Boston Properties LTD Partnership 10-K 28 Feb 18 2017 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 22, 2018	Jun. 30, 2017
Document Information [Line Items]
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Registrant Name	BOSTON PROPERTIES INC
Amendment Flag	false
Entity Central Index Key	1,037,540
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		154,339,610
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 18,949,156,391
Boston Properties Limited Partnership
Document Information [Line Items]
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Registrant Name	BOSTON PROPERTIES LTD PARTNERSHIP
Amendment Flag	false
Entity Central Index Key	1,043,121
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		0
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,172,718 and $6,760,078 at December 31, 2017 and 2016, respectively )	$ 21,096,642	$ 20,147,263
Less: accumulated depreciation (amounts related to VIEs of $(854,172) and $(758,640) at December 31, 2017 and 2016, respectively	(4,589,634)	(4,222,235)
Total real estate	16,507,008	15,925,028
Cash and cash equivalents (amounts related to VIEs of $304,955 and $253,999 at December 31, 2017 and 2016, respectively)	434,767	356,914
Cash held in escrows (amounts related to VIEs of $6,135 and $4,955 at December 31, 2017 and 2016, respectively)	70,602	63,174
Investments in securities	29,161	23,814
Tenant and other receivables, net (amounts related to VIEs of $27,057 and $23,525 at December 31, 2017 and 2016, respectively)	92,186	92,548
Accrued rental income, net (amounts related to VIEs of $242,589 and $224,185 at December 31, 2017 and 2016, respectively)	861,575	799,138
Deferred charges, net (amounts related to VIEs of $281,678 and $290,436 at December 31, 2017 and 2016, respectively)	679,038	686,163
Prepaid expenses and other assets (amounts related to VIEs of $33,666 and $42,718 at December 31, 2017 and 2016, respectively)	77,971	129,666
Investments in unconsolidated joint ventures	619,925	775,198
Total assets	19,372,233	18,851,643
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)	2,979,281	2,063,087
Unsecured senior notes, net	7,247,330	7,245,953
Unsecured line of credit	45,000	0
Unsecured term loan	0	0
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at December 31, 2017 and 2016, respectively)	0	307,093
Outside members’ notes payable (amounts related to VIEs of $0 and $180,000 at December 31, 2017 and 2016, respectively)	0	180,000
Accounts payable and accrued expenses (amounts related to VIEs of $106,683 and $110,457 at December 31, 2017 and 2016, respectively)	331,500	298,524
Dividends and distributions payable	139,040	130,308
Accrued interest payable (amounts related to VIEs of $6,907 and $162,226 at December 31, 2017 and 2016, respectively)	83,646	243,933
Other liabilities (amounts related to VIEs of $164,806 and $175,146 at December 31, 2017 and 2016, respectively)	443,980	450,821
Total liabilities	11,269,777	10,919,719
Commitments and contingencies	0	0
Equity / Capital:
Excess stock, $0.01 par value, 150,000,000 shares authorized, none issued or outstanding	0	0
Preferred stock, $0.01 par value, 50,000,000 shares authorized;
5.25% Series B cumulative redeemable preferred stock / units, liquidation preference $2,500 per share / unit, 80,000 shares / units issued and outstanding at December 31, 2016 and December 31, 2015, respectively	200,000	200,000
Common stock, $0.01 par value, 250,000,000 shares authorized,154,404,186 and 153,869,075 issued and 154,325,286 and 153,790,175 outstanding at December 31, 2017 and December 31, 2016, respectively	1,543	1,538
Additional paid-in capital	6,377,908	6,333,424
Dividends in excess of earnings	(712,343)	(693,694)
Treasury common stock at cost, 78,900 shares at December 31, 2017 and December 31, 2016	(2,722)	(2,722)
Accumulated other comprehensive loss	(50,429)	(52,251)
Total stockholders' equity attributable to Boston Properties, Inc.	5,813,957	5,786,295
Noncontrolling interests:
Common units of the Operating Partnership	604,739	614,982
Property partnerships	1,683,760	1,530,647
Total equity / capital	8,102,456	7,931,924
Total liabilities and equity / capital	19,372,233	18,851,643
Boston Properties Limited Partnership
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,172,718 and $6,760,078 at December 31, 2017 and 2016, respectively )	20,685,164	19,733,872
Less: accumulated depreciation (amounts related to VIEs of $(854,172) and $(758,640) at December 31, 2017 and 2016, respectively	(4,496,959)	(4,136,364)
Total real estate	16,188,205	15,597,508
Cash and cash equivalents (amounts related to VIEs of $304,955 and $253,999 at December 31, 2017 and 2016, respectively)	434,767	356,914
Cash held in escrows (amounts related to VIEs of $6,135 and $4,955 at December 31, 2017 and 2016, respectively)	70,602	63,174
Investments in securities	29,161	23,814
Tenant and other receivables, net (amounts related to VIEs of $27,057 and $23,525 at December 31, 2017 and 2016, respectively)	92,186	92,548
Accrued rental income, net (amounts related to VIEs of $242,589 and $224,185 at December 31, 2017 and 2016, respectively)	861,575	799,138
Deferred charges, net (amounts related to VIEs of $281,678 and $290,436 at December 31, 2017 and 2016, respectively)	679,038	686,163
Prepaid expenses and other assets (amounts related to VIEs of $33,666 and $42,718 at December 31, 2017 and 2016, respectively)	77,971	129,666
Investments in unconsolidated joint ventures	619,925	775,198
Total assets	19,053,430	18,524,123
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)	2,979,281	2,063,087
Unsecured senior notes, net	7,247,330	7,245,953
Unsecured line of credit	45,000	0
Unsecured term loan	0	0
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at December 31, 2017 and 2016, respectively)	0	307,093
Outside members’ notes payable (amounts related to VIEs of $0 and $180,000 at December 31, 2017 and 2016, respectively)	0	180,000
Accounts payable and accrued expenses (amounts related to VIEs of $106,683 and $110,457 at December 31, 2017 and 2016, respectively)	331,500	298,524
Dividends and distributions payable	139,040	130,308
Accrued interest payable (amounts related to VIEs of $6,907 and $162,226 at December 31, 2017 and 2016, respectively)	83,646	243,933
Other liabilities (amounts related to VIEs of $164,806 and $175,146 at December 31, 2017 and 2016, respectively)	443,980	450,821
Total liabilities	11,269,777	10,919,719
Commitments and contingencies	0	0
Noncontrolling interest:
Redeemable partnership units—16,810,378 and 17,079,511 common units and 818,343 and 904,588 long term incentive units outstanding at redemption value at December 31, 2017 and December 31, 2016, respectively	2,292,263	2,262,040
Preferred stock, $0.01 par value, 50,000,000 shares authorized;
5.25% Series B cumulative redeemable preferred stock / units, liquidation preference $2,500 per share / unit, 80,000 shares / units issued and outstanding at December 31, 2016 and December 31, 2015, respectively	193,623	193,623
Boston Properties Limited Partnership partners’ capital—1,719,540 and 1,717,743 general partner units and 152,605,746 and 152,072,432 limited partner units outstanding at December 31, 2017 and December 31, 2016, respectively	3,614,007	3,618,094
Accumulated other comprehensive loss	(58,825)	(60,853)
Noncontrolling interests:
Property partnerships	1,683,760	1,530,647
Total equity / capital	5,491,390	5,342,364
Total liabilities and equity / capital	$ 19,053,430	$ 18,524,123

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
General Partners' Capital Account, Units Outstanding (in units)	1,719,540
Limited Partners' Capital Account, Units Outstanding (in units)	152,605,746
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
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	154,404,186	153,869,075
Common stock, shares outstanding	154,325,286	153,790,175
Treasury common stock at cost, shares	78,900	78,900
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,172,718 and $6,760,078 at December 31, 2017 and 2016, respectively )	$ 21,096,642	$ 20,147,263
Less: accumulated depreciation (amounts related to VIEs of $(854,172) and $(758,640) at December 31, 2017 and 2016, respectively	(4,589,634)	(4,222,235)
Cash and cash equivalents (amounts related to VIEs of $304,955 and $253,999 at December 31, 2017 and 2016, respectively)	434,767	356,914
Cash held in escrows (amounts related to VIEs of $6,135 and $4,955 at December 31, 2017 and 2016, respectively)	70,602	63,174
Tenant and other receivables, net (amounts related to VIEs of $27,057 and $23,525 at December 31, 2017 and 2016, respectively)	92,186	92,548
Accrued rental income, net (amounts related to VIEs of $242,589 and $224,185 at December 31, 2017 and 2016, respectively)	861,575	799,138
Deferred charges, net (amounts related to VIEs of $281,678 and $290,436 at December 31, 2017 and 2016, respectively)	679,038	686,163
Prepaid expenses and other assets (amounts related to VIEs of $33,666 and $42,718 at December 31, 2017 and 2016, respectively)	77,971	129,666
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)	2,979,281	2,063,087
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at December 31, 2017 and 2016, respectively)	0	307,093
Accounts Payable and Accrued Liabilities	331,500	298,524
Accrued interest payable (amounts related to VIEs of $6,907 and $162,226 at December 31, 2017 and 2016, respectively)	83,646	243,933
Other liabilities (amounts related to VIEs of $164,806 and $175,146 at December 31, 2017 and 2016, respectively)	$ 443,980	$ 450,821
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Preferred stock, par value	$ 0.01	$ 0
Preferred stock, shares authorized	92,000	92,000
Series B Dividend Rate Percentage	5.25%	5.25%
Preferred stock / units, shares / units issued (in shares / units)	80,000	80,000
Series B Liquidation Preference Per Share/ Unit	$ 2,500	$ 2,500
Preferred stock / units, shares / units outstanding (in shares / units)	80,000	80,000
Boston Properties Limited Partnership
Redeemable Partnership Units Common Units Shares Outstanding (in units)	16,810,378	17,079,511
Redeemable Partnership Units Common Units Long Term Incentive Units At Redemption Value Units Outstanding (in units)	818,343	904,588
General Partners' Capital Account, Units Outstanding (in units)	1,719,540	1,717,743
Limited Partners' Capital Account, Units Outstanding (in units)	152,605,746	152,072,432
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,172,718 and $6,760,078 at December 31, 2017 and 2016, respectively )	$ 20,685,164	$ 19,733,872
Less: accumulated depreciation (amounts related to VIEs of $(854,172) and $(758,640) at December 31, 2017 and 2016, respectively	(4,496,959)	(4,136,364)
Cash and cash equivalents (amounts related to VIEs of $304,955 and $253,999 at December 31, 2017 and 2016, respectively)	434,767	356,914
Cash held in escrows (amounts related to VIEs of $6,135 and $4,955 at December 31, 2017 and 2016, respectively)	70,602	63,174
Tenant and other receivables, net (amounts related to VIEs of $27,057 and $23,525 at December 31, 2017 and 2016, respectively)	92,186	92,548
Accrued rental income, net (amounts related to VIEs of $242,589 and $224,185 at December 31, 2017 and 2016, respectively)	861,575	799,138
Deferred charges, net (amounts related to VIEs of $281,678 and $290,436 at December 31, 2017 and 2016, respectively)	679,038	686,163
Prepaid expenses and other assets (amounts related to VIEs of $33,666 and $42,718 at December 31, 2017 and 2016, respectively)	77,971	129,666
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)	2,979,281	2,063,087
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at December 31, 2017 and 2016, respectively)	0	307,093
Accounts Payable and Accrued Liabilities	331,500	298,524
Accrued interest payable (amounts related to VIEs of $6,907 and $162,226 at December 31, 2017 and 2016, respectively)	83,646	243,933
Other liabilities (amounts related to VIEs of $164,806 and $175,146 at December 31, 2017 and 2016, respectively)	$ 443,980	$ 450,821
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Series B Dividend Rate Percentage	5.25%	5.25%
Preferred stock / units, shares / units issued (in shares / units)	80,000	80,000
Series B Liquidation Preference Per Share/ Unit	$ 2,500	$ 2,500
Preferred stock / units, shares / units outstanding (in shares / units)	80,000	80,000
Variable Interest Entity, Primary Beneficiary [Member]
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,172,718 and $6,760,078 at December 31, 2017 and 2016, respectively )	$ 7,172,718	$ 6,760,078
Less: accumulated depreciation (amounts related to VIEs of $(854,172) and $(758,640) at December 31, 2017 and 2016, respectively	(854,172)	(758,640)
Cash and cash equivalents (amounts related to VIEs of $304,955 and $253,999 at December 31, 2017 and 2016, respectively)	304,955	253,999
Cash held in escrows (amounts related to VIEs of $6,135 and $4,955 at December 31, 2017 and 2016, respectively)	6,135	4,955
Tenant and other receivables, net (amounts related to VIEs of $27,057 and $23,525 at December 31, 2017 and 2016, respectively)	27,057	23,525
Accrued rental income, net (amounts related to VIEs of $242,589 and $224,185 at December 31, 2017 and 2016, respectively)	242,589	224,185
Deferred charges, net (amounts related to VIEs of $281,678 and $290,436 at December 31, 2017 and 2016, respectively)	281,678	290,436
Prepaid expenses and other assets (amounts related to VIEs of $33,666 and $42,718 at December 31, 2017 and 2016, respectively)	33,666	42,718
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)	2,939,183	2,018,483
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at December 31, 2017 and 2016, respectively)	0	307,093
Outside member's notes payable	0	180,000
Accounts Payable and Accrued Liabilities	106,683	110,457
Accrued interest payable (amounts related to VIEs of $6,907 and $162,226 at December 31, 2017 and 2016, respectively)	6,907	162,226
Other liabilities (amounts related to VIEs of $164,806 and $175,146 at December 31, 2017 and 2016, respectively)	164,806	175,146
Variable Interest Entity, Primary Beneficiary [Member] | Boston Properties Limited Partnership
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,172,718 and $6,760,078 at December 31, 2017 and 2016, respectively )	7,172,718	6,760,078
Less: accumulated depreciation (amounts related to VIEs of $(854,172) and $(758,640) at December 31, 2017 and 2016, respectively	(854,172)	(758,640)
Cash and cash equivalents (amounts related to VIEs of $304,955 and $253,999 at December 31, 2017 and 2016, respectively)	304,955	253,999
Cash held in escrows (amounts related to VIEs of $6,135 and $4,955 at December 31, 2017 and 2016, respectively)	6,135	4,955
Tenant and other receivables, net (amounts related to VIEs of $27,057 and $23,525 at December 31, 2017 and 2016, respectively)	27,057	23,525
Accrued rental income, net (amounts related to VIEs of $242,589 and $224,185 at December 31, 2017 and 2016, respectively)	242,589	224,185
Deferred charges, net (amounts related to VIEs of $281,678 and $290,436 at December 31, 2017 and 2016, respectively)	281,678	290,436
Prepaid expenses and other assets (amounts related to VIEs of $33,666 and $42,718 at December 31, 2017 and 2016, respectively)	33,666	42,718
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)	2,939,183	2,018,483
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at December 31, 2017 and 2016, respectively)	0	307,093
Outside member's notes payable	0	180,000
Accounts Payable and Accrued Liabilities	106,683	110,457
Accrued interest payable (amounts related to VIEs of $6,907 and $162,226 at December 31, 2017 and 2016, respectively)	6,907	162,226
Other liabilities (amounts related to VIEs of $164,806 and $175,146 at December 31, 2017 and 2016, respectively)	$ 164,806	$ 175,146

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Base rent	$ 2,049,368	$ 2,017,767	$ 1,964,732
Recoveries from tenants	367,500	358,975	355,508
Parking and other	105,000	100,910	101,981
Total rental revenue	2,521,868	2,477,652	2,422,221
Hotel revenue	45,603	44,884	46,046
Development and management services	34,605	28,284	22,554
Total revenue	2,602,076	2,550,820	2,490,821
Expenses
Rental	929,977	889,768	872,252
Hotel	32,059	31,466	32,084
General and administrative	113,715	105,229	96,319
Transaction costs	668	2,387	1,259
Impairment loss	0	1,783	0
Depreciation and amortization	617,547	694,403	639,542
Total expenses	1,693,966	1,725,036	1,641,456
Operating income	908,110	825,784	849,365
Other income (expense)
Income from unconsolidated joint ventures	11,232	8,074	22,770
Gain on sale of investment in unconsolidated joint venture	0	59,370	0
Interest and other income	5,783	7,230	6,777
Gains (losses) from investments in securities	3,678	2,273	(653)
Interest expense	(374,481)	(412,849)	(432,196)
Gains (losses) from early extinguishments of debt	496	(371)	(22,040)
Losses from interest rate contracts	0	(140)	0
Income before gains on sales of real estate	554,818	489,371	424,023
Gains on sales of real estate	7,663	80,606	375,895
Net income	562,481	569,977	799,918
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships	(47,832)	2,068	(149,855)
Noncontrolling interest - redeemable preferred units	0	0	(6)
Noncontrolling interest - common units of the Operating Partnership	(52,210)	(59,260)	(66,951)
Net income attributable to the Company	462,439	512,785	583,106
Preferred dividends / distributions	(10,500)	(10,500)	(10,500)
Net income attributable to the Company's common shareholders / unitholders	$ 451,939	$ 502,285	$ 572,606
Basic earnings per common share / unit attributable to the Company
Net income (in dollars per share / unit)	$ 2.93	$ 3.27	$ 3.73
Weighted average number of common shares / units outstanding (in shares / units)	154,190	153,715	153,471
Diluted earnings per common share / unit attributable to the Company
Diluted Earnings: Net income, Per Share / Unit Amount (in dollars per share / unit)	$ 2.93	$ 3.26	$ 3.72
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)	154,390	153,977	153,844
Dividends/Distributions per common share/unit	$ 3.05	$ 2.70	$ 3.85
Boston Properties Limited Partnership
Revenue
Base rent	$ 2,049,368	$ 2,017,767	$ 1,964,732
Recoveries from tenants	367,500	358,975	355,508
Parking and other	105,000	100,910	101,981
Total rental revenue	2,521,868	2,477,652	2,422,221
Hotel revenue	45,603	44,884	46,046
Development and management services	34,605	28,284	22,554
Total revenue	2,602,076	2,550,820	2,490,821
Expenses
Rental	929,977	889,768	872,252
Hotel	32,059	31,466	32,084
General and administrative	113,715	105,229	96,319
Transaction costs	668	2,387	1,259
Impairment loss	0	1,783	0
Depreciation and amortization	609,407	682,776	631,549
Total expenses	1,685,826	1,713,409	1,633,463
Operating income	916,250	837,411	857,358
Other income (expense)
Income from unconsolidated joint ventures	11,232	8,074	22,770
Gain on sale of investment in unconsolidated joint venture	0	59,370	0
Interest and other income	5,783	7,230	6,777
Gains (losses) from investments in securities	3,678	2,273	(653)
Interest expense	(374,481)	(412,849)	(432,196)
Gains (losses) from early extinguishments of debt	496	(371)	(22,040)
Losses from interest rate contracts	0	(140)	0
Income before gains on sales of real estate	562,958	500,998	432,016
Gains on sales of real estate	8,240	82,775	377,093
Net income	571,198	583,773	809,109
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships	(47,832)	2,068	(149,855)
Noncontrolling interest - redeemable preferred units	0	0	(6)
Net income attributable to the Company	523,366	585,841	659,248
Preferred dividends / distributions	(10,500)	(10,500)	(10,500)
Net income attributable to the Company's common shareholders / unitholders	$ 512,866	$ 575,341	$ 648,748
Basic earnings per common share / unit attributable to the Company
Net income (in dollars per share / unit)	$ 2.99	$ 3.36	$ 3.79
Weighted average number of common shares / units outstanding (in shares / units)	171,661	171,361	171,139
Diluted earnings per common share / unit attributable to the Company
Diluted Earnings: Net income, Per Share / Unit Amount (in dollars per share / unit)	$ 2.98	$ 3.35	$ 3.78
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)	171,861	171,623	171,512
Dividends/Distributions per common share/unit	$ 3.05	$ 2.70	$ 3.85

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income		$ 562,481	$ 569,977	$ 799,918
Other comprehensive loss:
Effective portion of interest rate contracts		(6,133)	(47,144)	(10,302)
Amortization of interest rate contracts	[1]	6,033	3,751	2,510
Other comprehensive loss		(100)	(43,393)	(7,792)
Comprehensive Income		562,381	526,584	792,126
Comprehensive income attributable to noncontrolling interests		(100,042)	(57,192)	(216,812)
Other comprehensive income (loss) attributable to noncontrolling interests		1,922	5,256	2,982
Comprehensive income attributable to the Company		464,261	474,648	578,296
Boston Properties Limited Partnership
Net income		571,198	583,773	809,109
Other comprehensive loss:
Effective portion of interest rate contracts		(6,133)	(47,144)	(10,302)
Amortization of interest rate contracts	[2]	6,033	3,751	2,510
Other comprehensive loss		(100)	(43,393)	(7,792)
Comprehensive Income		571,098	540,380	801,317
Comprehensive income attributable to noncontrolling interests		(45,704)	2,945	(147,433)
Other comprehensive income (loss) attributable to noncontrolling interests		2,128	877	2,428
Comprehensive income attributable to the Company		$ 525,394	$ 543,325	$ 653,884
[1]	Amounts reclassified from comprehensive income primarily to interest expense within Boston Properties, Inc.’s Consolidated Statements of Operations
[2]	Amounts reclassified from comprehensive income primarily to interest expense within Boston Properties Limited Partnership's Consolidated Statements of Operations.

