provides the lenders on a regular basis with the identity of the insurance companies in the Company's insurance programs. The ratings of some of the Company's insurers are below the rating requirements in some of the Company's loan agreements and the lenders for these loans could attempt to claim that an event of default has occurred under the loan. The Company believes it could obtain insurance with insurers which satisfy the rating requirements. Additionally, in the future, the Company's ability to obtain debt financing secured by individual properties, or the terms of such financing, may be adversely affected if lenders generally insist on ratings for insurers or amounts of insurance which are difficult to obtain or which result in a commercially unreasonable premium. There can be no assurance that a deficiency in the financial ratings of one or more of the Company's insurers will not have a material adverse effect on the Company.
	The Company continues to monitor the state of the insurance market in general, and the scope and costs of coverage for acts of terrorism and California earthquake risk in particular, but the Company cannot anticipate what coverage will be available on commercially reasonable terms in future policy years. There are other types of losses, such as from wars, for which the Company cannot obtain insurance at all or at a reasonable cost. With respect to such losses and losses from acts of terrorism, earthquakes or other catastrophic events, if the Company experiences a loss that is uninsured or that exceeds policy limits, the Company could lose the capital invested in the damaged properties, as well as the anticipated future revenues from those properties. Depending on the specific circumstances of each affected property, it is possible that the Company could be liable for mortgage indebtedness or other obligations related to the property. Any such loss could materially and adversely affect the Company's business and financial condition and results of operations.
	Legal Matters
	The Company is subject to various legal proceedings and claims that arise in the ordinary course of business. These matters are generally covered by insurance. Management believes that the final outcome of such matters will not have a material adverse effect on the financial position, results of operations or liquidity of the Company.
	State and Local Tax Matters
	Because the Company is organized and qualifies as a REIT, it is generally not subject to federal income taxes, but is subject to certain state and local taxes. In the normal course of business, certain entities through which the Company owns real estate either have undergone, or are currently undergoing, tax audits. Although the Company believes that it has substantial arguments in favor of its positions in the ongoing audits, in some instances there is no controlling precedent or interpretive guidance on the specific point at issue. Collectively, tax deficiency notices received to date from the jurisdictions conducting the ongoing audits have not been material. However, there can be no assurance that future audits will not occur with increased frequency or that the ultimate result of such audits will not have a material adverse effect on the Company’s results of operations.
	Environmental Matters
	It is the Company’s policy to retain independent environmental consultants to conduct or update Phase I environmental assessments (which generally do not involve invasive techniques such as soil or ground water sampling) and asbestos surveys in connection with the Company’s acquisition of properties. These pre-purchase environmental assessments have not revealed environmental conditions that the Company believes will have a material adverse effect on its business, assets, financial condition, results of operations or liquidity, and the Company is not otherwise aware of environmental conditions with respect to its properties that the Company believes would have such a material adverse effect. However, from time to time environmental conditions at the Company’s properties have required and may in the future require environmental testing and/or regulatory filings, as well as remedial action.
	In February 1999, the Company (through a joint venture) acquired from Exxon Corporation a property in Massachusetts that was formerly used as a petroleum bulk storage and distribution facility and was known by the state regulatory authority to contain soil and groundwater contamination. The Company developed an office park on the property. The Company engaged a specially licensed environmental consultant to oversee the management of contaminated soil and groundwater that was disturbed in the course of construction. Under the property acquisition agreement, Exxon agreed to (1) bear the liability arising from releases or discharges of oil and hazardous substances which occurred at the site prior to the Company’s ownership, (2) continue monitoring and/or remediating such releases and discharges as necessary and appropriate to comply with applicable requirements, and (3) indemnify the Company for certain losses arising from preexisting site conditions. Any indemnity claim may be subject to various defenses, and there can be no assurance that the amounts paid under the indemnity, if any, would be sufficient to cover the liabilities arising from any such releases and discharges.
	Environmental investigations at some of the Company’s properties and certain properties owned by affiliates of the Company have identified groundwater contamination migrating from off-site source properties. In each case the Company engaged a licensed environmental consultant to perform the necessary investigations and assessments and to prepare any required submittals to the regulatory authorities. In each case the environmental consultant concluded that the properties qualify under the regulatory program or the regulatory practice for a status which eliminates certain deadlines for conducting response actions at a site. The Company also believes that these properties qualify for liability relief under certain statutory provisions or regulatory practices regarding upgradient releases. Although the Company believes that the current or former owners of the upgradient source properties may bear responsibility for some or all of the costs of addressing the identified
	groundwater contamination, the Company will take such further response actions (if any) that it deems necessary or advisable. Other than periodic testing at some of these properties, no such additional response actions are anticipated at this time.
	Some of the Company’s properties and certain properties owned by the Company’s affiliates are located in urban, industrial and other previously developed areas where fill or current or historical uses of the areas have caused site contamination. Accordingly, it is sometimes necessary to institute special soil and/or groundwater handling procedures and/or include particular building design features in connection with development, construction and other property operations in order to achieve regulatory closure and/or ensure that contaminated materials are addressed in an appropriate manner. In these situations it is the Company’s practice to investigate the nature and extent of detected contamination and estimate the costs of required response actions and special handling procedures. The Company then uses this information as part of its decision-making process with respect to the acquisition and/or development of the property. For example, the Company owns a parcel in Massachusetts which was formerly used as a quarry/asphalt batching facility. Pre-purchase testing indicated that the site contained relatively low levels of certain contaminants. The Company has developed an office park on this property. Prior to and during redevelopment activities, the Company engaged a specially licensed environmental consultant to monitor environmental conditions at the site and prepare necessary regulatory submittals based on the results of an environmental risk characterization. A submittal has been made to the regulatory authorities in order to achieve regulatory closure at this site. The submittal included an environmental deed restriction that mandates compliance with certain protective measures in a portion of the site where low levels of residual soil contamination have been left in place in accordance with applicable laws.
	The Company expects that resolution of the environmental matters relating to the above will not have a material impact on its business, assets, financial condition, results of operations or liquidity. However, the Company cannot assure you that it has identified all environmental liabilities at its properties, that all necessary remediation actions have been or will be undertaken at the Company’s properties or that the Company will be indemnified, in full or at all, in the event that such environmental liabilities arise.
	Tax Protection Obligations
	In connection with the acquisition or contribution of three properties, the Company entered into agreements for the benefit of the selling or contributing parties which specifically state that until such time as the contributors do not hold at least a specified percentage of the OP Units owned by such person following the contribution of the properties, or until June 9, 2017 for 767 Fifth Avenue (the General Motors Building), the Operating Partnership will not sell or otherwise transfer the properties in a taxable transaction. If the Company does sell or transfer the properties in a taxable transaction, it would be liable to the contributors for contractual damages.

Noncontrolling_Interests

Noncontrolling Interests	12 Months Ended
	Dec. 31, 2013
Noncontrolling Interest [Abstract]	'
Noncontrolling Interests	'
	Noncontrolling Interests
	Noncontrolling interests relate to the interests in the Operating Partnership not owned by the Company and interests in consolidated property partnerships not wholly-owned by the Company. As of December 31, 2013, the noncontrolling interests consisted of 15,583,370 OP Units, 1,455,761 LTIP Units, 396,500 2011 OPP Units, 396,150 2012 OPP Units, 316,325 2013 MYLTIP Units, 666,116 Series Two Preferred Units (or 874,168 OP Units on an as converted basis) and 360,126 Series Four Preferred Units (not convertible into OP Units) held by parties other than the Company.
	Noncontrolling Interest—Redeemable Preferred Units of the Operating Partnership
	The Preferred Units at December 31, 2013 consisted of 666,116 Series Two Preferred Units, which bear a preferred distribution equal to the greater of (1) the distribution which would have been paid in respect of the Series Two Preferred Unit had such Series Two Preferred Unit been converted into an OP Unit (including both regular and special distributions) or (2) 6.00% per annum on a liquidation preference of $50.00 per unit, and are convertible into OP Units at a rate of $38.10 per Preferred Unit (1.312336 OP Units for each Preferred Unit). The holders of Series Two Preferred Units have the right to require the Operating Partnership to redeem their units for cash at the redemption price of $50.00 per unit on May 12, 2014. The holders also had the right to have their Series Two Preferred Units redeemed for cash on May 12, 2009, May 12, 2010, May 12, 2011, May 14, 2012 and May 14, 2013, although no holder exercised such right. Due to the holders' redemption option existing outside the control of the Company, the Series Two Preferred Units are presented outside of permanent equity in the Company's Consolidated Balance Sheets. In May 2014, the Company also has the right, subject to certain conditions, to call for redemption all of the outstanding Series Two Preferred Units for cash or to convert into OP Units any Series Two Preferred Units that have not been previously redeemed. In the event the Company calls the Series Two Preferred Units for redemption, the holders shall have the right to convert the Series Two Preferred Units into OP Units.
	During the years ended December 31, 2013 and 2012, 329,881 and 117,047 Series Two Preferred Units of the Operating Partnership, respectively, were converted by the holders into 432,914 and 153,605 OP Units, respectively. In addition, the Company paid the accrued preferred distributions due to the holders of Preferred Units that were converted.
	On February 15, 2013, the Operating Partnership paid a distribution on its outstanding Series Two Preferred Units of $0.85302 per unit. On May 15, 2013, the Operating Partnership paid a distribution on its outstanding Series Two Preferred Units of $0.85302 per unit. On August 15, 2013, the Operating Partnership paid a distribution on its outstanding Series Two Preferred Units of $0.85302 per unit. On November 15, 2013, the Operating Partnership paid a distribution on its outstanding Series Two Preferred Units of $0.85302 per unit.
	The Preferred Units at December 31, 2013 also included 360,126 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. In order to secure the performance of certain obligations by the holders, such Series Four Preferred Units are subject to forfeiture pursuant to the terms of a pledge agreement. 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 Operating Partnership to redeem all of their their units for cash at the redemption price of $50.00 per unit. The Operating Partnership 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. The Series Four Preferred Units that are subject to the security interest under the pledge agreement may not be redeemed until and unless such security interest is released. The Operating Partnership's first right to redeem the Series Four Preferred Units was a 30-day period beginning on August 29, 2013. Due to the holders' redemption option existing outside the control of the Company, the Series Four Preferred Units are presented outside of permanent equity in the Company's Consolidated Balance Sheets. On August 29, 2013, the Company's Operating Partnership redeemed approximately 861,400 Series Four Preferred Units for cash at the redemption price of $50.00 per unit plus accrued and unpaid distributions through the redemption date.
	On February 15, 2013, the Operating Partnership paid a distribution on its outstanding Series Four Preferred Units of $0.25 per unit. On May 15, 2013, the Operating Partnership paid a distribution on its outstanding Series Four Preferred Units of $0.25 per unit. On August 15, 2013, the Operating Partnership paid a distribution on its outstanding Series Four Preferred Units of $0.25 per unit. On November 15, 2013, the Operating Partnership 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 Operating Partnership for the years ended December 31, 2013, 2012 and 2011 (in thousands):
	Balance at December 31, 2010	$	55,652
	Net income	3,339
	Distributions	(3,339		)
	Balance at December 31, 2011	$	55,652
	Issuance of redeemable preferred units (Series Four Preferred Units)	79,405
	Net income	3,497
	Distributions	(3,497		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(18,329		)
	Conversion of redeemable preferred units (Series Two Preferred Units) to common units	(5,852		)
	Balance at December 31, 2012	$	110,876
	Net income	6,046
	Distributions	(6,046		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(43,070		)
	Conversion of redeemable preferred units (Series Two Preferred Units) to common units	(16,494		)
	Balance at December 31, 2013	$	51,312
	Noncontrolling Interest—Redeemable Interest in Property Partnership
	On October 4, 2012, the Company completed the formation of a joint venture, which owns and operates Fountain Square located in Reston, Virginia. The joint venture partner contributed the property valued at approximately $385.0 million and related mortgage indebtedness totaling approximately $211.3 million for a nominal 50% interest in the joint venture. The Company contributed cash totaling approximately $87.0 million for its nominal 50% interest, which cash was distributed to the joint venture partner. Pursuant to the joint venture agreement (i) the Company has rights to acquire the partner's nominal 50% interest and (ii) the partner has the right to cause the Company to acquire the partner's interest on January 4, 2016, in each case at a fixed price totaling approximately $102.0 million in cash. The fixed price option rights expire on January 31, 2016. The Company is consolidating this joint venture due to the Company's right to acquire the partner's nominal 50% interest. The Company initially recorded the noncontrolling interest at its acquisition-date fair value as temporary equity, due to the redemption option existing outside the control of the Company. The Company will accrete the changes in the redemption value quarterly over the period from the acquisition date to the earliest redemption date using the effective interest method.  The Company will record the accretion after the allocation of net income and distributions of cash flow to the noncontrolling interest account balance.
	The following table reflects the activity of the noncontrolling interest—redeemable interest in property partnership in the Company's Fountain Square consolidated joint venture for the for the years ended December 31, 2013 and 2012 (in thousands):
	Balance at December 31, 2011	$	—
	Acquisition-date fair value of redeemable interest	98,787
	Net loss	(719		)
	Distributions	(3,032		)
	Adjustment to reflect redeemable interest at redemption value	2,522
	Balance at December 31, 2012	$	97,558
	Net loss	(1,839		)
	Distributions	(4,585		)
	Adjustment to reflect redeemable interest at redemption value	8,475
	Balance at December 31, 2013	$	99,609
	Noncontrolling Interest—Common Units of the Operating Partnership
	During the years ended December 31, 2013 and 2012, 929,441 and 1,110,660 OP Units, respectively, were presented by the holders for redemption (including 432,914 and 153,605 OP Units, respectively, issued upon conversion of Series Two Preferred Units and 24,028 and 544,729 OP Units, respectively, issued upon conversion of LTIP Units) and were redeemed by the Company in exchange for an equal number of shares of Common Stock.
	At December 31, 2013, the Company had outstanding 396,500 2011 OPP Units and 396,150 2012 OPP Units and 316,325 2013 MYLTIP Units (See Note 17). Prior to the measurement date (January 31, 2014 for 2011 OPP Units (See Note 20), February 6, 2015 for 2012 OPP Units and February 4, 2016 for 2013 MYLTIP Units), holders of OPP Units and 2013 MYLTIP Units are entitled to receive per unit distributions equal to one-tenth (10%) of the regular quarterly distributions payable on an OP Unit, but will not be entitled to receive any special distributions. After the measurement date, the number of OPP Units and 2013 MYLTIP Units, both vested and unvested, that OPP and 2013 MYLTIP award recipients have earned, if any, based on the establishment of an outperformance pool, will be entitled to receive distributions in an amount per unit equal to distributions, both regular and special, payable on an OP Unit.
	On January 29, 2013, the Operating Partnership paid a distribution on the OP Units and LTIP Units in the amount of $0.65 per unit, and a distribution on the 2011 OPP Units and 2012 OPP Units in the amount of $0.065 per unit, to holders of record as of the close of business on December 31, 2012. On April 30, 2013, the Operating Partnership paid a distribution on the OP Units and LTIP Units in the amount of $0.65 per unit, and a distribution on the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units in the amount of $0.065 per unit, to holders of record as of the close of business on March 29, 2013. On July 31, 2013, the Operating Partnership paid a distribution on the OP Units and LTIP Units in the amount of $0.65 per unit, and a distribution on the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units in the amount of $0.065 per unit, to holders of record as of the close of business on June 28, 2013. On October 31, 2013, the Operating Partnership paid a distribution on the OP Units and LTIP Units in the amount of $0.65 per unit and a distribution on the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units in the amount of $0.065 per unit, to holders of record as of the close of business on September 30, 2013. On November 27, 2013, the Company, as general partner of the Operating Partnership, declared a special cash distribution on the OP Units and LTIP Units in the amount of $2.25 per unit payable on January 29, 2014 to holders of record as of the close of business on December 31, 2013. The special cash distribution was in addition to the regular quarterly distribution on the OP Units and LTIP Units of $0.65 per unit and the distribution on the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units in the amount of $0.065 per unit, in each case payable on January 29, 2014 to holders of record as of the close of business on December 31, 2013. Holders of the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units are not entitled to receive any special distributions. Holders of Series Two Preferred Units will participate in the special cash dividend (separately from their regular February 2014 distribution) on an as-converted basis in connection with their regular May 2014 distribution payment as provided in the Operating Partnership's partnership agreement.
	The Series Two Preferred Units may be converted into OP Units at the election of the holder thereof at any time. A holder of an OP Unit may present such OP Unit to the Operating Partnership for redemption at any time (subject to restrictions agreed upon at the time of issuance of OP Units to particular holders that may restrict such redemption right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, the Operating Partnership must redeem such OP Unit for cash equal to the then value of a share of common stock of the Company. The Company may, in its sole discretion, elect to assume and satisfy the redemption obligation by paying either cash or issuing one share of Common Stock. The value of the OP Units (not owned by the Company and including LTIP Units assuming that all conditions had been met for the conversion thereof) and Series Two Preferred Units (on an as converted basis) had all of such units been redeemed at December 31, 2013 was approximately $1.7 billion and $87.7 million, respectively, based on the closing price of the Company’s common stock of $100.37 per share on December 31, 2013.
	Noncontrolling Interest—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 $726.1 million at December 31, 2013 and approximately $(2.0) million at December 31, 2012, are included in Noncontrolling Interests—Property Partnerships on the accompanying Consolidated Balance Sheets.
	On February 7, 2013, the partner in the Company's Transbay Tower joint venture issued a notice that it was electing under the joint venture agreement to reduce its nominal ownership interest in the venture from 50% to 5%. On February 26, 2013, the Company issued a notice to the partner electing to proceed with the venture on that basis. As a result, the Company has a 95% nominal interest in and is consolidating the joint venture. Under the joint venture agreement, if certain return thresholds are achieved the partner will be entitled to an additional promoted interest. Also, under the agreement, (1) the partner has the right to cause the Company to purchase the partner's interest after the defined stabilization date and (2) the Company has the right to acquire the partner's interest on the third anniversary of the stabilization date, in each case at an agreed upon purchase price or appraised value. On March 26, 2013, the consolidated joint venture completed the acquisition of a land parcel in San Francisco, California which will support a 60-story, 1.4 million square foot office tower known as Transbay Tower. The purchase price for the land was approximately $192.0 million. The joint venture has commenced construction of the initial phase of the development consisting of building the project to grade (See Note 3).
	On May 31, 2013, the Company's two joint venture partners in 767 Venture, LLC (the entity that owns 767 Fifth Avenue(the General Motors Building) in New York City) transferred all of their interests in the joint venture to third parties. In connection with the transfer, the Company and its new joint venture partners modified the Company's relative decision making authority and consent rights with respect to the joint venture's assets and operations. These changes resulted in the Company having sufficient financial and operating control over 767 Venture, LLC such that the Company now accounts for the assets, liabilities and operations of 767 Venture, LLC on a consolidated basis in its financial statements instead of under the equity method of accounting. Upon consolidation, the Company recognized the new joint venture partners' aggregate 40% equity interest at its aggregate fair value of approximately $480.9 million within Noncontrolling Interests—Property Partnerships on the accompanying Consolidated Balance Sheets (See Notes 3 and 5).
	On October 9, 2013, the Company completed the sale of a 45% ownership interest in its Times Square Tower property for a gross sale price of $684.0 million in cash. Net cash proceeds totaled approximately $673.1 million, after the payment of transaction costs. In connection with the sale, the Company formed a joint venture with the buyer and will provide customary property management and leasing services to the joint venture. Times Square Tower is an approximately 1,246,000 net rentable square foot Class A office tower located in New York City. The transaction did not qualify as a sale of real estate for financial reporting purposes because the Company continues to control the joint venture and will therefore continue to account for the entity on a consolidated basis in its financial statements. The Company has accounted for the transaction as an equity transaction and has recognized noncontrolling interest in its consolidated balance sheets totaling approximately $243.5 million, which is equal to 45% of the carrying value of the total equity of the property immediately prior to the transaction. The difference between the net cash proceeds received and the noncontrolling interest recognized, which difference totals approximately $429.6 million, has not been reflected as a gain on sale of real estate in the Company’s consolidated statements of operations and has instead been reflected as an increase to Additional Paid-in Capital in the Company’s consolidated balance sheets (See Notes 3).

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Stockholders' Equity	'
	Stockholders’ Equity
	As of December 31, 2013, the Company had 152,983,101 shares of Common Stock outstanding.
	As of December 31, 2013, approximately $305.3 million remained available for issuance under the Company's $600 million “at the market” stock offering program. No shares were issued under the “at the market” stock offering program during the year ended December 31, 2013.
	During the year ended December 31, 2013, the Company did not issue any shares of Common Stock upon the exercise of options to purchase Common Stock by employees. During the year ended December 31, 2012, the Company issued 22,823 shares of Common Stock upon the exercise of options to purchase Common Stock by certain employees.
	During the years ended December 31, 2013 and 2012, the Company issued 929,441 and 1,110,660 shares of Common Stock, respectively, in connection with the redemption of an equal number of OP Units.
	On January 29, 2013, the Company paid a dividend in the amount of $0.65 per share of Common Stock to shareholders of record as of the close of business on December 31, 2012. On April 30, 2013, the Company paid a dividend in the amount of $0.65 per share of Common Stock to shareholders of record as of the close of business on March 29, 2013. On July 31, 2013, the Company paid a dividend in the amount of $0.65 per share of Common Stock to shareholders of record as of the close of business on June 28, 2013. On October 31, 2013, the Company paid a dividend in the amount of $0.65 per share of Common Stock to shareholders of record as of the close of business on September 30, 2013.
	On November 27, 2013, the Company's Board of Directors declared a special cash dividend of $2.25 per share of Common Stock payable on January 29, 2014 to shareholders of record as of the close of business on December 31, 2013. The special cash dividend was in addition to the regular quarterly dividend of $0.65 per share of Common Stock declared by the Company's Board of Directors and payable on January 29, 2014 to shareholders of record as of the close of business on December 31, 2013.
	On March 27, 2013, the Company completed an underwritten public offering of 80,000 shares (8,000,000 depositary shares each representing 1/100th of a share) of its newly designated 5.25% Series B Cumulative Redeemable Preferred Stock, at a price of $2,500.00 per share ($25.00 per depositary share). The net proceeds from this offering were approximately $193.6 million, after deducting the underwriting discount and transaction expenses. The Company contributed the net proceeds to the Operating Partnership in exchange for 80,000 Series B Preferred Units having terms and preferences generally mirroring those of the Series B Preferred Stock. The Company will pay 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. The Company may not redeem the Series B Preferred Stock prior to March 27, 2018, except in certain circumstances relating to the preservation of the Company's REIT status. On or after March 27, 2018, the Company, 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 the Company or its affiliates.
	On May 15, 2013, the Company paid a dividend on its outstanding Series B Preferred Stock of $32.8125 per share. On August 15, 2013, the Company paid a dividend on its outstanding Series B Preferred Stock of $32.8125 per share. On November 15, 2013, the Company paid a dividend on its outstanding Series B Preferred Stock of $32.8125 per share. On November 27, 2013, the Company's Board of Directors declared a dividend of $32.8125 per share of Series B Preferred Stock payable on February 18, 2014 to shareholders of record as of the close of business on February 7, 2014.
	During the year ended December 31, 2013, the Company issued 419,116 shares of Common Stock in connection with the exchange by holders of its Operating Partnership's 3.75% Exchangeable Senior Notes due 2036 (See Note 8).

Future_Minimum_Rents

Future Minimum Rents	12 Months Ended
	Dec. 31, 2013
Future Minimum Rents [Abstract]	'
Future Minimum Rents [Text Block]	'
	13.    Future Minimum Rents
	The properties are leased to tenants under net operating leases with initial term expiration dates ranging from 2014 to 2048. The future contractual minimum lease payments to be received (excluding operating expense reimbursements) by the Company as of December 31, 2013, under non-cancelable operating leases which expire on various dates through 2048, are as follows:
	Years Ending December 31,	(in thousands)
	2014	$	1,716,754
	2015	1,706,282
	2016	1,660,890
	2017	1,510,645
	2018	1,342,157
	Thereafter	6,674,466
	No single tenant represented more than 10.0% of the Company’s total rental revenue for the years ended December 31, 2013, 2012 and 2011.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
Segment Information	'
	Segment Information
	The Company’s segments are based on the Company’s method of internal reporting, which classifies its operations by both geographic area and property type. Beginning on January 1, 2014, the properties that were historically part of the Princeton region have been reflected as the suburban component of the New York region. The operations for the Princeton region, including the reclassification between Rental Operating Expenses and General and Administrative Expenses for the years ended December 31, 2013, 2012 and 2011 as detailed below, have been included in the New York region. Accordingly, amounts reflected below for the New York region have been adjusted to reflect the Company's retrospective inclusion of the Princeton region in the New York region. The Company’s segments by geographic area are Boston, New York, San Francisco and Washington, DC. Segments by property type include: Class A Office, Office/Technical, Residential and Hotel.
	Asset information by segment is not reported because the Company does not use this measure to assess performance. Therefore, depreciation and amortization expense is not allocated among segments. Interest and other income, development and management services, general and administrative expenses, transaction costs, interest expense, depreciation and amortization expense, gains (losses) from investments in securities, gains (losses) from early extinguishments of debt, income from unconsolidated joint ventures, gains on consolidation of joint ventures, impairment loss, discontinued operations and noncontrolling interests are not included in Net Operating Income as internal reporting addresses these items on a corporate level.
	Net Operating Income is not a measure of operating results or cash flows from operating activities as measured by accounting principles generally accepted in the United States of America, and it is not indicative of cash available to fund cash needs and should not be considered an alternative to cash flows as a measure of liquidity. All companies may not calculate Net Operating Income in the same manner. The Company considers Net Operating Income to be an appropriate supplemental measure to net income because it helps both investors and management to understand the core operations of the Company’s properties.
	We have modified the presentation of expenses to operate our San Francisco and Princeton regional offices to reflect the growing activity in our San Francisco region and to have a consistent presentation across our company. For San Francisco these expenses, which totaled approximately $6.7 million, $6.1 million and $6.0 million for the years ended December 31, 2013, 2012 and 2011, respectively, and for Princeton these expenses were approximately $1.4 million, $1.6 million and $1.5 million for the years ended December 31, 2013, 2012 and 2011, respectively, were previously included in Rental Operating Expenses and are now included in General and Administrative Expenses for all periods presented.
	On May 31, 2013, the Company's two joint venture partners in 767 Venture, LLC (the entity that owns 767 Fifth Avenue (the General Motors Building) located in New York City) transferred all of their interests in the joint venture to third parties (See Note 3). Effective as of May 31, 2013, the Company accounts for the assets, liabilities and operations of 767 Venture, LLC on a consolidated basis in its financial statements instead of under the equity method of accounting. Upon consolidation, the operations for this building are included in the New York region.
	Information by geographic area and property type (dollars in thousands):
	For the year ended December 31, 2013:
		Boston			New York				San				Washington,			Total
									Francisco				DC
	Rental Revenue:
	Class A Office	$	665,991		$	725,566			$	214,755			$	381,359		$	1,987,671
	Office/Technical	22,617			—				17,259				15,649			55,525
	Residential	4,395			—				—				17,923			22,318
	Hotel	40,330			—				—				—			40,330
	Total	733,333			725,566				232,014				414,931			2,105,844
	% of Grand Totals	34.82		%	34.46		%		11.02		%		19.7		%	100		%
	Rental Expenses:
	Class A Office	259,997			251,640				77,905				126,507			716,049
	Office/Technical	6,879			—				3,708				4,190			14,777
	Residential	1,823			—				—				10,307			12,130
	Hotel	28,447			—				—				—			28,447
	Total	297,146			251,640				81,613				141,004			771,403
	% of Grand Totals	38.52		%	32.62		%		10.58		%		18.28		%	100		%
	Net operating income	$	436,187		$	473,926			$	150,401			$	273,927		$	1,334,441
	% of Grand Totals	32.69		%	35.51		%		11.27		%		20.53		%	100		%
	For the year ended December 31, 2012:
		Boston			New York				San				Washington,			Total
									Francisco				DC
	Rental Revenue:
	Class A Office	$	617,652		$	543,194			$	208,177			$	346,402		$	1,715,425
	Office/Technical	22,460			—				494				16,264			39,218
	Residential	3,936			—				—				16,632			20,568
	Hotel	37,915			—				—				—			37,915
	Total	681,963			543,194				208,671				379,298			1,813,126
	% of Grand Totals	37.61		%	29.96		%		11.51		%		20.92		%	100		%
	Rental Expenses:
	Class A Office	242,904			187,987				75,542				111,049			617,482
	Office/Technical	6,499			—				149				3,966			10,614
	Residential	1,675			—				—				9,317			10,992
	Hotel	28,120			—				—				—			28,120
	Total	279,198			187,987				75,691				124,332			667,208
	% of Grand Totals	41.85		%	28.18		%		11.34		%		18.63		%	100		%
	Net operating income	$	402,765		$	355,207			$	132,980			$	254,966		$	1,145,918
	% of Grand Totals	35.15		%	31		%		11.6		%		22.25		%	100		%
	For the year ended December 31, 2011:
		Boston			New York				San				Washington,			Total
									Francisco				DC
	Rental Revenue:
	Class A Office	$	537,743		$	521,439			$	207,003			$	340,470		$	1,606,655
	Office/Technical	25,349			—				—				16,236			41,585
	Residential	985			—				—				5,632			6,617
	Hotel	34,529			—				—				—			34,529
	Total	598,606			521,439				207,003				362,338			1,689,386
	% of Grand Totals	35.43		%	30.87		%		12.25		%		21.45		%	100		%
	Rental Expenses:
	Class A Office	206,469			181,269				72,122				95,804			555,664
	Office/Technical	7,245			—				—				4,280			11,525
	Residential	521			—				—				4,958			5,479
	Hotel	26,128			—				—				—			26,128
	Total	240,363			181,269				72,122				105,042			598,796
	% of Grand Totals	40.14		%	30.27		%		12.05		%		17.54		%	100		%
	Net operating income	$	358,243		$	340,170			$	134,881			$	257,296		$	1,090,590
% of Grand Totals	32.85		%	31.19		%		12.37		%		23.59		%	100		%
The following is a reconciliation of Net Operating Income to net income attributable to Boston Properties, Inc.:
	Year ended December 31,
		2013			2012				2011
Net Operating Income		$	1,334,441		$	1,145,918			$	1,090,590
Add:
Development and management services income		29,695			34,060				33,406
Income from unconsolidated joint ventures		75,074			49,078				85,896
Gains on consolidation of joint ventures		385,991			—				—
Interest and other income		8,310			10,091				5,358
Gains (losses) from investments in securities		2,911			1,389				(443		)
Gains (losses) from early extinguishments of debt		122			(4,453		)		(1,494		)
Income from discontinued operations		8,022			9,806				10,876
Gains on sales of real estate from discontinued operations		112,829			36,877				—
Gain on forgiveness of debt from discontinued operations		20,182			—				—
Less:
General and administrative expense		115,329			90,129				87,101
Transaction costs		1,744			3,653				1,987
Depreciation and amortization expense		560,637			445,875				429,742
Interest expense		446,880			410,970				391,533
Impairment loss		8,306			—				—
Impairment loss from discontinued operations		3,241			—				—
Noncontrolling interest in property partnerships		1,347			3,792				1,558
Noncontrolling interest—redeemable preferred units of the Operating Partnership		6,046			3,497				3,339
Noncontrolling interest—common units of the Operating Partnership		70,085			30,125				35,007
Noncontrolling interest in discontinued operations—common units of the Operating Partnership		14,151			5,075				1,243
Net income attributable to Boston Properties, Inc.		$	749,811		$	289,650			$	272,679

Earnings_Per_Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	Earnings Per Share
	The following table provides a reconciliation of both the net income attributable to Boston Properties, Inc. and the number of common shares used in the computation of basic earnings per share (“EPS”), which is calculated by dividing net income attributable to Boston Properties, Inc. by the weighted-average number of common shares outstanding during the period. The terms of the Series Two Preferred Units enable the holders to obtain OP Units of the Operating Partnership, as well as Common Stock of the Company, and as a result these are considered participating securities. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are also participating securities. As such, unvested restricted common stock of the Company, LTIP Units, OPP Units and 2013 MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic EPS of the Company using the two-class method. Participating securities are included in the computation of diluted EPS of the Company using the if-converted method if the impact is dilutive. Because the OPP Units and 2013 MYLTIP Units require the Company 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 EPS calculation. Other potentially dilutive common shares, including stock options, restricted stock and other securities of the Operating Partnership that are exchangeable for the Company’s Common Stock, and the related impact on earnings, are considered when calculating diluted EPS.
		For the Year Ended December 31, 2013
		Income			Shares	Per Share
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per share amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties, Inc.	$	618,113		152,201	$	4.06
	Discontinued operations attributable to Boston Properties, Inc.	123,641			—	0.81
	Allocation of undistributed earnings to participating securities	(160		)	—	—
	Net income attributable to Boston Properties, Inc. common shareholders	$	741,594		152,201	$	4.87
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			320	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties, Inc. common shareholders	$	741,594		152,521	$	4.86
		For the Year Ended December 31, 2012
		Income			Shares	Per Share
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per share amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties, Inc.	$	248,042		150,120	$	1.65
	Discontinued operations attributable to Boston Properties, Inc.	41,608			—	0.28
	Net income attributable to Boston Properties, Inc. common shareholders	$	289,650		150,120	$	1.93
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			591	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties, Inc. common shareholders	$	289,650		150,711	$	1.92
		For the Year Ended December 31, 2011
		Income			Shares	Per Share
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per share amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties, Inc.	$	263,046		145,693	$	1.8
	Discontinued operations attributable to Boston Properties, Inc.	9,633			—	0.07
	Net income attributable to Boston Properties, Inc. common shareholders	$	272,679		145,693	$	1.87
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			525	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties, Inc. common shareholders	$	272,679		146,218	$	1.86

Employee_Benefit_Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2013
Employee Benefit Plans [Abstract]	'
Compensation and Employee Benefit Plans [Text Block]	'
	16.    Employee Benefit Plans
	Effective January 1, 1985, the predecessor of the Company adopted a 401(k) Savings Plan (the “Plan”) for its employees. Under the Plan, as amended, employees, as defined, are eligible to participate in the Plan after they have completed three months of service. Upon formation, the Company adopted the Plan and the terms of the Plan.
	Effective January 1, 2000, the Company amended the Plan by increasing the Company’s matching contribution to 200% of the first 3% from 200% of the first 2% of participant’s eligible earnings contributed (utilizing earnings that are not in excess of an amount established by the IRS ($255,000, $250,000 and $245,000 in 2013, 2012 and 2011, respectively), indexed for inflation) and by eliminating the vesting requirement. The Company’s aggregate matching contribution for the years ended December 31, 2013, 2012 and 2011 was $3.4 million, $3.2 million and $3.1 million, respectively.
	Effective January 1, 2001, the Company amended the Plan to provide a supplemental retirement contribution to certain employees who have at least ten years of service on January 1, 2001, and who are 40 years of age or older as of January 1, 2001. The maximum supplemental retirement contribution will not exceed the annual limit on contributions established by the IRS. The Company will record an annual supplemental retirement credit for the benefit of each participant. The Company’s supplemental retirement contribution and credit for the years ended December 31, 2013, 2012 and 2011 was $60,000, $78,000 and $62,000, respectively.
	The Company also maintains a deferred compensation plan that is designed to allow officers of the Company to defer a portion of their current income on a pre-tax basis and receive a tax-deferred return on these deferrals. The Company’s obligation under the plan is that of an unsecured promise to pay the deferred compensation to the plan participants in the future. At December 31, 2013 and 2012, the Company had maintained approximately $16.6 million and $12.2 million, respectively, in a separate account, which is not restricted as to its use. The Company’s liability under the plan is equal to the total amount of compensation deferred by the plan participants and earnings on the deferred compensation pursuant to investments elected by the plan participants. The Company’s liability as of December 31, 2013 and 2012 was $16.6 million and $12.2 million, respectively, which are included in the accompanying Consolidated Balance Sheets.