Consolidated Statements Of Stoc

Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Dividends In Excess Of Earnings [Member]	Treasury Stock, At Cost [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]
Equity, value at Dec. 31, 2014	$ 7,902,936	$ 1,531	$ 200,000	$ 6,270,257	$ (762,464)	$ (2,722)	$ (9,304)	$ 2,205,638
Equity, shares at Dec. 31, 2014		153,114,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of operating partnership units to common stock		424,000
Redemption of operating partnership units to common stock	0	$ 5		14,338				(14,343)
Allocated net income for the year	794,791				583,106			211,685
Dividends/distributions declared	(671,041)				(601,594)			(69,447)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	780			780
Net activity from stock option and incentive plan, shares		36,000
Net activity from stock option and incentive plan, value	40,265			5,814				34,451
Acquisition of redeemable noncontrolling interest in property partnership	(1,586)			(1,586)
Sale of interests in property partnerships	0			(1,053)				1,053
Contributions from noncontrolling interests in property partnerships	2,705							2,705
Distributions to noncontrolling interests in property partnerships	(170,049)							(170,049)
Dissolution of property partnership	(4,082)							(4,082)
Effective portion of interest rate contracts	(10,302)						(7,061)	(3,241)
Amortization of interest rate contracts	2,510						2,251	259
Reallocation of noncontrolling interest	0			17,137				(17,137)
Equity, value at Dec. 31, 2015	7,886,927	$ 1,536	200,000	6,305,687	(780,952)	(2,722)	(14,114)	2,177,492
Equity, shares at Dec. 31, 2015		153,580,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of operating partnership units to common stock		191,000
Redemption of operating partnership units to common stock	0	$ 2		6,459				(6,461)
Allocated net income for the year	569,977				512,785			57,192
Dividends/distributions declared	(474,614)				(425,527)			(49,087)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	730			730
Net activity from stock option and incentive plan, shares		13,000
Net activity from stock option and incentive plan, value	31,910			3,979				27,931
Sale of interests in property partnerships	0			1,195				(1,195)
Contributions from noncontrolling interests in property partnerships	11,951							11,951
Distributions to noncontrolling interests in property partnerships	(51,564)							(51,564)
Effective portion of interest rate contracts	(47,144)						(41,502)	(5,642)
Amortization of interest rate contracts	3,751						3,365	386
Reallocation of noncontrolling interest	0			15,374				(15,374)
Equity, value at Dec. 31, 2016	$ 7,931,924	$ 1,538	200,000	6,333,424	(693,694)	(2,722)	(52,251)	2,145,629
Equity, shares at Dec. 31, 2016	153,790,175	153,790,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of operating partnership units to common stock		495,000
Redemption of operating partnership units to common stock	$ 0	$ 5		16,911				(16,916)
Allocated net income for the year	562,481				462,439			100,042
Dividends/distributions declared	(535,310)				(480,816)			(54,494)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	795			795
Net activity from stock option and incentive plan, shares		34,000
Net activity from stock option and incentive plan, value	37,292			3,899				33,393
Cumulative effect of a change in accounting principle	(2,035)				(272)			(1,763)
Contributions from noncontrolling interests in property partnerships	161,585							161,585
Distributions to noncontrolling interests in property partnerships	(54,176)							(54,176)
Effective portion of interest rate contracts	(6,133)						(3,305)	(2,828)
Amortization of interest rate contracts	6,033						5,127	906
Reallocation of noncontrolling interest	0			22,879				(22,879)
Equity, value at Dec. 31, 2017	$ 8,102,456	$ 1,543	$ 200,000	$ 6,377,908	$ (712,343)	$ (2,722)	$ (50,429)	$ 2,288,499
Equity, shares at Dec. 31, 2017	154,325,286	154,325,000

Consolidated Statement of Partn

Consolidated Statement of Partners' Capital Statement - USD ($) $ in Thousands	Total	Boston Properties Limited Partnership
Beginning balance at Dec. 31, 2014		$ 3,639,916
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions		4,071
Acquisition of redeemable noncontrolling interest in property partnership	$ (1,586)	(1,586)
Net income allocable to general and limited partner units		592,297
Distributions		(601,594)
Other comprehensive Income (loss)		(4,810)
Unearned compensation		1,470
Conversion of redeemable partnership units		14,343
Adjustment to reflect redeemable partnership units at redemption value		40,415
Ending Balance at Dec. 31, 2015		3,684,522
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions		3,144
Net income allocable to general and limited partner units		526,581
Distributions		(425,527)
Other comprehensive Income (loss)		(38,137)
Unearned compensation		2,760
Conversion of redeemable partnership units		6,461
Adjustment to reflect redeemable partnership units at redemption value		51,913
Ending Balance at Dec. 31, 2016		3,811,717
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions		4,937
Net income allocable to general and limited partner units		471,156
Distributions		(480,816)
Other comprehensive Income (loss)		1,822
Cumulative effect of a change in accounting principle	$ (2,035)	(272)
Unearned compensation		(243)
Conversion of redeemable partnership units		16,916
Adjustment to reflect redeemable partnership units at redemption value		(17,587)
Ending Balance at Dec. 31, 2017		$ 3,807,630

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 562,481	$ 569,977	$ 799,918
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	617,547	694,403	639,542
Impairment loss	0	1,783	0
Non-cash compensation expense	35,361	32,911	29,183
Income from unconsolidated joint ventures	(11,232)	(8,074)	(22,770)
Gain on sale of investment in unconsolidated joint venture	0	(59,370)	0
Distributions of net cash flow from operations of unconsolidated joint ventures	26,858	24,955	8,469
(Gains) losses on investments in securities	(3,678)	(2,273)	653
Non-cash portion of interest expense	(1,284)	(35,052)	(42,271)
Settlement of accreted debt discount on redemption of unsecured senior notes	(1,980)	0	0
(Gains) losses from early extinguishments of debt	(13,280)	371	21,837
Gains on sales of real estate	(7,663)	(80,606)	(375,895)
Change in assets and liabilities:
Cash held in escrows	8,194	2,277	(18,284)
Tenant and other receivables, net	2,433	3,688	(46,326)
Accrued rental income, net	(58,355)	(28,127)	(73,911)
Prepaid expenses and other assets	51,425	52,923	(16,877)
Accounts payable and accrued expenses	10,482	15,666	(6,310)
Accrued interest payable	(160,521)	53,547	26,854
Other liabilities	(44,914)	(106,022)	(34,005)
Tenant leasing costs	(104,429)	(96,103)	(90,396)
Total adjustments	344,964	466,897	(507)
Net cash provided by operating activities	907,445	1,036,874	799,411
Cash flows from investing activities:
Acquisitions of real estate	(15,953)	(78,000)	0
Construction in progress	(608,404)	(500,350)	(374,664)
Building and other capital improvements	(222,482)	(150,640)	(112,755)
Tenant improvements	(205,331)	(230,298)	(144,572)
Proceeds from sales of real estate	29,810	122,750	602,600
Proceeds from sales of real estate placed in escrow	(29,810)	(122,647)	(200,612)
Proceeds from sales of real estate released from escrow	29,810	122,647	634,165
Cash placed in escrow for land sale contracts	0	0	(7,111)
Cash released from escrow for land sale contracts	0	1,596	5,312
Cash released from escrow for investing activities	9,230	6,694	0
Cash placed in escrow for investment in unconsolidated joint venture	(25,000)	0	0
Capital contributions to unconsolidated joint ventures	(109,015)	(575,795)	(38,207)
Capital distributions from unconsolidated joint ventures	251,000	20,440	24,527
Proceeds from sale of investment in unconsolidated joint venture	0	55,707	0
Investments in marketable securities	0	0	(667,335)
Investments in securities, net	(1,669)	(1,161)	(1,574)
Net cash used in investing activities	(897,814)	(1,329,057)	(280,226)
Cash flows from financing activities:
Proceeds from mortgage notes payable	2,300,000	0	0
Repayments of mortgage notes payable	(1,317,653)	(1,326,865)	(54,801)
Proceeds from unsecured senior notes	847,935	1,989,790	0
Redemption of unsecured senior notes	(848,020)	0	0
Borrowings on unsecured line of credit	580,000	25,000	0
Repayments of unsecured line of credit	(535,000)	(25,000)	0
Repayments of mezzanine notes payable	(306,000)	0	0
Repayments of outside members’ notes payable	(70,424)	0	0
Payments on capital lease obligations	(401)	(745)	(356)
Proceeds from real estate financing transaction	0	0	6,000
Payments on real estate financing transactions	(2,840)	(5,260)	(3,103)
Deposit on mortgage note payable interest rate lock	(23,200)	0	0
Return of deposit on mortgage note payable interest rate lock	23,200	0	0
Deferred financing costs	(50,705)	(16,121)	(1,510)
Net proceeds from equity transactions	241	(271)	799
Redemption of preferred units	0	0	(633)
Dividends and distributions	(526,578)	(671,626)	(1,226,199)
Contributions from noncontrolling interests in property partnerships	52,009	11,951	2,705
Acquisition of noncontrolling interest in property partnership	0	0	(108,499)
Distributions to noncontrolling interests in property partnerships	(54,342)	(55,474)	(172,949)
Net cash provided by (used in) financing activities	68,222	(74,621)	(1,558,546)
Net increase (decrease) in cash and cash equivalents	77,853	(366,804)	(1,039,361)
Cash and cash equivalents, beginning of year	356,914	723,718	1,763,079
Cash and cash equivalents, end of year	434,767	356,914	723,718
Supplemental disclosures:
Cash paid for interest	598,486	433,591	481,826
Interest capitalized	61,070	39,237	34,213
Non-cash investing and financing activities:
Write off of fully depreciated real estate	(124,891)	(206,721)	(45,455)
Change in real estate included in accounts payable and accrued expenses	27,978	(1,481)	74,985
Real estate acquired through capital lease	28,962	21,000	0
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	109,576	0	0
Marketable securities transferred in connection with the legal defeasance of mortgage note payable	0	0	667,335
Mortgage note payable legally defeased	0	0	640,500
Mortgage note payable assigned in connection with the sale of real estate	0	0	116,993
Dividends and distributions declared but not paid	139,040	130,308	327,320
Conversions of noncontrolling interests to stockholders’ equity	16,916	6,461	14,343
Issuance of restricted securities to employees and directors	35,989	33,615	43,355
Boston Properties Limited Partnership
Net income	571,198	583,773	809,109
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	609,407	682,776	631,549
Impairment loss	0	1,783	0
Non-cash compensation expense	35,361	32,911	29,183
Income from unconsolidated joint ventures	(11,232)	(8,074)	(22,770)
Gain on sale of investment in unconsolidated joint venture	0	(59,370)	0
Distributions of net cash flow from operations of unconsolidated joint ventures	26,858	24,955	8,469
(Gains) losses on investments in securities	(3,678)	(2,273)	653
Non-cash portion of interest expense	(1,284)	(35,052)	(42,271)
Settlement of accreted debt discount on redemption of unsecured senior notes	(1,980)	0	0
(Gains) losses from early extinguishments of debt	(13,280)	371	21,837
Gains on sales of real estate	(8,240)	(82,775)	(377,093)
Change in assets and liabilities:
Cash held in escrows	8,194	2,277	(18,284)
Tenant and other receivables, net	2,433	3,688	(46,326)
Accrued rental income, net	(58,355)	(28,127)	(73,911)
Prepaid expenses and other assets	51,425	52,923	(16,877)
Accounts payable and accrued expenses	10,482	15,666	(6,310)
Accrued interest payable	(160,521)	53,547	26,854
Other liabilities	(44,914)	(106,022)	(34,005)
Tenant leasing costs	(104,429)	(96,103)	(90,396)
Total adjustments	336,247	453,101	(9,698)
Net cash provided by operating activities	907,445	1,036,874	799,411
Cash flows from investing activities:
Acquisitions of real estate	(15,953)	(78,000)	0
Construction in progress	(608,404)	(500,350)	(374,664)
Building and other capital improvements	(222,482)	(150,640)	(112,755)
Tenant improvements	(205,331)	(230,298)	(144,572)
Proceeds from sales of real estate	29,810	122,750	602,600
Proceeds from sales of real estate placed in escrow	(29,810)	(122,647)	(200,612)
Proceeds from sales of real estate released from escrow	29,810	122,647	634,165
Cash placed in escrow for land sale contracts	0	0	(7,111)
Cash released from escrow for land sale contracts	0	1,596	5,312
Cash released from escrow for investing activities	9,230	6,694	0
Cash placed in escrow for investment in unconsolidated joint venture	(25,000)	0	0
Capital contributions to unconsolidated joint ventures	(109,015)	(575,795)	(38,207)
Capital distributions from unconsolidated joint ventures	251,000	20,440	24,527
Proceeds from sale of investment in unconsolidated joint venture	0	55,707	0
Investments in marketable securities	0	0	(667,335)
Investments in securities, net	(1,669)	(1,161)	(1,574)
Net cash used in investing activities	(897,814)	(1,329,057)	(280,226)
Cash flows from financing activities:
Proceeds from mortgage notes payable	2,300,000	0	0
Repayments of mortgage notes payable	(1,317,653)	(1,326,865)	(54,801)
Proceeds from unsecured senior notes	847,935	1,989,790	0
Redemption of unsecured senior notes	(848,020)	0	0
Borrowings on unsecured line of credit	580,000	25,000	0
Repayments of unsecured line of credit	(535,000)	(25,000)	0
Repayments of mezzanine notes payable	(306,000)	0	0
Repayments of outside members’ notes payable	(70,424)	0	0
Payments on capital lease obligations	(401)	(745)	(356)
Proceeds from real estate financing transaction	0	0	6,000
Payments on real estate financing transactions	(2,840)	(5,260)	(3,103)
Deposit on mortgage note payable interest rate lock	(23,200)	0	0
Return of deposit on mortgage note payable interest rate lock	23,200	0	0
Deferred financing costs	(50,705)	(16,121)	(1,510)
Net proceeds from equity transactions	241	(271)	799
Redemption of preferred units	0	0	(633)
Dividends and distributions	(526,578)	(671,626)	(1,226,199)
Contributions from noncontrolling interests in property partnerships	52,009	11,951	2,705
Acquisition of noncontrolling interest in property partnership	0	0	(108,499)
Distributions to noncontrolling interests in property partnerships	(54,342)	(55,474)	(172,949)
Net cash provided by (used in) financing activities	68,222	(74,621)	(1,558,546)
Net increase (decrease) in cash and cash equivalents	77,853	(366,804)	(1,039,361)
Cash and cash equivalents, beginning of year	356,914	723,718	1,763,079
Cash and cash equivalents, end of year	434,767	356,914	723,718
Supplemental disclosures:
Cash paid for interest	598,486	433,591	481,826
Interest capitalized	61,070	39,237	34,213
Non-cash investing and financing activities:
Write off of fully depreciated real estate	(123,714)	(202,388)	(45,455)
Change in real estate included in accounts payable and accrued expenses	27,978	(1,481)	74,985
Real estate acquired through capital lease	28,962	21,000	0
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	109,576	0	0
Marketable securities transferred in connection with the legal defeasance of mortgage note payable	0	0	667,335
Mortgage note payable legally defeased	0	0	640,500
Mortgage note payable assigned in connection with the sale of real estate	0	0	116,993
Dividends and distributions declared but not paid	139,040	130,308	327,320
Conversions of noncontrolling interests to stockholders’ equity	16,916	6,461	14,343
Issuance of restricted securities to employees and directors	$ 35,989	$ 33,615	$ 43,355

Organization

Organization	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Boston Properties, Inc., a Delaware corporation, is a fully integrated, self-administered and self-managed real estate investment trust (“REIT”). Boston Properties, Inc. is the sole general partner of Boston Properties Limited Partnership, its operating partnership and at December 31, 2017 owned an approximate 89.7% ( 89.5% at December 31, 2016 ) general and limited partnership interest in Boston Properties Limited Partnership. Unless stated otherwise or the context requires, the “Company” refers to Boston Properties, Inc. and its subsidiaries, including Boston Properties Limited Partnership and its consolidated subsidiaries. Partnership interests in Boston Properties Limited Partnership include: • common units of partnership interest (also referred to as “OP Units”), • long term incentive units of partnership interest (also referred to as “LTIP Units”), and • preferred units of partnership interest (also referred to as “Preferred Units”). Unless specifically noted otherwise, all references to OP Units exclude units held by Boston Properties, Inc. A holder of an OP Unit may present such OP Unit to Boston Properties Limited Partnership for redemption at any time (subject to restrictions agreed upon at the time of issuance of OP Units to particular holders that may restrict such redemption right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, Boston Properties Limited Partnership is obligated to redeem such OP Unit for cash equal to the value of a share of common stock of Boston Properties, Inc. (“Common Stock”) at such time. In lieu of a cash redemption, Boston Properties, Inc. may elect to acquire the OP Unit for one share of Common Stock. Because the number of shares of Common Stock outstanding at all times equals the number of OP Units that Boston Properties, Inc. owns, one share of Common Stock is generally the economic equivalent of one OP Unit, and the quarterly distribution that may be paid to the holder of an OP Unit equals the quarterly dividend that may be paid to the holder of a share of Common Stock. The Company uses LTIP Units as a form of equity-based award for annual long-term incentive equity compensation. The Company has also issued LTIP Units to employees in the form of (1) 2012 outperformance plan awards (“2012 OPP Units”) and (2) 2013, 2014, 2015, 2016 and 2017 multi-year, long-term incentive program awards (also referred to as “MYLTIP Units”), each of which, upon the satisfaction of certain performance and vesting conditions, is convertible into one OP Unit. The three -year measurement periods for the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units expired on February 6, 2015, February 4, 2016 and February 3, 2017, respectively, and Boston Properties, Inc.’s total stockholder return (“TSR”) was sufficient for employees to earn and therefore become eligible to vest in a portion of the awards. Unless and until they are earned, the rights, preferences and privileges of the 2015, 2016 and 2017 MYLTIP Units differ from other LTIP Units granted to employees (including the 2012 OPP Units, the 2013 MYLTIP Units and the 2014 MYLTIP Units, which have been earned). Therefore, unless specifically noted otherwise, all references to LTIP Units exclude the 2015, 2016 and 2017 MYLTIP Units. LTIP Units (including the 2012 OPP Units, the 2013 MYLTIP Units and the 2014 MYLTIP Units), whether vested or not, will receive the same quarterly per unit distributions as OP Units, which equal per share dividends on Common Stock (See Notes 11 , 17 and 20 ). At December 31, 2017 , there was one series of Preferred Units outstanding (i.e., Series B Preferred Units). The Series B Preferred Units were issued to Boston Properties, Inc. on March 27, 2013 in connection with the issuance of 80,000 shares ( 8,000,000 depositary shares each representing 1/100th of a share) of 5.25% Series B Cumulative Redeemable Preferred Stock (the “Series B Preferred Stock”). Boston Properties, Inc. contributed the net proceeds from the offering to Boston Properties Limited Partnership in exchange for 80,000 Series B Preferred Units having terms and preferences generally mirroring those of the Series B Preferred Stock (See Note 12 ). Properties At December 31, 2017 , the Company owned or had interests in a portfolio of 179 commercial real estate properties (the “Properties”) aggregating approximately 50.3 million net rentable square feet of primarily Class A office properties, including twelve properties under construction/redevelopment totaling approximately 6.2 million net rentable square feet. At December 31, 2017 , the Properties consisted of: • 167 office properties (including eight properties under construction/redevelopment); • six residential properties (including four properties under construction); • five retail properties; and • one hotel. The Company considers Class A office properties to be well located buildings that are professionally managed and maintained, attract high-quality tenants and command upper-tier rental rates, and that are modern structures or have been modernized to compete with newer buildings. Basis of Presentation Boston Properties, Inc. does not have any other significant assets, liabilities or operations, other than its investment in Boston Properties Limited Partnership, nor does it have employees of its own. Boston Properties Limited Partnership, not Boston Properties, Inc., generally executes all significant business relationships other than transactions involving securities of Boston Properties, Inc. All majority-owned subsidiaries and joint ventures over which the Company has financial and operating control and variable interest entities (“VIEs”) in which the Company has determined it is the primary beneficiary are included in the consolidated financial statements. All significant intercompany balances and transactions have been eliminated in consolidation. The Company accounts for all other unconsolidated joint ventures using the equity method of accounting. Accordingly, the Company’s share of the earnings of these joint ventures and companies is included in consolidated net income. Variable Interest Entities (VIEs) On January 1, 2016, the Company adopted Accounting Standards Update (“ASU”) ASU 2015-02, “Consolidation (Topic 810): Amendments to the Consolidation Analysis” (“ASU 2015-02”). ASU 2015-02 affects reporting entities that are required to evaluate whether they should consolidate certain legal entities. ASU 2015-02 (1) modifies the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities, (2) eliminates the presumption that a general partner should consolidate a limited partnership and (3) affects the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships. The Company reviewed all of its legal entities in accordance with ASU 2015-02 and concluded that certain of its legal entities, including Boston Properties Limited Partnership, which had been consolidated in accordance with the voting interest model, are now variable interest entities under the VIE model, as discussed below. The adoption of the guidance did not alter any of the Company’s consolidation conclusions, but resulted in additional disclosures. Consolidated VIEs are those where the Company is considered to be the primary beneficiary of a VIE. The primary beneficiary is the entity that has a controlling financial interest in the VIE, which is defined by the entity having both of the following characteristics: (1) the power to direct the activities that, when taken together, most significantly impact the VIE’s performance and (2) the obligation to absorb losses or the right to receive the returns from the VIE that could potentially be significant to the VIE. The Company has determined that it is the primary beneficiary for seven of the nine entities that are VIEs. Consolidated Variable Interest Entities As of December 31, 2017 , Boston Properties, Inc. has identified seven consolidated VIEs, including Boston Properties Limited Partnership. Excluding Boston Properties Limited Partnership, the VIEs are (1) the following five in-service properties: 767 Fifth Avenue (the General Motors Building), Time Square Tower, 601 Lexington Avenue, Atlantic Wharf Office Building and 100 Federal Street and (2) the entity that owns Salesforce Tower, which was partially placed in-service on December 1, 2017. The Company consolidates these VIEs because it is the primary beneficiary. The third parties’ interests in these consolidated entities, with the exception of Boston Properties Limited Partnership, are reflected as noncontrolling interests in property partnerships in the accompanying Consolidated Financial Statements (See Note 11 ). In addition, Boston Properties, Inc.’s only significant asset is its investment in Boston Properties Limited Partnership and, consequently, substantially all of Boston Properties, Inc.’s assets and liabilities are the assets and liabilities of Boston Properties Limited Partnership. Variable Interest Entities Not Consolidated The Company has determined that its 7750 Wisconsin Avenue LLC and Residential Tower Developer LLC joint ventures, which own 7750 Wisconsin Avenue and The Hub on Causeway - Residential, respectively, are VIEs. The Company does not consolidate these entities as the Company does not have the power to direct the activities that, when taken together, most significantly impact the VIE’s performance and, therefore, the Company is not considered to be the primary beneficiary.

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis Of Presentation And Summary Of Significant Accounting Policies	2. Summary of Significant Accounting Policies Real Estate Upon acquisitions of real estate, 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 tenants’ 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 an asset is not recoverable and exceeds its fair value. The evaluation of anticipated cash flows is highly subjective and is based in part on assumptions regarding anticipated hold period, future occupancy, rental rates and capital requirements that could differ materially from actual results in future periods. Because 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 an impairment has occurred, the affected assets must be reduced to their fair value, less cost to sell. Guidance in Accounting Standards Codification (“ASC”) 360 “Property Plant and Equipment” (“ASC 360”) 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. Discontinued operations presentation applies only to disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results (e.g., a disposal of a major geographical area, a major line of business, a major equity method investment or other major parts of an entity). The components of the property’s net income that are 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 Boston Properties, Inc.’s Board of Directors, or a committee thereof, and there are no known significant contingencies relating to the sale, such that a sale of the property 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 capitalizes acquisition costs that it incurs to effect an asset acquisition and expenses acquisition costs that it incurs to effect a business combination, including 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. Determination 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, involves a degree of judgment. The Company’s capitalization policy on development properties follows the 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 for 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, (2) occupied or held available for occupancy, and capitalizes only those costs associated with the portion under construction or (3) if activities necessary for the development of the property have been suspended. Interest costs capitalized for the years ended December 31, 2017 , 2016 and 2015 were $61.1 million , $39.2 million and $34.2 million , respectively. Salaries and related costs capitalized for the years ended December 31, 2017 , 2016 and 2015 were $13.2 million , $11.1 million and $10.4 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 “Business Combinations,” 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 . Cash Held in Escrows Escrows include amounts established pursuant to various agreements for security deposits, property taxes, insurance and other costs. Escrows also include cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties. 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 Boston Properties, Inc. 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, 2017 and 2016 , the Company had maintained approximately $29.2 million and $23.8 million , respectively, in a separate account, which is not restricted as to its use. The Company recognized gains (losses) of approximately $3.7 million , $2.3 million and $(0.7) million on its investments in the account associated with the Company’s deferred compensation plan during the years ended December 31, 2017 , 2016 and 2015 , 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 certain financing fees. Leasing costs include 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. Unamortized leasing costs are charged to expense upon the early termination of the lease. Fully amortized deferred leasing costs are removed from the books upon the expiration of the lease. Internal leasing salaries and related costs capitalized for the years ended December 31, 2017 , 2016 and 2015 were $5.0 million , $7.2 million and $5.5 million , respectively. Financing fees included in deferred charges consist of external fees and costs incurred to obtain the Company's revolving facility and if applicable, the delayed draw facility and construction financing arrangements where there are not sufficient amounts outstanding. Such financing costs have been deferred and are being amortized over the terms of the respective financing and included within interest expense. Unamortized financing costs are charged to expense upon the early repayment or significant modification of the financing. Fully amortized deferred financing costs are removed from the books upon the maturity of the debt. External fees and costs incurred to obtain mortgage financings and unsecured senior notes have been deferred and are presented as direct deductions from the carrying amounts of the corresponding debt liability. Such financing costs are being amortized over the terms of the respective financing and included within interest expense. Unamortized financing costs are charged to expense upon the early repayment or significant modification of the financing. Investments in Unconsolidated Joint Ventures The Company consolidates 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 substantive participating rights. 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 the right to receive the returns from the variable interest entity that could potentially be significant to the VIE. 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 noncontrolling 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. The ultimate realization of the investment in unconsolidated joint ventures is dependent on a number of factors, including the performance of each investment and market conditions. The Company will record an impairment charge if it determines that a decline in the value below the carrying value of an investment in an unconsolidated joint venture is other-than-temporary. 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. The combined summarized financial information of the unconsolidated joint ventures is disclosed in Note 5 . Revenue Recognition In general, the Company commences rental revenue recognition when the tenant takes possession of the leased space and the leased space is substantially ready for its intended use. 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 $54.8 million , $31.7 million and $80.0 million for the years ended December 31, 2017 , 2016 and 2015 , 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 acquired in-place “above-” and “below-market” leases at their fair values as rental revenue over the original term of the respective leases. The impact of the acquired in-place “above-” and “below-market” leases increased revenue by approximately $23.5 million , $30.2 million and $35.9 million for the years ended December 31, 2017 , 2016 and 2015 , 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 2018 $ 8,614 $ 32,152 2019 7,106 27,281 2020 5,394 10,736 2021 2,988 6,399 2022 315 5,669 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. 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 revenue is derived from room rentals and other sources such as charges to guests for telephone service, movie and vending commissions, meeting and banquet room revenue and laundry services. Hotel revenue is 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 records development fees as earned depending on the risk associated with each project. The Company recognizes development fees earned from joint venture projects equal to its cost plus profit 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 the 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 2114 . 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, 2017 , under non-cancelable ground leases which expire on various dates through 2114 , are as follows: Years Ending December 31, (in thousands) 2018 $ 11,349 2019 16,360 2020 25,552 2021 11,814 2022 8,894 Thereafter 576,315 Capital Leases The Company has three capital lease obligations with various initial term expiration dates through 2036. The following reflects the gross amount of assets recorded under capital leases by asset class at December 31, 2017 and December 31, 2016 (in thousands): December 31, 2017 2016 Buildings and improvements $ 23,636 $ 23,636 Construction in progress 28,962 — Total $ 52,598 $ 23,636 The future minimum lease payments, as of December 31, 2017, related to the three capital leases, through 2036 are as follows: Years Ending December 31, (in thousands) 2018 $ 913 2019 1,392 2020 2,097 2021 1,375 2022 930 Thereafter 74,185 Total expected minimum lease payments 80,892 Interest portion (29,296 ) Present value of expected net minimum lease payments $ 51,596 Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income available to common shareholders, as adjusted for undistributed earnings (if any) of certain securities issued by Boston Properties Limited 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 Boston Properties Limited Partnership that are exchangeable for Common Stock. Earnings Per Common Unit Basic earnings per common unit is computed by dividing net income available to common unitholders, as adjusted for undistributed earnings (if any) of certain securities issued by Boston Properties Limited Partnership, by the weighted average number of common units outstanding during the year. Diluted earnings per common unit reflects the potential dilution that could occur from units issuable in connection with awards under Boston Properties, Inc.’s stock-based compensation plans, including upon the exercise of stock options, and conversion of preferred units of Boston Properties Limited Partnership. 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. Boston Properties Limited Partnership determines the fair value of its unsecured senior notes using market prices. The inputs used in determining the fair value of Boston Properties Limited Partnership’s unsecured senior notes is categorized at a Level 1 basis (as defined in ASC 820 "Fair Value Measurements and Disclosures", the accounting standards for Fair Value Measurements and Disclosures) due to the fact that it uses quoted market rates to value these instruments. However, the inputs used in determining the fair value could be categorized at a level 2 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) if trading volumes are low. The Company determines the fair value of its mortgage notes payable using discounted cash flow analysis by discounting the spread between the future contractual interest payments and hypothetical future interest payments on mortgage debt based on current market rates for similar securities. In determining the current market rates, the Company adds its estimates of market spreads to the quoted yields on federal government treasury securities with similar maturity dates to its debt. The inputs used in determining the fair value of the Company’s mortgage notes payable and mezzanine notes payable are categorized at a level 3 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) due to the fact that the Company considers the rates used in the valuation techniques to be unobservable inputs. To the extent that there are outstanding borrowings under the unsecured line of credit, the Company utilizes a discounted cash flow methodology in order to estimate the fair value. To the extent that credit spreads have changed since the origination, the net present value of the difference between future contractual interest payments and future interest payments based on the Company’s estimate of a current market rate would represent the difference between the book value and the fair value. The Company’s estimate of a current market rate is based upon the rate, considering current market conditions and the Company’s specific credit profile, at which it estimates it could obtain similar borrowings. To the extent there are outstanding borrowings, this current market rate is estimated and therefore would be primarily based upon a level 3 input. Because the Company’s valuations of its financial instruments are based on these types of estimates, the actual fair values of its financial instruments may differ materially if the Company’s estimates do not prove to be accurate, and the Company’s estimated fair values for these instruments as of the end of the applicable reporting period are not necessarily indicative of estimated or actual fair values in future reporting periods. The following table presents the aggregate carrying value of the Company’s mortgage notes payable, net, mezzanine notes payable, unsecured senior notes, net and unsecured line of credit and the Company’s corresponding estimate of fair value as of December 31, 2017 and December 31, 2016 (in thousands): December 31, 2017 December 31, 2016 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Mortgage notes payable, net $ 2,979,281 $ 3,042,920 $ 2,063,087 $ 2,092,237 Mezzanine notes payable — — 307,093 308,344 Unsecured senior notes, net 7,247,330 7,461,615 7,245,953 7,428,077 Unsecured line of credit 45,000 45,000 — — Total $ 10,271,611 $ 10,549,535 $ 9,616,133 $ 9,828,658 The Company uses interest rate swap agreements to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. To comply with the provisions of ASC 820, the Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. Although the Company determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. The Company assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and determined that the credit valuation adjustments were not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. 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. Stock-Based Employee Compensation Plans At December 31, 2017 , the Company has a stock-based employee compensation plan. The Company accounts for the plan under the guidance in 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 t

Real Estate

Real Estate	12 Months Ended
	Dec. 31, 2017
Real Estate [Abstract]
Real Estate	3. Real Estate Boston Properties, Inc. Real estate consisted of the following at December 31, 2017 and December 31, 2016 (in thousands): 2017 2016 Land $ 5,080,679 $ 4,879,020 Land held for future development (1) 204,925 246,656 Buildings and improvements 12,284,164 11,890,626 Tenant improvements 2,219,608 2,060,315 Furniture, fixtures and equipment 37,928 32,687 Construction in progress 1,269,338 1,037,959 Total 21,096,642 20,147,263 Less: Accumulated depreciation (4,589,634 ) (4,222,235 ) $ 16,507,008 $ 15,925,028 _______________ (1) Includes pre-development costs. Boston Properties Limited Partnership Real estate consisted of the following at December 31, 2017 and December 31, 2016 (in thousands): 2017 2016 Land $ 4,976,303 $ 4,774,460 Land held for future development (1) 204,925 246,656 Buildings and improvements 11,977,062 11,581,795 Tenant improvements 2,219,608 2,060,315 Furniture, fixtures and equipment 37,928 32,687 Construction in progress 1,269,338 1,037,959 Total 20,685,164 19,733,872 Less: Accumulated depreciation (4,496,959 ) (4,136,364 ) $ 16,188,205 $ 15,597,508 _______________ (1) Includes pre-development costs. Development/Redevelopment On April 6, 2017, the Company commenced the construction of 145 Broadway, a build-to-suit Class A office project with approximately 485,000 net rentable square feet located in Cambridge, Massachusetts. On May 27, 2017, the Company completed and fully placed in-service Reservoir Place North, a Class A office redevelopment project with approximately 73,000 net rentable square feet located in Waltham, Massachusetts. On August 24, 2017, the Company entered into a 15 -year lease with the General Services Administration under which the Company will develop the new headquarters for the Transportation Security Administration (TSA). The TSA will occupy 100% of the office space of the approximately 634,000 net rentable square feet Class A office project and a parking garage at 6595 Springfield Center Drive located in Springfield, Virginia. Concurrently with the execution of the lease, the Company commenced development of the project and expects the building to be available for occupancy by the fourth quarter of 2020. On September 16, 2017, the Company completed and fully placed in-service 888 Boylston Street, a Class A office and retail project with approximately 417,000 net rentable square feet located in Boston, Massachusetts. On November 17, 2017, the Company partially placed in-service 191 Spring Street, a Class A office redevelopment project with approximately 171,000 net rentable square feet located in Lexington, Massachusetts. On November 28, 2017, the Company commenced construction of its 20 CityPoint development project totaling approximately 211,000 net rentable square feet of Class A office space located in Waltham, Massachusetts. On December 1, 2017, a consolidated entity in which the Company has a 95% interest partially placed in-service Salesforce Tower, a Class A office project with approximately 1,400,000 net rentable square feet located in San Francisco, California. On December 1, 2017, the Company entered into a 16 -year lease with a tenant for approximately 288,000 net rentable square feet of Class A office space to be located in the Company's 2100 Pennsylvania Avenue development project. In 2016, the Company entered into a development agreement with The George Washington University to pursue the development of 2100 Pennsylvania Avenue, a Class A office property with approximately 469,000 net rentable square feet on land parcels located in Washington, DC. The development agreement provides for the execution of a 75 -year ground lease for the property upon completion of the entitlement process and relocation of existing tenants anticipated to occur in 2019. Ground Lease On June 29, 2017, the Company executed a 99 -year ground lease (including extension options), with the right to purchase prior to 10 years after stabilization of the development project as defined in the lease, for land adjacent to the MacArthur BART station located in Oakland, California. The Company has commenced development of a 402 -unit residential building and supporting retail space on the site. The Company’s option to purchase the land, is considered a bargain purchase option and as a result, the Company has concluded that the lease should be accounted for as a capital lease. At the inception of the ground lease, the Company recorded an approximately $29.0 million capital lease asset and liability, which is reflected within Construction in Progress and Other Liabilities on the Company’s Consolidated Balance Sheets. Capital lease assets and liabilities are accounted for at the lower of fair market value or the present value of future minimum lease payments. This capital lease is for land only, therefore, the Company will not be depreciating the capital lease asset, because land is assumed to have an indefinite life. As of June 29, 2017, future minimum lease payments related to this capital lease are as follows (in thousands): Period from June 29, 2017 through December 31, 2017 $ 5 2018 10 2019 10 2020 10 2021 13 Thereafter 38,778 Total expected minimum lease payments 38,826 Interest portion (9,864 ) Present value of expected net minimum lease payments $ 28,962 Acquisitions On May 15, 2017, the Company acquired 103 Carnegie Center located in Princeton, New Jersey for a purchase price of approximately $15.8 million in cash. 103 Carnegie Center is an approximately 96,000 net rentable square foot Class A office property. The following table summarizes the allocation of the aggregate purchase price, including transaction costs, of 103 Carnegie Center at the date of acquisition (in thousands). Land $ 2,890 Building and improvements 11,229 Tenant improvements 871 In-place lease intangibles 2,389 Below-market lease intangible (1,426 ) Net assets acquired $ 15,953 The following table summarizes the estimated annual amortization of the acquired below-market lease intangibles and the acquired in-place lease intangibles for 103 Carnegie Center for the remainder of 2017 and each of the next four succeeding fiscal years (in thousands). Acquired In-Place Lease Intangibles Acquired Below- Market Lease Intangibles Period from May 15, 2017 through December 31, 2017 $ 660 $ (248 ) 2018 590 (363 ) 2019 367 (337 ) 2020 243 (308 ) 2021 96 (105 ) 103 Carnegie Center contributed approximately $1.7 million of revenue and approximately ( $0.3 million ) of earnings to the Company for the period from May 15, 2017 through December 31, 2017. Dispositions On April 19, 2017, the Company completed the sale of an approximately 9.5 -acre parcel of land at 30 Shattuck Road located in Andover, Massachusetts for a gross sale price of $5.0 million . Net cash proceeds totaled approximately $5.0 million , resulting in a gain on sale of real estate totaling approximately $3.7 million . On June 13, 2017, the Company completed the sale of 40 Shattuck Road located in Andover, Massachusetts for a gross sale price of $12.0 million . Net cash proceeds totaled approximately $11.9 million , resulting in a gain on sale of real estate totaling approximately $28,000 for Boston Properties, Inc. and approximately $0.6 million for Boston Properties Limited Partnership. 40 Shattuck Road is an approximately 122,000 net rentable square foot Class A office property. 40 Shattuck Road contributed approximately $ (28,000) of net loss to the Company for the period from January 1, 2017 through June 13, 2017 and contributed approximately $(50,000) and $0.3 million of net income (loss) to the Company for the years ended December 31, 2016 and 2015, respectively. On August 30, 2017, the Company completed the sale of its Reston Eastgate property located in Reston, Virginia for a gross sale price of $14.0 million . Net cash proceeds totaled approximately $13.2 million , resulting in a gain on sale of real estate totaling approximately $2.8 million . Reston Eastgate is a parcel of land containing approximately 21.7 acres located at 11011 Sunset Hills Road.

Deferred Charges

Deferred Charges	12 Months Ended
	Dec. 31, 2017
Deferred Charges [Abstract]
Deferred Charges	4. Deferred Charges Deferred charges consisted of the following at December 31, 2017 and December 31, 2016 (in thousands): 2017 2016 Leasing costs, including lease related intangibles $ 1,147,181 $ 1,132,092 Financing costs 14,991 6,094 1,162,172 1,138,186 Less: Accumulated amortization (483,134 ) (452,023 ) $ 679,038 $ 686,163 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 2018 $ 33,651 2019 27,333 2020 14,464 2021 8,777 2022 4,758

Investments in Unconsolidated J

Investments in Unconsolidated Joint Ventures	12 Months Ended
	Dec. 31, 2017
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	5. Investments in Unconsolidated Joint Ventures The investments in unconsolidated joint ventures consist of the following at December 31, 2017 and 2016 : Carrying Value of Investment (1) Entity Properties Nominal % Ownership December 31, December 31, (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (8,258 ) $ (8,134 ) The Metropolitan Square Associates LLC Metropolitan Square 20.0 % 3,339 2,004 BP/CRF 901 New York Avenue LLC 901 New York Avenue 25.0 % (2) (13,811 ) (10,564 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 39,710 41,605 Annapolis Junction NFM, LLC Annapolis Junction 50.0 % (4) 18,381 20,539 540 Madison Venture LLC 540 Madison Avenue 60.0 % 66,179 67,816 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (3,876 ) (3,389 ) 501 K Street LLC 1001 6th Street 50.0 % (5) 42,657 42,528 Podium Developer LLC The Hub on Causeway 50.0 % 67,120 29,869 Residential Tower Developer LLC The Hub on Causeway - Residential 50.0 % (6) 28,212 20,803 Hotel Tower Developer LLC The Hub on Causeway - Hotel 50.0 % 1,690 933 1265 Main Office JV LLC 1265 Main Street 50.0 % 4,641 4,779 BNY Tower Holdings LLC Dock 72 at the Brooklyn Navy Yard 50.0 % 72,104 33,699 CA-Colorado Center Limited Partnership Colorado Center 50.0 % 254,440 510,623 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % (6) 21,452 N/A $ 593,980 $ 753,111 _______________ (1) Investments with deficit balances aggregating approximately $25.9 million and $22.1 million at December 31, 2017 and 2016 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets. (2) The Company’s economic ownership has increased based on the achievement of certain return thresholds. (3) The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project. (4) The joint venture owns four in-service buildings and two undeveloped land parcels. (5) Under the joint venture agreement for this land parcel, the partner will be entitled to up to two additional payments from the venture based on increases in total entitled square footage of the project above 520,000 square feet and achieving certain project returns at stabilization. (6) This entity is a VIE (See Note 2 ). Certain of the Company’s unconsolidated joint venture agreements include provisions whereby, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exceptions under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. Under certain of the Company's joint venture agreements, if certain return thresholds are achieved the partners will be entitled to an additional promoted interest or payments. The combined summarized balance sheets of the Company’s unconsolidated joint ventures are as follows: December 31, December 31, (in thousands) ASSETS Real estate and development in process, net $ 1,768,996 $ 1,519,217 Other assets 367,743 297,263 Total assets $ 2,136,739 $ 1,816,480 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 1,437,440 $ 865,665 Other liabilities 99,215 67,167 Members’/Partners’ equity 600,084 883,648 Total liabilities and members’/partners’ equity $ 2,136,739 $ 1,816,480 Company’s share of equity $ 286,495 $ 450,662 Basis differentials (1) 307,485 302,449 Carrying value of the Company’s investments in unconsolidated joint ventures (2) $ 593,980 $ 753,111 _______________ (1) This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At December 31, 2017 and 2016 , there was an aggregate basis differential of approximately $322.5 million and $328.8 million , respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities. (2) Investments with deficit balances aggregating approximately $25.9 million and $22.1 million at December 31, 2017 and 2016 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets. The combined summarized statements of operations of the Company’s unconsolidated joint ventures are as follows: For the year ended December 31, 2017 2016 2015 (in thousands) Total revenue (1) $ 222,517 $ 177,182 $ 155,642 Expenses Operating 90,542 76,741 65,093 Depreciation and amortization 57,079 44,989 36,057 Total expenses 147,621 121,730 101,150 Operating income 74,896 55,452 54,492 Other expense Interest expense (46,371 ) (34,016 ) (32,176 ) Net income $ 28,525 $ 21,436 $ 22,316 Company’s share of net income (2) $ 18,439 $ 9,873 $ 22,031 Basis differential (3) (7,207 ) (1,799 ) 739 Income from unconsolidated joint ventures $ 11,232 $ 8,074 $ 22,770 Gain on sale of investment in unconsolidated joint venture $ — $ 59,370 $ — _______________ (1) Includes straight-line rent adjustments of approximately $21.7 million , $18.1 million and $3.9 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. (2) During the year ended December 31, 2015, the Company received a distribution of approximately $24.5 million , which was generated from the excess loan proceeds from the refinancing of 901 New York Avenue’s mortgage loan to a new 10 -year mortgage loan totaling $225.0 million . The Company’s allocation of income and distributions for the year ended December 31, 2015 was not proportionate to its nominal ownership interest as a result of the achievement of specified investment return thresholds, as provided for in the joint venture agreement. (3) Includes straight-line rent adjustments of approximately $1.9 million and $1.4 million for the years ended December 31, 2017 and 2016, respectively. Also includes net above-/below-market rent adjustments of approximately $2.9 million and $0.9 million for the years ended December 31, 2017 and 2016, respectively. On July 10, 2017, the Company acquired an additional 0.2% interest in the unconsolidated joint venture that owns Colorado Center located in Santa Monica, California for approximately $2.1 million in cash. Following the acquisition, the Company owns a 50% interest in the joint venture. The Company continues to account for the joint venture under the equity method of accounting as there were no changes to the rights of the members as a result of the acquisition. On July 28, 2017, the unconsolidated joint venture obtained mortgage financing collateralized by the property totaling $550.0 million . The mortgage financing bears interest at a fixed rate of 3.56% per annum and matures on August 9, 2027. The loan requires interest-only payments during the 10-year term of the loan, with the entire principal amount due at maturity. The joint venture distributed to the partners the net proceeds from the financing totaling $502.0 million , of which the Company’s share was $251.0 million . Colorado Center is a six -building office complex that sits on a 15 -acre site and contains an aggregate of approximately 1,118,000 net rentable square feet with an underground parking garage for 3,100 vehicles. On August 7, 2017, the Company entered into a joint venture with The Bernstein Companies to develop an approximately 733,000 net rentable square foot (subject to adjustment based on finalized building design) build-to-suit Class A office building and below-grade parking garage at 7750 Wisconsin Avenue in Bethesda, Maryland. The joint venture entered into a lease agreement with an affiliate of Marriott International, Inc. under which Marriott will lease 100% of the office building and garage for a term of 20 years, and the building will serve as Marriott’s new worldwide headquarters. Marriott has agreed to fund 100% of the related tenant improvement costs and leasing commissions for the office building. The Company will serve as co-development manager for the venture and expects to commence construction in 2018. The Company and The Bernstein Companies each own a 50% interest in the joint venture. For its initial contribution, The Bernstein Companies contributed land with an initial fair value of $72.0 million and cash and improvements aggregating approximately $4.9 million . The Company contributed cash and improvements aggregating approximately $20.8 million for its initial contribution, of which $11.0 million was distributed to The Bernstein Companies. In addition, the Company was required to fund $25.0 million into an escrow account to be used by the joint venture to fund future development costs. See also Note 10 . On September 6, 2017, a joint venture in which the Company has a 50% interest obtained construction financing with a total commitment of $204.6 million collateralized by its Hub on Causeway development project. The construction financing bears interest at a variable rate equal to LIBOR plus 2.25% per annum and matures on September 6, 2021, with two , one -year extension options, subject to certain conditions. The Hub on Causeway is an approximately 385,000 net rentable square foot project containing retail and office space located in Boston, Massachusetts. In connection with the construction financing, the Company obtained the right to complete the construction of the garage underneath the project being developed by an affiliate of its joint venture partner and obtain funding from the garage construction lender. The Company agreed to guarantee completion of the garage to the construction lender and an affiliate of its partner agreed to reimburse the Company for the partner’s share of any payments made under the guarantee. On December 1, 2017, a joint venture in which the Company has a 50% interest commenced construction of a residential project aggregating approximately 320,000 square feet comprised of 440 residential units at its Hub on Causeway mixed-use development project located in Boston, Massachusetts.

Mortgage Notes Payable, Net, Me

Mortgage Notes Payable, Net, Mezzanine Notes Payable and Outside Members’ Notes Payable	12 Months Ended
	Dec. 31, 2017
Loans Payable [Abstract]
6. Mortgage Notes Payable, Net, Mezzanine Notes Payable and Outside Members’ Notes Payable	6. Mortgage Notes Payable, Net, Mezzanine Notes Payable and Outside Members’ Notes Payable The Company had outstanding mortgage notes payable totaling approximately $3.0 billion and $2.1 billion as of December 31, 2017 and 2016 , 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 June 9, 2027 . Fixed rate mortgage notes payable totaled approximately $3.0 billion and $2.1 billion at December 31, 2017 and 2016 , respectively, with contractual interest rates ranging from 3.43% to 7.69% per annum at December 31, 2017 and 4.75% to 7.69% per annum at December 31, 2016 (with a weighted-average interest rate of 3.78% and 5.59% per annum (excluding the mezzanine notes payable) at December 31, 2017 and 2016 , respectively). There were no variable rate mortgage loans at December 31, 2017 and 2016 . On June 7, 2017, the Company’s consolidated entity in which it has a 60% ownership interest and that owns 767 Fifth Avenue (the General Motors Building) located in New York City completed the refinancing of the indebtedness that had been secured by direct and indirect interests in the property. The new mortgage financing has a principal amount of $2.3 billion , bears interest at a fixed interest rate of 3.43% per annum and matures on June 9, 2027. The loan requires monthly interest-only payments during the 10-year term of the loan, with the entire principal amount being due at maturity. The refinanced indebtedness consisted of (1) mortgage loans payable collateralized by the property aggregating $1.3 billion , (2) mezzanine loans payable aggregating $306.0 million , (3) additional mezzanine loans payable aggregating $294.0 million and (4) member loans aggregating $450.0 million with outstanding accrued interest payable totaling approximately $425.0 million . The mortgage loans required monthly interest-only payments at a weighted-average fixed interest rate of 5.95% per annum and were scheduled to mature on October 7, 2017. The mezzanine loans required interest-only payments at a weighted-average fixed interest rate of 6.02% per annum and were scheduled to mature on October 7, 2017. In addition, a subsidiary of the consolidated entity had acquired a lender’s interest in certain other mezzanine loans assumed during the acquisition of the property having an aggregate principal amount of $294.0 million and a stated interest rate of 6.02% per annum for a purchase price of approximately $263.1 million in cash. These mezzanine loans payable had been eliminated in consolidation and were canceled upon the refinancing of the indebtedness. The member loans bore interest at a fixed rate of 11.0% per annum and were scheduled to mature on June 9, 2017. A portion of the original purchase price of the property was financed with loans from the members on a pro rata basis equal to their percentage interest in the consolidated entity. The Company had eliminated in consolidation its member loan totaling $270.0 million and its share of the related accrued interest payable of approximately $255.0 million at the date of the refinancing. The remaining outside members’ notes payable and related accrued interest payable totaling $180.0 million and approximately $170.0 million , respectively, at the date of the refinancing had been reflected as Outside Members’ Notes Payable and within Accrued Interest Payable, respectively, on the Company’s Consolidated Balance Sheets. The net proceeds from the new financing were used to repay all of the outstanding accrued interest payable on the member loans and a portion of the outstanding principal balance of the member loans totaling approximately $176.1 million . In connection with the refinancing, the members of the Company’s consolidated entity contributed the remaining balance of the member notes payable totaling approximately $273.9 million (of which the Company’s share of approximately $164.4 million had been eliminated in consolidation) to equity in the consolidated entity (See Note 11 ). There was no prepayment penalty associated with the repayments. The Company recognized a gain from early extinguishment of debt totaling approximately $14.6 million primarily consisting of the acceleration of the remaining balance related to historical fair value debt adjustments. No mortgage loans at December 31, 2017 and one mortgage loan totaling approximately $1.3 billion at December 31, 2016 had been accounted for at its fair value on the date the mortgage loan was assumed in connection with the consolidation of real estate. The impact of recording mortgage loans at fair value resulted in a decrease to interest expense of approximately $19.6 million , $46.4 million and $55.0 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The cumulative liability related to the fair value adjustment was $33.8 million at December 31, 2016 and is included in mortgage notes payable, net in the Consolidated Balance Sheets. Contractual aggregate principal payments of mortgage notes payable at December 31, 2017 are as follows: Principal Payments (in thousands) 2018 $ 18,633 2019 19,670 2020 20,766 2021 40,182 2022 614,710 Thereafter 2,300,000 Total aggregate principal payments 3,013,961 Deferred financing costs, net (34,680 ) Total carrying value of mortgage notes payable, net $ 2,979,281