Stock_Option_and_Incentive_Pla

Stock Option and Incentive Plan	12 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock Option and Incentive Plan	'
	Stock Option and Incentive Plan
	At the Company's 2012 annual meeting of stockholders held on May 15, 2012, the stockholders of the Company approved the Boston Properties, Inc. 2012 Stock Option and Incentive Plan (the “2012 Plan”). The 2012 Plan replaced the 1997 Stock Option and Incentive Plan (the “1997 Plan”). The material terms of the 2012 Plan include, among other things: (1) the maximum number of shares of common stock reserved and available for issuance under the 2012 Plan is the sum of (i) 13,000,000 newly authorized shares, plus (ii) the number of shares available for grant under the 1997 Stock Plan immediately prior to the effective date of the 2012 Plan, plus (iii) any shares underlying grants under the 1997 Plan that are forfeited, cancelled or terminated (other than by exercise) in the future; (2) “full-value” awards (i.e., awards other than stock options) are multiplied by a 2.32 conversion ratio to calculate the number of shares available under the 2012 Plan that are used for each full-value award, as opposed to a 1.0 conversion ratio for each stock option awarded under the 2012 Plan; (3) shares tendered or held back for taxes will not be added back to the reserved pool under the 2012 Plan; (4) stock options may not be re-priced without stockholder approval; and (5) the term of the 2012 Plan is for ten years from the date of stockholder approval.
	On January 28, 2013, the Company's Compensation Committee approved multi-year long-term incentive program (MYLTIP) awards under the Company's 2012 Plan to officers and employees of the Company. MYLTIP awards utilize total return to shareholders ("TRS") over a three-year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will be based on the Company's TRS relative to (i) the Cohen & Steers Realty Majors Portfolio Index (50% weight) and (ii) the NAREIT Office Index adjusted to exclude the Company (50% weight). Earned awards will range from zero to a maximum of approximately $30.7 million depending on the Company's TRS relative to the two indices, with four tiers (threshold: approximately $5.1 million; target: approximately $10.2 million; high: approximately $20.5 million; exceptional: approximately $30.7 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 the Company's annualized TRS is less than 2% and (B) cause some awards to be earned in the event the Company's annualized TRS is more than 10% even though on a relative basis alone the Company's TRS would not result in any earned awards.
	Earned awards (if any) will vest 25% on February 4, 2016, 25% on February 4, 2017 and 50% on February 4, 2018, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by the Company without cause, termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 4, 2016, earned awards will be calculated based on TRS performance up to the date of the change of control. 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.
	On March 11, 2013, the Company announced that Owen D. Thomas would succeed Mortimer B. Zuckerman as the Company's Chief Executive Officer, effective April 2, 2013. On April 2, 2013, the Company issued 24,231 LTIP units, 38,926 2013 MYLTIP Units and 50,847 non-qualified stock options under the 2012 Plan to Mr. Thomas, pursuant to his employment agreement. Mr. Zuckerman will continue to serve as Executive Chairman for a transition period and thereafter is expected to continue to serve as the Non-Executive Chairman of the Board.  In connection with succession planning, the Company and Mr. Zuckerman entered into a Transition Benefits Agreement. If Mr. Zuckerman remains employed by the Company through July 1, 2014, he will be entitled to receive on January 1, 2015 a lump sum cash payment of $6.7 million and an equity award with a targeted value of approximately $11.1 million. The cash payment and equity award vest one-third on each of March 10, 2013, October 1, 2013 and July 1, 2014, subject to acceleration in certain circumstances. As a result, the Company recognized approximately $13.8 million of compensation expense during the year ended December 31, 2013. In addition, the agreement provides that if Mr. Zuckerman terminates his employment with the Company for any reason, voluntarily or involuntarily, he will become fully vested in any outstanding equity awards with time-based vesting. As a result, during the year ended December 31, 2013, the Company accelerated the remaining approximately $12.9 million of stock-based compensation expense associated with Mr. Zuckerman's unvested long-term equity awards.
	Under the Financial Accounting Standards Board's Accounting Standards Codification (“ASC”) 718 “Compensation-Stock Compensation” the MYLTIP awards granted to employees in February 2013 and granted to Mr. Thomas in April 2013 have an aggregate value of approximately $9.2 million, which amount will generally be amortized into earnings over the five-year plan period under the graded vesting method.
	The Company issued 36,730, 20,756 and 19,030 shares of restricted common stock and 184,733, 174,650 and 190,067 LTIP Units to employees and non-employee directors under the 1997 Plan and 2012 Plan during the years ended December 31, 2013, 2012 and 2011. The Company issued 252,220, 186,007 and 146,844 non-qualified stock options under the 1997 Plan during the years ended December 31, 2013, 2012 and 2011. The amounts issued during 2013 include the amounts issued to Mr. Thomas pursuant to his employment agreement, as discussed above. The Company issued 400,000 2011 OPP Units to employees under the 1997 Plan during the year ended December 31, 2011. The Company issued 400,000 2012 OPP Units to employees under the 1997 Plan during the year ended December 31, 2012. The Company issued 318,926 2013 MYLTIP Units to employees under the 2012 Plan during the year ended December 31, 2013, including the amounts issued to Mr. Thomas pursuant to his employment agreement, as discussed above. Employees and directors paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit, OPP Unit and 2013 MYLTIP Unit. An LTIP Unit is generally the economic equivalent of a share of restricted stock in the Company. 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 the Company’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. Non-qualified stock options, which are valued using the Black-Scholes option-pricing model, are recognized as an expense ratably over the corresponding employee service period. As the 2011 OPP Awards, 2012 OPP Awards and 2013 MYLTIP Awards are subject to both a service condition and a market condition, the Company recognizes the compensation expense related to the 2011 OPP Awards, 2012 OPP Awards and 2013 MYLTIP Awards 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 Dividends in Excess of Earnings in the Consolidated Balance Sheets. Aggregate stock-based compensation expense associated with restricted stock, non-qualified stock options, LTIP Units, 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units was approximately $43.9 million, $28.3 million and $28.3 million for the years ended December 31, 2013, 2012 and 2011, respectively. For the year ended December 31, 2013, stock-based compensation expense includes approximately $21.5 million consisting of the acceleration of the expense of the Company’s Executive Chairman’s stock-based compensation awards and the stock-based compensation awards associated with his transition benefits agreement related to the Company's succession planning. For the year ended December 31, 2012, stock-based compensation expense includes approximately $2.7 million consisting of the acceleration of vesting of the Company’s Chief Operating Officer’s stock-based compensation awards associated with his resignation. Upon the conclusion of the three-year measurement period in February 2011, the 2008 OPP Awards were not earned, the program was terminated and the Company accelerated the then remaining unrecognized compensation expense totaling approximately $4.3 million during the year ended December 31, 2011. At December 31, 2013, there was $17.6 million of unrecognized compensation expense related to unvested restricted stock and LTIP Units and $11.1 million of unrecognized compensation expense related to unvested 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 2.7 years (See Note 20).
	The shares of restricted stock were valued at approximately $3.9 million ($105.30 per share weighted-average), $2.2 million ($107.31 per share weighted-average) and $1.8 million ($93.40 per share weighted-average) for the years ended December 31, 2013, 2012 and 2011, respectively.
	LTIP Units were valued using a Monte Carlo simulation method model in accordance with the provisions of ASC 718 “Compensation—Stock Compensation” (“ASC 718”). LTIP Units issued during the years ended December 31, 2013, 2012 and 2011 were valued at approximately $17.8 million, $17.3 million and $16.5 million, respectively. The weighted-average per unit fair value of LTIP Unit grants in 2013, 2012 and 2011 was $96.13, $98.83 and $86.74, respectively. The per unit fair value of each LTIP Unit granted in 2013, 2012 and 2011 was estimated on the date of grant using the following assumptions; an expected life of 5.7 years, 5.8 years and 5.8 years, a risk-free interest rate of 1.03%, 0.94% and 2.22% and an expected price volatility of 26.0%, 29.1% and 30.0%, respectively.
	The non-qualified stock options granted during the years ended December 31, 2013, 2012 and 2011 had a weighted-average fair value on the date of grant of $18.46, $19.50 and $24.67 per option, respectively, which was computed using the Black-Scholes option-pricing model utilizing the following assumptions: an expected life of 6.0 years, 5.4 years and 6.0 years, a risk-free interest rate of 1.11%, 0.92% and 2.37%, an expected price volatility of 26.0%, 28.4% and 35.0% and an expected dividend yield of 3.0%, 2.9% and 3.0%, respectively. The exercise price of the options granted during the years ended December 31, 2013, 2012 and 2011 where $105.10, $107.23 and $92.71, respectively, which was the closing price of the Company’s common stock on the date of grant.
	A summary of the status of the Company’s stock options as of December 31, 2013, 2012 and 2011 and changes during the years then ended are presented below:
			Shares			Weighted
						Average
						Exercise
						Price
	Outstanding at December 31, 2010		324,938			$	32.65
	Granted		146,844			$	92.71
	Exercised		(316,159	)		$	32.63
	Canceled		—			$	—
	Outstanding at December 31, 2011		155,623			$	89.35
	Granted		186,007			$	107.23
	Exercised		(22,823	)		$	72.42
	Canceled		(24,280	)		$	100.15
	Outstanding at December 31, 2012		294,527			$	101.06
	Granted		252,220			$	104.5
	Exercised		—			$	—
	Canceled		—			$	—
	Special dividend adjustment		12,076			$	100.44
	Outstanding at December 31, 2013		558,823			$	100.43
	The following table summarizes information about stock options outstanding at December 31, 2013:
	Options Outstanding										Options Exercisable
	Exercise Prices				Number			Remaining	Exercise Price		Number Exercisable	Exercise Price
					Outstanding at			Contractual Life			at 12/31/13
					12/31/13
	$	90.71			131,837			7.1 years	$	90.71	80,240	$	90.71
	$	99.94			51,971			9.3 years	$	99.94	—	$	—
	$	102.83			205,821			9.1 years	$	102.83	48,026	$	102.83
	$	105.25			169,194			8.1 years	$	105.25	71,602	$	105.25
	The total intrinsic value of the outstanding and exercisable stock options as of December 31, 2013 was approximately $0.8 million. In addition, the Company had 91,496 and 13,633 options exercisable at a weighted-average exercise price of $98.92 and $54.32 at December 31, 2012 and 2011, respectively.
	The Company adopted the 1999 Non-Qualified Employee Stock Purchase Plan (the “Stock Purchase Plan”) to encourage the ownership of Common Stock by eligible employees. The Stock Purchase Plan became effective on January 1, 1999 with an aggregate maximum of 250,000 shares of Common Stock available for issuance. The Stock Purchase Plan provides for eligible employees to purchase on the business day immediately following the end of the biannual purchase periods (i.e., January 1-June 30 and July 1-December 31) shares of Common Stock at a purchase price equal to 85% of the average closing prices of the Common Stock during the last ten business days of the purchase period. The Company issued 6,442, 7,406 and 6,356 shares with the weighted average purchase price equal to $89.65 per share, $86.52 per share and $80.13 per share under the Stock Purchase Plan during the years ended December 31, 2013, 2012 and 2011, respectively.

Related_Party_Transactions

Related Party Transactions	156 Months Ended
	Dec. 31, 2013
Related Party Transaction [Line Items]	'
Related Party Transactions Disclosure [Text Block]	'
	18.    Related Party Transactions
	Prior to joining the Company effective January 2, 2014, Mr. John F. Powers provided commercial real estate brokerage services to the Company, on behalf of his prior employer, CBRE, in connection with certain leasing transactions. Mr. Powers received approximately $592,000 during the year ended December 31, 2013 in connection with these transactions. Mr. John F. Powers is a Senior Vice President of Boston Properties, Inc. and the Regional Manager of its New York office.
	A firm controlled by Mr. Raymond A. Ritchey’s brother was paid aggregate leasing commissions of approximately $868,000, $1,306,000 and $671,000 for the years ended December 31, 2013, 2012 and 2011, respectively, related to certain exclusive leasing arrangements for certain Northern Virginia properties. Mr. Ritchey is an Executive Vice President of Boston Properties, Inc.
	On June 30, 1998, the Company acquired from entities controlled by Mr. Alan B. Landis, a former director, a portfolio of properties known as the Carnegie Center Portfolio and Tower Center One and related operations and development rights (collectively, the “Carnegie Center Portfolio”). In connection with the acquisition of the Carnegie Center Portfolio, the Operating Partnership entered into a development agreement (the “Development Agreement”) with affiliates of Mr. Landis providing for up to approximately 2,000,000 square feet of development in or adjacent to the Carnegie Center office complex. An affiliate of Mr. Landis was entitled to a purchase price for each parcel developed under the Development Agreement calculated on the basis of $20 per rentable square foot of property developed. Another affiliate of Mr. Landis was eligible to earn a contingent payment for each developed property that achieves a stabilized return in excess of a target annual return ranging between 10.5% and 11%. The Development Agreement also provided that upon negotiated terms and conditions, the Company and Mr. Landis would form a development company to provide development services for these development projects and would share the expenses and profits, if any, of this new company. In addition, in connection with the acquisition of the Carnegie Center Portfolio, Mr. Landis became a director of the Company pursuant to an Agreement Regarding Directorship, dated as of June 30, 1998, with the Company (the “Directorship Agreement”). Under the Directorship Agreement, the Company agreed to nominate Mr. Landis for re-election as a director at each annual meeting of stockholders of the Company in a year in which his term expires, provided that specified conditions are met.
	On October 21, 2004, the Company entered into an agreement (the “2004 Agreement”) to modify several provisions of the Development Agreement. Under the terms of the 2004 Agreement, the Operating Partnership and affiliates of Mr. Landis amended the Development Agreement to limit the rights of Mr. Landis and his affiliates to participate in the development of properties under the Development Agreement. Among other things, Mr. Landis agreed that (1) Mr. Landis and his affiliates will have no right to participate in any entity formed to acquire land parcels or the development company formed by the Operating Partnership to provide development services under the Development Agreement, (2) Mr. Landis will have no right or obligation to play a role in development activities engaged in by the development company formed by the Operating Partnership under the Development Agreement or receive compensation from the development company and (3) the affiliate of Mr. Landis will have no right to receive a contingent payment for developed properties based on stabilized returns. In exchange, the Company (together with the Operating Partnership) agreed to:
	•	effective as of June 30, 1998, pay Mr. Landis $125,000 on January 1 of each year until the earlier of (A) January 1, 2018, (B) the termination of the Development Agreement or (C) the date on which all development properties under the Development Agreement have been conveyed pursuant to the Development Agreement, with $750,000, representing payments of this annual amount from 1998 to 2004, being paid upon execution of the 2004 Agreement; and
	•	pay an affiliate of Mr. Landis, in connection with the development of land parcels acquired under the Development Agreement, an aggregate fixed amount of $10.50 per rentable square foot of property developed (with a portion of this amount (i.e., $5.50) being subject to adjustment, in specified circumstances, based on future increases in the Consumer Price Index) in lieu of a contingent payment based on stabilized returns, which payment could have been greater or less than $10.50 per rentable square foot of property developed.
	The Operating Partnership also continues to be obligated to pay an affiliate of Mr. Landis the purchase price of $20 per rentable square foot of property developed for each land parcel acquired as provided in the original Development Agreement. During the 20-year term of the Development Agreement, until such time, if any, as the Operating Partnership elects to acquire a land parcel, an affiliate of Mr. Landis will remain responsible for all carrying costs associated with such land parcel. On July 24, 2007, the Company acquired from Mr. Landis 701 Carnegie Center, a land parcel located in Princeton, New Jersey for a purchase price of approximately $3.1 million.
	In addition, in connection with entering into the 2004 Agreement, Mr. Landis resigned as a director of the Company effective as of May 11, 2005 and agreed that the Company had no future obligation to nominate Mr. Landis as a director of the Company under the Directorship Agreement or otherwise. Mr. Landis did not resign because of a disagreement with the Company on any matter relating to its operations, policies or practices. Mitchell S. Landis, the Senior Vice President and Regional Manager of the Company’s Princeton, New Jersey region, is the brother of Alan B. Landis.
	In accordance with the Company’s 2012 Plan, and as approved by the Board of Directors, six non-employee directors made an election to receive deferred stock units in lieu of cash fees for 2013. The deferred stock units will be settled in shares of common stock upon the cessation of such director’s service on the Board of Directors. As a result of these elections, the aggregate cash fees otherwise payable to a non-employee director during a fiscal quarter are converted into a number of deferred stock units equal to the aggregate cash fees divided by the last reported sales price of a share of the Company’s common stock on the last trading of the applicable fiscal quarter. The deferred stock units are also credited with dividend equivalents as dividends are paid by the Company. At December 31, 2013 and 2012, the Company had outstanding 83,995 and 76,682 deferred stock units, respectively.

Selected_Interim_Financial_Inf

Selected Interim Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Financial Information [Text Block]	'
	9.    Selected Interim Financial Information (unaudited)
	The tables below reflect the Company’s selected quarterly information for the years ended December 31, 2013 and 2012. Total revenue and income from continuing operations amounts have been reclassified for properties qualifying for discontinued operations presentation (See Note 3).
		2013 Quarter Ended
		March 31,		June 30,		September 30,		December 31,
		(in thousands, except for per share amounts)
	Total revenue	$	477,826	$	510,033	$	571,481	$	576,199
	Income from continuing operations	$	38,496	$	503,446	$	82,311	$	79,395
	Net income attributable to Boston Properties, Inc.	$	47,854	$	452,417	$	152,677	$	88,719
	Income attributable to Boston Properties, Inc. per share—basic	$	0.32	$	2.95	$	1	$	0.58
	Income attributable to Boston Properties, Inc. per share—diluted	$	0.31	$	2.94	$	1	$	0.58
		2012 Quarter Ended
		March 31,		June 30,		September 30,		December 31,
		(in thousands, except for per share amounts)
	Total revenue	$	438,722	$	466,197	$	464,220	$	478,047
	Income from continuing operations	$	53,079	$	94,795	$	63,331	$	74,251
	Net income attributable to Boston Properties, Inc.	$	48,454	$	118,559	$	57,249	$	65,400
	Income attributable to Boston Properties, Inc. per share—basic	$	0.33	$	0.79	$	0.38	$	0.43
	Income attributable to Boston Properties, Inc. per share—diluted	$	0.33	$	0.78	$	0.38	$	0.43

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2013
Subsequent Events [Abstract]	'
Subsequent Events	'
	Subsequent Events
	On January 27, 2014, the Company's Compensation Committee approved the 2014 multi-year, long-term incentive program (the "2014 MYLTIP") awards under the Company's 2012 Plan to certain officers and employees of the Company. The 2014 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 the Company's TRS relative to (i) the Cohen & Steers Realty Majors Portfolio Index (50% weight) and (ii) the NAREIT Office Index adjusted to exclude the Company (50% weight). Earned awards will range from zero to a maximum of approximately $40.2 million depending on the Company's TRS relative to the two indices, with four tiers (threshold: approximately $6.7 million; target: approximately $13.4 million; high: approximately $26.8 million; exceptional: approximately $40.2 million) and linear interpolation between tiers. Earned awards measured on the basis of relative TRS performance are subject to an absolute TRS component in the form of relatively simple modifiers that (A) reduce the level of earned awards in the event the Company's annualized TRS is less than 0% and (B) cause some awards to be earned in the event the Company's annualized TRS is more than 12% even though on a relative basis alone the Company's TRS would not result in any earned awards.
	Earned awards (if any) will vest 50% on February 3, 2017 and 50% on February 3, 2018, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by the Company without cause, termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 3, 2017, earned awards will be calculated based on TRS performance up to the date of the change of control. The 2014 MYLTIP awards are in the form of LTIP Units issued on the grant date which (i) are subject to forfeiture to the extent awards are not earned and (ii) prior to the performance measurement date are only entitled to one-tenth (10%) of the regular quarterly distributions payable on common partnership units.
	Under the Financial Accounting Standards Board's Accounting Standards Codification (“ASC”) 718 “Compensation-Stock Compensation” the 2014 MYLTIP awards have an aggregate value of approximately $13.1 million, which amount will generally be amortized into earnings over the four-year plan period under the graded vesting method.
	On January 31, 2014, the Company issued 21,455 shares of restricted common stock and 109,718 LTIP units under the 2012 Plan to certain employees of the Company.
	On January 31, 2014, the measurement period for the Company’s 2011 OPP Awards expired and the Company’s TRS performance was not sufficient for employees to earn and therefore become eligible to vest in any of the 2011 OPP Awards. As a result, the Company accelerated the then remaining unrecognized compensation expense totaling approximately $1.2 million. Accordingly, all 2011 OPP Awards were automatically forfeited and the Operating Partnership repaid employees an amount equal to $0.25 (which is equal to what they paid upon acceptance of the award) multiplied by the number of 2011 OPP Awards they received.
	On February 10, 2014, the Company completed and fully placed in-service The Avant at Reston Town Center development project comprised of 359 apartment units and retail space aggregating approximately 355,000 square feet located in Reston, Virginia.
	On February 18, 2014, the Company's Operating Partnership repaid at maturity the $747.5 million aggregate principal amount outstanding of its 3.625% Exchangeable Senior Notes due 2014 plus accrued and unpaid interest thereon.

Real_Estate_and_Accumulated_De

Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2013
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]	'
Real Estate and Accumulated Depreciation Disclosure [Text Block]	'
	Boston Properties, Inc.
	Schedule 3 - Real Estate and Accumulated Depreciation
	December 31, 2013
	(dollars in thousands)
	Property Name		Type		Location	Encumbrances					Original				Costs			Land and Improvements		Building and		Land		Development		Total		Accumulated		Year(s) Built/	Depreciable
															Capitalized					Improvements		Held for		and				Depreciation		Renovated	Lives  (Years)
															Subsequent							Development		Construction
															to									in Progress
											Land		Building		Acquisition
	767 Fifth Avenue (The General Motors Building)		Office		New York, NY	$	1,463,143				$	1,796,252	$	1,532,654	$	4,481		$	1,796,252	$	1,537,135	$	—	$	—	3,333,387		$	28,901	1968	-1
	Embarcadero Center		Office		San Francisco, CA	360,133					179,697		847,410		314,292			195,985		1,145,414		—		—		1,341,399		472,324		1970/1989	-1
	Prudential Center		Office		Boston, MA	—					92,077		734,594		354,501			107,426		1,057,815		15,931		—		1,181,172		398,909		1965/1993/2002	-1
	399 Park Avenue		Office		New York, NY	—					339,200		700,358		107,604			354,107		793,055		—		—		1,147,162		219,938		1961	-1
	601 Lexington Avenue		Office		New York, NY	722,253					241,600		494,782		217,155			289,639		663,898		—		—		953,537		205,721		1977/1997	-1
	The John Hancock Tower and Garage		Office		Boston, MA	652,933					219,543		667,884		57,420			219,616		724,812		419		—		944,847		78,366		1976	-1
	Times Square Tower		Office		New York, NY	—					165,413		380,438		85,146			169,193		461,804		—		—		630,997		137,934		2004	-1
	100 Federal Street		Office		Boston, MA	—					131,067		435,954		6,020			131,067		441,760		214		—		573,041		29,060		1971-1975	-1
	Carnegie Center		Office		Princeton, NJ	—					105,107		377,259		66,866			103,064		443,817		2,206		145		549,232		169,587		1983-1999	-1
	Atlantic Wharf		Office		Boston, MA	—					63,988		454,537		11,644			63,988		466,181		—		—		530,169		39,697		2011	-1
	Fountain Square		Office		Reston, VA	226,604					56,853		306,298		3,877			56,853		310,175		—		—		367,028		15,460		1986-1990	-1
	510 Madison Avenue		Office		New York, NY	—					103,000		253,665		6,309			103,000		259,974		—		—		362,974		15,901		2012	-1
	599 Lexington Avenue		Office		New York, NY	750,000					81,040		100,507		123,179			87,852		216,874		—		—		304,726		144,094		1986	-1
	South of Market and Democracy Tower		Office		Reston, VA	—					13,603		237,479		9,790			13,687		247,185		—		—		260,872		50,831		2008-2009	-1
	Gateway Center		Office		San Francisco, CA	—					28,255		139,245		51,330			30,627		188,203		—		—		218,830		80,461		1984/1986/2002	-1
	Bay Colony Corporate Center		Office		Waltham, MA	—					18,789		148,451		47,332			18,789		195,783		—		—		214,572		21,339		1985-1989	-1
	2200 Pennsylvania Avenue		Office		Washington, DC	—					—		183,541		3,767			—		187,308		—		—		187,308		18,185		2011	-1
	Mountain View Research Park		Office		Mountain View, CA	—					106,162		76,137		2,196			106,162		78,333		—		—		184,495		3,013		1977-1981/2007-2013	-1
	One and Two Patriots Park		Office		Reston, VA	—					18,429		126,315		34,994			22,352		157,386		—		—		179,738		7,032		1987/1988/2012/2013	-1
	3200 Zanker Road		Office		San Jose, CA	—					36,705		82,863		24,669			36,997		103,496		3,744		—		144,237		23,165		1988	-1
	Reservoir Place		Office		Waltham, MA	—					18,605		92,619		27,446			20,118		118,552		—		—		138,670		52,829		1955/1987	-1
	1333 New Hampshire Avenue		Office		Washington, DC	—					34,032		85,660		9,061			35,394		93,359		—		—		128,753		30,392		1996	-1
	505 9th Street		Office		Washington, DC	121,360					38,885		83,719		5,692			42,082		86,214		—		—		128,296		20,358		2007	-1
	Kingstowne Towne Center		Office		Alexandria, VA	33,338					18,021		109,038		742			18,062		109,739		—		—		127,801		26,526		2003-2006	-1
	1330 Connecticut Avenue		Office		Washington, DC	—					25,982		82,311		16,286			27,135		97,444		—		—		124,579		29,518		1984	-1
	Capital Gallery		Office		Washington, DC	—					4,725		29,565		86,993			8,662		112,621		—		—		121,283		50,217		1981/2006	-1
	Weston Corporate Center		Office		Weston, MA	—					25,753		92,312		(123		)	25,854		92,088		—		—		117,942		10,921		2010	-1
	One Freedom Square		Office		Reston, VA	—					9,929		84,504		16,666			11,293		99,806		—		—		111,099		32,827		2000	-1
	One and Two Reston Overlook		Office		Reston, VA	—					16,456		66,192		26,635			17,561		91,722		—		—		109,283		31,144		1999	-1
	Two Freedom Square		Office		Reston, VA	—					13,930		77,739		13,816			15,420		90,065		—		—		105,485		37,294		2001	-1
	Seven Cambridge Center		Office		Cambridge, MA	—					3,457		97,136		2,880			4,125		99,348		—		—		103,473		47,498		2006	-1
	Five Cambridge Center		Office		Cambridge, MA	—					18,863		53,346		29,762			21,173		80,798		—		—		101,971		19,158		1981/1996	-1
	140 Kendrick Street		Office		Needham, MA	—					18,095		66,905		14,759			19,092		80,667		—		—		99,759		17,433		2000	-1
	Discovery Square		Office		Reston, VA	—					11,198		71,782		16,189			12,533		86,636		—		—		99,169		28,865		2001	-1
	Four Cambridge Center		Office		Cambridge, MA	—					19,104		52,078		11,872			20,785		62,269		—		—		83,054		10,761		1983/1998	-1
	Waltham Weston Corporate Center		Office		Waltham, MA	—					10,385		60,694		8,462			11,097		68,444		—		—		79,541		21,709		2003	-1
	77 CityPoint		Office		Waltham, MA	—					13,847		60,383		3,160			13,873		63,517		—		—		77,390		12,301		2008	-1
	230 CityPoint		Office		Waltham, MA	—					13,189		49,823		13,102			13,593		62,521		—		—		76,114		17,601		1992	-1
	North First Business Park		Office		San Jose, CA	—					58,402		13,069		4,010			23,377		16,215		35,889		—		75,481		10,208		1981	-1
	Seventeen Cambridge Center		Office		Cambridge, MA	—					18,080		51,262		—			18,080		51,262		—		—		69,342		1,080		2013	-1
	2440 West El Camino Real		Office		Mountain View, CA	—					16,741		51,285		502			16,741		51,787		—		—		68,528		4,390		1987/2003	-1
	Wisconsin Place		Office		Chevy Chase, MD	—					—		53,349		12,787			—		66,136		—		—		66,136		11,573		2009	-1
	Reston Corporate Center		Office		Reston, VA	—					9,135		50,857		5,346			10,148		55,190		—		—		65,338		21,034		1984	-1
	New Dominion Technology Park, Bldg. Two		Office		Herndon, VA	63,000					5,584		51,868		3,894			6,510		54,836		—		—		61,346		16,557		2004	-1
	Sumner Square		Office		Washington, DC	—					624		28,745		23,679			1,478		51,570		—		—		53,048		23,282		1985	-1
	New Dominion Technology Park, Bldg. One		Office		Herndon, VA	43,278					3,880		43,227		3,882			4,583		46,406		—		—		50,989		19,584		2001	-1
	200 West Street		Office		Waltham, MA	—					16,148		24,983		8,568			16,813		32,886		—		—		49,699		14,834		1999	-1
	191 Spring Street		Office		Lexington, MA	—					2,850		27,166		18,558			3,151		45,423		—		—		48,574		29,636		1971/1995	-1
	One Cambridge Center		Office		Cambridge, MA	—					134		25,110		20,608			548		45,304		—		—		45,852		24,914		1987	-1
	University Place		Office		Cambridge, MA	13,692					—		37,091		6,785			390		43,486		—		—		43,876		20,692		1985	-1
	2600 Tower Oaks Boulevard		Office		Rockville, MD	—					4,243		31,125		8,257			4,785		38,840		—		—		43,625		16,576		2001	-1
	Quorum Office Park		Office		Chelmsford, MA	—					3,750		32,454		5,672			5,187		36,689		—		—		41,876		12,748		2001	-1
	Three Patriots Park		Office		Reston, VA	—					3,594		32,977		3,013			4,009		35,575		—		—		39,584		12,465		2006	-1
	500 E Street		Office		Washington, DC	—					109		22,420		12,854			2,379		33,004		—		—		35,383		20,633		1987	-1
Eight Cambridge Center		Office		Cambridge, MA	—					850		25,042		8,507			1,323		33,076		—		—		34,399		11,139		1999	-1
Mountain View Technology Park		Office		Mountain View, CA	—					20,359		13,640		182			20,359		13,822		—		—		34,181		761		1972	-1
Three Cambridge Center		Office		Cambridge, MA	—					174		12,200		8,758			965		20,167		—		—		21,132		9,768		1987	-1
Ten Cambridge Center		Office		Cambridge, MA	—					1,299		12,943		6,117			2,395		17,964		—		—		20,359		11,337		1990	-1
201 Spring Street		Office		Lexington, MA	—					2,849		15,303		(154		)	3,124		14,874		—		—		17,998		6,034		1997	-1
40 Shattuck Road		Office		Andover, MA	—					709		14,740		2,453			893		17,009		—		—		17,902		5,547		2001	-1
Lexington Office Park		Office		Lexington, MA	—					998		1,426		13,762			1,264		14,922		—		—		16,186		10,566		1982	-1
92-100 Hayden Avenue		Office		Lexington, MA	—					594		6,748		7,819			802		14,359		—		—		15,161		9,914		1985	-1
33 Hayden Avenue		Office		Lexington, MA	—					266		3,234		10,283			425		13,358		—		—		13,783		7,486		1979	-1
181 Spring Street		Office		Lexington, MA	—					1,066		9,520		1,950			1,160		11,376		—		—		12,536		4,007		1999	-1
195 West Street		Office		Waltham, MA	—					1,611		6,652		4,175			1,858		10,580		—		—		12,438		6,187		1990	-1
91 Hartwell Avenue		Office		Lexington, MA	—					784		6,464		4,984			941		11,291		—		—		12,232		7,535		1985	-1
Eleven Cambridge Center		Office		Cambridge, MA	—					121		5,535		5,131			324		10,463		—		—		10,787		7,240		1984	-1
7501 Boston Boulevard, Building Seven		Office		Springfield, VA	—					665		9,273		544			791		9,691		—		—		10,482		3,895		1997	-1
7435 Boston Boulevard, Building One		Office		Springfield, VA	—					392		3,822		3,895			659		7,450		—		—		8,109		5,526		1982	-1
7450 Boston Boulevard, Building Three		Office		Springfield, VA	—					1,165		4,681		1,915			1,430		6,331		—		—		7,761		2,917		1987	-1
8000 Grainger Court, Building Five		Office		Springfield, VA	—					366		4,282		2,944			601		6,991		—		—		7,592		5,160		1984	-1
453 Ravendale Drive		Office		Mountain View, CA	—					5,477		1,090		230			5,477		1,320		—		—		6,797		142		1977	-1
7500 Boston Boulevard, Building Six		Office		Springfield, VA	—					138		3,749		2,590			406		6,071		—		—		6,477		4,133		1985	-1
7601 Boston Boulevard, Building Eight		Office		Springfield, VA	—					200		878		4,875			551		5,402		—		—		5,953		3,576		1986	-1
Fourteen Cambridge Center		Office		Cambridge, MA	—					110		4,483		1,223			273		5,543		—		—		5,816		3,805		1983	-1
7300 Boston Boulevard, Building Thirteen		Office		Springfield, VA	—					608		4,773		230			661		4,950		—		—		5,611		3,934		2002	-1
8000 Corporate Court, Building Eleven		Office		Springfield, VA	—					136		3,071		1,484			775		3,916		—		—		4,691		2,355		1989	-1
7374 Boston Boulevard, Building Four		Office		Springfield, VA	—					241		1,605		1,902			398		3,350		—		—		3,748		2,327		1984	-1
7375 Boston Boulevard, Building Ten		Office		Springfield, VA	—					23		2,685		1,007			93		3,622		—		—		3,715		2,261		1988	-1
7451 Boston Boulevard, Building Two		Office		Springfield, VA	—					249		1,542		1,313			613		2,491		—		—		3,104		2,131		1982	-1
32 Hartwell Avenue		Office		Lexington, MA	—					168		1,943		800			314		2,597		—		—		2,911		1,568		1968-1979/1987	-1
164 Lexington Road		Office		Billerica, MA	—					592		1,370		319			643		1,638		—		—		2,281		703		1982	-1
17 Hartwell Avenue		Office		Lexington, MA	—					26		150		1,002			65		1,113		—		—		1,178		639		1968	-1
Residences on The Avenue,		Residential		Washington, DC	—					—		119,874		(32		)	—		119,842		—		—		119,842		7,948		2011	-1
2221 I St., NW
The Lofts at Atlantic Wharf		Residential		Boston, MA	—					3,529		54,891		1,543			3,529		56,434		—		—		59,963		3,591		2011	-1
Cambridge Center Marriott		Hotel		Cambridge, MA	—					478		37,918		35,981			1,201		73,176		—		—		74,377		47,182		1986	-1
Cambridge Center East Garage		Garage		Cambridge, MA	—					—		35,035		1,487			103		36,419		—		—		36,522		6,684		1984	-1
Cambridge Center West Garage		Garage		Cambridge, MA	—					1,256		15,697		1,553			1,434		17,072		—		—		18,506		3,364		2006	-1
Cambridge Center North Garage		Garage		Cambridge, MA	—					1,163		11,633		1,085			1,163		12,718		—		—		13,881		8,157		1990	-1
250 West 55th Street		Development		New York, NY	—					—		—		818,243			16,305		45,476		—		756,462		818,243		483		N/A	N/A
Transbay Tower		Development		San Francisco, CA	—					—		—		255,406			—		—		—		255,406		255,406		—		N/A	N/A
680 Folsom Street		Development		San Francisco, CA	—					—		—		241,093			—		—		3,475		237,618		241,093		—		N/A	N/A
601 Massachusetts Avenue		Development		Washington, DC	—					—		—		121,694			—		—		—		121,694		121,694		—		N/A	N/A
535 Mission Street		Development		San Francisco, CA	—					—		—		113,274			—		—		—		113,274		113,274		—		N/A	N/A
The Avant at Reston Town Center Residential		Development		Reston, VA	—					—		—		107,022			12,741		55,701		—		38,580		107,022		160		N/A	N/A
Springfield Metro Center		Land		Springfield, VA	—					—		—		32,073			—		—		32,073		—		32,073		—		N/A	N/A
Plaza at Almaden		Land		San Jose, CA	—					—		—		29,003			—		—		29,003		—		29,003		—		N/A	N/A
Tower Oaks Master Plan		Land		Rockville, MD	—					—		—		28,976			—		—		28,976		—		28,976		—		N/A	N/A
Reston Signature Site		Land		Reston, VA	—					—		—		27,890			—		—		27,890		—		27,890		—		N/A	N/A
Prospect Hill		Land		Waltham, MA	—					—		—		24,197			—		667		23,530		—		24,197		—		N/A	N/A
Washingtonian North		Land		Gaithersburg, MD	—					—		—		18,290			—		—		18,290		—		18,290		—		N/A	N/A
6601 & 6605 Springfield Center Drive		Land		Springfield, VA	—					—		—		13,866			—		—		13,866		—		13,866		—		N/A	N/A
Waltham Office Center		Land		Waltham, MA	—					—		—		12,716			165		8,445		4,106		—		12,716		8,063		N/A	N/A
103 4th Avenue		Land		Waltham, MA	—					—		—		11,918			—		—		11,918		—		11,918		—		N/A	N/A
Cambridge Master Plan		Land		Cambridge, MA	—					—		—		11,153			—		—		11,153		—		11,153		—		N/A	N/A
Reston Gateway		Land		Reston, VA	—					—		—		9,682			—		—		9,682		—		9,682		—		N/A	N/A
Reston Eastgate		Land		Reston, VA	—					—		—		8,807			—		—		8,807		—		8,807		—		N/A	N/A
Crane Meadow		Land		Marlborough, MA	—					—		—		8,725			—		—		8,725		—		8,725		—		N/A	N/A
Broad Run Business Park		Land		Loudon County, VA	—					—		—		7,888			1,621		—		6,267		—		7,888		—		N/A	N/A
30 Shattuck Road		Land		Andover, MA	—					—		—		1,212			—		—		1,212		—		1,212		—		N/A	N/A
					$	4,449,734		(2	)	$	4,303,172	$	10,631,057	$	4,019,372		$	4,450,532	$	12,682,514	$	297,376	$	1,523,179	$	18,953,601	$	3,145,701
__________________
Note: Total Real Estate does not include Furniture, Fixtures and Equipment totaling approximately $25,164. Accumulated Depreciation does not include approximately $15,870 of accumulated depreciation related to Furniture, Fixtures and Equipment.
The aggregate cost and accumulated depreciation for tax purposes was approximately $14.8 billion and $2.6 billion, respectively.
-1	Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.
-2	Includes the unamortized balance of the historical fair value adjustment totaling approximately $191.2 million.
Boston Properties, Inc.
Real Estate and Accumulated Depreciation
December 31, 2013
(dollars in thousands)
A summary of activity for real estate and accumulated depreciation is as follows:
		2013			2012				2011
Real Estate:
Balance at the beginning of the year		$	14,869,887		$	13,363,113			$	12,740,892
Additions to/improvements of real estate		4,410,622			1,602,583				668,084
Assets sold/written-off		(326,908		)	(95,809		)		(45,863		)
Balance at the end of the year		$	18,953,601		$	14,869,887			$	13,363,113
Accumulated Depreciation:
Balance at the beginning of the year		$	2,919,479		$	2,626,324			$	2,308,665
Depreciation expense		419,908			367,625				362,636
Assets sold/written-off		(193,686		)	(74,470		)		(44,977		)
Balance at the end of the year		$	3,145,701		$	2,919,479			$	2,626,324
Note: Real Estate and Accumulated Depreciation amounts do not include Furniture, Fixtures and Equipment.