Derivative and Hedging Instrume

Derivative and Hedging Instruments (Notes)	12 Months Ended
	Dec. 31, 2017
Derivatives and Hedging Activities [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	7. Derivative Instruments and Hedging Activities During the year ended December 31, 2015, Boston Properties Limited Partnership commenced a planned interest rate hedging program and entered into 17 forward-starting interest rate swap contracts that fixed the 10 -year swap rate at a weighted-average rate of approximately 2.423% per annum on notional amounts aggregating $550.0 million . These interest rate swap contracts were entered into in advance of a financing with a target commencement date in September 2016 and maturity in September 2026. On August 17, 2016, in conjunction with Boston Properties Limited Partnership’s offering of its 2.750% senior unsecured notes due 2026, the Company terminated the forward-starting interest rate swap contracts and cash-settled the contracts by making cash payments to the counterparties aggregating approximately $49.3 million . The Company recognized approximately $0.1 million of losses on interest rate contracts during the year ended December 31, 2016 related to the partial ineffectiveness of the interest rate contracts. The Company is reclassifying into earnings, as an increase to interest expense, approximately $49.2 million (or approximately $4.9 million per year over the 10-year term of the 2.750% senior unsecured notes due 2026) of the amounts recorded in the Consolidated Balance Sheets within Accumulated Other Comprehensive Loss, which represents the effective portion of the applicable interest rate contracts. In addition, 767 Fifth Partners LLC, which is a subsidiary of the consolidated entity in which the Company has a 60% interest and owns 767 Fifth Avenue (the General Motors Building) in New York City, entered into 16 forward-starting interest rate swap contracts (including two contracts entered into during the year ended December 31, 2016 with notional amounts aggregating $50.0 million ) that fix the 10-year swap rate at a weighted-average rate of approximately 2.619% per annum on notional amounts aggregating $450.0 million . These interest rate swap contracts were entered into in advance of a financing with a target commencement date in June 2017 and maturity in June 2027. On April 24, 2017, the consolidated entity that owns 767 Fifth Avenue (the General Motors Building) located in New York City entered into an interest rate lock and commitment agreement with a group of lenders on a ten-year financing totaling $2.3 billion at a fixed interest rate of 3.43% per annum (See Note 6 ). In conjunction with the interest rate lock and commitment agreement, 767 Fifth Partners LLC terminated the forward-starting interest rate swap contracts and cash-settled the contracts by making cash payments to the counterparties aggregating approximately $14.4 million . 767 Fifth Partners LLC did not record any hedge ineffectiveness. The Company is reclassifying into earnings, as an increase to interest expense, approximately $14.4 million (or approximately $1.4 million per year over the 10-year term of the financing) of the amounts recorded in the Consolidated Balance Sheets within Accumulated Other Comprehensive Loss, which represents the effective portion of the applicable interest rate contracts. At December 31, 2017, there were no outstanding interest rate swap contracts. 767 Fifth Partners LLC’s interest rate swap contracts consisted of the following at December 31, 2016 (dollars in thousands): Derivative Instrument Aggregate Notional Amount Effective Date Maturity Date Strike Rate Range Balance Sheet Location Fair Value Low High Interest Rate Swaps $ 350,000 June 7, 2017 June 7, 2027 2.418 % - 2.950 % Other Liabilities $ (8,773 ) Interest Rate Swaps 100,000 June 7, 2017 June 7, 2027 2.336 % - 2.388 % Prepaid Expenses and Other Assets 509 $ 450,000 $ (8,264 ) Boston Properties Limited Partnership entered into the interest rate swap contracts designated and qualifying as cash flow hedges to reduce its exposure to the variability in future cash flows attributable to changes in the 10-year swap rate in contemplation of obtaining 10-year fixed-rate financing in September 2016. The Company’s 767 Fifth Partners LLC consolidated entity entered into the interest rate swap contracts designated and qualifying as cash flow hedges to reduce its exposure to the variability in future cash flows attributable to changes in the 10-year swap rate in contemplation of obtaining 10-year fixed-rate financing in June 2017. Boston Properties Limited Partnership has formally documented all of its relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking various hedge transactions. Boston Properties Limited Partnership also assesses and documents, both at the hedging instrument’s inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in cash flows associated with the hedged items. All components of the forward-starting interest rate swap contracts were included in the assessment of hedge effectiveness. The Company accounts for the effective portion of changes in the fair value of a derivative in accumulated other comprehensive 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. The Company classifies cash flows related to derivative instruments within its Consolidated Statements of Cash Flows consistent with the nature of the hedged item. The following table presents the location in the financial statements of the losses recognized related to the Company’s cash flow hedges for the years ended December 31, 2017 , 2016 and 2015 : Year ended December 31, 2017 2016 2015 (in thousands) Amount of loss related to the effective portion recognized in other comprehensive loss $ (6,133 ) $ (47,144 ) $ (10,302 ) Amount of loss related to the effective portion subsequently reclassified to earnings (1) $ (6,033 ) $ (3,751 ) $ (2,510 ) Amount of loss related to the ineffective portion and amount excluded from effectiveness testing $ — $ (140 ) $ — ___________ (1) During the year ended December 31, 2016, the Company accelerated the reclassification of amounts in other comprehensive loss to earnings as a result of the hedged forecasted transactions becoming probable not to occur. The accelerated amounts were a loss of approximately $0.2 million and are included in the table above. Boston Properties, Inc. The following table reflects the changes in accumulated other comprehensive loss for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ (9,304 ) Effective portion of interest rate contracts (10,302 ) Amortization of interest rate contracts 2,510 Other comprehensive loss attributable to noncontrolling interests 2,982 Balance at December 31, 2015 (14,114 ) Effective portion of interest rate contracts (47,144 ) Amortization of interest rate contracts 3,751 Other comprehensive loss attributable to noncontrolling interests 5,256 Balance at December 31, 2016 (52,251 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 6,033 Other comprehensive loss attributable to noncontrolling interests 1,922 Balance at December 31, 2017 $ (50,429 ) Boston Properties Limited Partnership The following table reflects the changes in accumulated other comprehensive loss for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ (12,973 ) Effective portion of interest rate contracts (10,302 ) Amortization of interest rate contracts 2,510 Other comprehensive loss attributable to noncontrolling interests in property partnership 2,428 Balance at December 31, 2015 (18,337 ) Effective portion of interest rate contracts (47,144 ) Amortization of interest rate contracts 3,751 Other comprehensive loss attributable to noncontrolling interests in property partnership 877 Balance at December 31, 2016 (60,853 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 6,033 Other comprehensive loss attributable to noncontrolling interests in property partnership 2,128 Balance at December 31, 2017 $ (58,825 )

Unsecured Senior Notes

Unsecured Senior Notes	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Unsecured Senior Notes	8. Unsecured Senior Notes The following summarizes the unsecured senior notes outstanding as of December 31, 2017 (dollars in thousands): Coupon/ Stated Rate Effective Rate(1) Principal Amount Maturity Date(2) 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 11 Year Unsecured Senior Notes 3.850 % 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 3.800 % 3.916 % 700,000 February 1, 2024 7 Year Unsecured Senior Notes 3.200 % 3.350 % 850,000 January 15, 2025 10 Year Unsecured Senior Notes 3.650 % 3.766 % 1,000,000 February 1, 2026 10 Year Unsecured Senior Notes 2.750 % 3.495 % 1,000,000 October 1, 2026 Total principal 7,300,000 Net unamortized discount (17,894 ) Deferred financing costs, net (34,776 ) Total $ 7,247,330 _______________ (1) Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs. (2) No principal amounts are due prior to maturity. On December 4, 2017, Boston Properties Limited Partnership completed a public offering of $850.0 million in aggregate principal amount of its 3.200% unsecured senior notes due 2025. The notes were priced at 99.757% of the principal amount to yield an effective rate (including financing fees) of approximately 3.350% per annum to maturity. The notes will mature on January 15, 2025, unless earlier redeemed. The aggregate net proceeds from the offering were approximately $841.1 million after deducting underwriting discounts and transaction expenses. On December 17, 2017, Boston Properties Limited Partnership completed the redemption of $850.0 million in aggregate principal amount of its 3.700% senior notes due November 15, 2018. The redemption price was approximately $865.5 million . The redemption price included approximately $2.8 million of accrued and unpaid interest to, but not including, the redemption date. Excluding the accrued and unpaid interest, the redemption price was approximately 101.49% of the principal amount being redeemed. The Company recognized a loss from early extinguishment of debt totaling approximately $13.9 million , which amount included the payment of the redemption premium totaling approximately $12.7 million . 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, 2017 , Boston Properties Limited Partnership was in compliance with each of these financial restrictions and requirements.

Unsecured Credit Facility

Unsecured Credit Facility	12 Months Ended
	Dec. 31, 2017
Unsecured Line of Credit [Abstract]
Unsecured Credit Facility [Text Block]	9. Unsecured Credit Facility On April 24, 2017, Boston Properties Limited Partnership amended and restated its revolving credit agreement (as amended and restated, the “2017 Credit Facility”). Among other things, the 2017 Credit Facility (1) increased the total commitment of the revolving line of credit (the “Revolving Facility”) from $1.0 billion to $1.5 billion , (2) extended the maturity date from July 26, 2018 to April 24, 2022, (3) reduced the per annum variable interest rates, and (4) added a $500.0 million delayed draw term loan facility (the “Delayed Draw Facility”) that permits Boston Properties Limited Partnership, until the first anniversary of the closing date, to draw upon up to four times a minimum of $50.0 million (or, if less, the remaining unused delayed draw term commitments), provided that amounts drawn under the Delayed Draw Facility and subsequently repaid may not be borrowed again. In addition, Boston Properties Limited Partnership may increase the total commitment under the 2017 Credit Facility by up to $500.0 million through increases in the Revolving Facility or the Delayed Draw Facility, or both, subject to syndication of the increase and other conditions. At Boston Properties Limited Partnership’s option, loans under the Revolving Facility and Delayed Draw Facility will bear interest at a rate per annum equal to (1) (a) in the case of loans denominated in Dollars, Euro or Sterling, LIBOR, and (b) in the case of loans denominated in Canadian Dollars, CDOR, in each case, plus a margin ranging from 77.5 to 155 basis points for the Revolving Commitment and 85 to 175 basis points for the Delayed Draw Facility, based on Boston Properties Limited Partnership’s credit rating or (2) an alternate base rate equal to the greatest of (x) the Administrative Agent’s prime rate, (y) the Federal Funds rate plus 0.50% or (z) LIBOR for a one -month period plus 1.00% , in each case, plus a margin ranging from 0 to 55 basis points for the Revolving Facility and 0 to 75 basis points for the Delayed Draw Facility, based on Boston Properties Limited Partnership’s credit rating. The 2017 Credit Facility also contains a competitive bid option for up to 65% of the Revolving Facility that allows banks that are part of the lender consortium to bid to make loan advances to Boston Properties Limited Partnership at a reduced interest rate. In addition, Boston Properties Limited Partnership is obligated to pay (1) in quarterly installments a facility fee on the total commitment under the Revolving Facility at a rate per annum ranging from 0.10% to 0.30% based on Boston Properties Limited Partnership’s credit rating, (2) an annual fee on the undrawn amount of each letter of credit equal to the LIBOR margin on the Revolving Facility and (3) a fee on the unused commitments under the Delayed Draw Facility equal to 0.15% per annum. Based on Boston Properties Limited Partnership’s December 31, 2017 credit rating, (1) the applicable Eurocurrency margins for the Revolving Facility and Delayed Draw Facility are 87.5 basis points and 95 basis points, respectively, (2) the alternate base rate margin is zero basis points for each of the Revolving Facility and Delayed Draw Facility and (3) the facility fee on the Revolving Facility commitment is 0.15% per annum. At December 31, 2017 there was $45.0 million outstanding on the 2017 Credit Facility. At December 31, 2016, there were no amounts outstanding on the credit facility. The 2017 Credit Facility contains customary representations and warranties, affirmative and negative covenants and events of default provisions, including failure to pay indebtedness, breaches of covenants, and bankruptcy and other insolvency events, which could result in the acceleration of all amounts and cancellation of all commitments outstanding under the Credit Agreement. Among other covenants, the 2017 Credit Facility requires that Boston Properties Limited Partnership maintain on an ongoing basis: (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 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, 2017 , Boston Properties Limited Partnership was in compliance with each of these financial and other covenant requirements.

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	10. Commitments and Contingencies General In the normal course of business, the Company guarantees its performance of services or indemnifies third parties against its negligence. In addition, in the normal course of business, the Company guarantees to certain tenants the obligations of its subsidiaries for the payment of tenant improvement allowances and brokerage commissions in connection with their leases and limited costs arising from delays in delivery of their premises. The Company has letter of credit and performance obligations related to lender and development requirements that total approximately $9.1 million . Certain of the Company’s joint venture agreements include provisions whereby, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exception, under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. From time to time under certain of the Company’s joint venture agreements, if certain return thresholds are achieved the partners will be entitled to an additional promoted interest or payments. See also Note 11 . From time to time, the Company (or ventures in which the Company has an ownership interest) has agreed, and may in the future agree, to (1) guarantee portions of the principal, interest and other amounts in connection with their borrowings, (2) provide customary environmental indemnifications and nonrecourse carve-outs (e.g., guarantees against fraud, misrepresentation and bankruptcy) in connection with their borrowings and (3) provide guarantees to lenders and other third parties for the completion of development projects. The Company has agreements with its outside partners whereby the partners agree to reimburse the joint venture for their share of any payments made under the guarantee. In some cases, the Company earns a fee from the applicable joint venture for providing the guarantee. In connection with the refinancing of 767 Fifth Avenue’s (the General Motors Building) secured loan by the Company’s consolidated joint venture entity, 767 Venture, LLC, the Company guaranteed the consolidated entity’s obligation to fund various reserves for tenant improvement costs and allowances, leasing commissions and free rent obligations in lieu of cash deposits. As of December 31, 2017 , the maximum funding obligation under the guarantee was approximately $193.4 million . The Company earns a fee from the joint venture for providing the guarantee and has an agreement with the outside partners to reimburse the joint venture for their share of any payments made under the guarantee. As of December 31, 2017 , no amounts related to the guarantee are recorded as liabilities in the Company’s consolidated financial statements. Pursuant to the lease agreement with Marriott, the Company has guaranteed the completion of the office building and parking garage on behalf of its 7750 Wisconsin Avenue joint venture and has also agreed to provide any financing guaranty that may be required with respect to third-party construction financing. The Company earns a fee from the joint venture for providing the guarantees and any amounts the Company pays under the guarantee(s) will be deemed to be capital contributions by the Company to the joint venture. The Company has also agreed to fund construction costs through capital contributions to the joint venture in the event of unavailability or insufficiency of third-party construction financing. In addition, the Company has guaranteed to Marriott, as hotel manager, the completion of a hotel being developed by an affiliate of The Bernstein Companies adjacent to the office property, for which the Company earns a fee from the affiliate of The Bernstein Companies. In addition, the Company entered into agreements with affiliates of The Bernstein Companies whereby the Company could be required to act as a mezzanine and/or mortgage lender and finance the construction of the hotel property. To secure such financing arrangements, affiliates of The Bernstein Companies are required to provide certain security, which varies depending on the specific loan, by pledges of their equity interest in the office property, a fee mortgage on the hotel property, or both. As of December 31, 2017 , no amounts related to the contingent aspect of any of the guarantees are recorded as liabilities in the Company’s consolidated financial statements. See also Note 5 . In 2009, the Company filed a general unsecured creditor’s claim against Lehman Brothers, Inc. for approximately $45.3 million related to its rejection of a lease at 399 Park Avenue in New York City. On January 10, 2014, the trustee for the liquidation of the business of Lehman Brothers allowed the Company’s claim in the amount of approximately $45.2 million . During 2014, the Company received an initial distribution totaling approximately $7.7 million . During the years ended December 31, 2017, 2016 and 2015, the Company received distributions aggregating approximately $0.4 million , $1.4 million and $8.1 million , respectively, which are included in Base Rent in the Consolidated Statements of Operations, leaving a remaining claim of approximately $27.6 million . The Company will continue to evaluate whether to attempt to sell the remaining claim or wait until the trustee distributes proceeds from the Lehman Brothers estate. Given the inherent uncertainties in bankruptcy proceedings, there can be no assurance as to the timing or amount of additional proceeds, if any, that the Company may ultimately realize on the remaining claim, whether by sale to a third party or by one or more distributions from the trustee. Accordingly, the Company has not recorded any estimated recoveries associated with this gain contingency within its Consolidated Financial Statements at December 31, 2017. 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, including those under development, of types and in amounts and with deductibles that it believes are in line with coverage customarily obtained by owners of similar properties. Certain properties owned in joint ventures with third parties are insured by the third party partner with insurance coverage of types and in amounts and with deductibles the Company believes are in line with coverage customarily obtained by owners of similar properties. In response to the uncertainty in the insurance market following the terrorist attacks of September 11, 2001, the Federal Terrorism Risk Insurance Act (as amended, “TRIA”) was enacted in November 2002 to require regulated insurers to make available coverage for “certified” acts of terrorism (as defined by the statute). The expiration date of TRIA was extended to December 31, 2014 by the Terrorism Risk Insurance Program Reauthorization Act of 2007 and further extended to December 31, 2020 by the Terrorism Risk Insurance Program Reauthorization Act of 2015 (“TRIPRA”), and the Company can provide no assurance that it will be extended further. Currently, the Company’s property insurance program per occurrence limits are $1.0 billion for its portfolio insurance program, including coverage for acts of terrorism other than nuclear, biological, chemical or radiological terrorism (“Terrorism Coverage”). The Company also carries $250 million of Terrorism Coverage for 601 Lexington Avenue, New York, New York (“601 Lexington Avenue”) in excess of the $1.0 billion of coverage in the Company’s property insurance program. Certain properties, including the General Motors Building located at 767 Fifth Avenue in New York, New York (“767 Fifth Avenue”), are currently insured in separate insurance programs. The property insurance program per occurrence limits for 767 Fifth Avenue are $1.625 billion , including Terrorism Coverage. The Company also currently carries nuclear, biological, chemical and radiological terrorism insurance coverage for acts of terrorism certified under TRIA (“NBCR Coverage”), which is provided by IXP as a direct insurer, for the properties in the Company's portfolio, including 767 Fifth Avenue, but excluding certain other properties owned in joint ventures with third parties or which the Company manages. The per occurrence limit for NBCR Coverage is $1.0 billion . Under TRIA, after the payment of the required deductible and coinsurance, the NBCR Coverage provided by IXP is backstopped by the Federal Government if the aggregate industry insured losses resulting from a certified act of terrorism exceed a “program trigger.” In 2017, the program trigger was $140 million and the coinsurance was 17% , however, both will increase in subsequent years pursuant to TRIPRA. If the Federal Government pays out for a loss under TRIA, it is mandatory that the Federal Government recoup the full amount of the loss from insurers offering TRIA coverage after the payment of the loss pursuant to a formula in TRIPRA. The Company may elect to terminate the NBCR Coverage if the Federal Government seeks recoupment for losses paid under TRIA, if there is a change in its portfolio or for any other reason. The Company intends to continue to monitor the scope, nature and cost of available terrorism insurance and maintain terrorism insurance in amounts and on terms that are commercially reasonable. The Company also currently carries earthquake insurance on its properties located in areas known to be subject to earthquakes in an amount and subject to self-insurance that the Company believes is commercially reasonable. In addition, this insurance is subject to a deductible in the amount of 3% of the value of the affected property. Specifically, the Company currently carries earthquake insurance which covers its San Francisco (including Salesforce Tower) and Los Angeles regions with a $240 million (increased from $170 million on March 1, 2017) per occurrence limit, and a $240 million (increased from $170 million on March 1, 2017) annual aggregate limit, $20 million of which is provided by IXP, as a direct insurer. Prior to March 1, 2017, the builders risk policy maintained for the development of Salesforce Tower in San Francisco included a $60 million per occurrence and annual aggregate limit of earthquake coverage. The amount of the Company’s earthquake insurance coverage may not be sufficient to cover losses from earthquakes. In addition, the amount of earthquake coverage could impact the Company’s ability to finance properties subject to earthquake risk. The Company may discontinue earthquake insurance or change the structure of its earthquake insurance program on some or all of its properties in the future if the premiums exceed the Company’s estimation of the value of the coverage. IXP, a captive insurance company which is a wholly-owned subsidiary of the Company, acts as a direct insurer with respect to a portion of the Company’s earthquake insurance coverage for its Greater San Francisco and Los Angeles properties and the Company’s NBCR Coverage. Insofar as the Company owns IXP, it is responsible for its liquidity and capital resources, and the accounts of IXP are part of the Company’s consolidated financial statements. In particular, if a loss occurs which is covered by the Company’s NBCR Coverage but is less than the applicable program trigger under TRIA, IXP would be responsible for the full amount of the loss without any backstop by the Federal Government. IXP would also be responsible for any recoupment charges by the Federal Government in the event losses are paid out and its insurance policy is maintained after the payout by the Federal Government. If the Company experiences a loss and IXP is required to pay under its insurance policy, the Company would ultimately record the loss to the extent of the required payment. Therefore, insurance coverage provided by IXP should not be considered as the equivalent of third-party insurance, but rather as a modified form of self-insurance. In addition, Boston Properties Limited Partnership has issued a guarantee to cover liabilities of IXP in the amount of $20.0 million . The mortgages on the Company’s properties typically contain requirements concerning the financial ratings of the insurers who provide policies covering the property. The Company provides the lenders on a regular basis with the identity of the insurance companies in the Company’s insurance programs. The ratings of some of the Company’s insurers are below the rating requirements in some of the Company’s loan agreements and the lenders for these loans could attempt to claim that an event of default has occurred under the loan. The Company believes it could obtain insurance with insurers which satisfy the rating requirements. Additionally, in the future, the Company’s ability to obtain debt financing secured by individual properties, or the terms of such financing, may be adversely affected if lenders generally insist on ratings for insurers or amounts of insurance which are difficult to obtain or which result in a commercially unreasonable premium. There can be no assurance that a deficiency in the financial ratings of one or more of the Company’s insurers will not have a material adverse effect on the Company. The Company continues to monitor the state of the insurance market in general, and the scope and costs of coverage for acts of terrorism and California earthquake risk in particular, but the Company cannot anticipate what coverage will be available on commercially reasonable terms in future policy years. There are other types of losses, such as from wars, for which the Company cannot obtain insurance at all or at a reasonable cost. With respect to such losses and losses from acts of terrorism, earthquakes or other catastrophic events, if the Company experiences a loss that is uninsured or that exceeds policy limits, the Company could lose the capital invested in the damaged properties, as well as the anticipated future revenues from those properties. Depending on the specific circumstances of each affected property, it is possible that the Company could be liable for mortgage indebtedness or other obligations related to the property. Any such loss could materially and adversely affect the Company’s business and financial condition and results of operations. 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 Boston Properties, Inc. 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, including potential issues associated with contaminant migration, assess potential liability risks 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, deal structure 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.