Summary_Of_Significant_Account1

Summary Of Significant Accounting Policies Summary Of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Real Estate	'
	Real Estate
	Upon acquisitions of real estate that constitutes a business, which includes the consolidation of previously unconsolidated joint ventures, the Company assesses the fair value of acquired tangible and intangible assets (including land, buildings, tenant improvements, “above-” and “below-market” leases, leasing and assumed financing origination costs, acquired in-place leases, other identified intangible assets and assumed liabilities, and allocates the purchase price to the acquired assets and assumed liabilities, including land and buildings as if vacant. The Company assesses and considers fair value based on estimated cash flow projections that utilize discount and/or capitalization rates that it deems appropriate, as well as available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known and anticipated trends, and market and economic conditions. The fair value of the tangible assets of an acquired property considers the value of the property as if it were vacant. The Company also considers an allocation of purchase price of other acquired intangibles, including acquired in-place leases that may have a customer relationship intangible value, including (but not limited to) the nature and extent of the existing relationship with the tenants, the tenant's credit quality and expectations of lease renewals. Based on its acquisitions to date, the Company's allocation to customer relationship intangible assets has been immaterial.
	The Company records acquired “above-” and “below-market” leases at their fair values (using a discount rate which reflects the risks associated with the leases acquired) equal to the difference between (1) the contractual amounts to be paid pursuant to each in-place lease and (2) management's estimate of fair market lease rates for each corresponding in-place lease, measured over a period equal to the remaining term of the lease for above-market leases and the initial term plus the term of any below-market fixed rate renewal options for below- market leases. Acquired “above-” and “below-market” lease values have been reflected within Prepaid Expenses and Other Assets and Other Liabilities, respectively, in the Company's Consolidated Balance Sheets. Other intangible assets acquired include amounts for in-place lease values that are based on the Company's evaluation of the specific characteristics of each tenant's lease. Factors to be considered include estimates of carrying costs during hypothetical expected lease-up periods considering current market conditions, and costs to execute similar leases. In estimating carrying costs, the Company includes real estate taxes, insurance and other operating expenses and estimates of lost rentals at market rates during the expected lease-up periods, depending on local market conditions. In estimating costs to execute similar leases, the Company considers leasing commissions, legal and other related expenses.
	Management reviews its long-lived assets for impairment following the end of each quarter and when there is an event or change in circumstances that indicates an impairment in value. An impairment loss is recognized if the carrying amount of its assets is not recoverable and exceeds its fair value. If such criteria are present, an impairment loss is recognized based on the excess of the carrying amount of the asset over its fair value. The evaluation of anticipated cash flows is highly subjective and is based in part on assumptions regarding future occupancy, rental rates and capital requirements that could differ materially from actual results in future periods. Since cash flows on properties considered to be “long-lived assets to be held and used” are considered on an undiscounted basis to determine whether an asset has been impaired, the Company's established strategy of holding properties over the long term directly decreases the likelihood of recording an impairment loss. If the Company's strategy changes or market conditions otherwise dictate an earlier sale date, an impairment loss may be recognized and such loss could be material. If the Company determines that impairment has occurred, the affected assets must be reduced to their fair value, less cost to sell.
	Accounting Standards Codification (“ASC”) ASC 360 "Property Plant and Equipment" requires that qualifying assets and liabilities and the results of operations that have been sold, or otherwise qualify as “held for sale,” be presented as discontinued operations in all periods presented if the property operations are expected to be eliminated and the Company will not have significant continuing involvement following the sale. The components of the property’s net income that is reflected as discontinued operations include the net gain (or loss) upon the disposition of the property held for sale, operating results, depreciation and interest expense (if the property is subject to a secured loan). The Company generally considers assets to be “held for sale” when the transaction has been approved by the Board of Directors, or a committee thereof, and there are no known significant contingencies relating to the sale, such that the property sale within one year is considered probable. Following the classification of a property as “held for sale,” no further depreciation is recorded on the assets, and the asset is written down to the lower of carrying value or fair market value, less cost to sell.
	Real estate is stated at depreciated cost. A variety of costs are incurred in the acquisition, development and leasing of properties. The cost of buildings and improvements includes the purchase price of property, legal fees and other acquisition costs. The Company expenses costs that it incurs to effect a business combination such as legal, due diligence and other closing related costs. Costs directly related to the development of properties are capitalized. Capitalized development costs include interest, internal wages, property taxes, insurance, and other project costs incurred during the period of development. After the determination is made to capitalize a cost, it is allocated to the specific component of a project that is benefited. Determinations of when a development project commences and capitalization begins, and when a development project is substantially complete and held available for occupancy and capitalization must cease, involve a degree of judgment. The Company’s capitalization policy on development properties is guided by guidance in ASC 835-20 “Capitalization of Interest” and ASC 970 “Real Estate – General.” The costs of land and buildings under development include specifically identifiable costs. The capitalized costs include pre-construction costs necessary to the development of the property, development costs, construction costs, interest costs, real estate taxes, salaries and related costs and other costs incurred during the period of development. The Company begins the capitalization of costs during the pre-construction period, which it defines as activities that are necessary to the development of the property. The Company considers a construction project as substantially completed and held available for occupancy upon the completion of tenant improvements, but no later than one year from cessation of major construction activity. The Company ceases capitalization on the portion (1) substantially completed and (2) occupied or held available for occupancy, and capitalizes only those costs associated with the portion under construction, or if activities necessary for the development of the property have been suspended. Interest costs capitalized for the years ended December 31, 2013, 2012 and 2011 were $68.2 million, $44.3 million and $48.2 million, respectively. Salaries and related costs capitalized for the years ended December 31, 2013, 2012 and 2011 were $7.7 million, $7.1 million and $6.5 million, respectively.
	Expenditures for repairs and maintenance are charged to operations as incurred. Significant betterments are capitalized. When assets are sold or retired, their costs and related accumulated depreciation are removed from the accounts with the resulting gains or losses reflected in net income or loss for the period.
	The Company computes depreciation and amortization on properties using the straight-line method based on estimated useful asset lives. In accordance with ASC 805, the Company allocates the acquisition cost of real estate to its components and depreciates or amortizes these assets (or liabilities) over their useful lives. The amortization of acquired “above-” and “below-market” leases and acquired in-place leases is recorded as an adjustment to revenue and depreciation and amortization, respectively, in the Consolidated Statements of Operations.
	Depreciation is computed on a straight-line basis over the estimated useful lives of the assets as follows:
	Land improvements		25 to 40 years
	Buildings and improvements		10 to 40 years
	Tenant improvements		Shorter of useful life or terms of related lease
	Furniture, fixtures, and equipment		3 to 7 years
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash on hand and investments with maturities of three months or less from the date of purchase. The majority of the Company’s cash and cash equivalents are held at major commercial banks which may at times exceed the Federal Deposit Insurance Corporation limit of $250,000. The Company has not experienced any losses to date on its invested cash.
Cash Held in Escrows	'
	Cash Held in Escrows
	Escrows include amounts established pursuant to various agreements for security deposits, property taxes, insurance and other costs.
Investments in Securities	'
	Investments in Securities
	The Company accounts for investments in trading securities at fair value, with gains or losses resulting from changes in fair value recognized currently in earnings. The designation of trading securities is generally determined at acquisition. The Company maintains a deferred compensation plan that is designed to allow officers of the Company to defer a portion of their current income on a pre-tax basis and receive a tax-deferred return on these deferrals. The Company’s obligation under the plan is that of an unsecured promise to pay the deferred compensation to the plan participants in the future. At December 31, 2013 and 2012, the Company had maintained approximately $16.6 million and $12.2 million, respectively, in a separate account, which is not restricted as to its use. The Company recognized gains (losses) of approximately $2.9 million, $1.4 million and $(0.4) million on its investments in the account associated with the Company’s deferred compensation plan during the years ended December 31, 2013, 2012 and 2011, respectively.
Tenant and Other Receivables	'
	Tenant and Other Receivables
	Tenant and other accounts receivable, other than accrued rents receivable, are expected to be collected within one year.
Deferred Charges	'
	Deferred Charges
	Deferred charges include leasing costs and financing fees. Leasing costs include an allocation for acquired intangible in-place lease values and direct and incremental fees and costs incurred in the successful negotiation of leases, including brokerage, legal, internal leasing employee salaries and other costs which have been deferred and are being amortized on a straight-line basis over the terms of the respective leases. Internal leasing salaries and related costs capitalized for the years ended December 31, 2013, 2012 and 2011 were $5.1 million, $5.6 million and $4.4 million, respectively. External fees and costs incurred to obtain long-term financing have been deferred and are being amortized over the terms of the respective loans and are included within interest expense. Unamortized financing and leasing costs are charged to expense upon the early repayment or significant modification of the financing or upon the early termination of the lease, respectively. Fully amortized deferred charges are removed from the books upon the expiration of the lease or maturity of the debt.
Investments in Unconsolidated Joint Ventures	'
	Investments in Unconsolidated Joint Ventures
	The Company consolidates variable interest entities (VIEs) in which it is considered to be the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. The primary beneficiary is defined by the entity having both of the following characteristics: (1) the power to direct the activities that, when taken together, most significantly impact the variable interest entity's performance, and (2) the obligation to absorb losses and right to receive the returns from the variable interest entity that would be significant to the variable interest entity. For ventures that are not VIEs the Company consolidates entities for which it has significant decision making control over the ventures' operations. The Company's judgment with respect to its level of influence or control of an entity involves the consideration of various factors including the form of the Company's ownership interest, its representation in the entity's governance, the size of its investment (including loans), estimates of future cash flows, its ability to participate in policy making decisions and the rights of the other investors to participate in the decision making process and to replace the Company as manager and/or liquidate the venture, if applicable. The Company's assessment of its influence or control over an entity affects the presentation of these investments in the Company's consolidated financial statements. In addition to evaluating control rights, the Company consolidates entities in which the outside partner has no substantive kick-out rights to remove the Company as the managing member.
	Accounts of the consolidated entity are included in the accounts of the Company and the non-controlling interest is reflected on the Consolidated Balance Sheets as a component of equity or in temporary equity between liabilities and equity. Investments in unconsolidated joint ventures are recorded initially at cost, and subsequently adjusted for equity in earnings and cash contributions and distributions. Any difference between the carrying amount of these investments on the balance sheet and the underlying equity in net assets is amortized as an adjustment to equity in earnings of unconsolidated joint ventures over the life of the related asset. Under the equity method of accounting, the net equity investment of the Company is reflected within the Consolidated Balance Sheets, and the Company's share of net income or loss from the joint ventures is included within the Consolidated Statements of Operations. The joint venture agreements may designate different percentage allocations among investors for profits and losses; however, the Company's recognition of joint venture income or loss generally follows the joint venture's distribution priorities, which may change upon the achievement of certain investment return thresholds. The Company may account for cash distributions in excess of its investment in an unconsolidated joint venture as income when the Company is not the general partner in a limited partnership and when the Company has neither the requirement nor the intent to provide financial support to the joint venture. The Company's investments in unconsolidated joint ventures are reviewed for impairment periodically and the Company records impairment charges when events or circumstances change indicating that a decline in the fair values below the carrying values has occurred and such decline is other-than-temporary, which is dependent on a number of factors, including the performance of each investment and market conditions.
	To the extent that the Company contributes assets to a joint venture, the Company’s investment in the joint venture is recorded at the Company’s cost basis in the assets that were contributed to the joint venture. To the extent that the Company’s cost basis is different than the basis reflected at the joint venture level, the basis difference is amortized over the life of the related asset and included in the Company’s share of equity in net income of the joint venture. In accordance with the provisions of ASC 970-323 “Investments—Equity Method and Joint Ventures” (“ASC 970-323”), the Company will recognize gains on the contribution of real estate to joint ventures, relating solely to the outside partner’s interest, to the extent the economic substance of the transaction is a sale.
Equity Offering Costs	'
	Equity Offering Costs
	Underwriting commissions and offering costs have been reflected as a reduction of additional paid-in capital
Treasury Stock	'
	Treasury Stock
	The Company’s share repurchases are reflected as treasury stock utilizing the cost method of accounting and are presented as a reduction to consolidated stockholders’ equity.
Dividends	'
	Dividends
	Earnings and profits, which determine the taxability of dividends to stockholders, will differ from income reported for financial reporting purposes due to the differences for federal income tax purposes in the treatment of gains/losses on the sale of real property, revenue and expense recognition, compensation expense, and in the estimated useful lives and basis used to compute depreciation.
	The tax treatment of common dividends per share for federal income tax purposes is as follows:
			For the year ended December 31,
			2013							2012								2011
			Per Share				%			Per Share				%				Per Share			%
	Ordinary income		$	2.31			48.71	%		$	2.29		0.5839	96.45	%	0.9093		$	2.06	0.9093	97.39	%
	Capital gain income		2.44				51.29	%		0.08			—	3.55	%	—		0.05		—	2.61	%
	Total		$	4.75		-1	100	%		$	2.37			100	%			$	2.11	1	100	%
	(1) The fourth quarter 2013 dividend of $2.90 per common share consists of a $2.25 per common share special dividend and a $0.65 per common share regular quarterly dividend of which approximately $2.44 per common share was allocable to 2013 and approximately $0.46 per common share is allocable to 2014.
Revenue Recognition	'
	Revenue Recognition
	Contractual rental revenue is reported on a straight-line basis over the terms of the respective leases. The impact of the straight-line rent adjustment increased revenue by approximately $65.8 million, $77.6 million and $77.0 million for the years ended December 31, 2013, 2012 and 2011, respectively, as the revenue recorded exceeded amounts billed. Accrued rental income, as reported on the Consolidated Balance Sheets, represents cumulative rental income earned in excess of rent payments received pursuant to the terms of the individual lease agreements. The Company maintains an allowance against accrued rental income for future potential tenant credit losses. The credit assessment is based on the estimated accrued rental income that is recoverable over the term of the lease. The Company also maintains an allowance for doubtful accounts for estimated losses resulting from the inability of tenants to make required rent payments. The computation of this allowance is based on the tenants’ payment history and current credit status, as well as certain industry or geographic specific credit considerations. If the Company’s estimates of collectability differ from the cash received, then the timing and amount of the Company’s reported revenue could be impacted. The credit risk is mitigated by the high quality of the Company’s existing tenant base, reviews of prospective tenants’ risk profiles prior to lease execution and consistent monitoring of the Company’s portfolio to identify potential problem tenants.
	In accordance with ASC 805, the Company recognizes rental revenue of acquired in-place “above-” and “below-market” leases at their fair values over the terms of the respective leases. The impact of the acquired in-place “above-” and “below-market” leases increased revenue by approximately $28.0 million, $14.6 million and $10.8 million for the years ended December 31, 2013, 2012 and 2011, respectively. The following table summarizes the scheduled amortization of the Company's acquired “above-” and “below-market” lease intangibles for each of the five succeeding years (in thousands).
			Acquired Above-Market Lease Intangibles				Acquired Below-Market Lease Intangibles
	2014		$	23,669			$	61,700
	2015		22,758				55,207
	2016		20,576				52,461
	2017		12,279				40,346
	2018		8,637				37,774
	Recoveries from tenants, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs are recognized as revenue in the period during which the expenses are incurred. Tenant reimbursements are recognized and presented in accordance with guidance in ASC 605-45 “Principal Agent Considerations” (“ASC 605-45”). ASC 605-45 requires that these reimbursements be recorded on a gross basis, as the Company is generally the primary obligor with respect to purchasing goods and services from third-party suppliers, has discretion in selecting the supplier and has credit risk. The Company also receives reimbursement of payroll and payroll related costs from third parties which the Company reflects on a net basis in accordance with ASC 605-45.
	The Company's parking revenues are derived from leases, monthly parking and transient parking. The Company recognizes parking revenue as earned.
	The Company’s hotel revenues are derived from room rentals and other sources such as charges to guests for telephone service, movie and vending commissions, meeting and banquet room revenue and laundry services. Hotel revenues are recognized as earned.
	The Company receives management and development fees from third parties. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis, because such fees are contingent upon the collection of rents. The Company reviews each development agreement and records development fees as earned depending on the risk associated with each project. Profit on development fees earned from joint venture projects is recognized as revenue to the extent of the third party partners’ ownership interest.
	Gains on sales of real estate are recognized pursuant to the provisions included in ASC 360-20 “Real Estate Sales” (“ASC 360-20”). The specific timing of a sale is measured against various criteria in ASC 360-20 related to the terms of the transaction and any continuing involvement in the form of management or financial assistance associated with the properties. If the sales criteria for the full accrual method are not met, the Company defers some or all of the gain recognition and accounts for the continued operations of the property by applying the finance, leasing, profit sharing, deposit, installment or cost recovery methods, as appropriate, until the sales criteria are met.
Ground Leases	'
	Ground Leases
	The Company has non-cancelable ground lease obligations with various initial term expiration dates through 2068. The Company recognizes ground rent expense on a straight-line basis over the terms of the respective ground lease agreements. The future contractual minimum lease payments to be made by the Company as of December 31, 2013, under non-cancelable ground leases which expire on various dates through 2068, are as follows:
	Years Ending December 31,	(in thousands)
	2014	$	13,184
	2015	13,507
	2016	13,732
	2017	13,963
	2018	14,198
	Thereafter	899,187
Earnings Per Share	'
	Earnings Per Share
	Basic earnings per share (“EPS”) is computed by dividing net income available to common shareholders, as adjusted for unallocated earnings (if any) of certain securities issued by the Operating Partnership, by the weighted average number of shares of Common Stock outstanding during the year. Diluted EPS reflects the potential dilution that could occur from shares issuable in connection with awards under stock-based compensation plans, including upon the exercise of stock options, and securities of the Operating Partnership that are exchangeable for Common Stock.
Fair Value of Financial Instruments	'
	Fair Value of Financial Instruments
	The carrying values of cash and cash equivalents, marketable securities, escrows, receivables, accounts payable, accrued expenses and other assets and liabilities are reasonable estimates of their fair values because of the short maturities of these 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 and unsecured exchangeable senior notes using market prices. The inputs used in determining the fair value of the Company’s unsecured senior notes and unsecured exchangeable senior notes is 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 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 December 31, 2013 and December 31, 2012 (in thousands):
		December 31, 2013										December 31, 2012
		Carrying						Estimated				Carrying					Estimated
		Amount						Fair Value				Amount					Fair Value
	Mortgage notes payable	$	4,449,734					$	4,545,283			$	3,102,485				$	3,256,940
	Mezzanine notes payable	311,040						311,064				—					—
	Unsecured senior notes	5,835,854						6,050,517				4,639,528					5,162,486
	Unsecured exchangeable senior notes	744,880				-1		750,266				1,170,356			-1		1,278,554
	Total	$	11,341,508					$	11,657,130			$	8,912,369				$	9,697,980
	_______________
	-1	Includes the net adjustment for the equity component allocation totaling approximately $2.4 million and $25.5 million at December 31, 2013 and December 31, 2012, respectively.
Derivative Instruments and Hedging Activities	'
	Derivative Instruments and Hedging Activities
	Derivative instruments and hedging activities require management to make judgments on the nature of its derivatives and their effectiveness as hedges. These judgments determine if the changes in fair value of the derivative instruments are reported in the Consolidated Statements of Operations as a component of net income or as a component of comprehensive income and as a component of equity on the consolidated balance sheets. While management believes its judgments are reasonable, a change in a derivative’s effectiveness as a hedge could materially affect expenses, net income and equity. The Company accounts for the effective portion of changes in the fair value of a derivative in 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.
Income Taxes	'
	Income Taxes
	The Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the “Code”), commencing with its taxable year ended December 31, 1997. As a result, the Company generally will not be subject to federal corporate income tax on its taxable income that is distributed to its stockholders. A REIT is subject to a number of organizational and operational requirements, including a requirement that it currently distribute at least 90% of its annual taxable income. The Company’s policy is to distribute at least 100% of its taxable income. Accordingly, the only provision for federal income taxes in the accompanying consolidated financial statements relates to the Company’s consolidated taxable REIT subsidiaries. The Company’s taxable REIT subsidiaries did not have significant tax provisions or deferred income tax items. The Company has no uncertain tax positions recognized as of December 31, 2013 and 2012.
	The Company owns a hotel property which is managed through a taxable REIT subsidiary. The hotel taxable REIT subsidiary, a wholly owned subsidiary of the Operating Partnership, is the lessee pursuant to the lease for the hotel property. As lessor, the Operating Partnership is entitled to a percentage of gross receipts from the hotel property. Marriott International, Inc. continues to manage the hotel property under the Marriott name and under terms of the existing management agreement. The hotel taxable REIT subsidiary is subject to tax at the federal and state level and, accordingly, the Company has recorded a tax provision in the Company’s Consolidated Statements of Operations for the years ended December 31, 2013, 2012 and 2011.
	The net difference between the tax basis and the reported amounts of the Company’s assets and liabilities is approximately $1.7 billion and $0.8 billion as of December 31, 2013 and 2012, respectively, which is primarily related to the difference in basis of contributed property and accrued rental income.
	Certain entities included in the Company’s consolidated financial statements are subject to certain state and local taxes. These taxes are recorded as operating expenses in the accompanying consolidated financial statements.
	The following table reconciles GAAP net income attributable to Boston Properties, Inc. to taxable income:
			For the year ended December 31,
			2013				2012				2011
			(in thousands)
	Net income attributable to Boston Properties, Inc.		$	749,811			$	289,650			$	272,679
	Straight-line rent adjustments		(74,445		)		(80,281		)		(77,422		)
	Book/Tax differences from depreciation and amortization		170,370				105,599				117,675
	Book/Tax differences on gains/losses from capital transactions		(124,413		)		(22,408		)		(38,443		)
	Book/Tax differences from stock-based compensation		42,146				19,660				827
	Other book/tax differences, net		(12,797		)		35,461				29,389
	Taxable income		$	750,672			$	347,681			$	304,705
Share-Based Employee Compensation Plans	'
	Stock-Based Employee Compensation Plans
	At December 31, 2013, the Company has a stock-based employee compensation plan. Effective January 1, 2005, the Company adopted early ASC 718 “Compensation – Stock Compensation” (“ASC 718”), which revised the fair value based method of accounting for share-based payment liabilities, forfeitures and modifications of stock-based awards and clarified previous guidance in several areas, including measuring fair value, classifying an award as equity or as a liability and attributing compensation cost to reporting periods.
Use of Estimatesin the Preperation of Financial Statements	'
	Use of Estimates in the Preparation of Financial Statements
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. These estimates include such items as depreciation and allowances for doubtful accounts. Actual results could differ from those estimates.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2013-02, "Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income" (“ASU No. 2013-02”). ASU No. 2013-02 requires an entity to provide information about the amounts reclassified out of accumulated other comprehensive income by component. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income, but only if the amount reclassified is required to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures that provide additional detail about those amounts. ASU No. 2013-02 is effective prospectively for reporting periods beginning after December 15, 2012. The Company’s adoption of ASU No. 2013-02 did not have a material impact on its consolidated financial statements.

Summary_Of_Significant_Account2

Summary Of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Fair Value, by Balance Sheet Grouping [Table Text Block]	'
		December 31, 2013										December 31, 2012
		Carrying						Estimated				Carrying					Estimated
		Amount						Fair Value				Amount					Fair Value
	Mortgage notes payable	$	4,449,734					$	4,545,283			$	3,102,485				$	3,256,940
	Mezzanine notes payable	311,040						311,064				—					—
	Unsecured senior notes	5,835,854						6,050,517				4,639,528					5,162,486
	Unsecured exchangeable senior notes	744,880				-1		750,266				1,170,356			-1		1,278,554
	Total	$	11,341,508					$	11,657,130			$	8,912,369				$	9,697,980
	_______________
	-1	Includes the net adjustment for the equity component allocation totaling approximately $2.4 million and $25.5 million at December 31, 2013 and December 31, 2012, respectively.
Gaap Reconciliation Of Net Income To Taxable Income, Table [Table Text Block]	'
	The following table reconciles GAAP net income attributable to Boston Properties, Inc. to taxable income:
			For the year ended December 31,
			2013				2012				2011
			(in thousands)
	Net income attributable to Boston Properties, Inc.		$	749,811			$	289,650			$	272,679
	Straight-line rent adjustments		(74,445		)		(80,281		)		(77,422		)
	Book/Tax differences from depreciation and amortization		170,370				105,599				117,675
	Book/Tax differences on gains/losses from capital transactions		(124,413		)		(22,408		)		(38,443		)
	Book/Tax differences from stock-based compensation		42,146				19,660				827
	Other book/tax differences, net		(12,797		)		35,461				29,389
	Taxable income		$	750,672			$	347,681			$	304,705
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	'
	The following table summarizes the scheduled amortization of the Company's acquired “above-” and “below-market” lease intangibles for each of the five succeeding years (in thousands).
			Acquired Above-Market Lease Intangibles				Acquired Below-Market Lease Intangibles
	2014		$	23,669			$	61,700
	2015		22,758				55,207
	2016		20,576				52,461
	2017		12,279				40,346
	2018		8,637				37,774
	The following table summarizes the scheduled amortization of the Company's acquired in-place lease intangibles for each of the five succeeding years (in thousands).
			Acquired In-Place Lease Intangibles
	2014		$	91,903
	2015		66,716
	2016		55,083
	2017		41,106
	2018		36,306
Schedule Of Future Contractual Minimum Lease Payments Under Non-Cancelable Ground Leases [Table Text Block]	'
	Years Ending December 31,	(in thousands)
	2014	$	13,184
	2015	13,507
	2016	13,732
	2017	13,963
	2018	14,198
	Thereafter	899,187
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes, Table [Table Text Block]	'
	The tax treatment of common dividends per share for federal income tax purposes is as follows:
			For the year ended December 31,
			2013							2012								2011
			Per Share				%			Per Share				%				Per Share			%
	Ordinary income		$	2.31			48.71	%		$	2.29		0.5839	96.45	%	0.9093		$	2.06	0.9093	97.39	%
	Capital gain income		2.44				51.29	%		0.08			—	3.55	%	—		0.05		—	2.61	%
	Total		$	4.75		-1	100	%		$	2.37			100	%			$	2.11	1	100	%
	(1) The fourth quarter 2013 dividend of $2.90 per common share consists of a $2.25 per common share special dividend and a $0.65 per common share regular quarterly dividend of which approximately $2.44 per common share was allocable to 2013 and approximately $0.46 per common share is allocable to 2014.
Property, Plant and Equipment [Table Text Block]	'
	Depreciation is computed on a straight-line basis over the estimated useful lives of the assets as follows:
	Land improvements		25 to 40 years
	Buildings and improvements		10 to 40 years
	Tenant improvements		Shorter of useful life or terms of related lease
	Furniture, fixtures, and equipment		3 to 7 years

Real_Estate_Tables

Real Estate (Tables)	12 Months Ended
	Dec. 31, 2013
Real Estate Properties [Line Items]	'
Schedule of Property Subject to or Available for Operating Lease [Table Text Block]	'
	Real estate consisted of the following at December 31 (in thousands):
			2013				2012
	Land		$	4,450,532			$	2,605,162
	Land held for future development		297,376				275,094
	Buildings and improvements		11,065,113				9,517,343
	Tenant improvements		1,617,401				1,435,508
	Furniture, fixtures and equipment		25,164				23,441
	Construction in progress		1,523,179				1,036,780
	Total		18,978,765				14,893,328
	Less: Accumulated depreciation		(3,161,571		)		(2,934,160		)
			$	15,817,194			$	11,959,168
Pro Forma In Connection With Acquisition	'
	The accompanying unaudited pro forma information for the years ended December 31, 2013 and 2012 is presented as if the operating property acquisitions of (1) Mountain View Research Park and Mountain View Technology Park on April 10, 2013 and the approximately $26.5 million gain on consolidation and (2) 767 Fifth Avenue (the General Motors Building) on May 31, 2013 and the approximately $359.5 million gain on consolidation, had occurred on January 1, 2012. This unaudited pro forma information is based upon the historical consolidated financial statements of the Company and should be read in conjunction with the consolidated financial statements and notes thereto. This pro forma information does not purport to represent what the actual results of operations of the Company would have been had the above occurred, nor do they purport to predict the results of operations of future periods.
	Pro Forma (Unaudited)	Year ended December 31,
	(in thousands, except per share data)	2013				2012
	Total revenue	$	2,257,098			$	2,149,391
	Income from continuing operations	$	302,354			$	634,457
	Net income attributable to Boston Properties, Inc.	$	400,017			$	626,174
	Basic earnings per share:
	Net income per share attributable to Boston Properties, Inc.	$	2.58			$	4.15
	Diluted earnings per share:
	Net income per share attributable to Boston Properties, Inc.	$	2.57			$	4.13
Summary Of The Discontinued Operations	'
	The following table summarizes the income from discontinued operations related to One Preserve Parkway, 10 & 20 Burlington Mall Road, 1301 New York Avenue, 303 Almaden Boulevard, Montvale Center and Bedford Business Park and the related gains on sales of real estate, gain on forgiveness of debt and impairment loss for the years ended December 31, 2013, 2012 and 2011:
		For the year ended December 31,
		2013				2012				2011
		(in thousands)
	Total revenue	$	20,138			$	32,607			$	36,734
	Expenses
	Operating	6,996				12,038				13,818
	Depreciation and amortization	4,760				8,169				9,442
	Total expenses	11,756				20,207				23,260
	Operating income	8,382				12,400				13,474
	Other expense
	Interest expense	360				2,594				2,598
	Income from discontinued operations	$	8,022			$	9,806			$	10,876
	Noncontrolling interest in income from discontinued operations – common units of the Operating Partnership	(803		)		(1,031		)		(1,243		)
	Income from discontinued operations attributable to Boston Properties, Inc.	$	7,219			$	8,775			$	9,633
	Gains on sales of real estate from discontinued operations	$	112,829			$	36,877			$	—
	Gain on forgiveness of debt from discontinued operations	20,182				—				—
	Impairment loss from discontinued operations	(3,241		)		—				—
	Noncontrolling interest in gains on sales of real estate, gain on forgiveness of debt and impairment loss from discontinued operations – common units of the Operating Partnership	(13,348		)		(4,044		)		—
	Gains on sales of real estate, gain on forgiveness of debt and impairment loss from discontinued operations attributable to Boston Properties, Inc.	$	116,422			$	32,833			$	—
Mountain View Research And Technology Parks [Member]	'
Real Estate Properties [Line Items]	'
Schedule Of Allocation Of The Aggregate Purchase Price Of Acquisition	'
	The following table summarizes the allocation of the aggregate purchase price of Mountain View Research Park and Mountain View Technology Park at the date of acquisition (in thousands) in accordance with the guidance in ASC 805 "Business Combinations."
	Land	$	126,521
	Building and improvements	82,451
	Tenant improvements	7,326
	In-place lease intangibles	23,279
	Above-market rents	843
	Below-market rents	(7,336		)
	Net assets acquired	$	233,084
767 5th Avenue (The General Motors Building) [Member]	'
Real Estate Properties [Line Items]	'
Schedule Of Allocation Of The Aggregate Purchase Price Of Acquisition	'
	The following table summarizes the allocation of the aggregate purchase price of 767 Fifth Avenue (the General Motors Building) at the date of consolidation on May 31, 2013 (in thousands) in accordance with the guidance in ASC 805 "Business Combinations."
	.
	Real estate and related intangibles recorded upon consolidation
	Land	$	1,796,252
	Building and improvements	1,447,446
	Tenant improvements	85,208
	In-place lease intangibles	357,781
	Above market rents	101,897
	Below market rents	(239,641		)
	Above market assumed debt adjustments	(192,943		)
		$	3,356,000
	Debt recorded upon consolidation
	Mortgage notes payable	$	(1,300,000	)
	Mezzanine notes payable	(306,000		)
	Members' notes payable	(450,000		)	-1
		$	(2,056,000	)
	Working capital recorded upon consolidation
	Cash and cash equivalents	$	79,468
	Cash held in escrows	2,403
	Tenant and other receivables	7,104
	Prepaid expenses and other assets	4,269
	Accounts payable and accrued expenses	(2,418		)
	Accrued interest payable	(182,369		)	-2
	Other liabilities	(6,304		)
		$	(97,847	)
	Noncontrolling interest recorded upon consolidation
	Noncontrolling interests	$	(520,000	)
	Noncontrolling interests - working capital	39,139
		$	(480,861	)
	Net assets recorded upon consolidation	$	721,292
	_______________
	(1) The Company's member loan totaling $270.0 million eliminates in consolidation.
	(2) The Company's share of the accrued interest payable on the members' loans totaling approximately $105.5 million eliminates in consolidation.

Deferred_Charges_Tables

Deferred Charges (Tables)	12 Months Ended
	Dec. 31, 2013
Deferred Charges [Abstract]	'
Deferred Charges	'
	Deferred charges consisted of the following at December 31, (in thousands):
		2013			2012
	Leasing costs, including lease related intangibles	$	1,183,204		$	790,740
	Financing costs	76,798			90,682
		1,260,002			881,422
	Less: Accumulated amortization	(375,552		)	(293,187		)
		$	884,450		$	588,235
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	'
	The following table summarizes the scheduled amortization of the Company's acquired “above-” and “below-market” lease intangibles for each of the five succeeding years (in thousands).
		Acquired Above-Market Lease Intangibles			Acquired Below-Market Lease Intangibles
	2014	$	23,669		$	61,700
	2015	22,758			55,207
	2016	20,576			52,461
	2017	12,279			40,346
	2018	8,637			37,774
	The following table summarizes the scheduled amortization of the Company's acquired in-place lease intangibles for each of the five succeeding years (in thousands).
		Acquired In-Place Lease Intangibles
	2014	$	91,903
	2015	66,716
	2016	55,083
	2017	41,106
	2018	36,306

Investments_in_Unconsolidated_1

Investments in Unconsolidated Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2013
Investments In Unconsolidated Joint Ventures [Abstract]	'
Investments In Unconsolidated Joint Ventures	'
	The investments in unconsolidated joint ventures consist of the following at December 31, 2013:
	Entity	Properties	Nominal %
			Ownership
	Square 407 Limited Partnership	Market Square North	50	%
	The Metropolitan Square Associates LLC	Metropolitan Square	51	%
	BP/CRF 901 New York Avenue LLC	901 New York Avenue	25	%	(1)
	WP Project Developer LLC	Wisconsin Place Land and Infrastructure	33.3	%	(2)
	RBP Joint Venture LLC	N/A	50	%	(3)
	Boston Properties Office Value-Added Fund, L.P.	N/A	39.5	%	-4
	Annapolis Junction NFM, LLC	Annapolis Junction	50	%	-5
	2 GCT Venture LLC	N/A	60	%	(6)
	540 Madison Venture LLC	540 Madison Avenue	60	%
	125 West 55th Street Venture LLC	N/A	60	%	-7
	500 North Capitol LLC	500 North Capitol Street, NW	30	%
	_______________
	-1	The Company’s economic ownership can increase based on the achievement of certain return thresholds.
	-2	The Company’s wholly-owned entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking and infrastructure of the project.
	-3	Eighth Avenue and 46th Street was sold on July 19, 2013.
	-4	The Company acquired Mountain View Research Park and Mountain View Technology Park from the Value-Added Fund on April 10, 2013 (See Note 3). As of December 31, 2013, the investment is comprised of undistributed cash.
	-5	Comprised of two buildings, one building under construction and two undeveloped land parcels.
	-6	Two Grand Central Tower was sold on October 25, 2011. As of December 31, 2013, the investment is comprised of undistributed cash.
	-7	125 West 55th Street was sold on May 30, 2013. As of December 31, 2013, the investment is comprised of undistributed cash.
Schedule Of Balance Sheets Of The Unconsolidated Joint Ventures [Text Block]	'
	The combined summarized balance sheets of the unconsolidated joint ventures are as follows:
		December 31,			December 31,
		2013			2012
		(in thousands)
	ASSETS
	Real estate and development in process, net	$	924,297		$	4,494,971
	Other assets	163,149			673,716
	Total assets	$	1,087,446		$	5,168,687
	LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY
	Mortgage and notes payable	$	749,732		$	3,039,922
	Other liabilities	28,830			792,888
	Members’/Partners’ equity	308,884			1,335,877
	Total liabilities and members’/partners’ equity	$	1,087,446		$	5,168,687
	Company’s share of equity	$	154,726		$	787,941
	Basis differentials (1)	(28,642		)	(128,025		)
	Carrying value of the Company’s investments in unconsolidated joint ventures	$	126,084		$	659,916
	_______________
	-1	This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from impairment of investments and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level.
Statements Of Operations Of The Joint Ventures	'
	The combined summarized statements of operations of the joint ventures are as follows:
		For the year ended December 31,
		2013			2012			2011
		(in thousands)
	Total revenue (1)	$	311,548		$	564,205		$	589,294
	Expenses
	Operating	105,319			162,665			170,404
	Depreciation and amortization	86,088			163,134			190,437
	Impairment losses	—			—			40,468
	Total expenses	191,407			325,799			401,309
	Operating income	120,141			238,406			187,985
	Other income (expense)
	Interest expense	(112,535		)	(224,645		)	(228,494		)
	Losses from early extinguishments of debt	(1,677		)	—			—
	Income (loss) from continuing operations	5,929			13,761			(40,509		)
	Gains on sales of real estate	14,207			990			—
	Net income (loss)	$	20,136		$	14,751		$	(40,509	)
	Company’s share of net income (loss)	$	4,612		$	6,863		$	(25,374	)
	Gains on sales of real estate	54,501			—			46,166
	Basis differential	(1,017		)	1,732			27,226
	Elimination of inter-entity interest on partner loan	16,978			40,483			37,878
	Income from unconsolidated joint ventures	$	75,074		$	49,078		$	85,896
	Gains on consolidation of joint ventures	$	385,991		$	—		$	—
	_______________
	-1	Includes straight-line rent adjustments of $7.8 million, $12.0 million and $21.9 million for the years ended December 31, 2013, 2012 and 2011, respectively. Includes net below-market rent adjustments of $33.7 million, $91.1 million and $120.3 million for the years ended December 31, 2013, 2012 and 2011, respectively. Total revenue for the year ended December 31, 2012 includes termination income totaling approximately $19.6 million (of which the Company's share is approximately $11.8 million) related to a lease termination with a tenant at 767 Fifth Avenue (The General Motors Building).

Mortgage_Notes_Payable_Schedul

Mortgage Notes Payable Schedule of Aggregate Principal Payments On Mortgage Notes (Tables)	12 Months Ended
	Dec. 31, 2013
Mortgage Notes Payable [Abstract]	'
Schedule of Aggregate Principal Payments On Mortgage Notes [Table Text Block]	'
	Contractual aggregate principal payments of mortgage notes payable at December 31, 2013 are as follows:
		Principal Payments
		(in thousands)
	2014	$	87,759
	2015	26,182
	2016	608,879
	2017	2,821,750
	2018	18,633
	Thereafter	695,327
	Total aggregate principal payments	4,258,530
	Unamortized balance of historical fair value adjustments	191,204
	Total carrying value of mortgage notes payable	$	4,449,734

Unsecured_Senior_Notes_Tables

Unsecured Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Schedule of Senior Notes	'
	The following summarizes the unsecured senior notes outstanding as of December 31, 2013 (dollars in thousands):
		Coupon/		Effective		Principal			Maturity Date(2)
		Stated Rate		Rate(1)		Amount
	12 Year Unsecured Senior Notes	5.625	%	5.693	%	$	300,000		April 15, 2015
	12 Year Unsecured Senior Notes	5	%	5.194	%	250,000			June 1, 2015
	10 Year Unsecured Senior Notes	5.875	%	5.967	%	700,000			October 15, 2019
	10 Year Unsecured Senior Notes	5.625	%	5.708	%	700,000			November 15, 2020
	10 Year Unsecured Senior Notes	4.125	%	4.289	%	850,000			May 15, 2021
	7 Year Unsecured Senior Notes	3.7	%	3.853	%	850,000			November 15, 2018
	11 Year Unsecured Senior Notes	3.85	%	3.954	%	1,000,000			February 1, 2023
	10.5 Year Unsecured Senior Notes	3.125	%	3.279	%	500,000			September 1, 2023
	10.5 Year Unsecured Senior Notes	3.8	%	3.916	%	700,000			February 1, 2024
	Total principal					5,850,000
	Net unamortized discount					(14,146		)
	Total					$	5,835,854
	_______________
	-1	Yield on issuance date including the effects of discounts on the notes and the amortization of financing costs.
	-2	No principal amounts are due prior to maturity.

Unsecured_Exchangeable_Senior_1

Unsecured Exchangeable Senior Notes (Tables)

12 Months Ended

Dec. 31, 2013

Debt Disclosure [Abstract]

'

Schedule of Unsecured Exchangeable Senior Notes

'

The following summarizes the unsecured exchangeable senior notes outstanding as of December 31, 2013 (dollars in thousands):

Coupon/

Effective

Exchange

Principal

First Optional

Maturity Date

Stated Rate

Rate (1)

Rate

Amount

Redemption Date by the

Company

3.625% Exchangeable Senior Notes

3.625

%

4.037

%

8.6974

-2

$

747,500

N/A

February 15, 2014

Net unamortized discount

(182

)

Adjustment for the equity component allocation, net of accumulated amortization

(2,438

)

Total

$

744,880

_______________

-1

Yield on issuance date including the effects of discounts on the notes but excluding the effects of the adjustment for the equity component allocation.

-2

The initial exchange rate is 8.5051 shares per $1,000 principal amount of the notes (or an initial exchange price of approximately $117.58 per share of Boston Properties, Inc.’s common stock). In addition, the Company entered into capped call transactions with affiliates of certain of the initial purchasers, which are intended to reduce the potential dilution upon future exchange of the notes. The capped call transactions were intended to increase the effective exchange price to the Company of the notes from $117.58 to approximately $137.17 per share (subject to adjustments), representing an overall effective premium of approximately 40% over the closing price on August 13, 2008 of $97.98 per share of Boston Properties, Inc.’s common stock. The net cost of the capped call transactions was approximately $44.4 million. In connection with the special dividend declared on November 27, 2013, the exchange rate of 8.5051 was adjusted to 8.6974 shares per $1,000 principal amount of notes effective as of December 31, 2013, resulting in an exchange price of approximately $114.98 per share of Boston Properties, Inc.'s common stock. As of December 31, 2013, the effective exchange price was $130.21 per share. The Operating Partnership repaid the notes on February 18, 2014 (See Note 20).

Noncontrolling_Interests_Table

Noncontrolling Interests (Tables)	12 Months Ended
	Dec. 31, 2013
Noncontrolling Interest [Abstract]	'
Schedule of Redeemable Interest in Property Partnerships [Table Text Block]	'
	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 for the years ended December 31, 2013 and 2012 (in thousands):
	Balance at December 31, 2011	$	—
	Acquisition-date fair value of redeemable interest	98,787
	Net loss	(719		)
	Distributions	(3,032		)
	Adjustment to reflect redeemable interest at redemption value	2,522
	Balance at December 31, 2012	$	97,558
	Net loss	(1,839		)
	Distributions	(4,585		)
	Adjustment to reflect redeemable interest at redemption value	8,475
	Balance at December 31, 2013	$	99,609
Schedule Of Redeemable Preferred Units of the Operating Partnership	'
	The following table reflects the activity of the noncontrolling interests—redeemable preferred units of the Operating Partnership for the years ended December 31, 2013, 2012 and 2011 (in thousands):
	Balance at December 31, 2010	$	55,652
	Net income	3,339
	Distributions	(3,339		)
	Balance at December 31, 2011	$	55,652
	Issuance of redeemable preferred units (Series Four Preferred Units)	79,405
	Net income	3,497
	Distributions	(3,497		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(18,329		)
	Conversion of redeemable preferred units (Series Two Preferred Units) to common units	(5,852		)
	Balance at December 31, 2012	$	110,876
	Net income	6,046
	Distributions	(6,046		)
	Redemption of redeemable preferred units (Series Four Preferred Units)	(43,070		)
	Conversion of redeemable preferred units (Series Two Preferred Units) to common units	(16,494		)
	Balance at December 31, 2013	$	51,312

Future_Minimum_Rents_Tables

Future Minimum Rents (Tables)	12 Months Ended
	Dec. 31, 2013
Future Minimum Rents [Abstract]	'
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	'
	Years Ending December 31,	(in thousands)
	2014	$	1,716,754
	2015	1,706,282
	2016	1,660,890
	2017	1,510,645
	2018	1,342,157
	Thereafter	6,674,466

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2013
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 year ended December 31, 2013:
		Boston			New York				San				Washington,			Total
									Francisco				DC
	Rental Revenue:
	Class A Office	$	665,991		$	725,566			$	214,755			$	381,359		$	1,987,671
	Office/Technical	22,617			—				17,259				15,649			55,525
	Residential	4,395			—				—				17,923			22,318
	Hotel	40,330			—				—				—			40,330
	Total	733,333			725,566				232,014				414,931			2,105,844
	% of Grand Totals	34.82		%	34.46		%		11.02		%		19.7		%	100		%
	Rental Expenses:
	Class A Office	259,997			251,640				77,905				126,507			716,049
	Office/Technical	6,879			—				3,708				4,190			14,777
	Residential	1,823			—				—				10,307			12,130
	Hotel	28,447			—				—				—			28,447
	Total	297,146			251,640				81,613				141,004			771,403
	% of Grand Totals	38.52		%	32.62		%		10.58		%		18.28		%	100		%
	Net operating income	$	436,187		$	473,926			$	150,401			$	273,927		$	1,334,441
	% of Grand Totals	32.69		%	35.51		%		11.27		%		20.53		%	100		%
	For the year ended December 31, 2012:
		Boston			New York				San				Washington,			Total
									Francisco				DC
	Rental Revenue:
	Class A Office	$	617,652		$	543,194			$	208,177			$	346,402		$	1,715,425
	Office/Technical	22,460			—				494				16,264			39,218
	Residential	3,936			—				—				16,632			20,568
	Hotel	37,915			—				—				—			37,915
	Total	681,963			543,194				208,671				379,298			1,813,126
	% of Grand Totals	37.61		%	29.96		%		11.51		%		20.92		%	100		%
	Rental Expenses:
	Class A Office	242,904			187,987				75,542				111,049			617,482
	Office/Technical	6,499			—				149				3,966			10,614
	Residential	1,675			—				—				9,317			10,992
	Hotel	28,120			—				—				—			28,120
	Total	279,198			187,987				75,691				124,332			667,208
	% of Grand Totals	41.85		%	28.18		%		11.34		%		18.63		%	100		%
	Net operating income	$	402,765		$	355,207			$	132,980			$	254,966		$	1,145,918
	% of Grand Totals	35.15		%	31		%		11.6		%		22.25		%	100		%
	For the year ended December 31, 2011:
		Boston			New York				San				Washington,			Total
									Francisco				DC
	Rental Revenue:
	Class A Office	$	537,743		$	521,439			$	207,003			$	340,470		$	1,606,655
	Office/Technical	25,349			—				—				16,236			41,585
	Residential	985			—				—				5,632			6,617
	Hotel	34,529			—				—				—			34,529
	Total	598,606			521,439				207,003				362,338			1,689,386
	% of Grand Totals	35.43		%	30.87		%		12.25		%		21.45		%	100		%
	Rental Expenses:
	Class A Office	206,469			181,269				72,122				95,804			555,664
	Office/Technical	7,245			—				—				4,280			11,525
	Residential	521			—				—				4,958			5,479
	Hotel	26,128			—				—				—			26,128
	Total	240,363			181,269				72,122				105,042			598,796
	% of Grand Totals	40.14		%	30.27		%		12.05		%		17.54		%	100		%
	Net operating income	$	358,243		$	340,170			$	134,881			$	257,296		$	1,090,590
	% of Grand Totals	32.85		%	31.19		%		12.37		%		23.59		%	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, Inc.:
		Year ended December 31,
			2013			2012				2011
	Net Operating Income		$	1,334,441		$	1,145,918			$	1,090,590
	Add:
	Development and management services income		29,695			34,060				33,406
	Income from unconsolidated joint ventures		75,074			49,078				85,896
	Gains on consolidation of joint ventures		385,991			—				—
	Interest and other income		8,310			10,091				5,358
	Gains (losses) from investments in securities		2,911			1,389				(443		)
	Gains (losses) from early extinguishments of debt		122			(4,453		)		(1,494		)
	Income from discontinued operations		8,022			9,806				10,876
	Gains on sales of real estate from discontinued operations		112,829			36,877				—
	Gain on forgiveness of debt from discontinued operations		20,182			—				—
	Less:
	General and administrative expense		115,329			90,129				87,101
	Transaction costs		1,744			3,653				1,987
	Depreciation and amortization expense		560,637			445,875				429,742
	Interest expense		446,880			410,970				391,533
	Impairment loss		8,306			—				—
	Impairment loss from discontinued operations		3,241			—				—
	Noncontrolling interest in property partnerships		1,347			3,792				1,558
	Noncontrolling interest—redeemable preferred units of the Operating Partnership		6,046			3,497				3,339
	Noncontrolling interest—common units of the Operating Partnership		70,085			30,125				35,007
	Noncontrolling interest in discontinued operations—common units of the Operating Partnership		14,151			5,075				1,243
	Net income attributable to Boston Properties, Inc.		$	749,811		$	289,650			$	272,679

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Computation Of Basic And Diluted Earnings Per Share	'
		For the Year Ended December 31, 2013
		Income			Shares	Per Share
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per share amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties, Inc.	$	618,113		152,201	$	4.06
	Discontinued operations attributable to Boston Properties, Inc.	123,641			—	0.81
	Allocation of undistributed earnings to participating securities	(160		)	—	—
	Net income attributable to Boston Properties, Inc. common shareholders	$	741,594		152,201	$	4.87
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			320	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties, Inc. common shareholders	$	741,594		152,521	$	4.86
		For the Year Ended December 31, 2012
		Income			Shares	Per Share
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per share amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties, Inc.	$	248,042		150,120	$	1.65
	Discontinued operations attributable to Boston Properties, Inc.	41,608			—	0.28
	Net income attributable to Boston Properties, Inc. common shareholders	$	289,650		150,120	$	1.93
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			591	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties, Inc. common shareholders	$	289,650		150,711	$	1.92
		For the Year Ended December 31, 2011
		Income			Shares	Per Share
		(Numerator)			(Denominator)	Amount
		(in thousands, except for per share amounts)
	Basic Earnings:
	Income from continuing operations attributable to Boston Properties, Inc.	$	263,046		145,693	$	1.8
	Discontinued operations attributable to Boston Properties, Inc.	9,633			—	0.07
	Net income attributable to Boston Properties, Inc. common shareholders	$	272,679		145,693	$	1.87
	Effect of Dilutive Securities:
	Stock Based Compensation and Exchangeable Senior Notes	—			525	(0.01		)
	Diluted Earnings:
	Net income attributable to Boston Properties, Inc. common shareholders	$	272,679		146,218	$	1.86

Stock_Option_and_Incentive_Pla1

Stock Option and Incentive Plan Stock Option and Incentive Plan and Stock Purchase Plan (Tables)	12 Months Ended
	Dec. 31, 2013
Stock Option and Incentive Plan and Stock Purchase Plan [Abstract]	'
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	'
			Shares			Weighted
						Average
						Exercise
						Price
	Outstanding at December 31, 2010		324,938			$	32.65
	Granted		146,844			$	92.71
	Exercised		(316,159	)		$	32.63
	Canceled		—			$	—
	Outstanding at December 31, 2011		155,623			$	89.35
	Granted		186,007			$	107.23
	Exercised		(22,823	)		$	72.42
	Canceled		(24,280	)		$	100.15
	Outstanding at December 31, 2012		294,527			$	101.06
	Granted		252,220			$	104.5
	Exercised		—			$	—
	Canceled		—			$	—
	Special dividend adjustment		12,076			$	100.44
	Outstanding at December 31, 2013		558,823			$	100.43
Schedule of Stock Options Outstanding [Table Text Block]	'
	The following table summarizes information about stock options outstanding at December 31, 2013:
	Options Outstanding										Options Exercisable
	Exercise Prices				Number			Remaining	Exercise Price		Number Exercisable	Exercise Price
					Outstanding at			Contractual Life			at 12/31/13
					12/31/13
	$	90.71			131,837			7.1 years	$	90.71	80,240	$	90.71
	$	99.94			51,971			9.3 years	$	99.94	—	$	—
	$	102.83			205,821			9.1 years	$	102.83	48,026	$	102.83
	$	105.25			169,194			8.1 years	$	105.25	71,602	$	105.25

Selected_Interim_Financial_Inf1

Selected Interim Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Schedule of Quarterly Financial Information [Table Text Block]	'
		2013 Quarter Ended
		March 31,		June 30,		September 30,		December 31,
		(in thousands, except for per share amounts)
	Total revenue	$	477,826	$	510,033	$	571,481	$	576,199
	Income from continuing operations	$	38,496	$	503,446	$	82,311	$	79,395
	Net income attributable to Boston Properties, Inc.	$	47,854	$	452,417	$	152,677	$	88,719
	Income attributable to Boston Properties, Inc. per share—basic	$	0.32	$	2.95	$	1	$	0.58
	Income attributable to Boston Properties, Inc. per share—diluted	$	0.31	$	2.94	$	1	$	0.58
		2012 Quarter Ended
		March 31,		June 30,		September 30,		December 31,
		(in thousands, except for per share amounts)
	Total revenue	$	438,722	$	466,197	$	464,220	$	478,047
	Income from continuing operations	$	53,079	$	94,795	$	63,331	$	74,251
	Net income attributable to Boston Properties, Inc.	$	48,454	$	118,559	$	57,249	$	65,400
	Income attributable to Boston Properties, Inc. per share—basic	$	0.33	$	0.79	$	0.38	$	0.43
	Income attributable to Boston Properties, Inc. per share—diluted	$	0.33	$	0.78	$	0.38	$	0.43

Organization_Details

Organization (Details) (USD $)

12 Months Ended

3 Months Ended

3 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Aug. 29, 2013

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Y

Commercial Real Estate Properties [Member]

Total Properties Under Construction [ Member]

Total Office Properties [ Member]

Class A Office Properties [Member]

Office Properties Under Construction [ Member]

Office Technical Properties [Member]

Hotel Property [ Member]

Retail Properties [ Member]

Residential Properties [Member]

Residential Properties Under Construction [Member]

Series Two Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Preferred Units [Member]

depositary shares [Member]

sqft

Real_Estate_Properties

sqft

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Real_Estate_Properties

Series B Cumulative Redeemable Preferred Stock [Member]

Vehicles

sqft

Real_Estate_Properties

acre

Real Estate Properties [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

89.50%

89.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OP unit conversion rate (in shares)

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number Of series Of preferred units outstanding

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OP Units for each Preferred Unit (in shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

1.312336

'

'

'

'

'

'

'

Preferred Units Liquidation Preference

'

'

'

'

'

'

'

'

'

'

'

'

'

$50

$50

$50

'

'

'

'

'

Quarterly Distributions to Series Four Preferred Units

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$0.25

'

'

'

'

'

'

Series Four Preferred Units Annual Dividend Payable Rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.00%

'

'

'

'

'

'

Number of real estate properties

'

'

'

175

9

167

128

8

39

1

4

3

1

'

'

'

'

'

'

'

'

Net Rentable Area

'

'

'

44,400,000

2,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of vehicles in structured parking

45,234

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Area of parking (in square feet)

15,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Area of undeveloped land parcels owned (in acres)

503.6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, shares outstanding

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

80,000

80,000

0

80,000

8,000,000

Preferred Stock, Dividend Rate, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.25%

'

'

'

'

Summary_Of_Significant_Account3

Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Y
Accounting Policies [Abstract]	'	'	'
Probable Sale Term of Property After Classified As Held For Sale (Years)	1	'	'
Maximum Period After Construction The Company Considers A Construction Project As Substantially Completed (In Years)	1	'	'
Interest costs capitalized	$68,152,000	$44,278,000	$48,178,000
Salaries And Related Costs Capitalized	7,700,000	7,100,000	6,500,000
Cash FDIC Insured Limit	250,000	'	'
Separate Unrestricted Cash For Deferred Compensation Plan.	16,600,000	12,200,000	'
Gains (losses) from investments in securities	2,911,000	1,389,000	-443,000
Internal Leasing Salaries And Related Costs Capitalized	5,100,000	5,600,000	4,400,000
Straight-line rent adjustments	-65,800,000	-77,600,000	-77,000,000
Above and below market rent adjustments, net	28,000,000	14,600,000	10,800,000
Ground Lease Expiration Date, Maximum	'2068	'	'
REIT Annual Taxable Income Distribution Requirement Percentage, Minimum	90.00%	'	'
Company Annual Taxable Income Distribution Percentage	100.00%	'	'
Net Difference Between Tax Basis And Company's Assets And Liabilities.	1,700,000,000	800,000,000	'
Misstatement of real estate operating expense	3,200,000	'	'
Interest and Other Income	8,310,000	10,091,000	5,358,000
Reclassification between general and administrative expense and real estate operating expenses	$8,100,000	$7,700,000	$7,500,000

Summary_Of_Significant_Account4

Summary Of Significant Accounting Policies Schedule of Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2013
Land Improvements [Member] | Minimum [Member]	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life (years)	'25 years
Land Improvements [Member] | Maximum [Member]	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life (years)	'40 years
Building and Building Improvements [Member] | Minimum [Member]	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life (years)	'10 years
Building and Building Improvements [Member] | Maximum [Member]	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life (years)	'40 years
Tenant Improvement [Member]	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life, description	'ShorterB ofB usefulB lifeB orB termsB ofB relatedB lease
Furniture, fixtures and equipment [Member] | Minimum [Member]	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life (years)	'3 years
Furniture, fixtures and equipment [Member] | Maximum [Member]	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life (years)	'7 years

Summary_Of_Significant_Account5

Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Summary Of Significant Accounting Policies [Line Items]	'		'
Mortgage notes payable	$4,449,734		$3,102,485
Mezzanine notes payable	311,040		0
Unsecured senior notes	5,835,854		4,639,528
Unsecured exchangeable senior notes	744,880		1,170,356
Total	4,258,530		'
Impact of accounting pronouncement	2,438		25,500
Carrying Amount [Member]	'		'
Summary Of Significant Accounting Policies [Line Items]	'		'
Mortgage notes payable	4,449,734		3,102,485
Mezzanine notes payable	311,040		0
Unsecured senior notes	5,835,854		4,639,528
Unsecured exchangeable senior notes	744,880	[1]	1,170,356	[1]
Total	11,341,508		8,912,369
Estimated Fair Value [Member]	'		'
Summary Of Significant Accounting Policies [Line Items]	'		'
Mortgage notes payable	4,545,283		3,256,940
Mezzanine notes payable	311,064		0
Unsecured senior notes	6,050,517		5,162,486
Unsecured exchangeable senior notes	750,266		1,278,554
Total	11,657,130		9,697,980
ASC 470-20 Adjustment [Member]	'		'
Summary Of Significant Accounting Policies [Line Items]	'		'
Impact of accounting pronouncement	$2,400		$25,500
[1]	Includes the net adjustment for the equity component allocation totaling approximately $2.4 million and $25.5 million at DecemberB 31, 2013 and DecemberB 31, 2012, respectively.

Summary_Of_Significant_Account6

Summary Of Significant Accounting Policies Schedule of Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011	Nov. 27, 2013
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]	'		'	'	'
Dividends Payable, Amount Per Share	'		'	'	$0.65
Special dividend (per share amount)	$2.25		'	'	'
Dividends Treatment For Federal Tax Purposes, Percentage	100.00%		100.00%	100.00%	'
Dividends treatment for federal tax purposes.	$4.75	[1]	$2.37	$2.11	'
Dividend Declared [Member]	'		'	'	'
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]	'		'	'	'
Dividends Payable, Amount Per Share	$2.90		'	'	'
non-special dividend [Member]	'		'	'	'
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]	'		'	'	'
Dividends Payable, Amount Per Share	$0.65		'	'	'
Allocated to fiscal two thousand thirteen [Member]	'		'	'	'
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]	'		'	'	'
Special dividend (per share amount)	$2.44		'	'	'
Capital Gains Income [Member]	'		'	'	'
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]	'		'	'	'
Dividends Treatment For Federal Tax Purposes, Percentage	51.29%		3.55%	2.61%	'
Dividends treatment for federal tax purposes.	$2.44		$0.08	$0.05	'
Ordinary Income [Member]	'		'	'	'
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]	'		'	'	'
Dividends Treatment For Federal Tax Purposes, Percentage	48.71%		96.45%	97.39%	'
Dividends treatment for federal tax purposes.	$2.31		$2.29	$2.06	'
Allocated to fiscal two thousand fourteen [Member]	'		'	'	'
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]	'		'	'	'
Special dividend (per share amount)	$0.46		'	'	'
[1]	The fourth quarter 2013 dividend of $2.90 per common share consists of a $2.25 per common share special dividend and a $0.65 per common share regular quarterly dividend of which approximately $2.44 per common share was allocable to 2013 and approximately $0.46 per common share is allocable to 2014.