Noncontrolling Interests

Noncontrolling Interests	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Noncontrolling Interests	11. Noncontrolling Interests Noncontrolling interests relate to the interests in Boston Properties Limited Partnership not owned by Boston Properties, Inc. and interests in consolidated property partnerships not wholly-owned by the Company. As of December 31, 2017 , the noncontrolling interests in Boston Properties Limited Partnership consisted of 16,810,378 OP Units, 818,343 LTIP Units (including 118,067 2012 OPP Units, 85,405 2013 MYLTIP Units and 25,107 2014 MYLTIP Units), 366,618 2015 MYLTIP Units, 473,360 2016 MYLTIP Units and 400,000 2017 MYLTIP Units held by parties other than Boston Properties, Inc. Noncontrolling Interest—Redeemable Preferred Units On June 25, 2015, Boston Properties Limited Partnership redeemed the remaining 12,667 Series Four Preferred Units for cash totaling approximately $0.6 million , plus accrued and unpaid distributions. The Series Four Preferred Units bore a preferred distribution equal to 2.00% per annum on a liquidation preference of $50.00 per unit and were not convertible into OP Units. The holders of Series Four Preferred Units had 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 Boston Properties Limited Partnership to redeem all of their units for cash at the redemption price of $50.00 per unit. Boston Properties Limited Partnership also had the right, at certain times and subject to certain conditions, to redeem all of the Series Four Preferred Units for cash at the redemption price of $50.00 per unit. In order to secure the performance of certain post-issuance obligations by the holders, all of such outstanding Series Four Preferred Units were subject to forfeiture pursuant to the terms of a pledge agreement and not eligible for redemption until the security interest was released and unless such security interest is released. Due to the holders’ redemption option existing outside the control of the Company, the Series Four Preferred Units were presented outside of permanent equity in the Company’s Consolidated Balance Sheets. The following table reflects the activity of the noncontrolling interests—redeemable preferred units for the year ended December 31, 2015 (in thousands): Balance at December 31, 2014 $ 633 Net income 6 Distributions (6 ) Redemption of redeemable preferred units (Series Four Preferred Units) (633 ) Balance at December 31, 2015 $ — Noncontrolling Interest—Redeemable Interest in Property Partnership On October 4, 2012, the Company completed the formation of a joint venture, that owns and operates Fountain Square located in Reston, Virginia. The joint venture partner contributed the property valued at approximately $385.0 million and related mortgage indebtedness totaling approximately $211.3 million for a 50% interest in the joint venture. The Company contributed cash totaling approximately $87.0 million for its 50% interest, which cash was distributed to the joint venture partner. Pursuant to the joint venture agreement (i) the Company had rights to acquire the partner’s 50% interest and (ii) the partner had 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 were to expire on January 31, 2016. The Company was consolidating this joint venture due to the Company’s right to acquire the partner’s 50% interest. The Company 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 was accreting 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 was recording the accretion after the allocation of net income and distributions of cash flow to the noncontrolling interest account balance. On August 6, 2015, the parties amended the joint venture agreement to require the Company to acquire its partner’s 50% interest on September 15, 2015 for approximately $100.9 million in cash. On September 15, 2015, the Company acquired its partner’s 50% interest in the consolidated entity that owns Fountain Square for cash of approximately $100.9 million plus working capital and closing prorations and the partner’s share of assumed mortgage indebtedness totaling approximately $105.6 million . The following table reflects the activity of the noncontrolling interest—redeemable interest in property partnership in the Company’s Fountain Square consolidated entity for the year ended December 31, 2015 (in thousands): Balance at December 31, 2014 $ 104,692 Net loss (7 ) Distributions (2,900 ) Adjustment to reflect redeemable interest at redemption value 5,128 Acquisition of interest (106,913 ) Balance at December 31, 2015 $ — Noncontrolling Interest—Common Units During the years ended December 31, 2017 and 2016 , 495,637 and 190,857 OP Units, respectively, were presented by the holders for redemption (including 36,486 and 103,847 OP Units, respectively, issued upon conversion of LTIP Units, 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units) and were redeemed by Boston Properties, Inc. in exchange for an equal number of shares of Common Stock. Boston Properties Limited Partnership exercised its right under the terms of its partnership agreement to convert an aggregate of 625,043 eligible LTIP Units (including an aggregate of 32,349 2012 OPP Units and 2013 MYLTIP Units) into Common Units effective as of May 2, 2016. These conversions were effected solely for administrative efficiency and had no substantive impact on the rights of Boston Properties Limited Partnership or the holders of these LTIP Units, as the economic and other rights of the LTIP Units converted were substantively identical to those of the Common Units. In the future, Boston Properties Limited Partnership intends to convert LTIP Units (including 2012 OPP Units and MYLTIP Units) into Common Units promptly after they become eligible for conversion. The May 2016 conversions were, and future conversions will be, effected at the election of Boston Properties Limited Partnership and are without regard to the investment intentions of the holders of the units. At December 31, 2017 , Boston Properties Limited Partnership had outstanding 366,618 2015 MYLTIP Units, 473,360 2016 MYLTIP Units and 400,000 2017 MYLTIP Units (See Note 17 ). Prior to the applicable measurement date (February 4, 2018 for 2015 MYLTIP Units (See Note 20 ), February 9, 2019 for 2016 MYLTIP Units and February 6, 2020 for 2017 MYLTIP Units), holders of MYLTIP Units will be entitled to receive per unit distributions equal to one-tenth ( 10% ) of the regular quarterly distributions payable on an OP Unit, but will not be entitled to receive any special distributions. After the measurement date, the number of MYLTIP Units, both vested and unvested, that MYLTIP award recipients have earned, if any, based on the establishment of a performance pool, will be entitled to receive distributions in an amount per unit equal to distributions, both regular and special, payable on an OP Unit. On February 6, 2015, the measurement period for the Company’s 2012 OPP Unit awards ended and Boston Properties, Inc.’s TSR performance was sufficient for employees to earn and therefore become eligible to vest in a portion of the 2012 OPP Unit awards. The final outperformance pool was determined to be approximately $32.1 million , or approximately 80% of the total maximum outperformance pool of $40.0 million . As a result, 174,549 2012 OPP Units were automatically forfeited. On February 4, 2016, the measurement period for the Company’s 2013 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 109.5% of target, or an aggregate of approximately $13.5 million . As a result, 205,762 2013 MYLTIP Units were automatically forfeited. On February 3, 2017, the measurement period for the Company’s 2014 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 27.7% of target or an aggregate of approximately $3.5 million (after giving effect to voluntary employee separations and the unallocated reserve). As a result, an aggregate of 447,386 2014 MYLTIP Units that had been previously granted were automatically forfeited. The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units and 2013 MYLTIP Units and, after the February 3, 2017 measurement date, the 2014 MYLTIP Units) and its distributions on the 2014 MYLTIP Units (prior to the February 3, 2017 measurement date), 2015 MYLTIP Units, 2016 MYLTIP Units and 2017 MYLTIP Units (after the February 7, 2017 issuance date) paid in 2017: Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit December 29, 2017 January 30, 2018 $0.80 $0.080 September 29, 2017 October 31, 2017 $0.75 $0.075 June 30, 2017 July 31, 2017 $0.75 $0.075 March 31, 2017 April 28, 2017 $0.75 $0.075 December 31, 2016 January 30, 2017 $0.75 $0.075 A holder of an OP Unit may present the OP Unit to Boston Properties Limited Partnership for redemption at any time (subject to restrictions agreed upon at the time of issuance of OP Units to particular holders that may restrict such redemption right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, Boston Properties Limited Partnership must redeem the OP Unit for cash equal to the then value of a share of common stock of Boston Properties, Inc. Boston Properties, Inc. may, in its sole discretion, elect to assume and satisfy the redemption obligation by paying either cash or issuing one share of Common Stock. The value of the OP Units (not owned by Boston Properties, Inc. and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units) assuming that all conditions had been met for the conversion thereof) had all of such units been redeemed at December 31, 2017 was approximately $2.3 billion based on the last reported price of a share of Common Stock on the New York Stock Exchange of $130.03 per share on December 29, 2017. Boston Properties Limited Partnership The following table reflects the activity of noncontrolling interests—redeemable common units of Boston Properties Limited Partnership for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ 2,310,046 Contributions 39,030 Net income 66,951 Distributions (69,447 ) Conversion of redeemable partnership units (14,343 ) Unearned compensation (4,579 ) Other comprehensive loss (554 ) Adjustment to reflect redeemable partnership units at redemption value (40,415 ) Balance at December 31, 2015 2,286,689 Contributions 31,395 Net income 59,260 Distributions (49,087 ) Conversion of redeemable partnership units (6,461 ) Unearned compensation (3,464 ) Other comprehensive loss (4,379 ) Adjustment to reflect redeemable partnership units at redemption value (51,913 ) Balance at December 31, 2016 2,262,040 Contributions 31,743 Net income 52,210 Distributions (54,494 ) Conversion of redeemable partnership units (16,916 ) Unearned compensation 1,650 Cumulative effect of a change in accounting principle (1,763 ) Other comprehensive income 206 Adjustment to reflect redeemable partnership units at redemption value 17,587 Balance at December 31, 2017 $ 2,292,263 Noncontrolling Interests—Property Partnerships The noncontrolling interests in property partnerships consist of the outside equity interests in ventures that are consolidated with the financial results of the Company because the Company exercises control over the entities that own the properties. The equity interests in these ventures that are not owned by the Company, totaling approximately $1.7 billion and $1.5 billion at December 31, 2017 and 2016, respectively, are included in Noncontrolling Interests—Property Partnerships on the accompanying Consolidated Balance Sheets. On September 18, 2015, a consolidated entity in which the Company has a 50% interest completed the sale of its 505 9th Street, N.W. property located in Washington, DC for approximately $318.0 million , including the assumption by the buyer of approximately $117.0 million of mortgage indebtedness. 505 9th Street, N.W. is an approximately 322,000 net rentable square foot Class A office building. Net cash proceeds totaled approximately $194.6 million , of which the partners’ share was approximately $97.3 million . The Company recognized a gain on sale of real estate totaling approximately $199.5 million and $199.7 million for Boston Properties, Inc. and Boston Properties Limited Partnership, respectively, of which approximately $101.1 million was allocated to the outside partners and is included within Noncontrolling Interests in Property Partnerships in the Company’s Consolidated Statements of Operations. On December 10, 2015, the consolidated entity was dissolved and the Company reclassified the remaining noncontrolling interest balance totaling approximately $4.1 million to Accounts Payable and Accrued Expenses on the Consolidated Balances Sheets, of which approximately $0.2 million was outstanding at December 31, 2016. No amount was outstanding as of December 31, 2017. On May 12, 2016, the partners in the Company’s consolidated entity that owns Salesforce Tower located in San Francisco, California amended the venture agreement. Under the original venture agreement, if the Company elects to fund the construction of Salesforce Tower without a construction loan (or a construction loan of less than 50% of project costs) and the venture has commenced vertical construction of the project, then the partner’s capital funding obligation shall be limited, in which event the Company shall fund up to 2.5% of the total project costs (i.e., 50% of the partner’s 5% interest in the venture) in the form of a loan to the partner. This loan would bear interest at the then prevailing market interest rates for construction loans. Under the amended agreement, the partners agreed to structure this funding by the Company as preferred equity rather than a loan. The preferred equity contributed by the Company shall earn a preferred return equal to LIBOR plus 3.00% per annum and shall be payable to the Company out of any distributions to which the partner would otherwise be entitled until such preferred equity and preferred return have been repaid to the Company. As of December 31, 2017 , the Company has contributed an aggregate of approximately $16.4 million of preferred equity to the venture. Also, under the joint venture agreement, (a) from and after the stabilization date, the partner has the right to cause the Company to purchase all (but not less than all) of the partner’s interest and (b) from and after the third anniversary of the stabilization date, the Company has the right to acquire all (but not less than all) of the partner’s interest, in each case at an agreed upon purchase price or appraised value. In addition, if certain threshold returns are achieved the partner will be entitled to receive an additional promoted interest. The term stabilization date is defined in the agreement to generally mean the first date after completion upon which Salesforce Tower is (1) at least 90% leased and (2) 50% occupied by tenants that are paying rent. The stabilization date has not yet occurred. On June 6, 2017, in conjunction with the refinancing of the indebtedness of the Company’s consolidated entity in which it has a 60% interest and that owns 767 Fifth Avenue (the General Motors Building) located in New York City, the members of the consolidated entity amended the limited liability company agreement to provide for the contribution of the remaining unpaid principal balance of the members’ notes payable totaling approximately $273.9 million (of which the Company’s share of approximately $164.4 million is eliminated in consolidation) to equity in the consolidated entity, resulting in an increase of approximately $109.6 million to Noncontrolling Interests in Property Partnerships on the Company’s Consolidated Balance Sheets (See Note 6 ). There were no changes to the ownership interests or rights of the members as a result of the amendment. The following table reflects the activity of the noncontrolling interests—property partnerships for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ 1,602,467 Capital contributions 3,758 Dissolution (4,082 ) Net income 144,734 Accumulated other comprehensive loss (2,428 ) Distributions (170,049 ) Balance at December 31, 2015 1,574,400 Capital contributions 10,756 Net loss (2,068 ) Accumulated other comprehensive loss (877 ) Distributions (51,564 ) Balance at December 31, 2016 1,530,647 Capital contributions (1) 161,585 Net loss 47,832 Accumulated other comprehensive loss (2,128 ) Distributions (54,176 ) Balance at December 31, 2017 $ 1,683,760 _______________ (1) Includes the contribution of the remaining unpaid principal balance of the members’ notes payable totaling $109,576 to equity in the consolidated entity that owns 767 Fifth Avenue (the General Motors Building).

Stockholders' Equity _ Partners

Stockholders' Equity / Partners' Capital	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	12. Stockholders’ Equity / Partners’ Capital Boston Properties, Inc. As of December 31, 2017 , Boston Properties, Inc. had 154,325,286 shares of Common Stock outstanding. On June 2, 2017, Boston Properties, Inc. renewed its “at the market” (“ATM”) stock offering program through which it may sell from time to time up to an aggregate of $600.0 million of its common stock through sales agents over a three -year period. This program replaced the Company’s prior $600.0 million ATM stock offering program that was scheduled to expire on June 3, 2017. The Company intends to use the net proceeds from any offering for general business purposes, which may include investment opportunities and debt reduction. No shares of common stock have been issued under this ATM stock offering program. During the year ended December 31, 2017, Boston Properties, Inc. issued 6,688 shares of Common Stock upon the exercise of options to purchase Common Stock. During the year ended December 31, 2016, there were no options to purchase Common Stock exercised. During the years ended December 31, 2017 and 2016 , Boston Properties, Inc. issued 495,637 and 190,857 shares of Common Stock, respectively, in connection with the redemption of an equal number of redeemable OP Units from limited partners. The following table presents Boston Properties, Inc.’s dividends per share and Boston Properties Limited Partnership’s distributions per OP Unit and LTIP Unit paid or payable in 2017 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) December 29, 2017 January 30, 2018 $0.80 $0.80 September 29, 2017 October 31, 2017 0.75 0.75 June 30, 2017 July 31, 2017 0.75 0.75 March 31, 2017 April 28, 2017 0.75 0.75 December 31, 2016 January 30, 2017 0.75 0.75 Preferred Stock As of December 31, 2017, Boston Properties, Inc. had 80,000 shares ( 8,000,000 depositary shares each representing 1/100th of a share) outstanding of its 5.25% Series B Cumulative Redeemable Preferred Stock with a liquidation preference of $2,500.00 per share ( $25.00 per depositary share). Boston Properties, Inc. pays cumulative cash dividends on the Series B Preferred Stock at a rate of 5.25% per annum of the $2,500.00 liquidation preference per share. Boston Properties, Inc. may not redeem the Series B Preferred Stock prior to March 27, 2018, except in certain circumstances relating to the preservation of Boston Properties, Inc.’s REIT status. On or after March 27, 2018, Boston Properties, Inc., at its option, may redeem the Series B Preferred Stock for a cash redemption price of $2,500.00 per share ( $25.00 per depositary share), plus all accrued and unpaid dividends. The Series B Preferred Stock is not redeemable by the holders, has no maturity date and is not convertible into any other security of Boston Properties, Inc. or its affiliates. The following table presents Boston Properties Inc.’s dividends per share on its outstanding Series B Preferred Stock paid or payable in 2017 : Record Date Payment Date Dividend (Per Share) February 2, 2018 February 15, 2018 $32.8125 November 3, 2017 November 15, 2017 32.8125 August 4, 2017 August 15, 2017 32.8125 May 5, 2017 May 15, 2017 32.8125 February 3, 2017 February 15, 2017 32.8125 Boston Properties Limited Partnership The following table presents the changes in the issued and outstanding partners’ capital units since January 1, 2015 : General Partner Units Limited Partner Units Total Partners’ Outstanding at December 31, 2014 1,710,644 151,403,301 153,113,945 Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan 59 6,140 6,199 Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net 340 35,246 35,586 Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units 4,049 420,187 424,236 Outstanding at December 31, 2015 1,715,092 151,864,874 153,579,966 Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan 72 5,623 5,695 Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net 172 13,485 13,657 Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units 2,407 188,450 190,857 Outstanding at December 31, 2016 1,717,743 152,072,432 153,790,175 Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan 21 6,296 6,317 Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net 111 33,046 33,157 Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units 1,665 493,972 495,637 Outstanding at December 31, 2017 1,719,540 152,605,746 154,325,286 As of December 31, 2017 , Boston Properties, Inc. owned 1,719,540 general partnership units and 152,605,746 limited partnership units. The following table reflects the activity of the Series B Preferred Units for the years ended December 31, 2017 , 2016 and 2015 (in thousands), which activity is included within Boston Properties Limited Partnership’s Consolidated Statements of Partners’ Capital: Balance at December 31, 2014 $ 193,623 Net income 10,500 Distributions (10,500 ) Balance at December 31, 2015 193,623 Net income 10,500 Distributions (10,500 ) Balance at December 31, 2016 193,623 Net income 10,500 Distributions (10,500 ) Balance at December 31, 2017 $ 193,623

Future Minimum Rents

Future Minimum Rents	12 Months Ended
	Dec. 31, 2017
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 2018 to 2046 . The future contractual minimum lease payments to be received (excluding operating expense reimbursements) by the Company as of December 31, 2017 , under non-cancelable operating leases which expire on various dates through 2046 , are as follows: Years Ending December 31, (in thousands) 2018 $ 1,962,841 2019 1,998,102 2020 1,920,002 2021 1,783,066 2022 1,596,719 Thereafter 11,160,780 No single tenant represented more than 10.0% of the Company’s total rental revenue for the years ended December 31, 2017 , 2016 and 2015 .

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Reporting Disclosure [Text Block]	14. Segment Information The following tables present reconciliations of Net Income Attributable to Boston Properties, Inc. Common Shareholders to Net Operating Income and Net Income Attributable to Boston Properties Limited Partnership Common Unitholders to Net Operating Income for the years ended December 31, 2017 , 2016 and 2015 . Boston Properties, Inc. Year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 451,939 $ 502,285 $ 572,606 Add: Preferred dividends 10,500 10,500 10,500 Noncontrolling interest—common units of the Operating Partnership 52,210 59,260 66,951 Noncontrolling interest—redeemable preferred units of the Operating Partnership — — 6 Noncontrolling interest in property partnerships 47,832 (2,068 ) 149,855 Losses from interest rate contracts — 140 — Interest expense 374,481 412,849 432,196 Depreciation and amortization expense 617,547 694,403 639,542 Impairment loss — 1,783 — Transaction costs 668 2,387 1,259 General and administrative expense 113,715 105,229 96,319 Less: Gains on sales of real estate 7,663 80,606 375,895 Gains (losses) from early extinguishments of debt 496 (371 ) (22,040 ) Gains (losses) from investments in securities 3,678 2,273 (653 ) Interest and other income 5,783 7,230 6,777 Gain on sale of investment in unconsolidated joint venture — 59,370 — Income from unconsolidated joint ventures 11,232 8,074 22,770 Development and management services income 34,605 28,284 22,554 Net Operating Income $ 1,605,435 $ 1,601,302 $ 1,563,931 Boston Properties Limited Partnership Year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 512,866 $ 575,341 $ 648,748 Add: Preferred distributions 10,500 10,500 10,500 Noncontrolling interest—redeemable preferred units — — 6 Noncontrolling interest in property partnerships 47,832 (2,068 ) 149,855 Losses from interest rate contracts — 140 — Interest expense 374,481 412,849 432,196 Depreciation and amortization expense 609,407 682,776 631,549 Impairment loss — 1,783 — Transaction costs 668 2,387 1,259 General and administrative expense 113,715 105,229 96,319 Less: Gains on sales of real estate 8,240 82,775 377,093 Gains (losses) from early extinguishments of debt 496 (371 ) (22,040 ) Gains (losses) from investments in securities 3,678 2,273 (653 ) Interest and other income 5,783 7,230 6,777 Gain on sale of investment in unconsolidated joint venture — 59,370 — Income from unconsolidated joint ventures 11,232 8,074 22,770 Development and management services income 34,605 28,284 22,554 Net Operating Income $ 1,605,435 $ 1,601,302 $ 1,563,931 Net operating income (“NOI”) is a non-GAAP financial measure equal to net income attributable to Boston Properties, Inc. common shareholders and net income attributable to Boston Properties Limited Partnership common unitholders, as applicable, the most directly comparable GAAP financial measures, plus (1) preferred dividends/distributions, net income attributable to noncontrolling interests, losses from interest rate contracts, interest expense, depreciation and amortization, impairment loss, transaction costs and general and administrative expense less (2) gains on sales of real estate, gains (losses) from early extinguishments of debt, gains (losses) from investments in securities, interest and other income, gain on sale of investment in unconsolidated joint venture, income from unconsolidated joint ventures and development and management services revenue. The Company believes NOI is useful to investors as a performance measure and believes it provides useful information to investors regarding its results of operations and financial condition because, when compared across periods, it reflects the impact on operations from trends in occupancy rates, rental rates, operating costs and acquisition and development activity on an unleveraged basis, providing perspective not immediately apparent from net income attributable to Boston Properties, Inc. common shareholders and net income attributable to Boston Properties Limited Partnership common unitholders. For example, interest expense is not necessarily linked to the operating performance of a real estate asset and is often incurred at the corporate level as opposed to the property level. Similarly, interest expense may be incurred at the property level even though the financing proceeds may be used at the corporate level (e.g., used for other investment activity). In addition, depreciation and amortization expense, because of historical cost accounting and useful life estimates, may distort operating performance measures at the property level. NOI presented by the Company may not be comparable to NOI reported by other REITs or real estate companies that define NOI differently. Asset information by segment is not reported because the Company does not use this measure to assess performance. Therefore, depreciation and amortization expense is not allocated among segments. Preferred dividends/distributions, noncontrolling interests, losses from interest rate contracts, interest expense, depreciation and amortization expense, impairment loss, transactions costs, general and administrative expense, gains on sales of real estate, gains (losses) from early extinguishments of debt, gains (losses) from investments in securities, interest and other income, gain on sale of investment in unconsolidated joint venture, income from unconsolidated joint ventures and development and management services income are not included in NOI as internal reporting addresses these items on a corporate level. The Company’s segments are based on the Company’s method of internal reporting which classifies its operations by both geographic area and property type. The Company’s segments by geographic area are Boston, New York, San Francisco and Washington, DC. Segments by property type include: Office, Residential and Hotel. Beginning on January 1, 2016, the properties that were historically included in the Company’s Office/Technical segment are now included in the Office segment to align with its method of internal reporting, which shifted after the disposition of 415 Main Street in Cambridge, Massachusetts. As such, the amounts previously included in Office/Technical are now included in Office for all periods presented. Information by geographic area and property type (dollars in thousands): For the year ended December 31, 2017 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 776,279 $ 969,371 $ 345,519 $ 414,103 $ 2,505,272 Residential 4,745 — — 11,851 16,596 Hotel 45,603 — — — 45,603 Total 826,627 969,371 345,519 425,954 2,567,471 % of Grand Totals 32.20 % 37.75 % 13.46 % 16.59 % 100.00 % Rental Expenses: Office 301,097 372,810 105,253 144,515 923,675 Residential 2,044 — — 4,258 6,302 Hotel 32,059 — — — 32,059 Total 335,200 372,810 105,253 148,773 962,036 % of Grand Totals 34.84 % 38.76 % 10.94 % 15.46 % 100.00 % Net operating income $ 491,427 $ 596,561 $ 240,266 $ 277,181 $ 1,605,435 % of Grand Totals 30.61 % 37.15 % 14.97 % 17.27 % 100.00 % For the year ended December 31, 2016 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 727,265 $ 1,012,518 $ 318,609 $ 402,561 $ 2,460,953 Residential 4,812 — — 11,887 16,699 Hotel 44,884 — — — 44,884 Total 776,961 1,012,518 318,609 414,448 2,522,536 % of Grand Totals 30.80 % 40.14 % 12.63 % 16.43 % 100.00 % Rental Expenses: Office 282,827 363,188 100,787 135,890 882,692 Residential 2,708 — — 4,368 7,076 Hotel 31,466 — — — 31,466 Total 317,001 363,188 100,787 140,258 921,234 % of Grand Totals 34.41 % 39.42 % 10.94 % 15.23 % 100.00 % Net operating income $ 459,960 $ 649,330 $ 217,822 $ 274,190 $ 1,601,302 % of Grand Totals 28.73 % 40.55 % 13.60 % 17.12 % 100.00 % For the year ended December 31, 2015 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 716,246 $ 1,000,030 $ 302,434 $ 384,628 $ 2,403,338 Residential 4,801 — — 14,082 18,883 Hotel 46,046 — — — 46,046 Total 767,093 1,000,030 302,434 398,710 2,468,267 % of Grand Totals 31.08 % 40.52 % 12.25 % 16.15 % 100.00 % Rental Expenses: Office 287,341 346,897 98,206 131,581 864,025 Residential 2,006 — — 6,221 8,227 Hotel 32,084 — — — 32,084 Total 321,431 346,897 98,206 137,802 904,336 % of Grand Totals 35.54 % 38.36 % 10.86 % 15.24 % 100.00 % Net operating income $ 445,662 $ 653,133 $ 204,228 $ 260,908 $ 1,563,931 % of Grand Totals 28.50 % 41.76 % 13.06 % 16.68 % 100.00 %