Summary_Of_Significant_Account7

Summary Of Significant Accounting Policies Schedule Of Future Contractual Minimum Lease Payments Under Non-Cancelable Ground Leases (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Summary of Significant Accounting Policies [Abstract]	'
2014	$13,184
2015	13,507
2016	13,732
2017	13,963
2018	14,198
Thereafter	$899,187

Summary_Of_Significant_Account8

Summary Of Significant Accounting Policies GAAP Reconciliation Of Net Income To Taxable Income (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of GAAP net income to taxable income [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Net income attributable to Boston Properties, Inc.	$88,719	$152,677	$452,417	$47,854	$65,400	$57,249	$118,559	$48,454	$749,811	$289,650	$272,679
Straight line rent adjustments	'	'	'	'	'	'	'	'	-74,445	-80,281	-77,422
Book/tax differences from depreciation and amortization	'	'	'	'	'	'	'	'	170,370	105,599	117,675
Book/tax differences on gains/losses from capital transactions	'	'	'	'	'	'	'	'	-124,413	-22,408	-38,443
Book/tax differences from stock-based compensation	'	'	'	'	'	'	'	'	42,146	19,660	827
Other book/tax differences, net	'	'	'	'	'	'	'	'	-12,797	35,461	29,389
Taxable Income	'	'	'	'	'	'	'	'	$750,672	$347,681	$304,705

Summary_Of_Significant_Account9

Summary Of Significant Accounting Policies Schedule of Finite Lived Intangible Assets Future Amortization Expense (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'
2014	$91,903
2015	66,716
2016	55,083
2017	41,106
2018	36,306
Acquired Above-Market Lease Intangibles [Member]	'
Finite-Lived Intangible Assets [Line Items]	'
2014	23,669
2015	22,758
2016	20,576
2017	12,279
2018	8,637
Acquired Below-Market Lease Intangibles [Member]	'
Finite-Lived Intangible Assets [Line Items]	'
2014	61,700
2015	55,207
2016	52,461
2017	40,346
2018	$37,774

Real_Estate_Narrative_Details

Real Estate (Narrative) (Details) (USD $)

3 Months Ended

12 Months Ended

0 Months Ended

0 Months Ended

3 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

7 Months Ended

0 Months Ended

3 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Feb. 06, 2013

Mar. 26, 2013

Feb. 26, 2013

Feb. 07, 2013

Mar. 22, 2013

Mar. 29, 2013

Apr. 25, 2013

Jun. 14, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Jun. 28, 2013

Apr. 10, 2013

Dec. 31, 2013

Apr. 10, 2013

Apr. 10, 2013

31-May-13

Dec. 31, 2013

Feb. 20, 2013

Mar. 31, 2013

Jun. 28, 2013

Aug. 22, 2013

Oct. 09, 2013

Dec. 20, 2013

Dec. 20, 2013

Dec. 31, 2013

Oct. 29, 2013

31-May-13

535 Mission [Member]

Transbay Tower [Member]

Transbay Tower [Member]

Transbay Tower [Member]

Two Patriots Park [Member]

Reston Signature Site [Member]

601 Massachusetts Avenue [Member]

Seventeen Cambridge Center [Member]

The Avant at Reston Town Center Residential [Member]

250 West 55th Street [Member]

680 Folsom Street [Member]

Plaza at Almaden [Member]

Plaza at Almaden [Member]

Mountain View Research And Technology Parks [Member]

Mountain View Research And Technology Parks [Member]

Mountain View Research [Member]

Mountain View Technology [Member]

767 5th Avenue (The General Motors Building) [Member]

767 5th Avenue (The General Motors Building) [Member]

Montvale Center [Member]

303 Almaden [Member]

303 Almaden [Member]

1301 New York Avenue [Member]

Time Square Tower [Member]

10 and 20 Burlington Mall Road [Member]

One Preserve Parkway [Member]

Cambridge Center Connector [Member]

Princeton Build to Suit [Member]

767 5th Avenue (The General Motors Building) [Member]

floor

floor

sqft

sqft

sqft

sqft

apartments

sqft

sqft

sqft

Buildings

Buildings

sqft

sqft

sqft

sqft

sqft

sqft

sqft

sqft

partners

sqft

sqft

sqft

sqft

sqft

Buildings

Real Estate Properties [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain on consolidation of joint ventures

'

'

'

'

'

'

'

'

$385,991,000

$0

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

$26,500,000

'

'

'

$359,500,000

'

'

'

'

'

'

'

'

'

'

$359,500,000

Payments to Acquire and Develop Real Estate

'

'

'

'

'

'

'

'

522,900,000

788,052,000

112,180,000

71,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Partners Joint Venture Ownership Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

5.00%

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

40.00%

'

'

'

'

'

'

'

'

'

'

'

Number of floors in building

'

'

'

'

'

'

'

'

'

'

'

27

60

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenues contributed by acquisitions

576,199,000

571,481,000

510,033,000

477,826,000

478,047,000

464,220,000

466,197,000

438,722,000

2,135,539,000

1,847,186,000

1,722,792,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

16,700,000

'

'

'

168,400,000

'

'

'

'

'

'

'

'

'

'

Earnings

'

'

'

'

'

'

'

'

678,120,000

640,321,000

605,166,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

400,000

'

'

'

8,400,000

'

'

'

'

'

'

'

'

'

'

Amount of debt extinguished

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25,000,000

'

'

'

'

'

'

'

'

'

Gain on forgiveness of debt from discontinued operations

'

'

'

'

'

'

'

'

20,182,000

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

20,200,000

'

'

'

'

'

'

'

'

'

Proceeds from the sale of real estate

'

'

'

'

'

'

'

'

250,078,000

61,963,000

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

121,500,000

'

29,400,000

59,900,000

'

'

'

Gain on sale of real estate from discontinued operations

'

'

'

'

'

'

'

'

112,829,000

36,877,000

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

86,400,000

'

20,500,000

5,900,000

'

'

'

Number of real estate properties

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

16

7

'

'

'

'

'

'

'

2

'

'

'

'

Net Rentable Area

'

'

'

'

'

'

'

'

'

'

'

307,000

1,400,000

'

'

256,000

250,000

478,000

195,000

355,000

989,000

525,000

'

840,000

'

'

604,000

135,000

1,800,000

'

'

'

158,000

201,000

1,246,000

152,000

184,000

43,000

130,000

'

Property placed in-service (percentage)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

63.00%

6.00%

1.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Portion allocation to noncontrolling interest based on carrying value of the total equity of the property prior to the sale

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

243,500,000

'

'

'

'

'

ownership interest sold (percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

45.00%

'

'

'

'

'

Contractual Sales Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

40,000,000

135,000,000

'

30,000,000

61,300,000

'

'

'

Number of apartment units

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

359

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment loss from discontinued operations

'

'

'

'

'

'

'

'

3,241,000

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,200,000

'

'

'

'

'

'

'

'

Number of Joint Venture Partners

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

Aggregate purchase price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

233,084,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payments to Acquire Land

'

'

'

'

'

'

'

'

'

'

'

'

192,000,000

'

'

'

27,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ownership Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

95.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment loss

'

'

'

'

'

'

'

'

8,306,000

0

0

'

'

'

'

'

'

'

'

'

'

'

8,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net Contractual Sales Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

121,700,000

684,000,000

'

'

'

'

'

Proceeds from sale of an interest in a real estate asset

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

673,100,000

'

'

'

'

'

Difference between net cash proceeds received and noncontrolling interest recognized

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$429,600,000

'

'

'

'

'

Real_Estate_Schedule_Of_Alloca

Real Estate (Schedule Of Allocation Of The Aggregate Purchase Price Of Acquisition) (Details) (USD $)	12 Months Ended			0 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 10, 2013	31-May-13		31-May-13
				Mountain View Research And Technology Parks [Member]	767 5th Avenue (The General Motors Building) [Member]		Consolidation, Eliminations [Member]
							767 5th Avenue (The General Motors Building) [Member]
Restructuring Cost and Reserve [Line Items]	'	'	'	'	'		'
Land	'	'	'	$126,521	$1,796,252		'
Building and improvements	'	'	'	82,451	1,447,446		'
Tenant Improvements	'	'	'	7,326	85,208		'
In-place lease Intangibles	'	'	'	23,279	357,781		'
Above market rents	'	'	'	843	101,897		'
Below market rents	'	'	'	7,336	239,641		'
Above Market Assumed Debt Adjustments	'	'	'	'	192,943		'
Real estate and related intangibles recorded upon consolidation	3,356,000	0	0	'	3,356,000		'
Mortgage notes payable	4,449,734	3,102,485	'	'	1,300,000		'
Mezzanine notes payable	311,040	0	'	'	306,000		'
Outside members' notes payable	180,000	0	'	'	450,000	[1]	270,000
Debt recorded upon consolidation	2,056,000	0	0	'	2,056,000		'
Cash and cash equivalents	79,468	0	0	'	79,468		'
Cash held in escrows	'	'	'	'	2,403		'
Tenant and other receivables	'	'	'	'	7,104		'
Prepaid expenses and other assets	'	'	'	'	4,269		'
Accounts payable and other expenses	'	'	'	'	2,418		'
Accrued interest payable	167,523	72,461	'	'	182,369	[2]	105,500
Other liabilities	'	'	'	'	6,304		'
Working capital recorded upon consolidation	177,315	0	0	'	97,847		'
Noncontrolling Interest	'	'	'	'	520,000		'
Noncontrolling Interest working capital	'	'	'	'	39,139		'
Noncontrolling interest in property partnerships recorded upon consolidation	480,861	0	0	'	480,861		'
Net Assets Recorded Upon Consolidation	'	'	'	'	721,292		'
Aggregate purchase price	'	'	'	$233,084	'		'
[1]	The Company's member loan totaling $270.0 million eliminates in consolidation.
[2]	The Company's share of the accrued interest payable on the members' loans totaling approximately $105.5 million eliminates in consolidation.

Real_Estate_Pro_Forma_In_Conne

Real Estate (Pro Forma In Connection With Acquisition) (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Real Estate [Abstract]	'	'
Total revenue	$2,257,098	$2,149,391
Income from continuing operations	302,354	634,457
Net income attributable to Boston Properties, Inc.	$400,017	$626,174
Basic earnings per share: Net income per share attributable to Boston Properties, Inc. (in dollars per share)	$2.58	$4.15
Diluted earnings per share: Net income per share attributable to Boston Properties, Inc. (in dollars per share)	$2.57	$4.13

Real_Estate_Summary_Of_The_Dis

Real Estate (Summary Of The Discontinued Operations (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Total revenue	$576,199	$571,481	$510,033	$477,826	$478,047	$464,220	$466,197	$438,722	$2,135,539	$1,847,186	$1,722,792
Expenses	'	'	'	'	'	'	'	'	'	'	'
Depreciation and amortization	'	'	'	'	'	'	'	'	560,637	445,875	429,742
Total expenses	'	'	'	'	'	'	'	'	1,457,419	1,206,865	1,117,626
Operating income	'	'	'	'	'	'	'	'	678,120	640,321	605,166
Other Expenses	'	'	'	'	'	'	'	'	'	'	'
Interest expense	'	'	'	'	'	'	'	'	446,880	410,970	391,533
Noncontrolling interest in income (loss) from discontinued operations - common units of the Operating Partnership	'	'	'	'	'	'	'	'	-14,151	-5,075	-1,243
Income from discontinued operations attributable to Boston Properties, Inc.	'	'	'	'	'	'	'	'	123,641	41,608	9,633
Gain on sale of real estate from discontinued operations	'	'	'	'	'	'	'	'	112,829	36,877	0
Gain on forgiveness of debt from discontinued operations	'	'	'	'	'	'	'	'	20,182	0	0
Impairment loss from discontinued operations	'	'	'	'	'	'	'	'	-3,241	0	0
10 & 20 Burlington Mall Road, One Preserve Parkway, 1301 New York Avenue, 303 Almaden Blvd, Montvale Center and Bedford Business Park [Member]	'	'	'	'	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Total revenue	'	'	'	'	'	'	'	'	20,138	32,607	36,734
Expenses	'	'	'	'	'	'	'	'	'	'	'
Operating	'	'	'	'	'	'	'	'	6,996	12,038	13,818
Depreciation and amortization	'	'	'	'	'	'	'	'	4,760	8,169	9,442
Total expenses	'	'	'	'	'	'	'	'	11,756	20,207	23,260
Operating income	'	'	'	'	'	'	'	'	8,382	12,400	13,474
Other Expenses	'	'	'	'	'	'	'	'	'	'	'
Interest expense	'	'	'	'	'	'	'	'	360	2,594	2,598
Income from discontinued operations	'	'	'	'	'	'	'	'	8,022	9,806	10,876
Noncontrolling interest in income (loss) from discontinued operations - common units of the Operating Partnership	'	'	'	'	'	'	'	'	-803	-1,031	-1,243
Income from discontinued operations attributable to Boston Properties, Inc.	'	'	'	'	'	'	'	'	7,219	8,775	9,633
Gain on sale of real estate from discontinued operations	'	'	'	'	'	'	'	'	112,829	36,877	0
Gain on forgiveness of debt from discontinued operations	'	'	'	'	'	'	'	'	20,182	0	0
Impairment loss from discontinued operations	'	'	'	'	'	'	'	'	-3,241	0	0
Noncontrolling interest in gain on sale of real estate, gain on forgiveness of debt and impairment loss from discontinued operations - common units of the Operating Partnership	'	'	'	'	'	'	'	'	-13,348	-4,044	0
Gain on sale of real estate, gain on forgiveness of debt and impairment loss from discontinued operations attributable to Boston Properties, Inc	'	'	'	'	'	'	'	'	$116,422	$32,833	'

Real_Estate_Schedule_of_Real_E

Real Estate Schedule of Real Estate Properties (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Real Estate [Abstract]	'	'
Land	$4,450,532	$2,605,162
Land held for future development	297,376	275,094
Buildings and improvements	11,065,113	9,517,343
Tenant improvements	1,617,401	1,435,508
Furniture, fixtures and equipment	25,164	23,441
Construction in progress	1,523,179	1,036,780
Total	18,978,765	14,893,328
Less: accumulated depreciation	-3,161,571	-2,934,160
Total real estate	$15,817,194	$11,959,168

Deferred_Charges_Details

Deferred Charges (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred Charges [Abstract]	'	'
Leasing costs, including lease related intangibles	$1,183,204	$790,740
Financing costs	76,798	90,682
Deferred charges, gross	1,260,002	881,422
Less: Accumulated amortization	-375,552	-293,187
Deferred charges, total	$884,450	$588,235

Deferred_Charges_Schedule_of_A

Deferred Charges Schedule of Acquired In-Place Lease Intangibles (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Charges [Abstract]	'
2014	$91,903
2015	66,716
2016	55,083
2017	41,106
2018	$36,306

Investments_in_Unconsolidated_2

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details)	12 Months Ended
	Dec. 31, 2013
Square 407 Limited Partnership [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'MarketB SquareB North
Equity Method Investment, Ownership Percentage	50.00%
The Metropolitan Square Associates LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'Metropolitan Square
Equity Method Investment, Ownership Percentage	51.00%
BP/CRF 901 New York Avenue LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'901B NewB YorkB Avenue	[1]
Equity Method Investment, Ownership Percentage	25.00%	[1]
WP Project Developer LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'Wisconsin Place Land and Infrastructure	[2]
Equity Method Investment, Ownership Percentage	33.30%	[2]
RBP Joint Venture LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'N/A	[3]
Equity Method Investment, Ownership Percentage	50.00%	[3]
Boston Properties Office Value-Added Fund, L.P. [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'N/A	[4]
Equity Method Investment, Ownership Percentage	39.50%	[4]
Annapolis Junction NFM, LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'Annapolis Junction	[5]
Equity Method Investment, Ownership Percentage	50.00%	[5]
Number of real estate properties	2
Number of buildings under construction	1
Parcels of undeveloped land	2
2 GCT Venture LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'N/A	[6]
Equity Method Investment, Ownership Percentage	60.00%	[6]
540 Madison Venture LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'540 Madison Avenue
Equity Method Investment, Ownership Percentage	60.00%
125 West 55th Street Venture LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'N/A	[7]
Equity Method Investment, Ownership Percentage	60.00%	[7]
500 North Capitol LLC [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Properties	'500 North Capitol Street, NW
Equity Method Investment, Ownership Percentage	30.00%
Entity Owning Land And Infrastructure Of Project [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Equity Method Investment, Ownership Percentage	33.30%
[1]	The Companybs economic ownership can increase based on the achievement of certain return thresholds.
[2]	The Companybs wholly-owned entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking and infrastructure of the project.
[3]	Eighth Avenue and 46th Street was sold on JulyB 19, 2013.
[4]	The Company acquired Mountain View Research Park and Mountain View Technology Park from the Value-Added Fund on April 10, 2013 (See Note 3). As of DecemberB 31, 2013, the investment is comprised of undistributed cash.
[5]	Comprised of two buildings, one building under construction and two undeveloped land parcels.
[6]	Two Grand Central Tower was sold on OctoberB 25, 2011. As of DecemberB 31, 2013, the investment is comprised of undistributed cash.
[7]	125 West 55th Street was sold on MayB 30, 2013. As of DecemberB 31, 2013, the investment is comprised of undistributed cash.

Investments_in_Unconsolidated_3

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
ASSETS	'		'
Real estate and development in process, net	$15,817,194		$11,959,168
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY	'		'
Mortgage and notes payable	4,449,734		3,102,485
Other liabilities	578,969		324,613
Total liabilities and equity	20,162,251		15,462,321
Carrying value of the Company's investments in unconsolidated joint ventures	126,084		659,916
Unconsolidated Joint Ventures [Member]	'		'
ASSETS	'		'
Real estate and development in process, net	924,297		4,494,971
Other assets	163,149		673,716
Total assets	1,087,446		5,168,687
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY	'		'
Mortgage and notes payable	749,732		3,039,922
Other liabilities	28,830		792,888
Members'/Partners' equity	308,884		1,335,877
Total liabilities and equity	1,087,446		5,168,687
Company's share of equity	154,726		787,941
Basis differentials	-28,642	[1]	-128,025	[1]
Carrying value of the Company's investments in unconsolidated joint ventures	$126,084		$659,916
[1]	This amount represents the aggregate difference between the Companybs historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from impairment of investments and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level.

Investments_in_Unconsolidated_4

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

3 Months Ended

12 Months Ended

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Schedule of Equity Method Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

Total revenue

$576,199,000

$571,481,000

$510,033,000

$477,826,000

$478,047,000

$464,220,000

$466,197,000

$438,722,000

$2,135,539,000

$1,847,186,000

$1,722,792,000

Expenses

'

'

'

'

'

'

'

'

'

'

'

Depreciation and amortization

'

'

'

'

'

'

'

'

560,637,000

445,875,000

429,742,000

Total expenses

'

'

'

'

'

'

'

'

1,457,419,000

1,206,865,000

1,117,626,000

Operating income

'

'

'

'

'

'

'

'

678,120,000

640,321,000

605,166,000

Other income (expense)

'

'

'

'

'

'

'

'

'

'

'

Interest expense

'

'

'

'

'

'

'

'

-446,880,000

-410,970,000

-391,533,000

Losses from early extinguishments of debt

'

'

'

'

'

'

'

'

122,000

-4,453,000

-1,494,000

Income (loss) from continuing operations

79,395,000

82,311,000

503,446,000

38,496,000

74,251,000

63,331,000

94,795,000

53,079,000

703,648,000

285,456,000

302,950,000

Net income (loss)

'

'

'

'

'

'

'

'

841,440,000

332,139,000

313,826,000

Income from unconsolidated joint ventures

'

'

'

'

'

'

'

'

75,074,000

49,078,000

85,896,000

Straight-line rent adjustments

'

'

'

'

'

'

'

'

65,800,000

77,600,000

77,000,000

Above and below market rent adjustments, net

'

'

'

'

'

'

'

'

28,000,000

14,600,000

10,800,000

Gain on consolidation of joint ventures

'

'

'

'

'

'

'

'

385,991,000

0

0

Unconsolidated Joint Ventures [Member]

'

'

'

'

'

'

'

'

'

'

'

Schedule of Equity Method Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

Total revenue

'

'

'

'

'

'

'

'

311,548,000

[1]

564,205,000

[1]

589,294,000

[1]

Expenses

'

'

'

'

'

'

'

'

'

'

'

Operating

'

'

'

'

'

'

'

'

105,319,000

162,665,000

170,404,000

Depreciation and amortization

'

'

'

'

'

'

'

'

86,088,000

163,134,000

190,437,000

Impairment losses

'

'

'

'

'

'

'

'

0

0

40,468,000

Total expenses

'

'

'

'

'

'

'

'

191,407,000

325,799,000

401,309,000

Operating income

'

'

'

'

'

'

'

'

120,141,000

238,406,000

187,985,000

Other income (expense)

'

'

'

'

'

'

'

'

'

'

'

Interest expense

'

'

'

'

'

'

'

'

-112,535,000

-224,645,000

-228,494,000

Losses from early extinguishments of debt

'

'

'

'

'

'

'

'

-1,677,000

0

0

Income (loss) from continuing operations

'

'

'

'

'

'

'

'

5,929,000

13,761,000

-40,509,000

Gains on sale of real estate

'

'

'

'

'

'

'

'

14,207,000

990,000

0

Net income (loss)

'

'

'

'

'

'

'

'

20,136,000

14,751,000

-40,509,000

Company's share of net income (loss)

'

'

'

'

'

'

'

'

4,612,000

6,863,000

-25,374,000

Gains on sale of real estate

'

'

'

'

'

'

'

'

54,501,000

0

46,166,000

Basis differential

'

'

'

'

'

'

'

'

-1,017,000

1,732,000

27,226,000

Elimination of inter-entity interest on partner loan

'

'

'

'

'

'

'

'

16,978,000

40,483,000

37,878,000

Income from unconsolidated joint ventures

'

'

'

'

'

'

'

'

75,074,000

49,078,000

85,896,000

Straight-line rent adjustments

'

'

'

'

'

'

'

'

7,800,000

12,000,000

21,900,000

Above and below market rent adjustments, net

'

'

'

'

'

'

'

'

33,700,000

91,100,000

120,300,000

Lease termination income

'

'

'

'

'

'

'

'

19,600,000

'

'

Company's share of lease termination income

'

'

'

'

'

'

'

'

11,800,000

'

'

Gain on consolidation of joint ventures

'

'

'

'

'

'

'

'

$385,991,000

$0

$0

[1]

Includes straight-line rent adjustments of $7.8 million, $12.0 million and $21.9 million for the years ended DecemberB 31, 2013, 2012 and 2011, respectively. Includes net below-market rent adjustments of $33.7 million, $91.1 million and $120.3 million for the years ended DecemberB 31, 2013, 2012 and 2011, respectively. Total revenue for the year ended DecemberB 31, 2012 includes termination income totaling approximately $19.6 million (of which the Company's share is approximately $11.8 million) related to a lease termination with a tenant at 767 Fifth Avenue (The General Motors Building).

Investment_in_unconsolidated_J

Investment in unconsolidated Joint Ventures (Narrative) (Details) (USD $)

12 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

30-May-13

31-May-13

Apr. 10, 2013

Apr. 10, 2013

Apr. 10, 2013

Oct. 29, 2013

Feb. 28, 2013

31-May-13

Mar. 31, 2013

Apr. 04, 2013

Sep. 26, 2013

Jun. 05, 2013

Jul. 19, 2013

30-May-13

Apr. 10, 2013

Jul. 19, 2013

31-May-13

31-May-13

31-May-13

Jun. 05, 2013

Jun. 05, 2013

Jun. 05, 2013

Oct. 29, 2013

Apr. 10, 2013

125 West 55thStreet [Member]

767 5th Avenue (The General Motors Building) [Member]

Mountain View Research And Technology Parks [Member]

Mountain View Research [Member]

Mountain View Technology [Member]

Annapolis Junction Building Six [Member]

Annapolis Junction Building Six [Member]

500 North Capitol [Member]

500 North Capitol [Member]

Annapolis Junction Building Seven [Member]

Annapolis Junction Building Seven [Member]

540 Madison Avenue [Member]

Eighth Avenue and Forty Sixth Street [Member]

Company [Member]

Company [Member]

Company [Member]

Construction Loans [Member]

Construction Loans [Member]

First Mortgage [Member]

First Mortgage [Member]

Prior to refinance first mortgage loan [Member]

Prior to refinance first mortgage loan [Member]

Prior to extension [Member]

Mountain View Research And Technology Parks [Member]

sqft

partners

sqft

sqft

sqft

Y

sqft

125 West 55thStreet [Member]

Mountain View Research And Technology Parks [Member]

Eighth Avenue and Forty Sixth Street [Member]

500 North Capitol [Member]

Company [Member]

500 North Capitol [Member]

540 Madison Avenue [Member]

540 Madison Avenue [Member]

Company [Member]

Annapolis Junction Building Six [Member]

500 North Capitol [Member]

540 Madison Avenue [Member]

Schedule of Equity Method Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Description of Variable Rate Basis

'

'

'

'

'

'

'LIBOR plus 2.00%

'LIBOR plus 2.50%

'LIBOR plus 1.65%

'

'

'

'

'

'

'

'

'

'

'LIBOR plus 1.65%

'

'

'LIBOR plus 1.50%

'

'

'

'

Equity Method Investment, Ownership Percentage

'

'

'

60.00%

'

'

'

'

50.00%

50.00%

30.00%

30.00%

50.00%

50.00%

60.00%

50.00%

'

'

'

'

'

'

'

'

'

'

39.50%

Imputed Sales Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$45,000,000

'

'

'

'

'

'

'

'

'

'

'

Net Rentable Area

'

'

'

588,000

'

'

'

'

119,000

119,000

'

231,000

'

125,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Sales Price

'

'

'

470,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Carrying Value of Debt Assumed in Sale

'

'

'

198,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Coupon/Stated Rate

3.63%

'

'

6.09%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.15%

'

5.20%

'

'

'

Cash Proceeds from the Sale of Real Estate Property

'

'

'

253,700,000

'

'

'

'

'

'

'

'

'

'

'

21,800,000

152,200,000

'

'

'

'

'

'

'

'

'

'

Gain on sales of real estate

'

'

'

43,200,000

'

'

'

'

'

'

'

'

'

'

'

12,600,000

'

'

11,300,000

'

'

'

'

'

'

'

'

Number of Joint Venture Partners

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Construction Loan Facility Borrowing Capacity

'

'

'

'

'

'

'

'

'

'

'

'

22,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Basis Spread on Variable Rate

'

'

'

'

'

'

2.00%

2.50%

1.65%

'

'

'

1.65%

'

'

'

'

'

'

1.65%

'

'

1.50%

'

'

'

'

Maturity date

15-Feb-14

'

'

10-Mar-20

'

'

31-May-14

22-Nov-14

17-Nov-14

'

'

'

4-Apr-16

'

'

'

'

'

'

14-Oct-14

'

6-Jun-23

5-Jun-18

11-Jul-13

'

17-Nov-13

'

Construction Loan

'

'

'

'

'

'

'

'

14,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gains (losses) from early extinguishments of debt

122,000

-4,453,000

-1,494,000

'

'

-400,000

'

'

'

'

'

'

'

'

'

'

'

-200,000

'

-1,000,000

-300,000

'

'

-300,000

-200,000

'

'

Proceeds from Issuance of Secured Debt

0

0

1,178,306,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

105,000,000

120,000,000

'

'

'

'

Repayments of Secured Debt

80,311,000

253,877,000

1,251,841,000

'

'

'

90,000,000

20,000,000

'

'

'

'

'

'

'

'

'

'

'

90,600,000

'

'

'

118,000,000

'

'

'

Repayments of Notes Payable

'

'

'

'

'

'

8,600,000

3,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of extensions

'

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Extension Option (in years)

'

'

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ownership upon acquisition

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

Gain on consolidation of joint ventures

$385,991,000

$0

$0

'

$359,500,000

$26,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mortgage_Notes_Payable_Schedul1

Mortgage Notes Payable Schedule Of Aggregate Principal Payments On Mortgage Notes (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Mortgage Notes Payable [Abstract]	'	'
2014	$87,759	'
2015	26,182	'
2016	608,879	'
2017	2,821,750	'
2018	18,633	'
Thereafter	695,327	'
Total	4,258,530	'
Unamoritized balance of histroical fair value adjustments	191,204	'
Total carrying value of mortgage notes payable	$4,449,734	$3,102,485

Mortgage_Notes_Payable_Narrati

Mortgage Notes Payable (Narrative) (Details) (USD $)

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

7 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Feb. 05, 2013

Dec. 31, 2013

31-May-13

Dec. 31, 2013

Feb. 20, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

31-May-13

31-May-13

Dec. 31, 2013

Dec. 31, 2013

Kingstowne One [Member]

140 Kendrick [Member]

767 5th Avenue (The General Motors Building) [Member]

767 5th Avenue (The General Motors Building) [Member]

Montvale Center [Member]

Minimum [Member]

Minimum [Member]

Fixed Rate Mortgages [Member]

Fixed Rate Mortgages [Member]

Variable Rate Mortgages [Member]

Variable Rate Mortgages [Member]

Mezzanine Debt [Member]

First Mortgage [Member]

Company [Member]

Consolidation, Eliminations [Member]

767 5th Avenue (The General Motors Building) [Member]

767 5th Avenue (The General Motors Building) [Member]

767 5th Avenue (The General Motors Building) [Member]

767 5th Avenue (The General Motors Building) [Member]

Mortgage Notes Payable [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mortgage notes payable

$4,449,734,000

$3,102,485,000

'

'

'

'

'

'

'

'

$4,400,000,000

$3,100,000,000

'

'

'

'

'

'

Number Real Estate Assets Used For Mortgage Loan Collateral

'

'

'

'

'

'

'

'

1

1

'

'

'

'

'

'

'

'

Final maturity date of mortgage notes

10-Apr-22

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual interest rate range, inimum

'

'

'

'

'

'

'

'

'

'

4.75%

4.75%

'

'

'

'

'

'

Contractual interest rate range, maximum

'

'

'

'

'

'

'

'

'

'

7.69%

9.93%

'

'

'

'

'

'

Contractual interest rate, weighted vverage interest rate

'

'

'

'

'

'

'

'

'

'

5.70%

5.65%

'

'

'

'

'

'

Number of variable rate mortgage loans

'

'

'

'

'

'

'

'

'

'

'

'

0

0

'

'

'

'

London Interbank Offered Rate

'

'

'

'

'

'

'

'

'

'

'

'

0.17%

0.21%

'

'

'

'

Maturity date

15-Feb-14

'

'

5-May-13

1-Jul-13

9-Jun-17

'

'

'

'

'

'

'

'

7-Oct-17

7-Oct-17

'

'

Amount of debt extinguished

'

'

'

'

'

'

'

25,000,000

'

'

'

'

'

'

'

'

'

'

Gain on forgiveness of debt from discontinued operations

20,182,000

0

0

'

'

'

'

20,200,000

'

'

'

'

'

'

'

'

'

'

Repayments of mortgage notes payable

80,311,000

253,877,000

1,251,841,000

17,000,000

47,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest at a fixed rate

3.63%

'

'

5.96%

7.51%

11.00%

'

'

'

'

'

'

'

'

6.02%

5.95%

'

'

Penalty for early repayment of debt

'

'

'

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

Gains (losses) from early extinguishments of debt

122,000

-4,453,000

-1,494,000

'

300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt recorded upon consolidation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

306,000,000

1,300,000,000

'

'

Number Of Mortgage Loans Accounted For Fair Value

4

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding balance of mortgage loans accounted for at fair value

2,200,000,000

951,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

nterest Expense Decrease Due To Recording Mortgage Loans At Fair Value

34,400,000

7,000,000

9,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cumulative Liability Related to the Fair Value of Debt Adjustment

191,200,000

38,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mortgage Loans Accounted For At Fair Value Upon Consolidation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

311,700,000

1,500,000,000

'

'

Interest Rate Used To Account For Mortgage Loan At Fai rValue Upon Consolidation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.53%

2.44%

'

'

Outside members' notes payable

180,000,000

0

'

'

'

450,000,000

'

'

'

'

'

'

'

'

'

'

180,000,000

270,000,000

Interest Payable

167,523,000

72,461,000

'

'

'

175,800,000

'

'

'

'

'

'

'

'

'

'

76,400,000

114,500,000

Interest Expense, Related Party

'

'

'

'

'

'

$16,000,000

'

'

'

'

'

'

'

'

'

'

'

Unsecured_Senior_Notes_Schedul

Unsecured Senior Notes Schedule of Unsecured Senior Notes (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	3.63%		'
Effective Rate	4.04%	[1]	'
Principal Amount	$747,500		'
Maturity date	15-Feb-14		'
Net unamortized discount	-14,146		-10,472
Total	5,835,854		4,639,528
Senior Notes [Member]	'		'
Debt Instrument [Line Items]	'		'
Principal Amount	5,850,000		'
Net unamortized discount	-14,146		'
Total	5,835,854		'
Senior Notes [Member] | Twelve Year Unsecured Senior Notes Five Point Six Nine Three Percent	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	5.63%		'
Effective Rate	5.69%	[2]	'
Principal Amount	300,000		'
Maturity date	15-Apr-15	[3]	'
Senior Notes [Member] | Twelve Year Unsecured Senior Notes Five Point One Nine Four Percent	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	5.00%		'
Effective Rate	5.19%	[2]	'
Principal Amount	250,000		'
Maturity date	1-Jun-15	[3]	'
Senior Notes [Member] | Ten Year Unsecured Senior Notes Five Point Nine Six Seven Percent	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	5.88%		'
Effective Rate	5.97%	[2]	'
Principal Amount	700,000		'
Maturity date	15-Oct-19	[3]	'
Senior Notes [Member] | Ten Year Unsecured Senior Notes Five Point Seven Zero Eight Percent	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	5.63%		'
Effective Rate	5.71%	[2]	'
Principal Amount	700,000		'
Maturity date	15-Nov-20	[3]	'
Senior Notes [Member] | Ten Year Unsecured Senior Notes Four Point Two Eight Nine Percent	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	4.13%		'
Effective Rate	4.29%	[2]	'
Principal Amount	850,000		'
Maturity date	15-May-21	[3]	'
Senior Notes [Member] | Seven Year Unsecured Senior Notes Three Point Eight Five Three Percent	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	3.70%		'
Effective Rate	3.85%	[2]	'
Principal Amount	850,000		'
Maturity date	15-Nov-18	[3]	'
Senior Notes [Member] | Eleven Year Unsecured Senior Notes Three Point Nine Five Four Percent	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	3.85%		'
Effective Rate	3.95%	[2]	'
Principal Amount	1,000,000		'
Maturity date	1-Feb-23	[3]	'
Senior Notes [Member] | Ten and Half Year Unsecured Senior Notes Three Point Two Seven Nine Percent [Member]	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	3.13%		'
Effective Rate	3.28%	[2]	'
Principal Amount	500,000		'
Maturity date	1-Sep-23		'
Senior Notes [Member] | Ten and Half Year Unsecured Senior Notes Three Point Nine One Six Percent [Member]	'		'
Debt Instrument [Line Items]	'		'
Coupon/Stated Rate	3.80%		'
Effective Rate	3.92%	[2]	'
Principal Amount	$700,000		'
Maturity date	1-Feb-24		'
[1]	Yield on issuance date including the effects of discounts on the notes but excluding the effects of the adjustment for the equity component allocation.
[2]	Yield on issuance date including the effects of discounts on the notes and the amortization of financing costs.
[3]	No principal amounts are due prior to maturity.

Unsecured_Senior_Notes_Unsecur

Unsecured Senior Notes Unsecured Senior Notes (Narrative) (Details) (USD $)	12 Months Ended				0 Months Ended		12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011	Apr. 11, 2013	Jun. 27, 2013	Dec. 31, 2013
					Three Point Two Seven Nine Percent Unsecured Senior Notes [Member]	Three Point Nine One Six Percent Unsecured Senior Notes [Member]	Senior Notes [Member]
Debt Instrument [Line Items]	'		'	'	'	'	'
Debt Instrument, Face Amount	'		'	'	$500,000,000	$700,000,000	'
Coupon/Stated Rate	3.63%		'	'	3.13%	3.80%	'
Senior Notes Pricing	'		'	'	99.38%	99.69%	'
Effective Rate	4.04%	[1]	'	'	3.28%	3.92%	'
Maturity date	15-Feb-14		'	'	1-Sep-23	1-Feb-24	'
Proceeds from unsecured senior notes	$1,194,753,000		$997,790,000	$848,019,000	$492,500,000	$691,900,000	'
Maximum Leverage Ratio	'		'	'	'	'	60.00%
Maximum Secured Debt Leverage Ratio	55.00%		'	'	'	'	50.00%
Minimum Interest Coverage Ratio	'		'	'	'	'	1.5
Minimum Unencumbered Asset Value Percentage Of Unsecured Debt	'		'	'	'	'	150.00%
[1]	Yield on issuance date including the effects of discounts on the notes but excluding the effects of the adjustment for the equity component allocation.

Unsecured_Exchangeable_Senior_2

Unsecured Exchangeable Senior Notes (Schedule of Unsecured Exchangeable Senior Notes) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Aug. 19, 2008	Aug. 13, 2008
Debt Disclosure [Abstract]	'		'	'	'
Coupon/Stated Rate	3.63%		'	'	'
Effective Rate	4.04%	[1]	'	'	'
Exchange Rate (in shares)	8.6974	[2]	'	'	'
Principal Amount	$747,500,000		'	'	'
Net unamortized discount	-182,000		-1,653,000	'	'
Adjustment for the equity component allocation, net of accumulated amortization	-2,438,000		-25,500,000	'	'
Total	744,880,000		1,170,356,000	'	'
Maturity date	15-Feb-14		'	'	'
Initial exchange on principal amount of note	1,000		'	1,000	'
Revised exchange price due to special dividend	$114.98		'	'	'
Initial exchange price per share	'		'	$117.58	'
Revised exchange price due to capped call transaction	'		'	$137.17	'
Premium over closing price	'		'	40.00%	'
Closing price per share of common stock (in dollars per share)	'		'	'	$97.98
Net cost of capped call transaction	'		'	$44,400,000	'
Revised exchange rate	8.6974		'	'	'
Effective exchange price	$130.21		'	'	'
Initial exchange rate (in shares)	'		'	8.5051	'
[1]	Yield on issuance date including the effects of discounts on the notes but excluding the effects of the adjustment for the equity component allocation.
[2]	The initial exchange rate is 8.5051 shares per $1,000 principal amount of the notes (or an initial exchange price of approximately $117.58 per share of Boston Properties, Inc.bs common stock). In addition, the Company entered into capped call transactions with affiliates of certain of the initial purchasers, which are intended to reduce the potential dilution upon future exchange of the notes. The capped call transactions were intended to increase the effective exchange price to the Company of the notes from $117.58 to approximately $137.17 per share (subject to adjustments), representing an overall effective premium of approximately 40% over the closing price on AugustB 13, 2008 of $97.98 per share of Boston Properties, Inc.bs common stock. The net cost of the capped call transactions was approximately $44.4 million. In connection with the special dividend declared on November 27, 2013, the exchange rate of 8.5051 was adjusted to 8.6974 shares per $1,000 principal amount of notes effective as of December 31, 2013, resulting in an exchange price of approximately $114.98 per share of Boston Properties, Inc.'s common stock. As of DecemberB 31, 2013, the effective exchange price was $130.21 per share. The Operating Partnership repaid the notes on February 18, 2014 (See Note 20).

Unsecured_Exchangeable_Senior_3

Unsecured Exchangeable Senior Notes (Narrative) (Details) (USD $)	12 Months Ended						0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2011	18-May-13	18-May-13	18-May-13
				3.750% Exchangeable Senior Notes [Member]	3.625% Exchangeable Senior Notes [Member]	2.875% Exchangeable Senior Notes [Member]	3.750% Exchangeable Senior Notes [Member]	Submitted for Exchange [Member]	Redeemed amount [Member]
								3.750% Exchangeable Senior Notes [Member]	3.750% Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'	'
Debt Instrument, Face Amount	'	'	'	$450,000,000	$747,500,000	$862,500,000	'	'	'
Coupon/Stated Rate	3.63%	'	'	3.75%	3.63%	2.88%	3.75%	'	'
Convertible Debt Effective Interest Rate	'	'	'	5.96%	6.56%	5.63%	'	'	'
Unsecured exchangeable senior notes	744,880,000	1,170,356,000	'	'	'	'	'	'	'
Net Of Adjustment For Equity Component Allocation	2,438,000	25,500,000	'	'	'	'	'	'	'
Debt Instrument Convertible Initial Carrying Amount Of The Equity Component	230,300,000	'	'	'	'	'	'	'	'
Deferred Financing Costs Equity Component	1,000,000	'	'	'	'	'	'	'	'
Debt Instrument, Convertible, Carrying Amount of Equity Component	91,900,000	148,500,000	'	'	'	'	'	'	'
Debt Instrument, Convertible, Interest Expense	34,800,000	48,400,000	66,300,000	'	'	'	'	'	'
Interest Expense Adjustment Related To Convertible Debt	23,100,000	29,100,000	38,800,000	'	'	'	'	'	'
Notes redemption date	'	'	'	'	'	'	18-May-13	'	'
Debt instrument redemption price percentage of principal	'	'	'	'	'	'	100.00%	'	'
Amount paid for repurchase	0	224,261,000	0	'	'	'	'	449,010,000	990,000
Common stock, shares issued	153,062,001	151,680,109	'	'	'	'	419,116	'	'
Gains (losses) from early extinguishments of debt	$122,000	($4,453,000)	($1,494,000)	'	'	'	($100,000)	'	'

Unsecured_Line_of_Credit_Detai

Unsecured Line of Credit (Details) (USD $)

12 Months Ended

0 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Jul. 26, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Y

After the Amendment [Member]

Prior to Amendment [Member]

Alternative Base Interest Rate Calculation [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Rate Based on Current Credit Rating [Member]

Rate Based on Current Credit Rating [Member]

Rate Based on Current Credit Rating [Member]

M

After the Amendment [Member]

Interest Rate Based on LIBOR or CDOR [Member]

Alternative Base Interest Rate Calculation [Member]

Interest Rate Based on LIBOR or CDOR [Member]

Alternative Base Interest Rate Calculation [Member]

Interest Rate Based on LIBOR or CDOR [Member]

Alternative Base Interest Rate Calculation [Member]

Current Rates Based on Credit Ratings [Member]

Line of Credit Facility [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Current Borrowing Capacity

'

'

$1,000,000,000

$750,000,000

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Maximum Borrowing Capacity

'

'

'

'

'

'

1,500,000,000

'

'

'

'

'

'

'

'

Line of Credit Facility, Expiration Date

'

'

26-Jul-18

24-Jun-14

'

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Unused Capacity, Commitment Fee Percentage

'

'

'

'

'

0.35%

'

'

'

0.13%

'

'

'

'

0.15%

Margin added to Calculated Interest Rate

'

'

'

'

'

'

'

1.70%

0.70%

'

0.93%

0.00%

1.00%

0.00%

'

Amount added to Federal Funds Rate to Calculate Interest Rate

'

'

'

'

0.50%

'

'

'

'

'

'

'

'

'

'

LIBOR Period Used to Calculate Interest Rate (in months)

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

Amount added to LIBOR to Calculate Interest Rate

'

'

'

'

1.00%

'

'

'

'

'

'

'

'

'

'

Line of Credit Facility, Amount Outstanding

$0

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

Leverage Ratio, Maximum

60.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Leverage Ratio Maximum Increasing Limit

65.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Leverage Ratio Reduction Limit

60.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Leverage Ratio Reduction Period, Years

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum Secured Debt Leverage Ratio

55.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fixed Charge Coverage Ratio Minimum.

1.4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum Unsecured Debt Leverage Ratio

60.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unsecured Debt Leverage Ratio Maximum Increasing Limit

65.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unsecured Debt Leverage Ratio Reduction Limit

60.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unsecured Debt Leverage Ratio Reduction Period, Years

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unsecured Debt Interest Coverage Ratio Minimum.

1.75

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Commitments_And_Contingencies_

Commitments And Contingencies (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
		Buildings
Commitments And Contingencies [Line Items]	'	'
Letter of credit and performance obligations	'	$13,900,000
Maturity Date	'	15-Feb-14
Property insurance program per occurrence limits	'	1,000,000,000
Per occurrence limit for NBCR Coverage	'	1,000,000,000
Value of program trigger	'	100,000,000
Coinsurance of program trigger	'	15.00%
Deductible in insurance as a percentage of the value of the affected property, San Francisco	5.00%	'
Per occurrence limit of the earthquake insurance which covers San Francisco region	120,000,000	'
Annual aggregate limit of the earthquake insurance which covers San Francisco region	120,000,000	'
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco	20,000,000	'
Earthquake Coverage Included In Builders Risk Policy For 535 Mission	15,000,000	'
Earthquake Coverage Included In Builders Risk Policy For Below Grade improvements for Transbay Tower	15,000,000	'
Operating partnership guarantee to cover liabilities of IXP	'	20,000,000
Contractual Tax Agreements Number Of Properties	'	3
Expiration of Tax Protection for the General Motors Buidling	'	9-Jun-17
767 Venture, LLC [Member]	'	'
Commitments And Contingencies [Line Items]	'	'
Maximum funding obligation	'	24,100,000
Property insurance program per occurrence limits	'	1,625,000,000
Coverage for acts of Terrorism certified under TRIA in excess of amount provided by NYXP, LLC, as a direct insurer	'	1,375,000,000
Coverage for acts of terrorism certified under TRIA covered by NYXP	'	250,000,000
John Hancock Tower [Member]	'	'
Commitments And Contingencies [Line Items]	'	'
Guarantee Obligation Related To Tenant Re-Leasing Costs	'	15,900,000
Maturity Date	'	6-Jan-17
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

Noncontrolling_Interests_Narra

Noncontrolling Interests (Narrative) (Details)	Dec. 31, 2013
Noncontrolling Interests [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Operating Partnership (OP) Units (in shares)	15,583,370
Long-Term Incentive Plan (LTIP) Units (in shares)	1,455,761
Series Two Preferred Units (in shares)	666,116
Convertible Operating Partnership (OP) Units (in shares)	874,168
Series Four Preferred Units (in shares)	360,126
OPP Units 2011 [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Outperformance awards in LTIP Units (in shares)	396,500
OPP Units 2012 [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Outperformance awards in LTIP Units (in shares)	396,150
MYLTIP 2013 [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Outperformance awards in LTIP Units (in shares)	316,325
Series Two Preferred Units [Member] | Noncontrolling Interests [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Series Two Preferred Units (in shares)	666,116

Noncontrolling_Interests_Redee

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

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Nov. 15, 2013

Aug. 15, 2013

15-May-13

Feb. 15, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Mar. 31, 2014

Aug. 29, 2013

Dec. 31, 2013

Nov. 15, 2013

Aug. 29, 2013

Aug. 15, 2013

15-May-13

Feb. 15, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

In Thousands, except Share data, unless otherwise specified

Noncontrolling Interests [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Two Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

Series Four Preferred Units [Member]

OP Units [Member]

OP Units [Member]

Redemption Year Two Thousand Fourteen [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

Noncontrolling Interests [Member]

D

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Series Two Preferred Units (in shares)

'

'

666,116

'

'

'

666,116

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Liquidation preference percentage

'

'

'

'

'

'

6.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Series Four Preferred Units Redeemed

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

861,400

'

'

'

'

'

'

'

'

'

Operating Units liquidation preference (in dollars per share)

'

'

'

'

'

'

$38.10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OP Units for each Preferred Unit (in shares)

'

'

'

1.312336

'

'

1.312336

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Dates Series Two Preferred holders can require Operating Partnership to redeem their units for cash

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12-May-14

Number of holders exercising redemption rights

'

'

'

'

'

'

0

'

'

'

'

0

0

0

0

'

'

'

'

'

'

'

'

'

'

'

Units converted (in shares)

'

'

'

'

329,881

117,047

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

432,914

153,605

'

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

'

'

'

'

'

'

'

$0.85

$0.85

$0.85

$0.85

'

'

'

'

'

'

'

$0.25

'

$0.25

$0.25

$0.25

'

'

'

Series Four Preferred Units

'

'

360,126

'

'

'

'

'

'

'

'

'

'

'

'

'

'

360,126

'

'

'

'

'

'

'

'

Series Four Preferred Units Annual Dividend Payable Rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.00%

'

2.00%

'

'

'

'

'

'

'

'

Preferred Units Liquidation Preference

'

'

'

$50

'

'

$50

'

'

'

'

'

'

'

'

$50

$50

$50

'

'

'

'

'

'

'

'

First opportunity to redeem Series Four Preferred Units (in days)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

30

'

'

'

'

'

'

Redeemable preferred units of the Operating Partnership

$51,312

$110,876

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Noncontrolling_Interests_Redee1

Noncontrolling Interests (Redeemable Preferred Units) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]	'	'	'
Beginning Balance	$110,876	'	'
Net income	6,046	3,497	3,339
Redemption of redeemable preferred units (Series Four Preferred Units)	-43,070	-18,329	0
Conversion of redeemable preferred units (Series Two Preferred Units) to common units	16,494	5,852	'
Ending Balance	51,312	110,876	'
Redeemable Preferred Units [Member]	'	'	'
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]	'	'	'
Beginning Balance	110,876	55,652	55,652
Issuance of redeemable preferred units (Series Four Preferred Units	'	79,405	'
Net income	6,046	3,497	3,339
Distributions	-6,046	-3,497	-3,339
Redemption of redeemable preferred units (Series Four Preferred Units)	-43,070	-18,329	'
Conversion of redeemable preferred units (Series Two Preferred Units) to common units	-16,494	-5,852	'
Ending Balance	$51,312	$110,876	$55,652

Noncontrolling_Interests_Redee2

Noncontrolling Interests Redeemable interest in property partnerships (narrative) (Details) (Fountain Square [Member], USD $)	0 Months Ended
	Oct. 04, 2012
Fountain Square [Member]	'
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'
Aggregate purchase price	$385,000,000
Debt recorded upon consolidation	211,300,000
Ownership Percentage	50.00%
Consideration paid	87,000,000
Ownership Percentage by Parent	50.00%
Future Fixed Price to Acquire Remaining Portion of Joint venture	$102,000,000
Fixed Price Option Expiration Date	31-Jan-16

Noncontrolling_Interests_Redee3

Noncontrolling Interests Redeemable Property Partnerships (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]	'	'
Beginning Balance	$97,558	$0
Acquisition Date Fair Value of Redeemable Interest	'	98,787
Net Loss	-1,839	-719
Distributions	-4,585	-3,032
Adjustment to Reflect Redeemable Interest at Redemption Value	8,475	2,522
Ending Balance	$99,609	$97,558

Common_Units_Narrative_Details

(Common Units) (Narrative) (Details) (USD $)

Aug. 13, 2008

Oct. 31, 2013

Jul. 31, 2013

Apr. 30, 2013

Jan. 29, 2013

Dec. 31, 2013

Dec. 31, 2012

Nov. 27, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Nov. 27, 2013

OP Units [Member]

OP Units [Member]

OP Units [Member]

OP Units [Member]

OP Units [Member]

OP Units [Member]

OP Units [Member]

OPP Units 2011 [Member]

OPP Units 2012 [Member]

MYLTIP 2013 [Member]

OP Units [Member]

Quarter 4 2012 [Member]

Quarter 4 2012 [Member]

Quarter 1 2013 [Member]

Quarter 1 2013 [Member]

Quarter 2 2013 [Member]

Quarter 2 2013 [Member]

Quarter 3 2013 [Member]

Quarter 3 2013 [Member]

Quarter 4 2013 [Member]

Quarter 4 2013 [Member]

special dividend [Member]

Y

OP Units [Member]

OP Units [Member]

OP Units [Member]

OP Units [Member]

OP Units [Member]

OP Units [Member]

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Distributions Declared To OP And LTIP Units Per Unit

'

'

'

'

'

'

'

$0.65

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$2.25

Distributions Declared To OPP Units and MYLTIP Units Per Unit

'

'

'

'

'

'

'

$0.07

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OP Units for redemption (in shares)

'

'

'

'

'

929,441

1,110,660

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Redemption of OP units issued on conversion of Series Two Preferred Units (in shares)

'

'

'

'

'

432,914

153,605

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Redemption of OP units issued on conversion of LTIP Units (in shares)

'

'

'

'

'

24,028

544,729

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outperformance awards in LTIP Units (in shares)

'

'

'

'

'

'

'

'

396,500

396,150

316,325

'

'

'

'

'

'

'

'

'

'

'

'

Outperformance Awards LTIP Units distribution as percentage of OP Unit distribution prior to measurement date

'

'

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Distributions made to OP and LTIP units per unit (in dollars per share)

'

$0.65

$0.65

$0.65

$0.65

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Distribution paid to outperformance awards, OPP Units and MYLTIP Units (in dollars per share)

'

$0.07

$0.07

$0.07

$0.07

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Distribution Made to Limited Partner, Date of Record

'

'

'

'

'

'

'

'

'

'

'

'

'

31-Dec-12

'

29-Mar-13

'

28-Jun-13

'

30-Sep-13

'

31-Dec-13

'

Dividend payable date

'

'

'

'

'

'

'

'

'

'

'

'

29-Jan-13

29-Jan-13

30-Apr-13

30-Apr-13

31-Jul-13

31-Jul-13

31-Oct-13

31-Oct-13

29-Jan-14

29-Jan-14

'

Dividends Payable, Date Declared

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

27-Nov-13

27-Nov-13

'

Restriction on redemption of OP Unit to Common Stock (in years)

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Redemption of OP Unit equivalence to Common Stock (in shares)

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common units of operating partnership if converted value

'

'

'

'

'

$1,700,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Value of Series Two Preferred Units assuming conversion

'

'

'

'

'

$87,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Closing price of common stock (in dollars per share)

$97.98

'

'

'

'

'

'

'

'

'

'

$100.37

'

'

'

'

'

'

'

'

'

'

'

Noncontrolling_Interests_Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) (USD $)	12 Months Ended			0 Months Ended					0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 26, 2013	Feb. 26, 2013	Feb. 07, 2013	31-May-13	Oct. 09, 2013	31-May-13
				Transbay Tower [Member]	Transbay Tower [Member]	Transbay Tower [Member]	767 5th Avenue (The General Motors Building) [Member]	Time Square Tower [Member]	767 5th Avenue (The General Motors Building) [Member]
				floor			sqft	sqft	partners
				sqft
Noncontrolling Interest [Line Items]	'	'	'	'	'	'	'	'	'
Partners Joint Venture Ownership Percentage	'	'	'	'	5.00%	50.00%	40.00%	'	'
Ownership Percentage	'	'	'	'	95.00%	'	'	'	'
Number of floors in building	'	'	'	60	'	'	'	'	'
Net Rentable Area	'	'	'	1,400,000	'	'	1,800,000	1,246,000	'
Payments to Acquire Land	'	'	'	$192,000,000	'	'	'	'	'
Number of Joint Venture Partners	'	'	'	'	'	'	'	'	2
Noncontrolling interest in property partnerships recorded upon consolidation	480,861,000	0	0	'	'	'	480,861,000	'	'
ownership interest sold (percent)	'	'	'	'	'	'	'	45.00%	'
Net Contractual Sales Price	'	'	'	'	'	'	'	684,000,000	'
Proceeds from sale of an interest in a real estate asset	'	'	'	'	'	'	'	673,100,000	'
Portion allocation to noncontrolling interest based on carrying value of the total equity of the property prior to the sale	'	'	'	'	'	'	'	243,500,000	'
Difference between net cash proceeds received and noncontrolling interest recognized	'	'	'	'	'	'	'	429,600,000	'
Property partnerships	$726,132,000	($1,964,000)	'	'	'	'	'	'	'

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)

0 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

3 Months Ended

12 Months Ended

Oct. 31, 2013

Jul. 31, 2013

Apr. 30, 2013

Mar. 27, 2013

Jan. 29, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Nov. 27, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 27, 2018

Dec. 31, 2013

Nov. 15, 2013

Aug. 15, 2013

15-May-13

Mar. 31, 2014

Mar. 27, 2018

Dec. 31, 2013

Nov. 27, 2013

Mar. 27, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Nov. 27, 2013

Mar. 31, 2014

Atm Program [Member]

Issued in conjunction with debt exchange for 3.75% exchangeable senior notes [Member]

Quarter 4 2012 [Member]

Quarter 1 2013 [Member]

Quarter 2 2013 [Member]

Quarter 3 2013 [Member]

Quarter 4 2013 [Member]

Depositary shares of Series B Cumulative Redeemable Preferred [Member]

Depositary shares of Series B Cumulative Redeemable Preferred [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

special dividend [Member]

depositary shares [Member]

Quarter 2 2013 [Member]

Quarter 3 2013 [Member]

Quarter 4 2013 [Member]

Quarter 1 2014 [Member]

Series B Cumulative Redeemable Preferred Stock [Member]

Class of Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Ratio of depository shares to shares of Series B Preferred Stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.01

'

'

'

'

'

'

'

Common stock, shares outstanding

'

'

'

'

'

152,983,101

151,601,209

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'

'

'

'

'

'

'

$600,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

At the market stock offering program remaining amount available for issuance

'

'

'

'

'

'

'

'

'

305,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares of Common Stock upon the exercise of options to purchase Common Stock by certain employees

'

'

'

'

'

0

22,823

316,159

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'

'

'

929,441

1,110,660

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Dividend payable date

'

'

'

'

'

'

'

'

'

'

'

29-Jan-13

30-Apr-13

31-Jul-13

31-Oct-13

29-Jan-14

'

'

'

'

'

'

'

'

'

'

'

15-May-13

15-Aug-13

15-Nov-13

18-Feb-14

'

'

Dividends Payable, Amount Per Share

'

'

'

'

'

'

'

'

$0.65

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$32.81

'

'

'

'

'

'

$2.25

'

Dividend paid on common stock (in dollars per share)

$0.65

$0.65

$0.65

'

$0.65

'

'

'

'

'

'

'

'

'

'

'

'

'

$32.81

$32.81

$32.81

'

'

'

'

'

'

'

'

'

'

'

'

Dividend shareholder of record date

'

'

'

'

'

'

'

'

'

'

'

31-Dec-12

29-Mar-13

28-Jun-13

30-Sep-13

31-Dec-13

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7-Feb-14

'

'

Dividends Payable, Date Declared

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

27-Nov-13

'

'

'

'

'

'

'

'

'

'

'

'

'

'

27-Nov-13

'

'

Preferred stock, shares outstanding

'

'

'

'

'

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

80,000

'

80,000

'

'

0

'

'

'

'

'

8,000,000

Preferred Stock, Dividend Rate, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.25%

'

'

'

'

'

'

'

'

'

'

'

Series B Liquidation Preference Per Share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$25

$25

'

'

'

'

$2,500

$2,500

'

'

$0

'

'

'

'

'

'

Proceeds from Issuance of Preferred Stock and Preference Stock

'

'

'

$193,600,000

'

$193,623,000

$0

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock Issued During Period, Shares, New Issues

'

'

'

'

'

'

'

'

'

'

419,116

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Coupon/Stated Rate

'

'

'

'

'

3.63%

'

'

'

'

3.75%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Future_Minimum_Rents_Schedule_

Future Minimum Rents Schedule of Future Minimum Rents Payable for Operating Leases (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Future Minimum Rents [Abstract]	'
2014	$1,716,754
2015	1,706,282
2016	1,660,890
2017	1,510,645
2018	1,342,157
Thereafter	$6,674,466

Future_Minimum_Rents_Narrative

Future Minimum Rents Narrative (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	tenants	tenants	tenants
Future Minimum Rent [Line Items]	'	'	'
Number Of Tenants Above Concentration Amount.	0	0	0
Concentration Risk, Percentage	10.00%	10.00%	10.00%
Minimum [Member]	'	'	'
Future Minimum Rent [Line Items]	'	'	'
Initial Term Lease Expiration Date	'2014	'	'
Maximum [Member]	'	'	'
Future Minimum Rent [Line Items]	'	'	'
Initial Term Lease Expiration Date	'2048	'	'

Segment_Information_Schedule_O

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'
Rental Revenue: Class A Office	$1,987,671	$1,715,425	$1,606,655
Rental Revenue: Office/Technical	55,525	39,218	41,585
Rental Revenue: Residential	22,318	20,568	6,617
Rental Revenue: Hotel	40,330	37,915	34,529
Rental Revenue Total	2,105,844	1,813,126	1,689,386
Rental Revenue: % of Grand Totals	100.00%	100.00%	100.00%
Rental Expenses: Class A Office	716,049	617,482	555,664
Rental Expenses: Office/Technical	14,777	10,614	11,525
Rental Expenses: Residential	12,130	10,992	5,479
Rental Expenses: Hotel	28,447	28,120	26,128
Rental Expenses: Total	771,403	667,208	598,796
Rental Expenses: % Of Grand Totals	100.00%	100.00%	100.00%
Net operating Income	1,334,441	1,145,918	1,090,590
Net operating Income: % of Grand Totals	100.00%	100.00%	100.00%
Boston [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Rental Revenue: Class A Office	665,991	617,652	537,743
Rental Revenue: Office/Technical	22,617	22,460	25,349
Rental Revenue: Residential	4,395	3,936	985
Rental Revenue: Hotel	40,330	37,915	34,529
Rental Revenue Total	733,333	681,963	598,606
Rental Revenue: % of Grand Totals	34.82%	37.61%	35.43%
Rental Expenses: Class A Office	259,997	242,904	206,469
Rental Expenses: Office/Technical	6,879	6,499	7,245
Rental Expenses: Residential	1,823	1,675	521
Rental Expenses: Hotel	28,447	28,120	26,128
Rental Expenses: Total	297,146	279,198	240,363
Rental Expenses: % Of Grand Totals	38.52%	41.85%	40.14%
Net operating Income	436,187	402,765	358,243
Net operating Income: % of Grand Totals	32.69%	35.15%	32.85%
New York [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Rental Revenue: Class A Office	725,566	543,194	521,439
Rental Revenue: Office/Technical	0	0	0
Rental Revenue: Residential	0	0	0
Rental Revenue: Hotel	0	0	0
Rental Revenue Total	725,566	543,194	521,439
Rental Revenue: % of Grand Totals	34.46%	29.96%	30.87%
Rental Expenses: Class A Office	251,640	187,987	181,269
Rental Expenses: Office/Technical	0	0	0
Rental Expenses: Residential	0	0	0
Rental Expenses: Hotel	0	0	0
Rental Expenses: Total	251,640	187,987	181,269
Rental Expenses: % Of Grand Totals	32.62%	28.18%	30.27%
Net operating Income	473,926	355,207	340,170
Net operating Income: % of Grand Totals	35.51%	31.00%	31.19%
San Francisco [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Rental Revenue: Class A Office	214,755	208,177	207,003
Rental Revenue: Office/Technical	17,259	494	0
Rental Revenue: Residential	0	0	0
Rental Revenue: Hotel	0	0	0
Rental Revenue Total	232,014	208,671	207,003
Rental Revenue: % of Grand Totals	11.02%	11.51%	12.25%
Rental Expenses: Class A Office	77,905	75,542	72,122
Rental Expenses: Office/Technical	3,708	149	0
Rental Expenses: Residential	0	0	0
Rental Expenses: Hotel	0	0	0
Rental Expenses: Total	81,613	75,691	72,122
Rental Expenses: % Of Grand Totals	10.58%	11.34%	12.05%
Net operating Income	150,401	132,980	134,881
Net operating Income: % of Grand Totals	11.27%	11.60%	12.37%
Washington, DC [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Rental Revenue: Class A Office	381,359	346,402	340,470
Rental Revenue: Office/Technical	15,649	16,264	16,236
Rental Revenue: Residential	17,923	16,632	5,632
Rental Revenue: Hotel	0	0	0
Rental Revenue Total	414,931	379,298	362,338
Rental Revenue: % of Grand Totals	19.70%	20.92%	21.45%
Rental Expenses: Class A Office	126,507	111,049	95,804
Rental Expenses: Office/Technical	4,190	3,966	4,280
Rental Expenses: Residential	10,307	9,317	4,958
Rental Expenses: Hotel	0	0	0
Rental Expenses: Total	141,004	124,332	105,042
Rental Expenses: % Of Grand Totals	18.28%	18.63%	17.54%
Net operating Income	$273,927	$254,966	$257,296
Net operating Income: % of Grand Totals	20.53%	22.25%	23.59%

Segment_Information_Schedule_O1

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Development and management services income	'	'	'	'	'	'	'	'	$29,695	$34,060	$33,406
Income from unconsolidated joint ventures	'	'	'	'	'	'	'	'	75,074	49,078	85,896
Gains on consolidation of joint ventures	'	'	'	'	'	'	'	'	385,991	0	0
Interest and other income	'	'	'	'	'	'	'	'	8,310	10,091	5,358
Gains (losses) from investments in securities	'	'	'	'	'	'	'	'	2,911	1,389	-443
Gains (losses) from early extinguishments of debt	'	'	'	'	'	'	'	'	122	-4,453	-1,494
Income from discontinued operations	'	'	'	'	'	'	'	'	8,022	9,806	10,876
Gain on sale of real estate from discontinued operations	'	'	'	'	'	'	'	'	112,829	36,877	0
Gain on forgiveness of debt from discontinued operations	'	'	'	'	'	'	'	'	20,182	0	0
General and administrative expense	'	'	'	'	'	'	'	'	115,329	90,129	87,101
Transaction costs	'	'	'	'	'	'	'	'	1,744	3,653	1,987
Depreciation and amortization expense	'	'	'	'	'	'	'	'	560,637	445,875	429,742
Interest expense	'	'	'	'	'	'	'	'	446,880	410,970	391,533
Impairment loss	'	'	'	'	'	'	'	'	8,306	0	0
Impairment loss from discontinued operations	'	'	'	'	'	'	'	'	3,241	0	0
Noncontrolling interest in property partnerships	'	'	'	'	'	'	'	'	1,347	3,792	1,558
Noncontrolling interest-redeemable preferred units of the Operating Partnership	'	'	'	'	'	'	'	'	6,046	3,497	3,339
Noncontrolling interest-common units of the Operating Partnership	'	'	'	'	'	'	'	'	70,085	30,125	35,007
Noncontrolling interest in discontinued operations-common units of the Operating Partnership	'	'	'	'	'	'	'	'	14,151	5,075	1,243
Net income attributable to Boston Properties, Inc.	88,719	152,677	452,417	47,854	65,400	57,249	118,559	48,454	749,811	289,650	272,679
Business Intersegment, Eliminations [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net Operating Income	'	'	'	'	'	'	'	'	1,334,441	1,145,918	1,090,590
Development and management services income	'	'	'	'	'	'	'	'	29,695	34,060	33,406
Income from unconsolidated joint ventures	'	'	'	'	'	'	'	'	75,074	49,078	85,896
Gains on consolidation of joint ventures	'	'	'	'	'	'	'	'	385,991	0	0
Interest and other income	'	'	'	'	'	'	'	'	8,310	10,091	5,358
Gains (losses) from investments in securities	'	'	'	'	'	'	'	'	2,911	1,389	-443
Gains (losses) from early extinguishments of debt	'	'	'	'	'	'	'	'	122	-4,453	-1,494
Income from discontinued operations	'	'	'	'	'	'	'	'	8,022	9,806	10,876
Gain on sale of real estate from discontinued operations	'	'	'	'	'	'	'	'	112,829	36,877	0
Gain on forgiveness of debt from discontinued operations	'	'	'	'	'	'	'	'	20,182	0	0
General and administrative expense	'	'	'	'	'	'	'	'	115,329	90,129	87,101
Transaction costs	'	'	'	'	'	'	'	'	1,744	3,653	1,987
Depreciation and amortization expense	'	'	'	'	'	'	'	'	560,637	445,875	429,742
Interest expense	'	'	'	'	'	'	'	'	446,880	410,970	391,533
Impairment loss	'	'	'	'	'	'	'	'	8,306	0	0
Impairment loss from discontinued operations	'	'	'	'	'	'	'	'	3,241	0	0
Noncontrolling interest in property partnerships	'	'	'	'	'	'	'	'	1,347	3,792	1,558
Noncontrolling interest-redeemable preferred units of the Operating Partnership	'	'	'	'	'	'	'	'	6,046	3,497	3,339
Noncontrolling interest-common units of the Operating Partnership	'	'	'	'	'	'	'	'	70,085	30,125	35,007
Noncontrolling interest in discontinued operations-common units of the Operating Partnership	'	'	'	'	'	'	'	'	14,151	5,075	1,243
Net income attributable to Boston Properties, Inc.	'	'	'	'	'	'	'	'	$749,811	$289,650	$272,679

Segment_Information_Segment_re

Segment Information Segment reporting (narrative) (Details) (USD $)	12 Months Ended									0 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	31-May-13
				Princeton [Member]	Princeton [Member]	Princeton [Member]	San Francisco [Member]	San Francisco [Member]	San Francisco [Member]	767 5th Avenue (The General Motors Building) [Member]
										partners
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'
Reclassification between general and administrative expense and real estate operating expenses	$8.10	$7.70	$7.50	$1.40	$1.60	$1.50	$6.70	$6.10	$6	'
Number of Joint Venture Partners	'	'	'	'	'	'	'	'	'	2