Earnings Per Share _ Common Uni

Earnings Per Share / Common Unit	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	15. Earnings Per Share / Common Unit Boston Properties, Inc. The following table provides a reconciliation of both the net income attributable to Boston Properties, Inc. common shareholders and the number of common shares used in the computation of basic earnings per share (“EPS”), which is calculated by dividing net income attributable to Boston Properties, Inc. common shareholders by the weighted-average number of common shares outstanding during the period. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities. As such, unvested restricted common stock of Boston Properties, Inc. and Boston Properties Limited Partnership’s LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic EPS of Boston Properties, Inc. using the two -class method. Participating securities are included in the computation of diluted EPS of Boston Properties, Inc. using the if-converted method if the impact is dilutive. Because the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units required, and the 2015-2017 MYLTIP Units require, Boston Properties, Inc. to outperform absolute and relative return thresholds, unless such thresholds have been met by the end of the applicable reporting period, Boston Properties, Inc. excludes such units from the diluted EPS calculation. Other potentially dilutive common shares, including stock options, restricted stock and other securities of Boston Properties Limited Partnership that are exchangeable for Boston Properties, Inc.’s Common Stock, and the related impact on earnings, are considered when calculating diluted EPS. For the Year Ended December 31, 2017 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 451,939 154,190 $ 2.93 Effect of Dilutive Securities: Stock Based Compensation — 200 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 451,939 154,390 $ 2.93 For the Year Ended December 31, 2016 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 502,285 153,715 $ 3.27 Allocation of undistributed earnings to participating securities (283 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 502,002 153,715 $ 3.27 Effect of Dilutive Securities: Stock Based Compensation — 262 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 502,002 153,977 $ 3.26 For the Year Ended December 31, 2015 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 572,606 153,471 $ 3.73 Effect of Dilutive Securities: Stock Based Compensation — 373 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 572,606 153,844 $ 3.72 Boston Properties Limited Partnership The following table provides a reconciliation of both the net income attributable to Boston Properties Limited Partnership common unitholders and the number of common units used in the computation of basic earnings per common unit, which is calculated by dividing net income attributable to Boston Properties Limited Partnership common unitholders by the weighted-average number of common units outstanding during the period. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities. As such, unvested restricted common stock of Boston Properties, Inc. and Boston Properties Limited Partnership’s LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic earnings per common unit using the two -class method. Participating securities are included in the computation of diluted earnings per common unit using the if-converted method if the impact is dilutive. Because the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units required, and the 2015-2017 MYLTIP Units require, Boston Properties, Inc. to outperform absolute and relative return thresholds, unless such thresholds have been met by the end of the applicable reporting period, Boston Properties Limited Partnership excludes such units from the diluted earnings per common unit calculation. Other potentially dilutive common units and the related impact on earnings are considered when calculating diluted earnings per common unit. Included in the number of units (the denominator) below are approximately 17,471,000 , 17,646,000 and 17,668,000 redeemable common units for the years ended December 31, 2017 , 2016 and 2015 , respectively. For the Year Ended December 31, 2017 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 512,866 171,661 $ 2.99 Effect of Dilutive Securities: Stock Based Compensation — 200 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 512,866 171,861 $ 2.98 For the Year Ended December 31, 2016 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 575,341 171,361 $ 3.36 Allocation of undistributed earnings to participating securities (316 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 575,025 171,361 $ 3.36 Effect of Dilutive Securities: Stock Based Compensation — 262 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 575,025 171,623 $ 3.35 For the Year Ended December 31, 2015 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 648,748 171,139 $ 3.79 Effect of Dilutive Securities: Stock Based Compensation — 373 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 648,748 171,512 $ 3.78

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
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. Under the Plan, as amended, the Company’s matching contribution equals 200% of the first 3% of participant’s eligible earnings contributed (utilizing earnings that are not in excess of an amount established by the IRS ( $270,000 , $265,000 and $265,000 in 2017 , 2016 and 2015 , respectively), indexed for inflation) with no vesting requirement. The Company’s aggregate matching contribution for the years ended December 31, 2017 , 2016 and 2015 was $4.1 million , $4.0 million and $3.7 million , respectively. The Plan also provides for supplemental retirement contributions to certain employees who had at least ten years of service on January 1, 2001, and who were 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, 2017 , 2016 and 2015 was $18,000 , $21,000 and $42,000 , respectively. The Company also maintains a deferred compensation plan that is designed to allow officers of Boston Properties, Inc. 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, 2017 and 2016 , the Company had maintained approximately $29.2 million and $23.8 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, 2017 and 2016 was $29.2 million and $23.8 million , respectively, which are included in the accompanying Consolidated Balance Sheets.

Stock Option and Incentive Plan

Stock Option and Incentive Plan	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	17. Stock Option and Incentive Plan At Boston Properties, Inc.’s 2012 annual meeting of stockholders held on May 15, 2012, its stockholders 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, canceled 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 25, 2017, Boston Properties, Inc.’s Compensation Committee approved the 2017 MYLTIP awards under its 2012 Plan to certain officers and employees of Boston Properties, Inc. The 2017 MYLTIP awards utilize Boston Properties, Inc.’s total stockholder return (“TSR”) over a three -year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will be based on Boston Properties, Inc.’s TSR relative to (i) the Cohen & Steers Realty Majors Portfolio Index ( 50% weight) and (ii) the Nareit Office Index adjusted to include Vornado Realty Trust ( 50% weight). Earned awards will range from zero to a maximum of approximately $42.7 million depending on Boston Properties, Inc.’s TSR relative to the two indices, with four tiers (threshold: approximately $10.7 million ; target: approximately $21.3 million ; high: approximately $32.0 million ; exceptional: approximately $42.7 million ) and linear interpolation between tiers. Earned awards measured on the basis of relative TSR performance are subject to an absolute TSR component in the form of relatively simple modifiers that (A) reduce the level of earned awards in the event Boston Properties, Inc.’s annualized TSR is less than 0% and (B) cause some awards to be earned in the event Boston Properties, Inc.’s annualized TSR is more than 12% even though on a relative basis alone Boston Properties, Inc.’s TSR would not result in any earned awards. Earned awards (if any) will vest 50% on February 6, 2020 and 50% on February 6, 2021, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by Boston Properties, Inc. without cause, or termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 6, 2020, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2017 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 and no special distributions. Under ASC 718, the 2017 MYLTIP awards have an aggregate value of approximately $17.7 million , which amount will generally be amortized into earnings over the four -year plan period under the graded vesting method. On February 3, 2017, the measurement period for the Company’s 2014 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 27.7% of target or an aggregate of approximately $3.5 million (after giving effect to voluntary employee separations and the unallocated reserve). As a result, an aggregate of 447,386 2014 MYLTIP Units that had been previously granted were automatically forfeited. On February 4, 2016, the measurement period for the Company’s 2013 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 109.5% of target or an aggregate of approximately $13.5 million . As a result, 205,762 2013 MYLTIP Units were automatically forfeited. On February 6, 2015, the measurement period for the Company’s 2012 OPP Unit awards ended and Boston Properties, Inc.’s TSR performance was sufficient for employees to earn and therefore become eligible to vest in a portion of the 2012 OPP Unit awards. The final outperformance pool was determined to be approximately $32.1 million , or approximately 80% of the total maximum outperformance pool of $40.0 million . As a result, 174,549 2012 OPP Units were automatically forfeited. On March 11, 2013, Boston Properties, Inc. announced that Owen D. Thomas would succeed Mortimer B. Zuckerman as its Chief Executive Officer, effective April 2, 2013. Mr. Zuckerman continued to serve as Executive Chairman for a transition period which was completed effective as of the close of business on December 31, 2014 and thereafter served as the non-executive Chairman of the Board of Boston Properties, Inc. until May 17, 2016. In connection with succession planning, Boston Properties, Inc. and Mr. Zuckerman entered into a Transition Benefits Agreement. Because Mr. Zuckerman remained employed by Boston Properties, Inc. through July 1, 2014, he was 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 vested one-third on each of March 10, 2013, October 1, 2013 and July 1, 2014. Boston Properties, Inc. issued 37,414 , 22,067 and 34,150 shares of restricted common stock and Boston Properties Limited Partnership issued 113,918 , 147,872 and 190,563 (including 85,962 LTIP Units issued on January 1, 2015 to Mortimer B. Zuckerman, non-executive Chairman of the Board of Boston Properties, Inc., pursuant to the Transition Benefits Agreement dated March 10, 2013) LTIP Units to employees and non-employee directors under the 2012 Plan during the years ended December 31, 2017 , 2016 and 2015 , respectively. Boston Properties, Inc. did not issue any non-qualified stock options under the 2012 Plan during the years ended December 31, 2017 , 2016 and 2015. Boston Properties Limited Partnership issued 400,000 2017 MYLTIP Units, 475,004 2016 MYLTIP Units and 375,000 2015 MYLTIP Units to employees under the 2012 Plan during the years ended December 31, 2017, 2016 and 2015, respectively. Employees and non-employee directors paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit, OPP Unit and MYLTIP Unit. When issued, LTIP Units are not economically equivalent in value to a share of Common Stock, but over time can increase in value to one-for-one parity with Common Stock if there is sufficient appreciation in the value of the Company’s assets. The aggregate value of the LTIP Units is included in noncontrolling interests in the Consolidated Balance Sheets. Grants of restricted stock and LTIP Units to employees vest in four equal annual installments. Restricted stock is measured at fair value on the date of grant based on the number of shares granted and the closing price of Boston Properties, Inc.’s Common Stock on the date of grant as quoted on the New York Stock Exchange. Such value is recognized as an expense ratably over the corresponding employee service period. 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 2012 OPP Awards, 2013 MYLTIP Awards, 2014 MYLTIP Awards, 2015 MYLTIP Awards, 2016 MYLTIP Awards and 2017 MYLTIP Awards are subject to both a service condition and a market condition, the Company recognizes the compensation expense related to the 2012 OPP Awards, 2013 MYLTIP Awards, 2014 MYLTIP Awards, 2015 MYLTIP Awards 2016 MYLTIP Awards and 2017 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. The Company recognizes forfeitures as they occur on its awards of stock-based compensation (See Note 2). Dividends paid on both vested and unvested shares of restricted stock are charged directly to Dividends in Excess of Earnings in Boston Properties, Inc.’s Consolidated Balance Sheets and Partners’ Capital in Boston Properties Limited Partnership’s Consolidated Balance Sheets. Aggregate stock-based compensation expense associated with restricted stock, non-qualified stock options, LTIP Units, 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units and 2017 MYLTIP Units was approximately $33.2 million , $30.6 million and $26.9 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. At December 31, 2017 , there was (1) an aggregate of approximately $19.2 million of unrecognized compensation expense related to unvested restricted stock, LTIP Units, 2013 MYLTIP Units and 2014 MYLTIP Units and (2) an aggregate of approximately $21.0 million of unrecognized compensation expense related to unvested 2015 MYLTIP Units, 2016 MYLTIP Units and 2017 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 2.3 years . The shares of restricted stock were valued at approximately $4.9 million ( $130.32 per share weighted-average), $2.5 million ( $113.51 per share weighted-average) and $4.8 million ( $140.88 per share weighted-average) for the years ended December 31, 2017 , 2016 and 2015 , respectively. LTIP Units were valued using a Monte Carlo simulation method model in accordance with the provisions of ASC 718. LTIP Units issued during the years ended December 31, 2017 , 2016 and 2015 were valued at approximately $13.6 million , $15.4 million and $13.5 million (excluding the number issued to Mr. Zuckerman, as discussed above), respectively. The weighted-average per unit fair value of LTIP Unit grants in 2017 , 2016 and 2015 was $119.41 , $103.83 and $128.94 , respectively. The per unit fair value of each LTIP Unit granted in 2017 , 2016 and 2015 was estimated on the date of grant using the following assumptions; an expected life of 5.7 years , 5.7 years and 5.7 years , a risk-free interest rate of 2.14% , 1.61% and 1.47% and an expected price volatility of 28.0% , 33.0% and 26.0% , respectively. There were no non-qualified stock options granted during the years ended December 31, 2017 , 2016 and 2015 . A summary of the status of Boston Properties, Inc.’s stock options as of December 31, 2017 , 2016 and 2015 and changes during the years then ended are presented below: Shares Weighted-Average Exercise Price Outstanding at December 31, 2014 553,312 $ 97.21 Exercised (11,447 ) $ 92.50 Special dividend adjustment 5,264 $ 96.38 Outstanding at December 31, 2015 547,129 $ 96.38 Exercised — $ — Outstanding at December 31, 2016 547,129 $ 96.38 Exercised (6,688 ) $ 99.15 Outstanding at December 31, 2017 540,441 $ 96.35 The following table summarizes information about Boston Properties, Inc.’s stock options outstanding at December 31, 2017 : Options Outstanding Options Exercisable Number Outstanding at 12/31/17 Weighted-Average Remaining Contractual Life Exercise Price Number Exercisable at 12/31/17 Exercise Price 118,502 3.1 years $ 86.86 118,502 $ 86.86 54,282 5.3 years $ 95.69 54,282 $ 95.69 202,030 5.1 years $ 98.46 202,030 $ 98.46 165,627 4.1 years $ 100.77 165,627 $ 100.77 The total intrinsic value of the outstanding and exercisable stock options as of December 31, 2017 was approximately $18.2 million . In addition, Boston Properties, Inc. had 514,360 and 465,371 options exercisable at a weighted-average exercise price of $96.32 and $96.10 at December 31, 2016 and 2015, respectively. Boston Properties, Inc. 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. Boston Properties, Inc. issued 6,317 , 5,695 and 6,199 shares with the weighted average purchase price equal to $105.97 per share, $109.27 per share and $108.73 per share under the Stock Purchase Plan during the years ended December 31, 2017 , 2016 and 2015 , respectively.

Related Party Transactions

Related Party Transactions	180 Months Ended
	Dec. 31, 2015
Related Party Transaction [Line Items]
Related Party Transactions Disclosure [Text Block]	18. Related Party Transactions Prior to joining Boston Properties, Inc. 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 $22,000 , $315,000 and $616,000 during the years ended December 31, 2017 , 2016 and 2015 , respectively, in connection with these transactions. Mr. John F. Powers is an Executive 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 $368,000 , $374,000 and $384,000 for the years ended December 31, 2017 , 2016 and 2015 , respectively, related to certain exclusive leasing arrangements for certain Northern Virginia properties. Mr. Ritchey is a Senior Executive Vice President of Boston Properties, Inc. In accordance with Boston Properties, Inc.’s 2012 Plan, and as approved by its Board of Directors, five non-employee directors made elections to receive deferred stock units in lieu of cash fees for 2017 . 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 of Boston Properties, Inc. 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 Boston Properties, Inc.’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 Boston Properties, Inc. On May 17, 2016, in connection with the cessation of a director’s service on the Board of Directors of Boston Properties, Inc., Boston Properties, Inc. issued 1,507 shares of common stock in settlement of the director’s outstanding deferred stock units. At December 31, 2017 and 2016 , Boston Properties, Inc. had outstanding 105,479 and 99,035 deferred stock units, respectively.

Selected Interim Financial Info

Selected Interim Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	19. Selected Interim Financial Information (unaudited) Boston Properties, Inc. The tables below reflect Boston Properties, Inc.’s selected quarterly information for the years ended December 31, 2017 and 2016 . 2017 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per share amounts) Total revenue $ 632,228 $ 656,907 $ 657,712 $ 655,229 Income before gains on sales of real estate $ 115,431 $ 163,243 $ 144,813 $ 131,331 Net income attributable to Boston Properties, Inc. common shareholders $ 97,083 $ 133,709 $ 117,337 $ 103,829 Income attributable to Boston Properties, Inc. per share—basic $ 0.63 $ 0.87 $ 0.76 $ 0.67 Income attributable to Boston Properties, Inc. per share—diluted $ 0.63 $ 0.87 $ 0.76 $ 0.67 2016 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per share amounts) Total revenue $ 665,985 $ 623,546 $ 625,228 $ 636,061 Income before gains on sales of real estate $ 148,599 $ 117,357 $ 58,521 $ 164,894 Net income attributable to Boston Properties, Inc. common shareholders $ 181,747 $ 96,597 $ 76,753 $ 147,214 Income attributable to Boston Properties, Inc. per share—basic $ 1.18 $ 0.63 $ 0.50 $ 0.96 Income attributable to Boston Properties, Inc. per share—diluted $ 1.18 $ 0.63 $ 0.50 $ 0.96 Boston Properties Limited Partnership The tables below reflect Boston Properties Limited Partnership’s selected quarterly information for the years ended December 31, 2017 and 2016 . 2017 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per unit amounts) Total revenue $ 632,228 $ 656,907 $ 657,712 $ 655,229 Income before gains on sales of real estate $ 117,578 $ 165,328 $ 146,767 $ 133,285 Net income attributable to Boston Properties Limited Partnership common unitholders $ 110,662 $ 151,844 $ 132,693 $ 117,667 Income attributable to Boston Properties Limited Partnership per unit—basic $ 0.64 $ 0.88 $ 0.77 $ 0.69 Income attributable to Boston Properties Limited Partnership per unit—diluted $ 0.64 $ 0.88 $ 0.77 $ 0.68 2016 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per unit amounts) Total revenue $ 665,985 $ 623,546 $ 625,228 $ 636,061 Income before gains on sales of real estate $ 150,586 $ 119,341 $ 63,687 $ 167,384 Net income attributable to Boston Properties Limited Partnership common unitholders $ 207,296 $ 109,938 $ 91,306 $ 166,801 Income attributable to Boston Properties Limited Partnership per unit—basic $ 1.21 $ 0.64 $ 0.53 $ 0.97 Income attributable to Boston Properties Limited Partnership per unit—diluted $ 1.21 $ 0.64 $ 0.53 $ 0.97

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	20. Subsequent Events On January 9, 2018, the Company completed the sale of its 500 E Street, S.W. property located in Washington, DC for a net contract sale price of approximately $118.6 million , which exceeds its carrying value. 500 E Street, S.W. is an approximately 262,000 net rentable square foot Class A office property. On January 24, 2018, the Company entered into a lease agreement with a tenant for a build-to-suit project with approximately 276,000 net rentable square feet of Class A office space at the Company's 17Fifty Presidents Street development project located in Reston, Virginia. The Company expects that the building will be complete and available for occupancy during the first quarter of 2020. On January 31, 2018, the Company partially placed in-service its Signature at Reston development project comprised of 508 apartment units and retail space aggregating approximately 515,000 square feet located in Reston, Virginia. On February 2, 2018 and February 6, 2018, Boston Properties, Inc. issued an aggregate of 18,226 shares of restricted common stock and Boston Properties Limited Partnership issued an aggregate of 195,546 LTIP units under the 2012 Plan to certain employees of Boston Properties, Inc. On February 4, 2018, the measurement period for the Company’s 2015 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 22.0% of target or an aggregate of approximately $3.6 million (after giving effect to voluntary employee separations). As a result, an aggregate of 337,847 2015 MYLTIP Units that had been previously granted were automatically forfeited. On February 6, 2018, Boston Properties, Inc.’s Compensation Committee approved the 2018 Multi-Year Long-Term Incentive Program (the “2018 MYLTIP”) awards under Boston Properties, Inc.’s 2012 Plan to certain officers and employees of Boston Properties, Inc. The 2018 MYLTIP awards utilize Boston Properties, Inc.’s total stockholder return (“TSR”) over a three -year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will be based on Boston Properties, Inc.’s TSR relative to (i) the Cohen & Steers Realty Majors Portfolio Index ( 50% weight) and (ii) the Nareit Office Index adjusted to include Vornado Realty Trust ( 50% weight). Earned awards will range from zero to a maximum of approximately $32.3 million depending on Boston Properties, Inc.’s TSR relative to the two indices, with a target of approximately $16.2 million and linear interpolation between zero and maximum. Earned awards measured on the basis of relative TSR performance are subject to an absolute TSR component in the form of relatively simple modifiers that (A) reduce the level of earned awards in the event Boston Properties, Inc.’s annualized TSR is less than 0% and (B) cause some awards to be earned in the event Boston Properties, Inc.’s annualized TSR is more than 12% even though on a relative basis alone Boston Properties, Inc.’s TSR would not result in any earned awards. Earned awards (if any) will vest 50% on February 5, 2021 and 50% on February 5, 2022, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by Boston Properties, Inc. without cause, or termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 5, 2021, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2018 MYLTIP awards are in the form of LTIP Units issued on the grant date which (i) are subject to forfeiture to the extent awards are not earned and (ii) prior to the performance measurement date are only entitled to one-tenth ( 10% ) of the regular quarterly distributions payable on common partnership units. Under ASC 718, the 2018 MYLTIP awards have an aggregate value of approximately $13.3 million , which amount will generally be amortized into earnings over the four -year plan period under the graded vesting method. On February 23, 2018, the Company entered into a lease agreement with Fannie Mae to lease approximately 850,000 net rentable square feet of Class A office space at the Company's Reston Gateway development project located in Reston, Virginia. The initial phase of the project will consist of approximately 1.0 million net rentable square feet. The Company expects to begin construction in the second half of 2018 upon receipt of all necessary approvals.