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic Earnings:	'	'	'	'	'	'	'	'	'	'	'
Income from continuing operations attributable to Boston Properties, Inc., Income (Numerator)	'	'	'	'	'	'	'	'	$618,113	$248,042	$263,046
Net income attributable to Boston Properties Inc., Shares (Denominator)	'	'	'	'	'	'	'	'	152,201	150,120	145,693
Income from continuing operations attributable to Boston Properties, Inc., Per Share Amount (in dollars per share)	'	'	'	'	'	'	'	'	$4.06	$1.65	$1.80
Discontinued operations attributable to Boston Properties, Inc., Income (Numerator)	'	'	'	'	'	'	'	'	123,641	41,608	9,633
Discontinued operations attributable to Boston Properties, Inc., Per Share Amount (in dollars per share)	'	'	'	'	'	'	'	'	$0.81	$0.28	$0.07
Net Income Loss Available To Boston Properties, Inc. Common Stockholders	'	'	'	'	'	'	'	'	741,594	289,650	272,679
Allocation of undistributed earnings to participating securities	'	'	'	'	'	'	'	'	-160	'	'
Allocation of undistributed earnings to participating securities (in shares)	'	'	'	'	'	'	'	'	$0	'	'
Net income attributable to Boston Properties Inc., Per Share Amount (in dollars per share)	$0.58	$1	$2.95	$0.32	$0.43	$0.38	$0.79	$0.33	$4.87	$1.93	$1.87
Effect of Dilutive Securities:	'	'	'	'	'	'	'	'	'	'	'
Stock Based Compensation and Exchangeable Senior Notes, Income (Numerator)	'	'	'	'	'	'	'	'	0	0	0
Stock Based Compensation and Exchangeable Senior Notes, Shares (Denominator)	'	'	'	'	'	'	'	'	320	591	525
Stock Based Compensation and Exchangeable Senior Notes Per Share Amount	'	'	'	'	'	'	'	'	($0.01)	($0.01)	($0.01)
Diluted Earnings:	'	'	'	'	'	'	'	'	'	'	'
Diluted Earnings: Net income, Income (Numerator)	'	'	'	'	'	'	'	'	$741,594	$289,650	$272,679
Diluted Earnings: Net income, Shares (Denominator)	'	'	'	'	'	'	'	'	152,521	150,711	146,218
Diluted Earnings: Net income, Per Share Amount (in dollars per share)	$0.58	$1	$2.94	$0.31	$0.43	$0.38	$0.78	$0.33	$4.86	$1.92	$1.86

Employee_Benefit_Plans_Details

Employee Benefit Plans (Details) (USD $)	12 Months Ended			156 Months Ended	168 Months Ended	180 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 1999
	M			Y
				age
Employee Benefit Plans [Abstract]	'	'	'	'	'	'
Eligibility Period For 401K Savings Plan In Months	3	'	'	'	'	'
Employer Matching Contribution, Percent of Match	'	'	'	'	200.00%	200.00%
Employer Matching Contribution, Percent of Employees' Gross Pay	'	'	'	'	3.00%	2.00%
Maximum Eligible Earnings As Established By IRS For Matching Contributions	$255,000	$250,000	$245,000	'	'	'
Employer Contribution Amount	3,400,000	3,200,000	3,100,000	'	'	'
Years Of Service For Supplemental Retirement Contribution	'	'	'	10	'	'
Age Of Employee For Supplemental Retirement Contribution	'	'	'	40	'	'
Annual Supplemental Retirement Contribution And Credit Total.	60,000	78,000	62,000	'	'	'
Separate Unrestricted Cash For Deferred Compensation Plan.	16,600,000	12,200,000	'	16,600,000	16,600,000	'
Deferred Compensation Liability	$16,600,000	$12,200,000	'	$16,600,000	$16,600,000	'

Stock_Option_and_Incentive_Pla2

Stock Option and Incentive Plan (Narrative) (Details) (USD $)

Jan. 31, 2014

Mar. 11, 2013

15-May-12

Jan. 28, 2013

Dec. 31, 2013

Jan. 28, 2013

Jan. 28, 2013

Jan. 28, 2013

Jan. 28, 2013

Jan. 28, 2013

Jan. 28, 2013

Apr. 02, 2013

Sep. 30, 2013

Dec. 31, 2013

Mar. 11, 2013

Jan. 28, 2013

Jan. 28, 2013

Jan. 28, 2013

Jan. 28, 2013

Jan. 28, 2013

Two Thousand Twelve Stock Option and Incentive Plan [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

Exceptional [Member]

Minimum [Member]

Maximum [Member]

Threshold [Member]

Target [Member]

High [Member]

Chief Executive Officer [Member]

Board of Directors Chairman [Member]

Board of Directors Chairman [Member]

Board of Directors Chairman [Member]

Cohen & Steers Realty Majors Portfolio Index [Member]

NAREIT Office Index adjusted [Member]

MYLTIP Vesting 2016 [Member]

MYLTIP Vesting 2017 [Member]

MYLTIP Vesting 2018 [Member]

Y

Y

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

indices

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Tiers

'

'

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

TRS measurement (in years)

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

25.00%

50.00%

Vesting Date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4-Feb-16

4-Feb-17

4-Feb-18

Distributions percent before measurement date

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Additional Shares Authorized

'

'

13,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other Than Stock Options Awards Conversion Ratio

'

'

2.32

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock Option Awards Conversion Ratio

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock Option and Incentive Plan Term Period

'

'

10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted Percentage of Index Used to Compare to TRS

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

50.00%

'

'

'

Potential Awards Earned

'

'

'

'

'

'

$0

$30,700,000

'

'

'

'

'

'

'

'

'

'

'

'

Indices Used to Compare TRS

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount of Each Tier

'

'

'

'

'

30,700,000

'

'

5,100,000

10,200,000

20,500,000

'

'

'

'

'

'

'

'

'

Percentage of annualized TRS for Reduction of Earned Awards

'

'

'

2.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage to Cause Some Awards to be Earned Even if on a Relative Basis it Would Not Result in any Earned Awards

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

LTIP units issued (in shares)

109,718

'

'

'

'

'

'

'

'

'

'

24,231

'

'

'

'

'

'

'

'

MYLTIP units issued

'

'

'

'

318,926

'

'

'

'

'

'

38,926

'

'

'

'

'

'

'

'

Non-qualified stock options issued (in shares)

'

'

'

'

'

'

'

'

'

'

'

50,847

'

'

'

'

'

'

'

'

Cash Payment Related to Transition Agreement

'

6,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Target Equity Award Compensation Associated with Transition Agreement

'

'

'

'

'

'

'

'

'

'

'

'

'

'

11,100,000

'

'

'

'

'

Compensation Expense associated with Transition Agreement

'

'

'

'

'

'

'

'

'

'

'

'

'

13,800,000

'

'

'

'

'

'

Acceleration of Stock Based Compensation in Association with Transition Agreement

'

'

'

'

'

'

'

'

'

'

'

'

12,900,000

'

'

'

'

'

'

'

Value of MYLTIP Awards

'

'

'

$9,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

MYLTIP Value Amortized Into Earnings, Years

'

'

'

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock_Option_and_Incentive_Pla3

Stock Option and Incentive Plan (Restricted Stock) (Narrative) (Details) (USD $)

12 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jan. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Jan. 28, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jan. 31, 2014

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Stock [Member]

LTIP Units [Member]

LTIP Units [Member]

LTIP Units [Member]

OPP Units Two Thousand And Eight [Member]

LTIPs And Restricted Stock [Member]

LTIPs, OPP and MYLTIP Awards [Member]

OPP Units 2012 [Member]

MYLTIP 2013 [Member]

MYLTIP 2013 [Member]

Non Qualified Stock Options [Member]

Non Qualified Stock Options [Member]

Non Qualified Stock Options [Member]

OPP Units 2011 [Member]

OPP Units 2011 [Member]

Unvested 2011 and 2012 OPP Units [Member]

Non-Qualified Employee Stock Purchase Plan [Member]

Non-Qualified Employee Stock Purchase Plan [Member]

Non-Qualified Employee Stock Purchase Plan [Member]

Board of Directors Chairman [Member]

Executive Vice President [Member]

Y

VestingInstallments

Y

D

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares issued

153,062,001

151,680,109

'

'

36,730

20,756

19,030

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

LTIP units issued (in shares)

'

'

'

109,718

'

'

'

184,733

174,650

190,067

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Non-qualified stock options issued (in shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

252,220

186,007

146,844

'

'

'

'

'

'

'

'

2012 OPP units issued (in shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

400,000

'

'

'

'

'

'

400,000

'

'

'

'

'

'

MYLTIP units issued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

318,926

'

'

'

'

'

'

'

'

'

'

'

Employee and director payment per share (in dollars per share)

'

'

'

'

$0.01

'

'

'

'

'

'

'

$0.25

'

'

'

'

'

'

$0.25

'

'

'

'

'

'

'

Vesting annual installments

'

'

'

'

'

'

'

'

'

'

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock-based compensation associated with restricted stock, non-qualified options, LTIP Units, 2008 OPP Units, 2011 OPP Units, and 2012 OPP Units

$43,900,000

$28,300,000

$28,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$21,500,000

$2,700,000

Compensation Expense associated with Transition Agreement

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

13,800,000

'

TRS measurement (in years)

'

'

'

'

'

'

'

'

'

'

3

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

Accelerated Compensation Expenses Related To 2008 Opp Units

'

'

4,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unrecognized compensation expenses

'

'

'

'

'

'

'

'

'

'

'

17,600,000

'

'

'

'

'

'

'

'

'

11,100,000

'

'

'

'

'

Weighted-average period (years)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'2 years 8 months 12 days

'

'

'

'

'

Value of shares of common stock

1,530,000

1,516,000

'

'

3,900,000

2,200,000

1,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Employee's weighted average cost per share (in dollars per share)

'

'

'

'

$105.30

$107.31

$93.40

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Value of LTIP units issued

'

'

'

'

'

'

'

17,800,000

17,300,000

16,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Per unit fair value weighted-average (in dollars per share)

'

'

'

'

'

'

'

$96.13

$98.83

$86.74

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected life assumed to calculate per unit fair value per LTIP unit (years)

'

'

'

'

'

'

'

'5 years 8 months 12 days

'5 years 9 months 19 days

'5 years 9 months 19 days

'

'

'

'

'

'

'6 years 0 months 0 days

'5 years 4 months 24 days

'6 years 0 months 0 days

'

'

'

'

'

'

'

'

Risk-free rate

'

'

'

'

'

'

'

1.03%

0.94%

2.22%

'

'

'

'

'

'

1.11%

0.92%

2.37%

'

'

'

'

'

'

'

'

Expected price volatility

'

'

'

'

'

'

'

26.00%

29.10%

30.00%

'

'

'

'

'

'

26.00%

28.40%

35.00%

'

'

'

'

'

'

'

'

Expected dividend rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3.00%

2.90%

3.00%

'

'

'

'

'

'

'

'

Weighted-average grant date fair value (in dollars per share)

$104.50

$107.23

$92.71

'

'

'

'

'

'

'

'

'

'

'

'

'

$18.46

$19.50

$24.67

'

'

'

'

'

'

'

'

Weighted-average exercise price (in dollars per share)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$105.10

$107.23

$92.71

'

'

'

'

'

'

'

'

Exercisable, Weighted Average Exercise Price

'

$98.92

$54.32

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum Common Stock available for issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

250,000

'

'

'

'

Employee Common Stock options, percent of average closing price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

Number Of Days Used In Calculation, Average Closing Prices Of Common Stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10

'

'

'

'

Shares issued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,442

7,406

6,356

'

'

Shares issued, weighted-average purchase price per share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$89.65

$86.52

$80.13

'

'

Number Exercisable at 12/31/2010

'

91,496

13,633

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total intrinsic value of the outstanding and exercisable stock options

$800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock_Option_and_Incentive_Pla4

Stock Option and Incentive Plan Schedule of Stock Options Status (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'	'	'
Beginning Outstanding, Shares	294,527	155,623	324,938
Beginning Oustanding, Weighted Average Exercise Price	$101.06	$89.35	$32.65
Granted, Shares	252,220	186,007	146,844
Granted, Weighted Average Exercise Price	$104.50	$107.23	$92.71
Exercised, Shares	0	-22,823	-316,159
Exercised, Weighted Averge Exercise Price	$0	$72.42	$32.63
Canceled, Shares	0	-24,280	0
Canceled, Weighted Average Exercise Price	$0	$100.15	$0
Special dividend adjustment (shares)	12,076	'	'
Special dividend adjustment weighted average exercise price	$100.44	'	'
Ending Outstanding, Shares	558,823	294,527	155,623
Ending Oustanding, Weighted Average Exercise Pric	$100.43	$101.06	$89.35

Stock_Option_and_Incentive_Pla5

Stock Option and Incentive Plan Schedule of Stock Options Outstanding (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
					Exercise Price of $90.71 [Member]	Exercise Price of $99.94 [Member]	Exercise Price of $102.83 [Member]	Exercise Price of $105.25 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'	'	'	'	'
Exercise Price	'	'	'	'	$90.71	$99.94	$102.83	$105.25
Weighted Average Remaining Contractual Life (Years)	'	'	'	'	'7 years 1 month 6 days	'9 years 3 months 18 days	'9 years 1 month 6 days	'8 years 1 month 6 days
Number Outstanding at 12/31/13,	558,823	294,527	155,623	324,938	131,837	51,971	205,821	169,194
Outstanding, Weighted Average Exercise Price	$100.43	$101.06	$89.35	$32.65	$90.71	$99.94	$102.83	$105.25
Number Exercisable at 12/31/2013	'	91,496	13,633	'	80,240	0	48,026	71,602
Exercisable, Weighted Average Exercise Price	'	$98.92	$54.32	'	$90.71	$0	$102.83	$105.25

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)

12 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

76 Months Ended

110 Months Ended

186 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jul. 24, 2007

Jun. 30, 1998

Dec. 31, 2013

Dec. 31, 2007

Dec. 31, 2004

Oct. 20, 2004

Dec. 31, 2013

Dec. 31, 2013

nonemployeedirectors

New York regional manager [Member]

Brother of Executive Vice President [Member]

Brother of Executive Vice President [Member]

Brother of Executive Vice President [Member]

Former Director [Member]

Former Director [Member]

Former Director [Member]

Former Director [Member]

Former Director [Member]

Affiliate of Former Director [Member]

Affiliate of Former Director [Member]

Affiliate of Former Director [Member]

sqft

Y

Related Party Transaction [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate leasing commissions paid to related parties

'

'

$592,000

$868,000

$1,306,000

$671,000

'

'

'

'

'

'

'

'

Related Party Acquisition Date

'

'

'

'

'

'

24-Jul-07

30-Jun-98

'

'

'

'

'

'

Square Feet of Development

'

'

'

'

'

'

'

'

'

'

'

'

'

2,000,000

Purchase price per rentable square feet of property developed.

'

'

'

'

'

'

'

'

'

'

'

'

'

20

Target Annual Return Minimum

'

'

'

'

'

'

'

'

'

'

'

10.50%

'

'

Target Annual Return Maximum.

'

'

'

'

'

'

'

'

'

'

'

11.00%

'

'

Annual Development Agreement Payments.

'

'

'

'

'

'

'

'

125,000

'

'

'

'

'

Development Agreement Payment Made For 1998 Through 2004

'

'

'

'

'

'

'

'

'

'

750,000

'

'

'

Aggregate Fixed Rentable Per Square Foot Of Developed Property.

'

'

'

'

'

'

'

'

'

'

'

'

10.5

'

Adjustment To Aggregate Fixed Amount Per Square Foot Of Developed Property

'

'

'

'

'

'

'

'

'

'

'

'

5.5

'

Term of Development Agreement., Years

'

'

'

'

'

'

'

'

'

'

'

'

'

20

Number Of Non employee Directors Electing To Receive Deferred Stock Units

6

'

'

'

'

'

'

'

'

'

'

'

'

'

Purchase Price of Land Parcel

'

'

'

'

'

'

'

'

'

$3,100,000

'

'

'

'

Deferred Stock Units Outstanding

83,995

76,682

'

'

'

'

'

'

'

'

'

'

'

'

Selected_Interim_Financial_Inf2

Selected Interim Financial Information (unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Total revenue	$576,199	$571,481	$510,033	$477,826	$478,047	$464,220	$466,197	$438,722	$2,135,539	$1,847,186	$1,722,792
Income from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	79,395	82,311	503,446	38,496	74,251	63,331	94,795	53,079	703,648	285,456	302,950
Net income attributable to Boston Properties, Inc.	$88,719	$152,677	$452,417	$47,854	$65,400	$57,249	$118,559	$48,454	$749,811	$289,650	$272,679
Income attributable to Boston Properties Inc., per share basic	$0.58	$1	$2.95	$0.32	$0.43	$0.38	$0.79	$0.33	$4.87	$1.93	$1.87
Income attributable to Boston Properties Inc., per share diluted	$0.58	$1	$2.94	$0.31	$0.43	$0.38	$0.78	$0.33	$4.86	$1.92	$1.86

Subsequent_Events_subsequent_E

Subsequent Events subsequent Events (Details) (USD $)

12 Months Ended

0 Months Ended

0 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jan. 31, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 31, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 27, 2014

Jan. 31, 2014

Feb. 10, 2014

Feb. 18, 2014

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

OPP Units 2011 [Member]

High [Member]

Minimum [Member]

Maximum [Member]

Threshold [Member]

Target [Member]

Exceptional [Member]

MYLTIP Vesting 2017 [Member]

MYLTIP vesting 2018 [Member]

Restricted Stock [Member]

The Avant at Reston Town Center Residential [Member]

3.625% Exchangeable Senior Notes [Member]

tiers

Cohen & Steers Realty Majors Portfolio Index [Member]

NAREIT Office Index adjusted [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

MYLTIP 2014 [Member]

apartments

Y

sqft

indices

Subsequent Event [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount of Each Tier

'

'

'

'

'

'

'

'

$26,800,000

'

'

$6,700,000

$13,400,000

$40,200,000

'

'

'

'

'

Weighted Percentage of Index Used to Compare to TRS

'

'

'

'

'

50.00%

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

Potential Awards Earned

'

'

'

'

'

'

'

'

'

0

40,200,000

'

'

'

'

'

'

'

'

Indices Used to Compare TRS

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Tiers

'

'

'

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of annualized TRS for Reduction of Earned Awards

'

'

'

'

0.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage to Cause Some Awards to be Earned Even if on a Relative Basis it Would Not Result in any Earned Awards

'

'

'

'

12.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

50.00%

'

'

'

Vesting Date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3-Feb-17

3-Feb-18

'

'

'

Distributions percent before measurement date

'

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Value of MYLTIP Awards

'

'

'

'

13,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares issued

153,062,001

151,680,109

'

'

'

'

'

'

'

'

'

'

'

'

'

'

21,455

'

'

LTIP units issued (in shares)

'

'

'

109,718

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accelerated Compensation Expenses Related To 2011 OPP Units

'

'

'

'

'

'

'

1,200,000

'

'

'

'

'

'

'

'

'

'

'

Employee and director payment per share (in dollars per share)

'

'

'

'

'

'

'

$0.25

'

'

'

'

'

'

'

'

'

'

'

Number of apartment units

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

359

'

Net Rentable Area

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

355,000

'

Coupon/Stated Rate

3.63%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3.63%

Repayments of Unsecured Debt

$0

$224,261,000

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$747,500,000

TRS measurement (in years)

'

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Real_Estate_and_Accumulated_De1