Real Estate and Accumulated Dep

Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2017
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation Disclosure [Text Block]	Item 15. Exhibits and Financial Statement Schedules (a) Financial Statement Schedule Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 767 Fifth Avenue (the General Motors Building) Office New York, NY $ 2,267,041 $ 1,796,252 $ 1,532,654 $ 135,559 $ 1,796,252 $ 1,668,213 $ — $ — $ 3,464,465 $ 222,981 1968 2013 (1) Prudential Center Office Boston, MA — 92,077 948,357 501,709 115,638 1,426,505 — — 1,542,143 511,605 1965/1993/2002/2016-2017 1998/1999/2000 (1) Embarcadero Center Office San Francisco, CA — 179,697 847,410 366,780 195,987 1,197,900 — — 1,393,887 596,100 1970/1989 1998-1999 (1) 399 Park Avenue Office New York, NY — 339,200 700,358 181,418 354,107 866,869 — — 1,220,976 310,262 1961 2002 (1) 601 Lexington Avenue Office New York, NY 672,142 241,600 494,782 290,590 289,639 634,134 — 103,199 1,026,972 254,932 1977/1997 2001 (1) 200 Clarendon Street and Garage Office Boston, MA — 219,543 667,884 139,189 219,616 799,991 7,009 — 1,026,616 161,471 1976 2010 (1) 250 West 55th Street Office New York, NY — 285,263 603,167 43,296 285,263 646,463 — — 931,726 72,058 2014 2007 (1) Carnegie Center Office Princeton, NJ — 107,997 389,359 157,960 108,948 543,514 2,854 — 655,316 228,171 1983-2016 1998/1999/2000/2007/2014/2017 (1) 100 Federal Street Office Boston, MA — 131,067 435,954 79,035 131,067 514,989 — — 646,056 97,630 1971-1975/2017 2012 (1) Times Square Tower Office New York, NY — 165,413 380,438 87,050 169,193 463,708 — — 632,901 191,435 2004 2000 (1) Atlantic Wharf Office Boston, MA — 63,988 454,537 17,473 63,988 472,010 — — 535,998 101,525 2011 2007 (1) Fountain Square Office Reston, VA — 56,853 306,298 17,834 56,853 320,474 3,658 — 380,985 60,098 1986-1990 2012 (1) 510 Madison Avenue Office New York, NY — 103,000 253,665 23,875 103,000 277,540 — — 380,540 54,056 2012 2010 (1) 599 Lexington Avenue Office New York, NY — 81,040 100,507 165,350 87,852 259,045 — — 346,897 165,739 1986 1997 (1) 680 Folsom Street Office San Francisco, CA — 72,545 219,766 7,545 72,545 227,311 — — 299,856 30,577 2014 2012 (1) South of Market and Democracy Tower Office Reston, VA — 13,603 237,479 14,991 13,687 252,386 — — 266,073 87,711 2008-2009 2003 (1) 601 Massachusetts Avenue Office Washington, DC — 95,310 165,173 2,353 95,322 167,514 — — 262,836 12,177 2016 2008 (1) Bay Colony Corporate Center Office Waltham, MA — 18,789 148,451 73,418 18,789 221,869 — — 240,658 57,320 1985-1989 2011 (1) Gateway Center Office San Francisco, CA — 28,255 139,245 59,019 30,627 195,892 — — 226,519 102,634 1984/1986/2002 1999 (1) 535 Mission Street Office San Francisco, CA — 40,933 148,378 3,259 40,933 151,637 — — 192,570 14,637 2015 2013 (1) 2200 Pennsylvania Avenue Office Washington, DC — — 183,541 4,907 — 188,448 — — 188,448 46,780 2011 2008 (1) Mountain View Research Park Office Mountain View, CA — 95,066 68,373 8,136 95,066 76,509 — — 171,575 15,146 1977-1981/2007-2013 2013 (1) Reservoir Place Office Waltham, MA — 18,605 104,124 43,255 20,108 145,876 — — 165,984 66,230 1955/1987/2017 1997/1998 (1) 1330 Connecticut Avenue Office Washington, DC — 25,982 82,311 32,839 27,135 113,997 — — 141,132 22,530 1984 2004 (1) 1333 New Hampshire Avenue Office Washington, DC — 34,032 85,660 11,473 35,382 95,783 — — 131,165 40,499 1996 2003 (1) Kingstowne Towne Center Office Alexandria, VA — 18,021 109,038 1,371 18,062 110,368 — — 128,430 39,048 2003-2006 2007 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building One Freedom Square Office Reston, VA — 9,929 84,504 32,618 11,293 115,758 — — 127,051 50,313 2000 2003 (1) Capital Gallery Office Washington, DC — 4,725 29,565 89,514 8,662 115,142 — — 123,804 66,009 1981/2006 2007 (1) Weston Corporate Center Office Weston, MA — 25,753 92,312 (123 ) 25,854 92,088 — — 117,942 23,125 2010 2001 (1) Two Freedom Square Office Reston, VA — 13,930 77,739 23,379 15,420 99,628 — — 115,048 47,936 2001 2003 (1) One and Two Reston Overlook Office Reston, VA — 16,456 66,192 25,111 16,179 91,580 — — 107,759 44,626 1999 2000 (1) Discovery Square Office Reston, VA — 11,198 71,782 24,414 12,533 94,861 — — 107,394 43,184 2001 2003 (1) 140 Kendrick Street Office Needham, MA — 18,095 66,905 17,492 19,092 83,400 — — 102,492 29,013 2000 2004 (1) 355 Main Street Office Cambridge, MA — 18,863 53,346 27,450 21,173 78,486 — — 99,659 26,915 1981/1996/2013 2006 (1) 10 CityPoint Office Waltham, MA — 1,953 85,752 2,833 2,116 88,422 — — 90,538 4,673 2016 1997 (1) 90 Broadway Office Cambridge, MA — 19,104 52,078 17,180 20,785 67,577 — — 88,362 19,254 1983/1998/2013 2006 (1) 230 CityPoint Office Waltham, MA — 13,189 49,823 25,236 13,593 74,655 — — 88,248 26,562 1992 2005 (1) Waltham Weston Corporate Center Office Waltham, MA — 10,385 60,694 11,030 11,097 71,012 — — 82,109 30,036 2003 1999 (1) 77 CityPoint Office Waltham, MA — 13,847 60,383 5,703 13,873 66,060 — — 79,933 23,044 2008 2001 (1) 3625-3635 Peterson Way Office Santa Clara, CA — 63,206 14,879 138 63,206 14,879 138 — 78,223 5,120 1979 2016 (1) North First Business Park Office San Jose, CA — 58,402 13,069 4,416 23,377 16,600 35,910 — 75,887 15,839 1981 2007 (1) 300 Binney Street Office Cambridge, MA — 18,080 51,262 140 18,080 51,402 — — 69,482 7,755 2013 2009 (1) 2440 West El Camino Real Office Mountain View, CA — 16,741 51,285 1,287 16,741 52,572 — — 69,313 10,790 1987/2003 2011 (1) Wisconsin Place Office Chevy Chase, MD — — 53,349 14,907 — 68,256 — — 68,256 19,775 2009 2004 (1) Reston Corporate Center Office Reston, VA — 9,135 50,857 6,236 10,148 56,080 — — 66,228 26,769 1984 1998 (1) New Dominion Technology Park, Bldg. Two Office Herndon, VA — 5,584 51,868 4,157 6,510 55,099 — — 61,609 23,652 2004 1998 (1) 200 West Street Office Waltham, MA — 16,148 24,983 10,673 16,813 34,991 — — 51,804 21,140 1999 1997 (1) New Dominion Technology Park, Bldg. One Office Herndon, VA 32,691 3,880 43,227 3,882 4,583 46,406 — — 50,989 25,940 2001 1998 (1) Sumner Square Office Washington, DC — 624 28,745 19,000 1,478 46,891 — — 48,369 23,570 1985 1999 (1) 255 Main Street Office Cambridge, MA — 134 25,110 21,583 548 46,279 — — 46,827 28,250 1987 1997 (1) University Place Office Cambridge, MA 7,407 — 37,091 9,007 390 45,708 — — 46,098 26,295 1985 1998 (1) 2600 Tower Oaks Boulevard Office Rockville, MD — 4,243 31,125 9,867 4,785 40,450 — — 45,235 21,020 2001 1998 (1) Quorum Office Park Office Chelmsford, MA — 3,750 32,454 5,813 5,187 36,830 — — 42,017 16,594 2001 2000 (1) 500 E Street Office Washington, DC — 109 22,420 14,743 2,379 34,893 — — 37,272 23,781 1987 1997 (1) 150 Broadway Office Cambridge, MA — 850 25,042 8,540 1,323 33,109 — — 34,432 16,933 1999 1997 (1) 325 Main Street Office Cambridge, MA — 174 12,200 11,963 965 23,372 — — 24,337 12,852 1987/2013 1997 (1) 105 Broadway Office Cambridge, MA — 1,299 12,943 8,214 2,395 20,061 — — 22,456 13,493 1990 1997 (1) Lexington Office Park Office Lexington, MA — 998 1,426 18,219 1,264 19,379 — — 20,643 13,404 1982 1997 (1) 201 Spring Street Office Lexington, MA — 2,849 15,303 694 3,124 15,722 — — 18,846 7,931 1997 1997 (1) The Point Office Waltham, MA — 6,395 10,040 409 6,480 10,364 — — 16,844 714 2015 2007 (1) 92-100 Hayden Avenue Office Lexington, MA — 594 6,748 8,181 802 14,721 — — 15,523 12,495 1985 1997 (1) 91 Hartwell Avenue Office Lexington, MA — 784 6,464 8,269 941 14,576 — — 15,517 9,849 1985 1997 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 690 Folsom Street Office San Francisco, CA — 3,219 11,038 1,157 3,219 12,195 — — 15,414 1,295 2015 2012 (1) 181 Spring Street Office Lexington, MA — 1,066 9,520 2,318 1,160 11,744 — — 12,904 5,194 1999 1997 (1) 195 West Street Office Waltham, MA — 1,611 6,652 4,340 1,858 10,745 — — 12,603 7,963 1990 1997 (1) 33 Hayden Avenue Office Lexington, MA — 266 3,234 8,381 425 11,456 — — 11,881 8,211 1979 1997 (1) 7501 Boston Boulevard, Building Seven Office Springfield, VA — 665 9,273 819 791 9,966 — — 10,757 4,848 1997 1997 (1) 7435 Boston Boulevard, Building One Office Springfield, VA — 392 3,822 3,997 659 7,552 — — 8,211 5,510 1982 1997 (1) 250 Binney Street Office Cambridge, MA — 110 4,483 3,593 273 7,913 — — 8,186 5,066 1983 1997 (1) 8000 Grainger Court, Building Five Office Springfield, VA — 366 4,282 3,375 601 7,422 — — 8,023 5,644 1984 1997 (1) 7450 Boston Boulevard, Building Three Office Springfield, VA — 1,165 4,681 1,773 1,430 6,189 — — 7,619 3,451 1987 1998 (1) 453 Ravendale Drive Office Mountain View, CA — 5,477 1,090 408 5,477 1,498 — — 6,975 472 1977 2012 (1) 17 Hartwell Avenue Office Lexington, MA — 26 150 6,252 65 6,363 — — 6,428 1,098 1968 1997 (1) 7601 Boston Boulevard, Building Eight Office Springfield, VA — 200 878 5,052 551 5,579 — — 6,130 4,263 1986 1997 (1) 7300 Boston Boulevard, Building Thirteen Office Springfield, VA — 608 4,773 709 661 5,429 — — 6,090 2,785 2002 1997 (1) 7500 Boston Boulevard, Building Six Office Springfield, VA — 138 3,749 1,655 406 5,136 — — 5,542 3,965 1985 1997 (1) 8000 Corporate Court, Building Eleven Office Springfield, VA — 136 3,071 1,596 774 4,029 — — 4,803 2,909 1989 1997 (1) 7374 Boston Boulevard, Building Four Office Springfield, VA — 241 1,605 1,913 398 3,361 — — 3,759 2,578 1984 1997 (1) 7375 Boston Boulevard, Building Ten Office Springfield, VA — 23 2,685 938 93 3,553 — — 3,646 2,570 1988 1997 (1) 7451 Boston Boulevard, Building Two Office Springfield, VA — 249 1,542 1,659 613 2,837 — — 3,450 2,429 1982 1997 (1) 32 Hartwell Avenue Office Lexington, MA — 168 1,943 1,012 314 2,809 — — 3,123 1,974 1968/1979/1987 1997 (1) 164 Lexington Road Office Billerica, MA — 592 1,370 319 643 1,638 — — 2,281 868 1982 1997 (1) The Avant at Reston Town Center Residential Reston, VA — 20,350 91,995 830 20,350 92,825 — — 113,175 9,780 2014 2010 (1) The Lofts at Atlantic Wharf Residential Boston, MA — 3,529 54,891 1,768 3,529 56,659 — — 60,188 9,622 2011 2007 (1) Boston Marriott Cambridge Hotel Cambridge, MA — 478 37,918 38,799 1,201 75,994 — — 77,195 47,753 1986 1997 (1) Kendall Center Green Garage Garage Cambridge, MA — — 35,035 7,448 103 42,380 — — 42,483 10,779 1984 2006 (1) Kendall Center Yellow Garage Garage Cambridge, MA — 1,256 15,697 1,621 1,434 17,140 — — 18,574 5,181 2006 2004 (1) Kendall Center Blue Garage Garage Cambridge, MA — 1,163 11,633 2,283 1,579 13,500 — — 15,079 9,209 1990 1997 (1) Salesforce Tower Development San Francisco, CA — — — 947,106 200,349 55,318 — 691,439 947,106 116 N/A 2013 N/A Signature at Reston Development Reston, VA — — — 203,650 — — — 203,650 203,650 — N/A 2013 N/A Proto Kendall Square Development Cambridge, MA — — — 82,905 — — — 82,905 82,905 — N/A 2015 N/A 145 Broadway Development Cambridge, MA — 121 — 79,979 324 — — 79,776 80,100 — NA 1997 N/A 191 Spring Street Development Lexington, MA — 2,850 27,166 35,174 3,151 46,288 — 15,751 65,190 19,034 1971/1995 1997 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 6595 Springfield Center Drive (TSA Headquarters) Development Springfield, VA — — — 41,918 — — — 41,918 41,918 — N/A 2007 N/A MacArthur Station Residences Development Oakland, CA — — — 37,644 — — — 37,644 37,644 — N/A N/A N/A 20 CityPoint Development Waltham, MA — — — 13,056 — — — 13,056 13,056 — N/A 2007 N/A Tower Oaks Master Plan Land Rockville, MD — — — 29,419 — — 29,419 — 29,419 — N/A 1998 N/A Plaza at Almaden Land San Jose, CA — — — 29,085 — — 29,085 — 29,085 — N/A 2006 N/A Springfield Metro Center Land Springfield, VA — — — 19,684 — — 19,684 — 19,684 — N/A 2007 N/A 214 Third Avenue Land Waltham, MA — — — 13,815 — — 13,815 — 13,815 — N/A 2006 N/A Reston Gateway Land Reston, VA — — — 13,730 — — 13,730 — 13,730 — N/A 1998 N/A 103 Fourth Avenue Land Waltham, MA — — — 12,115 — — 12,115 — 12,115 — N/A 2007 N/A Crane Meadow Land Marlborough, MA — — — 8,836 — — 8,836 — 8,836 — N/A 2000 N/A Washingtonian North Land Gaithersburg, MD — — — 7,645 — — 7,645 — 7,645 — N/A 1998 N/A 2100 Pennsylvania Avenue Land Washington, DC — — — 6,543 — — 6,543 — 6,543 — N/A N/A N/A Fourth and Harrison Land San Francisco, CA — — — 5,659 — — 5,659 — 5,659 — N/A N/A N/A North First Master Plan Land San Jose, CA — — — 3,018 — — 3,018 — 3,018 — N/A 2007 N/A Broad Run Business Park Land Loudoun County, VA — — — 2,367 — — 2,367 — 2,367 — N/A 1998 N/A Kendall Center Master Plan Land Cambridge, MA — — — 2,207 — — 2,207 — 2,207 — N/A N/A N/A Weston Quarry Land Weston, MA — — — 1,194 — — 1,194 — 1,194 — N/A 2001 N/A Reston Overlook Master Plan Land Reston, VA — — — 39 — — 39 — 39 — N/A 2000 N/A $ 2,979,281 (2 ) $ 4,762,002 $ 11,634,050 $ 4,662,662 $ 5,080,679 $ 14,503,772 $ 204,925 (3 ) $ 1,269,338 $ 21,058,714 $ 4,566,570 Note: Total Real Estate does not include Furniture, Fixtures and Equipment totaling approximately $37,928 . Accumulated Depreciation does not include approximately $23,064 of accumulated depreciation related to Furniture, Fixtures and Equipment. The aggregate cost and accumulated depreciation for tax purposes was approximately $17.3 billion and $3.6 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 unamortized deferred financing costs totaling approximately $(34.7) million . (3) Includes pre-development costs. Boston Properties, Inc. Real Estate and Accumulated Depreciation December 31, 2017 , 2016 and 2015 (dollars in thousands) A summary of activity for real estate and accumulated depreciation is as follows: 2017 2016 2015 Real Estate: Balance at the beginning of the year $ 20,114,576 $ 19,451,683 $ 19,208,417 Additions to/improvements of real estate 1,099,286 977,287 700,792 Assets sold/written-off (155,148 ) (314,394 ) $ (457,526 ) Balance at the end of the year $ 21,058,714 $ 20,114,576 $ 19,451,683 Accumulated Depreciation: Balance at the beginning of the year $ 4,201,891 $ 3,905,940 $ 3,529,978 Depreciation expense 497,059 560,024 486,450 Assets sold/written-off (132,380 ) (264,073 ) (110,488 ) Balance at the end of the year $ 4,566,570 $ 4,201,891 $ 3,905,940 Note: Real Estate and Accumulated Depreciation amounts do not include Furniture, Fixtures and Equipment.
Boston Properties Limited Partnership
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation Disclosure [Text Block]	Boston Properties Limited Partnership Schedule III—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building 767 Fifth Avenue (the General Motors Building) Office New York, NY $ 2,267,041 $ 1,796,252 $ 1,532,654 $ 135,559 $ 1,796,252 $ 1,668,213 $ — $ — $ 3,464,465 $ 222,981 1968 2013 (1) Prudential Center Office Boston, MA — 92,077 948,357 441,339 100,540 1,381,233 — — 1,481,773 497,960 1965/1993/2002/2016-2017 1998/1999/2000 (1) Embarcadero Center Office San Francisco, CA — 179,697 847,410 304,399 180,420 1,151,086 — — 1,331,506 581,932 1970/1989 1998-1999 (1) 399 Park Avenue Office New York, NY — 339,200 700,358 121,810 339,200 822,168 — — 1,161,368 296,763 1961 2002 (1) 200 Clarendon Street and Garage Office Boston, MA — 219,543 667,884 139,189 219,616 799,991 7,009 — 1,026,616 161,471 1976 2010 (1) 601 Lexington Avenue Office New York, NY 672,142 241,600 494,782 253,504 279,281 607,406 — 103,199 989,886 246,814 1977/1997 2001 (1) 250 West 55th Street Office New York, NY — 285,263 603,167 43,296 285,263 646,463 — — 931,726 72,058 2014 2007 (1) 100 Federal Street Office Boston, MA — 131,067 435,954 79,035 131,067 514,989 — — 646,056 97,630 1971-1975/2017 2012 (1) Carnegie Center Office Princeton, NJ — 107,997 389,359 140,642 104,617 530,527 2,854 — 637,998 224,256 1983-2016 1998/1999/2000/2007/2014/2017 (1) Times Square Tower Office New York, NY — 165,413 380,438 49,071 159,694 435,228 — — 594,922 182,850 2004 2000 (1) Atlantic Wharf Office Boston, MA — 63,988 454,537 17,473 63,988 472,010 — — 535,998 101,525 2011 2007 (1) Fountain Square Office Reston, VA — 56,853 306,298 17,834 56,853 320,474 3,658 — 380,985 60,098 1986-1990 2012 (1) 510 Madison Avenue Office New York, NY — 103,000 253,665 23,875 103,000 277,540 — — 380,540 54,056 2012 2010 (1) 599 Lexington Avenue Office New York, NY — 81,040 100,507 138,108 81,040 238,615 — — 319,655 159,586 1986 1997 (1) 680 Folsom Street Office San Francisco, CA — 72,545 219,766 7,545 72,545 227,311 — — 299,856 30,577 2014 2012 (1) South of Market and Democracy Tower Office Reston, VA — 13,603 237,479 14,655 13,603 252,134 — — 265,737 87,651 2008-2009 2003 (1) 601 Massachusetts Avenue Office Washington, DC — 95,310 165,173 2,341 95,310 167,514 — — 262,824 12,177 2016 2008 (1) Bay Colony Corporate Center Office Waltham, MA — 18,789 148,451 73,418 18,789 221,869 — — 240,658 57,320 1985-1989 2011 (1) Gateway Center Office San Francisco, CA — 28,255 139,245 52,630 29,029 191,101 — — 220,130 101,191 1984/1986/2002 1999 (1) 535 Mission Street Office San Francisco, CA — 40,933 148,378 3,259 40,933 151,637 — — 192,570 14,637 2015 2013 (1) 2200 Pennsylvania Avenue Office Washington, DC — — 183,541 4,907 — 188,448 — — 188,448 46,780 2011 2008 (1) Mountain View Research Park Office Mountain View, CA — 95,066 68,373 8,136 95,066 76,509 — — 171,575 15,146 1977-1981/2007-2013 2013 (1) Reservoir Place Office Waltham, MA — 18,605 104,124 39,180 19,089 142,820 — — 161,909 65,309 1955/1987/2017 1997/1998 (1) 1330 Connecticut Avenue Office Washington, DC — 25,982 82,311 28,226 25,982 110,537 — — 136,519 21,484 1984 2004 (1) Kingstowne Towne Center Office Alexandria, VA — 18,021 109,038 1,207 18,021 110,245 — — 128,266 39,018 2003-2006 2007 (1) 1333 New Hampshire Avenue Office Washington, DC — 34,032 85,660 6,079 34,032 91,739 — — 125,771 39,279 1996 2003 (1) One Freedom Square Office Reston, VA — 9,929 84,504 26,981 9,883 111,531 — — 121,414 49,037 2000 2003 (1) Weston Corporate Center Office Weston, MA — 25,753 92,312 (123 ) 25,854 92,088 — — 117,942 23,125 2010 2001 (1) Capital Gallery Office Washington, DC — 4,725 29,565 79,383 6,128 107,545 — — 113,673 63,717 1981/2006 2007 (1) Two Freedom Square Office Reston, VA — 13,930 77,739 17,167 13,866 94,970 — — 108,836 46,532 2001 2003 (1) One and Two Reston Overlook Office Reston, VA — 16,456 66,192 20,693 15,074 88,267 — — 103,341 43,627 1999 2000 (1) Boston Properties Limited Partnership Schedule 3—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building Discovery Square Office Reston, VA — 11,198 71,782 18,869 11,146 90,703 — — 101,849 41,928 2001 2003 (1) 355 Main Street Office Cambridge, MA — 18,863 53,346 27,152 21,098 78,263 — — 99,361 26,850 1981/1996/2013 2006 (1) 140 Kendrick Street Office Needham, MA — 18,095 66,905 13,502 18,095 80,407 — — 98,502 28,111 2000 2004 (1) 10 CityPoint Office Waltham, MA — 1,953 85,752 2,670 1,953 88,422 — — 90,375 4,673 2016 1997 (1) 90 Broadway Office Cambridge, MA — 19,104 52,078 17,001 20,741 67,442 — — 88,183 19,220 1983/1998/2013 2006 (1) 230 CityPoint Office Waltham, MA — 13,189 49,823 23,619 13,189 73,442 — — 86,631 26,200 1992 2005 (1) 77 CityPoint Office Waltham, MA — 13,847 60,383 5,598 13,847 65,981 — — 79,828 23,024 2008 2001 (1) Waltham Weston Corporate Center Office Waltham, MA — 10,385 60,694 8,043 10,350 68,772 — — 79,122 29,359 2003 1999 (1) 3625-3635 Peterson Way Office Santa Clara, CA — 63,206 14,879 138 63,206 14,879 138 — 78,223 5,120 1979 2016 (1) North First Business Park Office San Jose, CA — 58,402 13,069 4,393 23,371 16,583 35,910 — 75,864 15,839 1981 2007 (1) 300 Binney Street Office Cambridge, MA — 18,080 51,262 140 18,080 51,402 — — 69,482 7,755 2013 2009 (1) 2440 West El Camino Real Office Mountain View, CA — 16,741 51,285 1,287 16,741 52,572 — — 69,313 10,790 1987/2003 2011 (1) Wisconsin Place Office Chevy Chase, MD — — 53,349 14,907 — 68,256 — — 68,256 19,775 2009 2004 (1) Reston Corporate Center Office Reston, VA — 9,135 50,857 3,625 9,496 54,121 — — 63,617 26,178 1984 1998 (1) New Dominion Technology Park, Bldg. Two Office Herndon, VA — 5,584 51,868 412 5,574 52,290 — — 57,864 22,801 2004 1998 (1) 200 West Street Office Waltham, MA — 16,148 24,983 8,012 16,148 32,995 — — 49,143 20,538 1999 1997 (1) New Dominion Technology Park, Bldg. One Office Herndon, VA 32,691 3,880 43,227 1,072 3,880 44,299 — — 48,179 25,304 2001 1998 (1) Sumner Square Office Washington, DC — 624 28,745 16,920 958 45,331 — — 46,289 23,103 1985 1999 (1) 255 Main Street Office Cambridge, MA — 134 25,110 19,927 134 45,037 — — 45,171 27,878 1987 1997 (1) University Place Office Cambridge, MA 7,407 — 37,091 7,557 27 44,621 — — 44,648 25,971 1985 1998 (1) 2600 Tower Oaks Boulevard Office Rockville, MD — 4,243 31,125 7,704 4,244 38,828 — — 43,072 20,529 2001 1998 (1) Quorum Office Park Office Chelmsford, MA — 3,750 32,454 4,115 4,762 35,557 — — 40,319 16,211 2001 2000 (1) 500 E Street Office Washington, DC — 109 22,420 11,503 1,569 32,463 — — 34,032 23,051 1987 1997 (1) 150 Broadway Office Cambridge, MA — 850 25,042 6,535 822 31,605 — — 32,427 16,477 1999 1997 (1) 325 Main Street Office Cambridge, MA — 174 12,200 11,192 772 22,794 — — 23,566 12,675 1987/2013 1997 (1) 105 Broadway Office Cambridge, MA — 1,299 12,943 6,108 1,868 18,482 — — 20,350 13,015 1990 1997 (1) Lexington Office Park Office Lexington, MA — 998 1,426 17,455 1,073 18,806 — — 19,879 13,235 1982 1997 (1) 201 Spring Street Office Lexington, MA — 2,849 15,303 (405 ) 2,849 14,898 — — 17,747 7,681 1997 1997 (1) The Point Office Waltham, MA — 6,395 10,040 409 6,480 10,364 — — 16,844 714 2015 2007 (1) 690 Folsom Street Office San Francisco, CA — 3,219 11,038 1,157 3,219 12,195 — — 15,414 1,295 2015 2012 (1) 91 Hartwell Avenue Office Lexington, MA — 784 6,464 7,642 784 14,106 — — 14,890 9,705 1985 1997 (1) 92-100 Hayden Avenue Office Lexington, MA — 594 6,748 7,452 619 14,175 — — 14,794 12,329 1985 1997 (1) 181 Spring Street Office Lexington, MA — 1,066 9,520 1,941 1,066 11,461 — — 12,527 5,109 1999 1997 (1) 195 West Street Office Waltham, MA — 1,611 6,652 3,351 1,611 10,003 — — 11,614 7,736 1990 1997 (1) 33 Hayden Avenue Office Lexington, MA — 266 3,234 7,744 266 10,978 — — 11,244 8,067 1979 1997 (1) Boston Properties Limited Partnership Schedule 3—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building 7501 Boston Boulevard, Building Seven Office Springfield, VA — 665 9,273 314 665 9,587 — — 10,252 4,732 1997 1997 (1) 250 Binney Street Office Cambridge, MA — 110 4,483 2,939 110 7,422 — — 7,532 4,922 1983 1997 (1) 7435 Boston Boulevard, Building One Office Springfield, VA — 392 3,822 3,304 486 7,032 — — 7,518 5,354 1982 1997 (1) 8000 Grainger Court, Building Five Office Springfield, VA — 366 4,282 2,781 453 6,976 — — 7,429 5,511 1984 1997 (1) 7450 Boston Boulevard, Building Three Office Springfield, VA — 1,165 4,681 1,359 1,327 5,878 — — 7,205 3,354 1987 1998 (1) 453 Ravendale Drive Office Mountain View, CA — 5,477 1,090 408 5,477 1,498 — — 6,975 472 1977 2012 (1) 17 Hartwell Avenue Office Lexington, MA — 26 150 6,095 26 6,245 — — 6,271 1,062 1968 1997 (1) 7300 Boston Boulevard, Building Thirteen Office Springfield, VA — 608 4,773 497 608 5,270 — — 5,878 2,737 2002 1997 (1) 7601 Boston Boulevard, Building Eight Office Springfield, VA — 200 878 4,359 378 5,059 — — 5,437 4,107 1986 1997 (1) 7500 Boston Boulevard, Building Six Office Springfield, VA — 138 3,749 1,122 273 4,736 — — 5,009 3,845 1985 1997 (1) 8000 Corporate Court, Building Eleven Office Springfield, VA — 136 3,071 1,245 686 3,766 — — 4,452 2,826 1989 1997 (1) 7375 Boston Boulevard, Building Ten Office Springfield, VA — 23 2,685 757 47 3,418 — — 3,465 2,532 1988 1997 (1) 7374 Boston Boulevard, Building Four Office Springfield, VA — 241 1,605 1,530 303 3,073 — — 3,376 2,494 1984 1997 (1) 7451 Boston Boulevard, Building Two Office Springfield, VA — 249 1,542 1,346 535 2,602 — — 3,137 2,357 1982 1997 (1) 32 Hartwell Avenue Office Lexington, MA — 168 1,943 426 168 2,369 — — 2,537 1,840 1968/1979/1987 1997 (1) 164 Lexington Road Office Billerica, MA — 592 1,370 117 592 1,487 — — 2,079 819 1982 1997 (1) The Avant at Reston Town Center Residential Reston, VA — 20,350 91,995 830 20,350 92,825 — — 113,175 9,780 2014 2010 (1) The Lofts at Atlantic Wharf Residential Boston, MA — 3,529 54,891 1,768 3,529 56,659 — — 60,188 9,622 2011 2007 (1) Boston Marriott Cambridge Hotel Cambridge, MA — 478 37,918 35,908 478 73,826 — — 74,304 47,101 1986 1997 (1) Kendall Center Green Garage Garage Cambridge, MA — — 35,035 7,034 — 42,069 — — 42,069 10,687 1984 2006 (1) Kendall Center Yellow Garage Garage Cambridge, MA — 1,256 15,697 909 1,256 16,606 — — 17,862 5,024 2006 2004 (1) Kendall Center Blue Garage Garage Cambridge, MA — 1,163 11,633 618 1,163 12,251 — — 13,414 8,834 1990 1997 (1) Salesforce Tower Development San Francisco, CA — — — 947,106 200,349 55,318 — 691,439 947,106 116 N/A 2013 N/A Signature at Reston Development Reston, VA — — — 203,650 — — — 203,650 203,650 — N/A 2013 N/A Proto Kendall Square Development Cambridge, MA — — — 82,905 — — — 82,905 82,905 — N/A 2015 N/A 145 Broadway Development Cambridge, MA — 121 — 79,776 121 — — 79,776 79,897 — NA 1997 N/A 191 Spring Street Development Lexington, MA — 2,850 27,166 34,542 2,850 45,957 — 15,751 64,558 18,934 1971/1995 1997 (1) 6595 Springfield Center Drive (TSA Headquarters) Development Springfield, VA — — — 41,918 — — — 41,918 41,918 — N/A 2007 N/A Boston Properties Limited Partnership Schedule 3—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building MacArthur Station Residences Development Oakland, CA — — — 37,644 — — — 37,644 37,644 — N/A N/A N/A 20 CityPoint Development Waltham, MA — — — 13,056 — — — 13,056 13,056 — N/A 2007 N/A Tower Oaks Master Plan Land Rockville, MD — — — 29,419 — — 29,419 — 29,419 — N/A 1998 N/A Plaza at Almaden Land San Jose, CA — — — 29,085 — — 29,085 — 29,085 — N/A 2006 N/A Springfield Metro Center Land Springfield, VA — — — 19,684 — — 19,684 — 19,684 — N/A 2007 N/A 214 Third Avenue Land Waltham, MA — — — 13,815 — — 13,815 — 13,815 — N/A 2006 N/A Reston Gateway Land Reston, VA — — — 13,730 — — 13,730 — 13,730 — N/A 1998 N/A 103 Fourth Avenue Land Waltham, MA — — — 12,115 — — 12,115 — 12,115 — N/A 2007 N/A Crane Meadow Land Marlborough, MA — — — 8,836 — — 8,836 — 8,836 — N/A 2000 N/A Washingtonian North Land Gaithersburg, MD — — — 7,645 — — 7,645 — 7,645 — N/A 1998 N/A 2100 Pennsylvania Avenue Land Washington, DC — — — 6,543 — — 6,543 — 6,543 — N/A N/A N/A Fourth and Harrison Land San Francisco, CA — — — 5,659 — — 5,659 — 5,659 — N/A N/A N/A North First Master Plan Land San Jose, CA — — — 3,018 — — 3,018 — 3,018 — N/A 2007 N/A Broad Run Business Park Land Loudoun County, VA — — — 2,367 — — 2,367 — 2,367 — N/A 1998 N/A Kendall Center Master Plan Land Cambridge, MA — — — 2,207 — — 2,207 — 2,207 — N/A N/A N/A Weston Quarry Land Weston, MA — — — 1,194 — — 1,194 — 1,194 — N/A 2001 N/A Reston Overlook Master Plan Land Reston, VA — — — 39 — — 39 — 39 — N/A 2000 N/A $ 2,979,281 (2 ) $ 4,762,002 $ 11,634,050 $ 4,251,184 $ 4,976,303 $ 14,196,670 $ 204,925 (3 ) $ 1,269,338 $ 20,647,236 $ 4,473,895 Note: Total Real Estate does not include Furniture, Fixtures and Equipment totaling approximately $37,928 . Accumulated Depreciation does not include approximately $23,064 of accumulated depreciation related to Furniture, Fixtures and Equipment. The aggregate cost and accumulated depreciation for tax purposes was approximately $19.3 billion and $4.1 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 unamortized deferred financing costs totaling approximately $(34.7) million . (3) Includes pre-development costs. Boston Properties Limited Partnership Real Estate and Accumulated Depreciation December 31, 2017 , 2016 and 2015 (dollars in thousands) A summary of activity for real estate and accumulated depreciation is as follows: 2017 2016 2015 Real Estate: Balance at the beginning of the year $ 19,701,185 $ 19,031,289 $ 18,786,572 Additions to/improvements of real estate 1,099,286 977,287 700,792 Assets sold/written-off (153,235 ) (307,391 ) (456,075 ) Balance at the end of the year $ 20,647,236 $ 19,701,185 $ 19,031,289 Accumulated Depreciation: Balance at the beginning of the year $ 4,116,020 $ 3,826,862 $ 3,458,640 Depreciation expense 488,919 548,397 478,457 Assets sold/written-off (131,044 ) (259,239 ) (110,235 ) Balance at the end of the year $ 4,473,895 $ 4,116,020 $ 3,826,862 Note: Real Estate and Accumulated Depreciation amounts do not include Furniture, Fixtures and Equipment.