Real Estate and Accumulated Depreciation Schedule of Real Estate and Accumulated Depreciation (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Real Estate and Accumulated Depreciation [Line Items]	'		'
Type	'Office		'
Location	'Reston, VA		'
Encumbrances	$4,449,734,000	[1]	'
Original Land	4,303,172,000		'
Original Building	10,631,057,000		'
Costs Capitalized Subsequent to Acquisition	4,019,372,000		'
Land and improvements	4,450,532,000		'
Buildings and Improvements	12,682,514,000		'
Land Held for Development	297,376,000		'
Development and Construction in Progress	1,523,179,000		'
Total	18,953,601,000		'
Accumulated Depreciation	3,145,701,000		'
Furniture, fixtures and equipment	25,164,000		23,441,000
Furniture, fixtures and equipment accumulated depreciation	15,870,000		'
Real Estate Aggregate Cost For Tax Purposes	14,800,000,000		'
Real Estate Aggregate Accumulated Depreciation For Tax Purposes	2,600,000,000		'
Real Estate and Accumulated Depreciation, Life Used for Depreciation	'40 years 0 months 0 days		'
Unamoritized balance of histroical fair value adjustments	191,204,000		'
767 5th Avenue (The General Motors Building) [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'767 Fifth Avenue (The General Motors Building)		'
Type	'Office		'
Location	'New York, NY		'
Encumbrances	1,463,143,000		'
Original Land	1,796,252,000		'
Original Building	1,532,654,000		'
Costs Capitalized Subsequent to Acquisition	4,481,000		'
Land and improvements	1,796,252,000		'
Buildings and Improvements	1,537,135,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	3,333,387,000		'
Accumulated Depreciation	28,901,000		'
Year(s) built / renovated	'1968		'
Depreciable Lives (Years)	'-1	[2]	'
Embarcadero Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Embarcadero Center		'
Type	'Office		'
Location	'SanB Francisco,B CA		'
Encumbrances	360,133,000		'
Original Land	179,697,000		'
Original Building	847,410,000		'
Costs Capitalized Subsequent to Acquisition	314,292,000		'
Land and improvements	195,985,000		'
Buildings and Improvements	1,145,414,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	1,341,399,000		'
Accumulated Depreciation	472,324,000		'
Year(s) built / renovated	'1970/1989		'
Depreciable Lives (Years)	'-1	[2]	'
Prudential Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Prudential Center		'
Type	'Office		'
Location	'Boston, MA		'
Original Land	92,077,000		'
Original Building	734,594,000		'
Costs Capitalized Subsequent to Acquisition	354,501,000		'
Land and improvements	107,426,000		'
Buildings and Improvements	1,057,815,000		'
Land Held for Development	15,931,000		'
Development and Construction in Progress	0		'
Total	1,181,172,000		'
Accumulated Depreciation	398,909,000		'
Year(s) built / renovated	'1965/1993/2002		'
Depreciable Lives (Years)	'-1	[2]	'
399 Park Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'399 Park Avenue		'
Type	'Office		'
Location	'New York, NY		'
Original Land	339,200,000		'
Original Building	700,358,000		'
Costs Capitalized Subsequent to Acquisition	107,604,000		'
Land and improvements	354,107,000		'
Buildings and Improvements	793,055,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	1,147,162,000		'
Accumulated Depreciation	219,938,000		'
Year(s) built / renovated	'1961		'
Depreciable Lives (Years)	'-1	[2]	'
601 Lexington Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'601 Lexington Avenue		'
Type	'Office		'
Location	'New York, NY		'
Encumbrances	722,253,000		'
Original Land	241,600,000		'
Original Building	494,782,000		'
Costs Capitalized Subsequent to Acquisition	217,155,000		'
Land and improvements	289,639,000		'
Buildings and Improvements	663,898,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	953,537,000		'
Accumulated Depreciation	205,721,000		'
Year(s) built / renovated	'1977/1997		'
Depreciable Lives (Years)	'-1	[2]	'
The John Hancock Tower And Garage [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'The John Hancock Tower and Garage		'
Type	'Office		'
Location	'Boston, MA		'
Encumbrances	652,933,000		'
Original Land	219,543,000		'
Original Building	667,884,000		'
Costs Capitalized Subsequent to Acquisition	57,420,000		'
Land and improvements	219,616,000		'
Buildings and Improvements	724,812,000		'
Land Held for Development	419,000		'
Development and Construction in Progress	0		'
Total	944,847,000		'
Accumulated Depreciation	78,366,000		'
Year(s) built / renovated	'1976		'
Depreciable Lives (Years)	'-1	[2]	'
Times Square Tower [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Times Square Tower		'
Type	'Office		'
Location	'New York, NY		'
Original Land	165,413,000		'
Original Building	380,438,000		'
Costs Capitalized Subsequent to Acquisition	85,146,000		'
Land and improvements	169,193,000		'
Buildings and Improvements	461,804,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	630,997,000		'
Accumulated Depreciation	137,934,000		'
Year(s) built / renovated	'2004		'
Depreciable Lives (Years)	'-1	[2]	'
100 Federal Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'100 Federal Street		'
Type	'Office		'
Location	'Boston, MA		'
Original Land	131,067,000		'
Original Building	435,954,000		'
Costs Capitalized Subsequent to Acquisition	6,020,000		'
Land and improvements	131,067,000		'
Buildings and Improvements	441,760,000		'
Land Held for Development	214,000		'
Development and Construction in Progress	0		'
Total	573,041,000		'
Accumulated Depreciation	29,060,000		'
Year(s) built / renovated	'1971-1975		'
Depreciable Lives (Years)	'-1	[2]	'
Carnegie Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Carnegie Center		'
Type	'Office		'
Location	'Princeton, NJ		'
Original Land	105,107,000		'
Original Building	377,259,000		'
Costs Capitalized Subsequent to Acquisition	66,866,000		'
Land and improvements	103,064,000		'
Buildings and Improvements	443,817,000		'
Land Held for Development	2,206,000		'
Development and Construction in Progress	145,000		'
Total	549,232,000		'
Accumulated Depreciation	169,587,000		'
Year(s) built / renovated	'1983-1999		'
Depreciable Lives (Years)	'-1	[2]	'
Atlantic Wharf [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Atlantic Wharf		'
Type	'Office		'
Location	'Boston, MA		'
Original Land	63,988,000		'
Original Building	454,537,000		'
Costs Capitalized Subsequent to Acquisition	11,644,000		'
Land and improvements	63,988,000		'
Buildings and Improvements	466,181,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	530,169,000		'
Accumulated Depreciation	39,697,000		'
Year(s) built / renovated	'2011		'
Depreciable Lives (Years)	'-1	[2]	'
Fountain Square [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Fountain Square		'
Type	'Office		'
Location	'Reston, VA		'
Encumbrances	226,604,000		'
Original Land	56,853,000		'
Original Building	306,298,000		'
Costs Capitalized Subsequent to Acquisition	3,877,000		'
Land and improvements	56,853,000		'
Buildings and Improvements	310,175,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	367,028,000		'
Accumulated Depreciation	15,460,000		'
Year(s) built / renovated	'1986-1990		'
Depreciable Lives (Years)	'-1	[2]	'
510 Madison Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'510 Madison Avenue		'
Type	'Office		'
Location	'New York, NY		'
Original Land	103,000,000		'
Original Building	253,665,000		'
Costs Capitalized Subsequent to Acquisition	6,309,000		'
Land and improvements	103,000,000		'
Buildings and Improvements	259,974,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	362,974,000		'
Accumulated Depreciation	15,901,000		'
Year(s) built / renovated	'2012		'
Depreciable Lives (Years)	'-1	[2]	'
599 Lexington Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'599 Lexington Avenue		'
Type	'Office		'
Location	'New York, NY		'
Encumbrances	750,000,000		'
Original Land	81,040,000		'
Original Building	100,507,000		'
Costs Capitalized Subsequent to Acquisition	123,179,000		'
Land and improvements	87,852,000		'
Buildings and Improvements	216,874,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	304,726,000		'
Accumulated Depreciation	144,094,000		'
Year(s) built / renovated	'1986		'
Depreciable Lives (Years)	'-1	[2]	'
Gateway Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Gateway Center		'
Type	'Office		'
Location	'SanB Francisco,B CA		'
Original Land	28,255,000		'
Original Building	139,245,000		'
Costs Capitalized Subsequent to Acquisition	51,330,000		'
Land and improvements	30,627,000		'
Buildings and Improvements	188,203,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	218,830,000		'
Accumulated Depreciation	80,461,000		'
Year(s) built / renovated	'1984/1986/2002		'
Depreciable Lives (Years)	'-1	[2]	'
Bay Colony Corporate Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Bay Colony Corporate Center		'
Type	'Office		'
Location	'Waltham,B MA		'
Original Land	18,789,000		'
Original Building	148,451,000		'
Costs Capitalized Subsequent to Acquisition	47,332,000		'
Land and improvements	18,789,000		'
Buildings and Improvements	195,783,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	214,572,000		'
Accumulated Depreciation	21,339,000		'
Year(s) built / renovated	'1985-1989		'
Depreciable Lives (Years)	'-1	[2]	'
South of Market and Democracy Tower [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'South of Market and Democracy Tower		'
Type	'Office		'
Location	'Reston,B VA		'
Original Land	13,603,000		'
Original Building	237,479,000		'
Costs Capitalized Subsequent to Acquisition	9,790,000		'
Land and improvements	13,687,000		'
Buildings and Improvements	247,185,000		'
Development and Construction in Progress	0		'
Accumulated Depreciation	50,831,000		'
Year(s) built / renovated	'2008-2009		'
Depreciable Lives (Years)	'-1	[2]	'
Mountain View Research [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Mountain View Research Park		'
Type	'Office		'
Location	'Mountain View, CA		'
Original Land	106,162,000		'
Original Building	76,137,000		'
Costs Capitalized Subsequent to Acquisition	2,196,000		'
Land and improvements	106,162,000		'
Buildings and Improvements	78,333,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	184,495,000		'
Accumulated Depreciation	3,013,000		'
Year(s) built / renovated	'1977-1981/2007-2013		'
Depreciable Lives (Years)	'-1	[2]	'
2200 Pennsylvania Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'2200 Pennsylvania Avenue		'
Type	'Office		'
Location	'Washington,B DC		'
Original Building	183,541,000		'
Costs Capitalized Subsequent to Acquisition	3,767,000		'
Land and improvements	0		'
Buildings and Improvements	187,308,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	187,308,000		'
Accumulated Depreciation	18,185,000		'
Year(s) built / renovated	'2011		'
Depreciable Lives (Years)	'-1	[2]	'
One and Two Patriots Park [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'One and Two Patriots Park		'
Original Land	18,429,000		'
Original Building	126,315,000		'
Costs Capitalized Subsequent to Acquisition	34,994,000		'
Land and improvements	22,352,000		'
Buildings and Improvements	157,386,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	179,738,000		'
Accumulated Depreciation	7,032,000		'
Year(s) built / renovated	'1987/1988/2012/2013		'
Depreciable Lives (Years)	'-1	[2]	'
Reservoir Place [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Reservoir Place		'
Type	'Office		'
Location	'Waltham, MA		'
Original Land	18,605,000		'
Original Building	92,619,000		'
Costs Capitalized Subsequent to Acquisition	27,446,000		'
Land and improvements	20,118,000		'
Buildings and Improvements	118,552,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	138,670,000		'
Accumulated Depreciation	52,829,000		'
Year(s) built / renovated	'1955/1987		'
Depreciable Lives (Years)	'-1	[2]	'
3200 Zanker Road [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'3200 Zanker Road		'
Type	'Office		'
Location	'San Jose, CA		'
Original Land	36,705,000		'
Original Building	82,863,000		'
Costs Capitalized Subsequent to Acquisition	24,669,000		'
Land and improvements	36,997,000		'
Buildings and Improvements	103,496,000		'
Land Held for Development	3,744,000		'
Development and Construction in Progress	0		'
Total	144,237,000		'
Accumulated Depreciation	23,165,000		'
Year(s) built / renovated	'1988		'
Depreciable Lives (Years)	'-1	[2]	'
505 9th Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'505 9th Street		'
Type	'Office		'
Location	'Washington,B DC		'
Encumbrances	121,360,000		'
Original Land	38,885,000		'
Original Building	83,719,000		'
Costs Capitalized Subsequent to Acquisition	5,692,000		'
Land and improvements	42,082,000		'
Buildings and Improvements	86,214,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	128,296,000		'
Accumulated Depreciation	20,358,000		'
Year(s) built / renovated	'2007		'
Depreciable Lives (Years)	'-1	[2]	'
1333 New Hampshire Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'1333 New Hampshire Avenue		'
Type	'Office		'
Location	'Washington,B DC		'
Original Land	34,032,000		'
Original Building	85,660,000		'
Costs Capitalized Subsequent to Acquisition	9,061,000		'
Land and improvements	35,394,000		'
Buildings and Improvements	93,359,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	128,753,000		'
Accumulated Depreciation	30,392,000		'
Year(s) built / renovated	'1996		'
Depreciable Lives (Years)	'-1	[2]	'
Kingstowne Towne Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Kingstowne Towne Center		'
Type	'Office		'
Location	'Alexandria,B VA		'
Encumbrances	33,338,000		'
Original Land	18,021,000		'
Original Building	109,038,000		'
Costs Capitalized Subsequent to Acquisition	742,000		'
Land and improvements	18,062,000		'
Buildings and Improvements	109,739,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	127,801,000		'
Accumulated Depreciation	26,526,000		'
Year(s) built / renovated	'2003-2006		'
Depreciable Lives (Years)	'-1	[2]	'
Capital Gallery [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Capital Gallery		'
Type	'Office		'
Location	'Washington,B DC		'
Original Land	4,725,000		'
Original Building	29,565,000		'
Costs Capitalized Subsequent to Acquisition	86,993,000		'
Land and improvements	8,662,000		'
Buildings and Improvements	112,621,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	121,283,000		'
Accumulated Depreciation	50,217,000		'
Year(s) built / renovated	'1981/2006		'
Depreciable Lives (Years)	'-1	[2]	'
1330 Connecticut Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'1330 Connecticut Avenue		'
Type	'Office		'
Location	'Washington,B DC		'
Original Land	25,982,000		'
Original Building	82,311,000		'
Costs Capitalized Subsequent to Acquisition	16,286,000		'
Land and improvements	27,135,000		'
Buildings and Improvements	97,444,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	124,579,000		'
Accumulated Depreciation	29,518,000		'
Year(s) built / renovated	'1984		'
Depreciable Lives (Years)	'-1	[2]	'
601 Massachusetts Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'601 Massachusetts Avenue		'
Type	'Development		'
Location	'Washington,B DC		'
Costs Capitalized Subsequent to Acquisition	121,694,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	0		'
Development and Construction in Progress	121,694,000		'
Total	121,694,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
535 Mission [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'535 Mission Street		'
Type	'Development		'
Location	'San Francisco, CA		'
Costs Capitalized Subsequent to Acquisition	113,274,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	0		'
Development and Construction in Progress	113,274,000		'
Total	113,274,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Weston Corporate Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Weston Corporate Center		'
Type	'Office		'
Location	'Weston, MA		'
Original Land	25,753,000		'
Original Building	92,312,000		'
Costs Capitalized Subsequent to Acquisition	-123,000		'
Land and improvements	25,854,000		'
Buildings and Improvements	92,088,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	117,942,000		'
Accumulated Depreciation	10,921,000		'
Year(s) built / renovated	'2010		'
Depreciable Lives (Years)	'-1	[2]	'
One Freedom Square [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'One Freedom Square		'
Type	'Office		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	9,929,000		'
Original Building	84,504,000		'
Costs Capitalized Subsequent to Acquisition	16,666,000		'
Land and improvements	11,293,000		'
Buildings and Improvements	99,806,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	111,099,000		'
Accumulated Depreciation	32,827,000		'
Year(s) built / renovated	'2000		'
Depreciable Lives (Years)	'-1	[2]	'
One And Two Reston Overlook [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'One and Two Reston Overlook		'
Type	'Office		'
Location	'Reston,B VA		'
Encumbrances	0		'
Original Land	16,456,000		'
Original Building	66,192,000		'
Costs Capitalized Subsequent to Acquisition	26,635,000		'
Land and improvements	17,561,000		'
Buildings and Improvements	91,722,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	109,283,000		'
Accumulated Depreciation	31,144,000		'
Year(s) built / renovated	'1999		'
Depreciable Lives (Years)	'-1	[2]	'
Two Freedom Square [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Two Freedom Square		'
Type	'Office		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	13,930,000		'
Original Building	77,739,000		'
Costs Capitalized Subsequent to Acquisition	13,816,000		'
Land and improvements	15,420,000		'
Buildings and Improvements	90,065,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	105,485,000		'
Accumulated Depreciation	37,294,000		'
Year(s) built / renovated	'2001		'
Depreciable Lives (Years)	'-1	[2]	'
Seven Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Seven Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	3,457,000		'
Original Building	97,136,000		'
Costs Capitalized Subsequent to Acquisition	2,880,000		'
Land and improvements	4,125,000		'
Buildings and Improvements	99,348,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	103,473,000		'
Accumulated Depreciation	47,498,000		'
Year(s) built / renovated	'2006		'
Depreciable Lives (Years)	'-1	[2]	'
Discovery Square [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Discovery Square		'
Type	'Office		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	11,198,000		'
Original Building	71,782,000		'
Costs Capitalized Subsequent to Acquisition	16,189,000		'
Land and improvements	12,533,000		'
Buildings and Improvements	86,636,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	99,169,000		'
Accumulated Depreciation	28,865,000		'
Year(s) built / renovated	'2001		'
Depreciable Lives (Years)	'-1	[2]	'
140 Kendrick Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'140 Kendrick Street		'
Type	'Office		'
Location	'Needham, MA		'
Encumbrances	0		'
Original Land	18,095,000		'
Original Building	66,905,000		'
Costs Capitalized Subsequent to Acquisition	14,759,000		'
Land and improvements	19,092,000		'
Buildings and Improvements	80,667,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	99,759,000		'
Accumulated Depreciation	17,433,000		'
Year(s) built / renovated	'2000		'
Depreciable Lives (Years)	'-1	[2]	'
Five Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Five Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	18,863,000		'
Original Building	53,346,000		'
Costs Capitalized Subsequent to Acquisition	29,762,000		'
Land and improvements	21,173,000		'
Buildings and Improvements	80,798,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	101,971,000		'
Accumulated Depreciation	19,158,000		'
Year(s) built / renovated	'1981/1996		'
Depreciable Lives (Years)	'-1	[2]	'
77 CityPoint [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'77 CityPoint		'
Type	'Office		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	13,847,000		'
Original Building	60,383,000		'
Costs Capitalized Subsequent to Acquisition	3,160,000		'
Land and improvements	13,873,000		'
Buildings and Improvements	63,517,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	77,390,000		'
Accumulated Depreciation	12,301,000		'
Year(s) built / renovated	'2008		'
Depreciable Lives (Years)	'-1	[2]	'
North First Business Park [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'North First Business Park		'
Type	'Office		'
Location	'San Jose, CA		'
Encumbrances	0		'
Original Land	58,402,000		'
Original Building	13,069,000		'
Costs Capitalized Subsequent to Acquisition	4,010,000		'
Land and improvements	23,377,000		'
Buildings and Improvements	16,215,000		'
Land Held for Development	35,889,000		'
Development and Construction in Progress	0		'
Total	75,481,000		'
Accumulated Depreciation	10,208,000		'
Year(s) built / renovated	'1981		'
Depreciable Lives (Years)	'-1	[2]	'
230 CityPoint [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'230 CityPoint		'
Type	'Office		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	13,189,000		'
Original Building	49,823,000		'
Costs Capitalized Subsequent to Acquisition	13,102,000		'
Land and improvements	13,593,000		'
Buildings and Improvements	62,521,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	76,114,000		'
Accumulated Depreciation	17,601,000		'
Year(s) built / renovated	'1992		'
Depreciable Lives (Years)	'-1	[2]	'
Four Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Four Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	19,104,000		'
Original Building	52,078,000		'
Costs Capitalized Subsequent to Acquisition	11,872,000		'
Land and improvements	20,785,000		'
Buildings and Improvements	62,269,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	83,054,000		'
Accumulated Depreciation	10,761,000		'
Year(s) built / renovated	'1983/1998		'
Depreciable Lives (Years)	'-1	[2]	'
Waltham Weston Corporate Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Waltham Weston Corporate Center		'
Type	'Office		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	10,385,000		'
Original Building	60,694,000		'
Costs Capitalized Subsequent to Acquisition	8,462,000		'
Land and improvements	11,097,000		'
Buildings and Improvements	68,444,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	79,541,000		'
Accumulated Depreciation	21,709,000		'
Year(s) built / renovated	'2003		'
Depreciable Lives (Years)	'-1	[2]	'
2440 West El Camino Real [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'2440 West El Camino Real		'
Type	'Office		'
Location	'MountainB View,B CA		'
Encumbrances	0		'
Original Land	16,741,000		'
Original Building	51,285,000		'
Costs Capitalized Subsequent to Acquisition	502,000		'
Land and improvements	16,741,000		'
Buildings and Improvements	51,787,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	68,528,000		'
Accumulated Depreciation	4,390,000		'
Year(s) built / renovated	'1987/2003		'
Depreciable Lives (Years)	'-1	[2]	'
Wisconsin Place [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Wisconsin Place		'
Type	'Office		'
Location	'ChevyB Chase,B MD		'
Encumbrances	0		'
Original Land	0		'
Original Building	53,349,000		'
Costs Capitalized Subsequent to Acquisition	12,787,000		'
Land and improvements	0		'
Buildings and Improvements	66,136,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	66,136,000		'
Accumulated Depreciation	11,573,000		'
Year(s) built / renovated	'2009		'
Depreciable Lives (Years)	'-1	[2]	'
Reston Corporate Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Reston Corporate Center		'
Type	'Office		'
Location	'Reston,B VA		'
Encumbrances	0		'
Original Land	9,135,000		'
Original Building	50,857,000		'
Costs Capitalized Subsequent to Acquisition	5,346,000		'
Land and improvements	10,148,000		'
Buildings and Improvements	55,190,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	65,338,000		'
Accumulated Depreciation	21,034,000		'
Year(s) built / renovated	'1984		'
Depreciable Lives (Years)	'-1	[2]	'
New Dominion Technology Park, Bldg. Two [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'New Dominion Technology Park, Bldg. Two		'
Type	'Office		'
Location	'Herndon,B VA		'
Encumbrances	63,000,000		'
Original Land	5,584,000		'
Original Building	51,868,000		'
Costs Capitalized Subsequent to Acquisition	3,894,000		'
Land and improvements	6,510,000		'
Buildings and Improvements	54,836,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	61,346,000		'
Accumulated Depreciation	16,557,000		'
Year(s) built / renovated	'2004		'
Depreciable Lives (Years)	'-1	[2]	'
Sumner Square [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Sumner Square		'
Type	'Office		'
Location	'Washington,B DC		'
Encumbrances	0		'
Original Land	624,000		'
Original Building	28,745,000		'
Costs Capitalized Subsequent to Acquisition	23,679,000		'
Land and improvements	1,478,000		'
Buildings and Improvements	51,570,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	53,048,000		'
Accumulated Depreciation	23,282,000		'
Year(s) built / renovated	'1985		'
Depreciable Lives (Years)	'-1	[2]	'
New Dominion Technology Park, Bldg. One [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'New Dominion Technology Park, Bldg. One		'
Type	'Office		'
Location	'Herndon,B VA		'
Encumbrances	43,278,000		'
Original Land	3,880,000		'
Original Building	43,227,000		'
Costs Capitalized Subsequent to Acquisition	3,882,000		'
Land and improvements	4,583,000		'
Buildings and Improvements	46,406,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	50,989,000		'
Accumulated Depreciation	19,584,000		'
Year(s) built / renovated	'2001		'
Depreciable Lives (Years)	'-1	[2]	'
200 West Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'200 West Street		'
Type	'Office		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	16,148,000		'
Original Building	24,983,000		'
Costs Capitalized Subsequent to Acquisition	8,568,000		'
Land and improvements	16,813,000		'
Buildings and Improvements	32,886,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	49,699,000		'
Accumulated Depreciation	14,834,000		'
Year(s) built / renovated	'1999		'
Depreciable Lives (Years)	'-1	[2]	'
191 Spring Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'191 Spring Street		'
Type	'Office		'
Location	'Lexington,B MA		'
Encumbrances	0		'
Original Land	2,850,000		'
Original Building	27,166,000		'
Costs Capitalized Subsequent to Acquisition	18,558,000		'
Land and improvements	3,151,000		'
Buildings and Improvements	45,423,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	48,574,000		'
Accumulated Depreciation	29,636,000		'
Year(s) built / renovated	'1971/1995		'
Depreciable Lives (Years)	'-1	[2]	'
University Place [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'University Place		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	13,692,000		'
Original Land	0		'
Original Building	37,091,000		'
Costs Capitalized Subsequent to Acquisition	6,785,000		'
Land and improvements	390,000		'
Buildings and Improvements	43,486,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	43,876,000		'
Accumulated Depreciation	20,692,000		'
Year(s) built / renovated	'1985		'
Depreciable Lives (Years)	'-1	[2]	'
2600 Tower Oaks Boulevard [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'2600 Tower Oaks Boulevard		'
Type	'Office		'
Location	'Rockville, MD		'
Encumbrances	0		'
Original Land	4,243,000		'
Original Building	31,125,000		'
Costs Capitalized Subsequent to Acquisition	8,257,000		'
Land and improvements	4,785,000		'
Buildings and Improvements	38,840,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	43,625,000		'
Accumulated Depreciation	16,576,000		'
Year(s) built / renovated	'2001		'
Depreciable Lives (Years)	'-1	[2]	'
Quorum Office Park [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Quorum Office Park		'
Type	'Office		'
Location	'Chelmsford,B MA		'
Encumbrances	0		'
Original Land	3,750,000		'
Original Building	32,454,000		'
Costs Capitalized Subsequent to Acquisition	5,672,000		'
Land and improvements	5,187,000		'
Buildings and Improvements	36,689,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	41,876,000		'
Accumulated Depreciation	12,748,000		'
Year(s) built / renovated	'2001		'
Depreciable Lives (Years)	'-1	[2]	'
One Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'One Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	134,000		'
Original Building	25,110,000		'
Costs Capitalized Subsequent to Acquisition	20,608,000		'
Land and improvements	548,000		'
Buildings and Improvements	45,304,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	45,852,000		'
Accumulated Depreciation	24,914,000		'
Year(s) built / renovated	'1987		'
Depreciable Lives (Years)	'-1	[2]	'
Three Patriots Park [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Three Patriots Park		'
Type	'Office		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	3,594,000		'
Original Building	32,977,000		'
Costs Capitalized Subsequent to Acquisition	3,013,000		'
Land and improvements	4,009,000		'
Buildings and Improvements	35,575,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	39,584,000		'
Accumulated Depreciation	12,465,000		'
Year(s) built / renovated	'2006		'
Depreciable Lives (Years)	'-1	[2]	'
500 E Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'500 E Street		'
Type	'Office		'
Location	'Washington,B DC		'
Encumbrances	0		'
Original Land	109,000		'
Original Building	22,420,000		'
Costs Capitalized Subsequent to Acquisition	12,854,000		'
Land and improvements	2,379,000		'
Buildings and Improvements	33,004,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	35,383,000		'
Accumulated Depreciation	20,633,000		'
Year(s) built / renovated	'1987		'
Depreciable Lives (Years)	'-1	[2]	'
Eight Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Eight Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	850,000		'
Original Building	25,042,000		'
Costs Capitalized Subsequent to Acquisition	8,507,000		'
Land and improvements	1,323,000		'
Buildings and Improvements	33,076,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	34,399,000		'
Accumulated Depreciation	11,139,000		'
Year(s) built / renovated	'1999		'
Depreciable Lives (Years)	'-1	[2]	'
Mountain View Technology [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Mountain View Technology Park		'
Type	'Office		'
Location	'Mountain View, CA		'
Encumbrances	0		'
Original Land	20,359,000		'
Original Building	13,640,000		'
Costs Capitalized Subsequent to Acquisition	182,000		'
Land and improvements	20,359,000		'
Buildings and Improvements	13,822,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	34,181,000		'
Accumulated Depreciation	761,000		'
Year(s) built / renovated	'1972		'
Depreciable Lives (Years)	'-1	[2]	'
Ten Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Ten Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	1,299,000		'
Original Building	12,943,000		'
Costs Capitalized Subsequent to Acquisition	6,117,000		'
Land and improvements	2,395,000		'
Buildings and Improvements	17,964,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	20,359,000		'
Accumulated Depreciation	11,337,000		'
Year(s) built / renovated	'1990		'
Depreciable Lives (Years)	'-1	[2]	'
Three Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Three Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	174,000		'
Original Building	12,200,000		'
Costs Capitalized Subsequent to Acquisition	8,758,000		'
Land and improvements	965,000		'
Buildings and Improvements	20,167,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	21,132,000		'
Accumulated Depreciation	9,768,000		'
Year(s) built / renovated	'1987		'
Depreciable Lives (Years)	'-1	[2]	'
201 Spring Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'201 Spring Street		'
Type	'Office		'
Location	'Lexington,B MA		'
Encumbrances	0		'
Original Land	2,849,000		'
Original Building	15,303,000		'
Costs Capitalized Subsequent to Acquisition	-154,000		'
Land and improvements	3,124,000		'
Buildings and Improvements	14,874,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	17,998,000		'
Accumulated Depreciation	6,034,000		'
Year(s) built / renovated	'1997		'
Depreciable Lives (Years)	'-1	[2]	'
40 Shattuck Road [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'40 Shattuck Road		'
Type	'Office		'
Location	'Andover, MA		'
Encumbrances	0		'
Original Land	709,000		'
Original Building	14,740,000		'
Costs Capitalized Subsequent to Acquisition	2,453,000		'
Land and improvements	893,000		'
Buildings and Improvements	17,009,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	17,902,000		'
Accumulated Depreciation	5,547,000		'
Year(s) built / renovated	'2001		'
Depreciable Lives (Years)	'-1	[2]	'
Lexington Office Park [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Lexington Office Park		'
Type	'Office		'
Location	'Lexington,B MA		'
Encumbrances	0		'
Original Land	998,000		'
Original Building	1,426,000		'
Costs Capitalized Subsequent to Acquisition	13,762,000		'
Land and improvements	1,264,000		'
Buildings and Improvements	14,922,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	16,186,000		'
Accumulated Depreciation	10,566,000		'
Year(s) built / renovated	'1982		'
Depreciable Lives (Years)	'-1	[2]	'
92 - 100 Hayden Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'92-100 Hayden Avenue		'
Type	'Office		'
Location	'Lexington,B MA		'
Encumbrances	0		'
Original Land	594,000		'
Original Building	6,748,000		'
Costs Capitalized Subsequent to Acquisition	7,819,000		'
Land and improvements	802,000		'
Buildings and Improvements	14,359,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	15,161,000		'
Accumulated Depreciation	9,914,000		'
Year(s) built / renovated	'1985		'
Depreciable Lives (Years)	'-1	[2]	'
6601 and 6605 Springfield Center Drive [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'6601B & 6605 Springfield Center Drive		'
Type	'Land		'
Location	'Springfield,B VA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	13,866,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	13,866,000		'
Development and Construction in Progress	0		'
Total	13,866,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
181 Spring Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'181 Spring Street		'
Type	'Office		'
Location	'Lexington,B MA		'
Encumbrances	0		'
Original Land	1,066,000		'
Original Building	9,520,000		'
Costs Capitalized Subsequent to Acquisition	1,950,000		'
Land and improvements	1,160,000		'
Buildings and Improvements	11,376,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	12,536,000		'
Accumulated Depreciation	4,007,000		'
Year(s) built / renovated	'1999		'
Depreciable Lives (Years)	'-1	[2]	'
195 West Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'195 West Street		'
Type	'Office		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	1,611,000		'
Original Building	6,652,000		'
Costs Capitalized Subsequent to Acquisition	4,175,000		'
Land and improvements	1,858,000		'
Buildings and Improvements	10,580,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	12,438,000		'
Accumulated Depreciation	6,187,000		'
Year(s) built / renovated	'1990		'
Depreciable Lives (Years)	'-1	[2]	'
91 Hartwell Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'91 Hartwell Avenue		'
Type	'Office		'
Location	'Lexington,B MA		'
Encumbrances	0		'
Original Land	784,000		'
Original Building	6,464,000		'
Costs Capitalized Subsequent to Acquisition	4,984,000		'
Land and improvements	941,000		'
Buildings and Improvements	11,291,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	12,232,000		'
Accumulated Depreciation	7,535,000		'
Year(s) built / renovated	'1985		'
Depreciable Lives (Years)	'-1	[2]	'
Waltham Office Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Waltham Office Center		'
Type	'Land		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	12,716,000		'
Land and improvements	165,000		'
Buildings and Improvements	8,445,000		'
Land Held for Development	4,106,000		'
Development and Construction in Progress	0		'
Total	12,716,000		'
Accumulated Depreciation	8,063,000		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Eleven Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Eleven Cambridge Center		'
Type	'Office		'
Location	'Cambridge,B MA		'
Encumbrances	0		'
Original Land	121,000		'
Original Building	5,535,000		'
Costs Capitalized Subsequent to Acquisition	5,131,000		'
Land and improvements	324,000		'
Buildings and Improvements	10,463,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	10,787,000		'
Accumulated Depreciation	7,240,000		'
Year(s) built / renovated	'1984		'
Depreciable Lives (Years)	'-1	[2]	'
7501 Boston Boulevard, Building Seven [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7501 Boston Boulevard, Building Seven		'
Type	'Office		'
Location	'Springfield,B VA		'
Encumbrances	0		'
Original Land	665,000		'
Original Building	9,273,000		'
Costs Capitalized Subsequent to Acquisition	544,000		'
Land and improvements	791,000		'
Buildings and Improvements	9,691,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	10,482,000		'
Accumulated Depreciation	3,895,000		'
Year(s) built / renovated	'1997		'
Depreciable Lives (Years)	'-1	[2]	'
33 Hayden Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'33 Hayden Avenue		'
Type	'Office		'
Location	'Lexington,B MA		'
Encumbrances	0		'
Original Land	266,000		'
Original Building	3,234,000		'
Costs Capitalized Subsequent to Acquisition	10,283,000		'
Land and improvements	425,000		'
Buildings and Improvements	13,358,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	13,783,000		'
Accumulated Depreciation	7,486,000		'
Year(s) built / renovated	'1979		'
Depreciable Lives (Years)	'-1	[2]	'
7435 Boston Boulevard, Building One [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7435 Boston Boulevard, Building One		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	392,000		'
Original Building	3,822,000		'
Costs Capitalized Subsequent to Acquisition	3,895,000		'
Land and improvements	659,000		'
Buildings and Improvements	7,450,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	8,109,000		'
Accumulated Depreciation	5,526,000		'
Year(s) built / renovated	'1982		'
Depreciable Lives (Years)	'-1	[2]	'
7450 Boston Boulevard, Building Three [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7450 Boston Boulevard, Building Three		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	1,165,000		'
Original Building	4,681,000		'
Costs Capitalized Subsequent to Acquisition	1,915,000		'
Land and improvements	1,430,000		'
Buildings and Improvements	6,331,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	7,761,000		'
Accumulated Depreciation	2,917,000		'
Year(s) built / renovated	'1987		'
Depreciable Lives (Years)	'-1	[2]	'
8000 Grainger Court, Building Five [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'8000 Grainger Court, Building Five		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	366,000		'
Original Building	4,282,000		'
Costs Capitalized Subsequent to Acquisition	2,944,000		'
Land and improvements	601,000		'
Buildings and Improvements	6,991,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	7,592,000		'
Accumulated Depreciation	5,160,000		'
Year(s) built / renovated	'1984		'
Depreciable Lives (Years)	'-1	[2]	'
453 Ravendale Drive [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'453 Ravendale Drive		'
Type	'Office		'
Location	'Mountain View, CA		'
Encumbrances	0		'
Original Land	5,477,000		'
Original Building	1,090,000		'
Costs Capitalized Subsequent to Acquisition	230,000		'
Land and improvements	5,477,000		'
Buildings and Improvements	1,320,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	6,797,000		'
Accumulated Depreciation	142,000		'
Year(s) built / renovated	'1977		'
Depreciable Lives (Years)	'-1	[2]	'
7500 Boston Boulevard, Building Six [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7500 Boston Boulevard, Building Six		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	138,000		'
Original Building	3,749,000		'
Costs Capitalized Subsequent to Acquisition	2,590,000		'
Land and improvements	406,000		'
Buildings and Improvements	6,071,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	6,477,000		'
Accumulated Depreciation	4,133,000		'
Year(s) built / renovated	'1985		'
Depreciable Lives (Years)	'-1	[2]	'
7601 Boston Boulevard, Building Eight [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7601 Boston Boulevard, Building Eight		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	200,000		'
Original Building	878,000		'
Costs Capitalized Subsequent to Acquisition	4,875,000		'
Land and improvements	551,000		'
Buildings and Improvements	5,402,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	5,953,000		'
Accumulated Depreciation	3,576,000		'
Year(s) built / renovated	'1986		'
Depreciable Lives (Years)	'-1	[2]	'
Fourteen Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Fourteen Cambridge Center		'
Type	'Office		'
Location	'Cambridge, MA		'
Encumbrances	0		'
Original Land	110,000		'
Original Building	4,483,000		'
Costs Capitalized Subsequent to Acquisition	1,223,000		'
Land and improvements	273,000		'
Buildings and Improvements	5,543,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	5,816,000		'
Accumulated Depreciation	3,805,000		'
Year(s) built / renovated	'1983		'
Depreciable Lives (Years)	'-1	[2]	'
7300 Boston Boulevard, Building Thirteen [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7300 Boston Boulevard, Building Thirteen		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	608,000		'
Original Building	4,773,000		'
Costs Capitalized Subsequent to Acquisition	230,000		'
Land and improvements	661,000		'
Buildings and Improvements	4,950,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	5,611,000		'
Accumulated Depreciation	3,934,000		'
Year(s) built / renovated	'2002		'
Depreciable Lives (Years)	'-1	[2]	'
8000 Corporate Court, Building Eleven [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'8000 Corporate Court, Building Eleven		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	136,000		'
Original Building	3,071,000		'
Costs Capitalized Subsequent to Acquisition	1,484,000		'
Land and improvements	775,000		'
Buildings and Improvements	3,916,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	4,691,000		'
Accumulated Depreciation	2,355,000		'
Year(s) built / renovated	'1989		'
Depreciable Lives (Years)	'-1	[2]	'
7374 Boston Boulevard, Building Four [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7374 Boston Boulevard, Building Four		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	241,000		'
Original Building	1,605,000		'
Costs Capitalized Subsequent to Acquisition	1,902,000		'
Land and improvements	398,000		'
Buildings and Improvements	3,350,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	3,748,000		'
Accumulated Depreciation	2,327,000		'
Year(s) built / renovated	'1984		'
Depreciable Lives (Years)	'-1	[2]	'
7375 Boston Boulevard, Building Ten [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7375 Boston Boulevard, Building Ten		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	23,000		'
Original Building	2,685,000		'
Costs Capitalized Subsequent to Acquisition	1,007,000		'
Land and improvements	93,000		'
Buildings and Improvements	3,622,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	3,715,000		'
Accumulated Depreciation	2,261,000		'
Year(s) built / renovated	'1988		'
Depreciable Lives (Years)	'-1	[2]	'
7451 Boston Boulevard, Building Two [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'7451 Boston Boulevard, Building Two		'
Type	'Office		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	249,000		'
Original Building	1,542,000		'
Costs Capitalized Subsequent to Acquisition	1,313,000		'
Land and improvements	613,000		'
Buildings and Improvements	2,491,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	3,104,000		'
Accumulated Depreciation	2,131,000		'
Year(s) built / renovated	'1982		'
Depreciable Lives (Years)	'-1	[2]	'
32 Hartwell Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'32 Hartwell Avenue		'
Type	'Office		'
Location	'Lexington, MA		'
Encumbrances	0		'
Original Land	168,000		'
Original Building	1,943,000		'
Costs Capitalized Subsequent to Acquisition	800,000		'
Land and improvements	314,000		'
Buildings and Improvements	2,597,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	2,911,000		'
Accumulated Depreciation	1,568,000		'
Year(s) built / renovated	'1968-1979/1987		'
Depreciable Lives (Years)	'-1	[2]	'
164 Lexington Road [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'164 Lexington Road		'
Type	'Office		'
Location	'Billerica, MA		'
Encumbrances	0		'
Original Land	592,000		'
Original Building	1,370,000		'
Costs Capitalized Subsequent to Acquisition	319,000		'
Land and improvements	643,000		'
Buildings and Improvements	1,638,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	2,281,000		'
Accumulated Depreciation	703,000		'
Year(s) built / renovated	'1982		'
Depreciable Lives (Years)	'-1	[2]	'
Seventeen Hartwell Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'17 Hartwell Avenue		'
Type	'Office		'
Location	'Lexington, MA		'
Encumbrances	0		'
Original Land	26,000		'
Original Building	150,000		'
Costs Capitalized Subsequent to Acquisition	1,002,000		'
Land and improvements	65,000		'
Buildings and Improvements	1,113,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	1,178,000		'
Accumulated Depreciation	639,000		'
Year(s) built / renovated	'1968		'
Depreciable Lives (Years)	'-1	[2]	'
Residences on The Avenue, Two Two Two One I St., NW [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Residences on The Avenue, 2221 I St., NW		'
Type	'Residential		'
Location	'Washington, DC		'
Encumbrances	0		'
Original Land	0		'
Original Building	119,874,000		'
Costs Capitalized Subsequent to Acquisition	-32,000		'
Land and improvements	0		'
Buildings and Improvements	119,842,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	119,842,000		'
Accumulated Depreciation	7,948,000		'
Year(s) built / renovated	'2011		'
Depreciable Lives (Years)	'-1	[2]	'
The Lofts At Atlantic Wharf [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'The Lofts at Atlantic Wharf		'
Type	'Residential		'
Location	'Boston, MA		'
Encumbrances	0		'
Original Land	3,529,000		'
Original Building	54,891,000		'
Costs Capitalized Subsequent to Acquisition	1,543,000		'
Land and improvements	3,529,000		'
Buildings and Improvements	56,434,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	59,963,000		'
Accumulated Depreciation	3,591,000		'
Year(s) built / renovated	'2011		'
Depreciable Lives (Years)	'-1	[2]	'
Cambridge Center Marriott [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Cambridge Center Marriott		'
Type	'Hotel		'
Location	'Cambridge, MA		'
Encumbrances	0		'
Original Land	478,000		'
Original Building	37,918,000		'
Costs Capitalized Subsequent to Acquisition	35,981,000		'
Land and improvements	1,201,000		'
Buildings and Improvements	73,176,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	74,377,000		'
Accumulated Depreciation	47,182,000		'
Year(s) built / renovated	'1986		'
Depreciable Lives (Years)	'-1	[2]	'
Cambridge Center East Garage [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Cambridge Center East Garage		'
Type	'Garage		'
Location	'Cambridge, MA		'
Encumbrances	0		'
Original Land	0		'
Original Building	35,035,000		'
Costs Capitalized Subsequent to Acquisition	1,487,000		'
Land and improvements	103,000		'
Buildings and Improvements	36,419,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	36,522,000		'
Accumulated Depreciation	6,684,000		'
Year(s) built / renovated	'1984		'
Depreciable Lives (Years)	'-1	[2]	'
Cambridge Center West Garage [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Cambridge Center West Garage		'
Type	'Garage		'
Location	'Cambridge, MA		'
Encumbrances	0		'
Original Land	1,256,000		'
Original Building	15,697,000		'
Costs Capitalized Subsequent to Acquisition	1,553,000		'
Land and improvements	1,434,000		'
Buildings and Improvements	17,072,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	18,506,000		'
Accumulated Depreciation	3,364,000		'
Year(s) built / renovated	'2006		'
Depreciable Lives (Years)	'-1	[2]	'
Cambridge Center North Garage [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Cambridge Center North Garage		'
Type	'Garage		'
Location	'Cambridge, MA		'
Encumbrances	0		'
Original Land	1,163,000		'
Original Building	11,633,000		'
Costs Capitalized Subsequent to Acquisition	1,085,000		'
Land and improvements	1,163,000		'
Buildings and Improvements	12,718,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	13,881,000		'
Accumulated Depreciation	8,157,000		'
Year(s) built / renovated	'1990		'
Depreciable Lives (Years)	'-1	[2]	'
250 West 55th Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'250 West 55th Street		'
Type	'Development		'
Location	'New York, NY		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	818,243,000		'
Land and improvements	16,305,000		'
Buildings and Improvements	45,476,000		'
Land Held for Development	0		'
Development and Construction in Progress	756,462,000		'
Total	818,243,000		'
Accumulated Depreciation	483,000		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Transbay Tower [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Transbay Tower		'
Type	'Development		'
Location	'San Francisco, CA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	255,406,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	0		'
Development and Construction in Progress	255,406,000		'
Total	255,406,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
680 Folsom Street [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'680 Folsom Street		'
Type	'Development		'
Location	'San Francisco, CA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	241,093,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	3,475,000		'
Development and Construction in Progress	237,618,000		'
Total	241,093,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
The Avant at Reston Town Center Residential [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'The Avant at Reston Town Center Residential		'
Type	'Development		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	107,022,000		'
Land and improvements	12,741,000		'
Buildings and Improvements	55,701,000		'
Land Held for Development	0		'
Development and Construction in Progress	38,580,000		'
Total	107,022,000		'
Accumulated Depreciation	160,000		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Seventeen Cambridge Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Seventeen Cambridge Center		'
Type	'Office		'
Location	'Cambridge, MA		'
Encumbrances	0		'
Original Land	18,080,000		'
Original Building	51,262,000		'
Costs Capitalized Subsequent to Acquisition	0		'
Land and improvements	18,080,000		'
Buildings and Improvements	51,262,000		'
Land Held for Development	0		'
Development and Construction in Progress	0		'
Total	69,342,000		'
Accumulated Depreciation	1,080,000		'
Year(s) built / renovated	'2013		'
Depreciable Lives (Years)	'(1)	[2]	'
Plaza at Almaden [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Plaza at Almaden		'
Type	'Land		'
Location	'San Jose, CA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	29,003,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	29,003,000		'
Development and Construction in Progress	0		'
Total	29,003,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Springfield Metro Center [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Springfield Metro Center		'
Type	'Land		'
Location	'Springfield, VA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	32,073,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	32,073,000		'
Development and Construction in Progress	0		'
Total	32,073,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Tower Oaks Master Plan [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Tower Oaks Master Plan		'
Type	'Land		'
Location	'Rockville, MD		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	28,976,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	28,976,000		'
Development and Construction in Progress	0		'
Total	28,976,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Reston Signature Site [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Reston Signature Site		'
Type	'Land		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	27,890,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	27,890,000		'
Development and Construction in Progress	0		'
Total	27,890,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Prospect Hill [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Prospect Hill		'
Type	'Land		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	24,197,000		'
Land and improvements	0		'
Buildings and Improvements	667,000		'
Land Held for Development	23,530,000		'
Development and Construction in Progress	0		'
Total	24,197,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Washingtonian North [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Washingtonian North		'
Type	'Land		'
Location	'Gaithersburg, MD		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	18,290,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	18,290,000		'
Development and Construction in Progress	0		'
Total	18,290,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
103 4th Avenue [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'103 4th Avenue		'
Type	'Land		'
Location	'Waltham, MA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	11,918,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	11,918,000		'
Development and Construction in Progress	0		'
Total	11,918,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Cambridge Master Plan [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Cambridge Master Plan		'
Type	'Land		'
Location	'Cambridge, MA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	11,153,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	11,153,000		'
Development and Construction in Progress	0		'
Total	11,153,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Reston Gateway [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Reston Gateway		'
Type	'Land		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	9,682,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	9,682,000		'
Development and Construction in Progress	0		'
Total	9,682,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Reston Eastgate [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Reston Eastgate		'
Type	'Land		'
Location	'Reston, VA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	8,807,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	8,807,000		'
Development and Construction in Progress	0		'
Total	8,807,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Crane Meadow [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Crane Meadow		'
Type	'Land		'
Location	'Marlborough, MA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	8,725,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	8,725,000		'
Development and Construction in Progress	0		'
Total	8,725,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Broad Run Business Park [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'Broad Run Business Park		'
Type	'Land		'
Location	'LoudonB County,B VA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	7,888,000		'
Land and improvements	1,621,000		'
Buildings and Improvements	0		'
Land Held for Development	6,267,000		'
Development and Construction in Progress	0		'
Total	7,888,000		'
Accumulated Depreciation	0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
30 Shattuck Road [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Real Estate And Accumulated Depreciation Name of Property	'30 Shattuck Road		'
Type	'Land		'
Location	'Andover, MA		'
Encumbrances	0		'
Original Land	0		'
Original Building	0		'
Costs Capitalized Subsequent to Acquisition	1,212,000		'
Land and improvements	0		'
Buildings and Improvements	0		'
Land Held for Development	1,212,000		'
Development and Construction in Progress	0		'
Total	1,212,000		'
Accumulated Depreciation	$0		'
Year(s) built / renovated	'N/A		'
Depreciable Lives (Years)	'N/A		'
Minimum [Member]	'		'
Real Estate and Accumulated Depreciation [Line Items]	'		'
Life Used for Depreciation	'life of the lease		'
[1]	(2)Includes the unamortized balance of the historical fair value adjustment totaling approximately $191.2 million.
[2]	(1)Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.

Real_Estate_and_Accumulated_De2

Real Estate and Accumulated Depreciation Activity of Real Estate and Accumulated Depreciation (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]	'	'	'
Real Estate, Balance at the beginning of the year	$14,869,887	$13,363,113	$12,740,892
Real Estate, Additions to / improvements of real estate	4,410,622	1,602,583	668,084
Real Estate, Assets sold / written off	-326,908	-95,809	-45,863
Real Estate, Balance at the end of the year	18,953,601	14,869,887	13,363,113
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]	'	'	'
Accumulated depreciation, Balance at beginning of the year	2,919,479	2,626,324	2,308,665
Accumulated depreciation, Depreciation expense	419,908	367,625	362,636
Accumulated depreciatio, Assets sold / written off	-193,686	-74,470	-44,977
Accumulated depreciation, Balance at end of the year	$3,145,701	$2,919,479	$2,626,324