Real Estate and Accumulated D30

Real Estate and Accumulated Depreciation Activity of Real Estate and Accumulated Depreciation (Notes)	12 Months Ended
	Dec. 31, 2017
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Text Block]	Item 15. Exhibits and Financial Statement Schedules (a) Financial Statement Schedule Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 767 Fifth Avenue (the General Motors Building) Office New York, NY $ 2,267,041 $ 1,796,252 $ 1,532,654 $ 135,559 $ 1,796,252 $ 1,668,213 $ — $ — $ 3,464,465 $ 222,981 1968 2013 (1) Prudential Center Office Boston, MA — 92,077 948,357 501,709 115,638 1,426,505 — — 1,542,143 511,605 1965/1993/2002/2016-2017 1998/1999/2000 (1) Embarcadero Center Office San Francisco, CA — 179,697 847,410 366,780 195,987 1,197,900 — — 1,393,887 596,100 1970/1989 1998-1999 (1) 399 Park Avenue Office New York, NY — 339,200 700,358 181,418 354,107 866,869 — — 1,220,976 310,262 1961 2002 (1) 601 Lexington Avenue Office New York, NY 672,142 241,600 494,782 290,590 289,639 634,134 — 103,199 1,026,972 254,932 1977/1997 2001 (1) 200 Clarendon Street and Garage Office Boston, MA — 219,543 667,884 139,189 219,616 799,991 7,009 — 1,026,616 161,471 1976 2010 (1) 250 West 55th Street Office New York, NY — 285,263 603,167 43,296 285,263 646,463 — — 931,726 72,058 2014 2007 (1) Carnegie Center Office Princeton, NJ — 107,997 389,359 157,960 108,948 543,514 2,854 — 655,316 228,171 1983-2016 1998/1999/2000/2007/2014/2017 (1) 100 Federal Street Office Boston, MA — 131,067 435,954 79,035 131,067 514,989 — — 646,056 97,630 1971-1975/2017 2012 (1) Times Square Tower Office New York, NY — 165,413 380,438 87,050 169,193 463,708 — — 632,901 191,435 2004 2000 (1) Atlantic Wharf Office Boston, MA — 63,988 454,537 17,473 63,988 472,010 — — 535,998 101,525 2011 2007 (1) Fountain Square Office Reston, VA — 56,853 306,298 17,834 56,853 320,474 3,658 — 380,985 60,098 1986-1990 2012 (1) 510 Madison Avenue Office New York, NY — 103,000 253,665 23,875 103,000 277,540 — — 380,540 54,056 2012 2010 (1) 599 Lexington Avenue Office New York, NY — 81,040 100,507 165,350 87,852 259,045 — — 346,897 165,739 1986 1997 (1) 680 Folsom Street Office San Francisco, CA — 72,545 219,766 7,545 72,545 227,311 — — 299,856 30,577 2014 2012 (1) South of Market and Democracy Tower Office Reston, VA — 13,603 237,479 14,991 13,687 252,386 — — 266,073 87,711 2008-2009 2003 (1) 601 Massachusetts Avenue Office Washington, DC — 95,310 165,173 2,353 95,322 167,514 — — 262,836 12,177 2016 2008 (1) Bay Colony Corporate Center Office Waltham, MA — 18,789 148,451 73,418 18,789 221,869 — — 240,658 57,320 1985-1989 2011 (1) Gateway Center Office San Francisco, CA — 28,255 139,245 59,019 30,627 195,892 — — 226,519 102,634 1984/1986/2002 1999 (1) 535 Mission Street Office San Francisco, CA — 40,933 148,378 3,259 40,933 151,637 — — 192,570 14,637 2015 2013 (1) 2200 Pennsylvania Avenue Office Washington, DC — — 183,541 4,907 — 188,448 — — 188,448 46,780 2011 2008 (1) Mountain View Research Park Office Mountain View, CA — 95,066 68,373 8,136 95,066 76,509 — — 171,575 15,146 1977-1981/2007-2013 2013 (1) Reservoir Place Office Waltham, MA — 18,605 104,124 43,255 20,108 145,876 — — 165,984 66,230 1955/1987/2017 1997/1998 (1) 1330 Connecticut Avenue Office Washington, DC — 25,982 82,311 32,839 27,135 113,997 — — 141,132 22,530 1984 2004 (1) 1333 New Hampshire Avenue Office Washington, DC — 34,032 85,660 11,473 35,382 95,783 — — 131,165 40,499 1996 2003 (1) Kingstowne Towne Center Office Alexandria, VA — 18,021 109,038 1,371 18,062 110,368 — — 128,430 39,048 2003-2006 2007 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building One Freedom Square Office Reston, VA — 9,929 84,504 32,618 11,293 115,758 — — 127,051 50,313 2000 2003 (1) Capital Gallery Office Washington, DC — 4,725 29,565 89,514 8,662 115,142 — — 123,804 66,009 1981/2006 2007 (1) Weston Corporate Center Office Weston, MA — 25,753 92,312 (123 ) 25,854 92,088 — — 117,942 23,125 2010 2001 (1) Two Freedom Square Office Reston, VA — 13,930 77,739 23,379 15,420 99,628 — — 115,048 47,936 2001 2003 (1) One and Two Reston Overlook Office Reston, VA — 16,456 66,192 25,111 16,179 91,580 — — 107,759 44,626 1999 2000 (1) Discovery Square Office Reston, VA — 11,198 71,782 24,414 12,533 94,861 — — 107,394 43,184 2001 2003 (1) 140 Kendrick Street Office Needham, MA — 18,095 66,905 17,492 19,092 83,400 — — 102,492 29,013 2000 2004 (1) 355 Main Street Office Cambridge, MA — 18,863 53,346 27,450 21,173 78,486 — — 99,659 26,915 1981/1996/2013 2006 (1) 10 CityPoint Office Waltham, MA — 1,953 85,752 2,833 2,116 88,422 — — 90,538 4,673 2016 1997 (1) 90 Broadway Office Cambridge, MA — 19,104 52,078 17,180 20,785 67,577 — — 88,362 19,254 1983/1998/2013 2006 (1) 230 CityPoint Office Waltham, MA — 13,189 49,823 25,236 13,593 74,655 — — 88,248 26,562 1992 2005 (1) Waltham Weston Corporate Center Office Waltham, MA — 10,385 60,694 11,030 11,097 71,012 — — 82,109 30,036 2003 1999 (1) 77 CityPoint Office Waltham, MA — 13,847 60,383 5,703 13,873 66,060 — — 79,933 23,044 2008 2001 (1) 3625-3635 Peterson Way Office Santa Clara, CA — 63,206 14,879 138 63,206 14,879 138 — 78,223 5,120 1979 2016 (1) North First Business Park Office San Jose, CA — 58,402 13,069 4,416 23,377 16,600 35,910 — 75,887 15,839 1981 2007 (1) 300 Binney Street Office Cambridge, MA — 18,080 51,262 140 18,080 51,402 — — 69,482 7,755 2013 2009 (1) 2440 West El Camino Real Office Mountain View, CA — 16,741 51,285 1,287 16,741 52,572 — — 69,313 10,790 1987/2003 2011 (1) Wisconsin Place Office Chevy Chase, MD — — 53,349 14,907 — 68,256 — — 68,256 19,775 2009 2004 (1) Reston Corporate Center Office Reston, VA — 9,135 50,857 6,236 10,148 56,080 — — 66,228 26,769 1984 1998 (1) New Dominion Technology Park, Bldg. Two Office Herndon, VA — 5,584 51,868 4,157 6,510 55,099 — — 61,609 23,652 2004 1998 (1) 200 West Street Office Waltham, MA — 16,148 24,983 10,673 16,813 34,991 — — 51,804 21,140 1999 1997 (1) New Dominion Technology Park, Bldg. One Office Herndon, VA 32,691 3,880 43,227 3,882 4,583 46,406 — — 50,989 25,940 2001 1998 (1) Sumner Square Office Washington, DC — 624 28,745 19,000 1,478 46,891 — — 48,369 23,570 1985 1999 (1) 255 Main Street Office Cambridge, MA — 134 25,110 21,583 548 46,279 — — 46,827 28,250 1987 1997 (1) University Place Office Cambridge, MA 7,407 — 37,091 9,007 390 45,708 — — 46,098 26,295 1985 1998 (1) 2600 Tower Oaks Boulevard Office Rockville, MD — 4,243 31,125 9,867 4,785 40,450 — — 45,235 21,020 2001 1998 (1) Quorum Office Park Office Chelmsford, MA — 3,750 32,454 5,813 5,187 36,830 — — 42,017 16,594 2001 2000 (1) 500 E Street Office Washington, DC — 109 22,420 14,743 2,379 34,893 — — 37,272 23,781 1987 1997 (1) 150 Broadway Office Cambridge, MA — 850 25,042 8,540 1,323 33,109 — — 34,432 16,933 1999 1997 (1) 325 Main Street Office Cambridge, MA — 174 12,200 11,963 965 23,372 — — 24,337 12,852 1987/2013 1997 (1) 105 Broadway Office Cambridge, MA — 1,299 12,943 8,214 2,395 20,061 — — 22,456 13,493 1990 1997 (1) Lexington Office Park Office Lexington, MA — 998 1,426 18,219 1,264 19,379 — — 20,643 13,404 1982 1997 (1) 201 Spring Street Office Lexington, MA — 2,849 15,303 694 3,124 15,722 — — 18,846 7,931 1997 1997 (1) The Point Office Waltham, MA — 6,395 10,040 409 6,480 10,364 — — 16,844 714 2015 2007 (1) 92-100 Hayden Avenue Office Lexington, MA — 594 6,748 8,181 802 14,721 — — 15,523 12,495 1985 1997 (1) 91 Hartwell Avenue Office Lexington, MA — 784 6,464 8,269 941 14,576 — — 15,517 9,849 1985 1997 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 690 Folsom Street Office San Francisco, CA — 3,219 11,038 1,157 3,219 12,195 — — 15,414 1,295 2015 2012 (1) 181 Spring Street Office Lexington, MA — 1,066 9,520 2,318 1,160 11,744 — — 12,904 5,194 1999 1997 (1) 195 West Street Office Waltham, MA — 1,611 6,652 4,340 1,858 10,745 — — 12,603 7,963 1990 1997 (1) 33 Hayden Avenue Office Lexington, MA — 266 3,234 8,381 425 11,456 — — 11,881 8,211 1979 1997 (1) 7501 Boston Boulevard, Building Seven Office Springfield, VA — 665 9,273 819 791 9,966 — — 10,757 4,848 1997 1997 (1) 7435 Boston Boulevard, Building One Office Springfield, VA — 392 3,822 3,997 659 7,552 — — 8,211 5,510 1982 1997 (1) 250 Binney Street Office Cambridge, MA — 110 4,483 3,593 273 7,913 — — 8,186 5,066 1983 1997 (1) 8000 Grainger Court, Building Five Office Springfield, VA — 366 4,282 3,375 601 7,422 — — 8,023 5,644 1984 1997 (1) 7450 Boston Boulevard, Building Three Office Springfield, VA — 1,165 4,681 1,773 1,430 6,189 — — 7,619 3,451 1987 1998 (1) 453 Ravendale Drive Office Mountain View, CA — 5,477 1,090 408 5,477 1,498 — — 6,975 472 1977 2012 (1) 17 Hartwell Avenue Office Lexington, MA — 26 150 6,252 65 6,363 — — 6,428 1,098 1968 1997 (1) 7601 Boston Boulevard, Building Eight Office Springfield, VA — 200 878 5,052 551 5,579 — — 6,130 4,263 1986 1997 (1) 7300 Boston Boulevard, Building Thirteen Office Springfield, VA — 608 4,773 709 661 5,429 — — 6,090 2,785 2002 1997 (1) 7500 Boston Boulevard, Building Six Office Springfield, VA — 138 3,749 1,655 406 5,136 — — 5,542 3,965 1985 1997 (1) 8000 Corporate Court, Building Eleven Office Springfield, VA — 136 3,071 1,596 774 4,029 — — 4,803 2,909 1989 1997 (1) 7374 Boston Boulevard, Building Four Office Springfield, VA — 241 1,605 1,913 398 3,361 — — 3,759 2,578 1984 1997 (1) 7375 Boston Boulevard, Building Ten Office Springfield, VA — 23 2,685 938 93 3,553 — — 3,646 2,570 1988 1997 (1) 7451 Boston Boulevard, Building Two Office Springfield, VA — 249 1,542 1,659 613 2,837 — — 3,450 2,429 1982 1997 (1) 32 Hartwell Avenue Office Lexington, MA — 168 1,943 1,012 314 2,809 — — 3,123 1,974 1968/1979/1987 1997 (1) 164 Lexington Road Office Billerica, MA — 592 1,370 319 643 1,638 — — 2,281 868 1982 1997 (1) The Avant at Reston Town Center Residential Reston, VA — 20,350 91,995 830 20,350 92,825 — — 113,175 9,780 2014 2010 (1) The Lofts at Atlantic Wharf Residential Boston, MA — 3,529 54,891 1,768 3,529 56,659 — — 60,188 9,622 2011 2007 (1) Boston Marriott Cambridge Hotel Cambridge, MA — 478 37,918 38,799 1,201 75,994 — — 77,195 47,753 1986 1997 (1) Kendall Center Green Garage Garage Cambridge, MA — — 35,035 7,448 103 42,380 — — 42,483 10,779 1984 2006 (1) Kendall Center Yellow Garage Garage Cambridge, MA — 1,256 15,697 1,621 1,434 17,140 — — 18,574 5,181 2006 2004 (1) Kendall Center Blue Garage Garage Cambridge, MA — 1,163 11,633 2,283 1,579 13,500 — — 15,079 9,209 1990 1997 (1) Salesforce Tower Development San Francisco, CA — — — 947,106 200,349 55,318 — 691,439 947,106 116 N/A 2013 N/A Signature at Reston Development Reston, VA — — — 203,650 — — — 203,650 203,650 — N/A 2013 N/A Proto Kendall Square Development Cambridge, MA — — — 82,905 — — — 82,905 82,905 — N/A 2015 N/A 145 Broadway Development Cambridge, MA — 121 — 79,979 324 — — 79,776 80,100 — NA 1997 N/A 191 Spring Street Development Lexington, MA — 2,850 27,166 35,174 3,151 46,288 — 15,751 65,190 19,034 1971/1995 1997 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 6595 Springfield Center Drive (TSA Headquarters) Development Springfield, VA — — — 41,918 — — — 41,918 41,918 — N/A 2007 N/A MacArthur Station Residences Development Oakland, CA — — — 37,644 — — — 37,644 37,644 — N/A N/A N/A 20 CityPoint Development Waltham, MA — — — 13,056 — — — 13,056 13,056 — N/A 2007 N/A Tower Oaks Master Plan Land Rockville, MD — — — 29,419 — — 29,419 — 29,419 — N/A 1998 N/A Plaza at Almaden Land San Jose, CA — — — 29,085 — — 29,085 — 29,085 — N/A 2006 N/A Springfield Metro Center Land Springfield, VA — — — 19,684 — — 19,684 — 19,684 — N/A 2007 N/A 214 Third Avenue Land Waltham, MA — — — 13,815 — — 13,815 — 13,815 — N/A 2006 N/A Reston Gateway Land Reston, VA — — — 13,730 — — 13,730 — 13,730 — N/A 1998 N/A 103 Fourth Avenue Land Waltham, MA — — — 12,115 — — 12,115 — 12,115 — N/A 2007 N/A Crane Meadow Land Marlborough, MA — — — 8,836 — — 8,836 — 8,836 — N/A 2000 N/A Washingtonian North Land Gaithersburg, MD — — — 7,645 — — 7,645 — 7,645 — N/A 1998 N/A 2100 Pennsylvania Avenue Land Washington, DC — — — 6,543 — — 6,543 — 6,543 — N/A N/A N/A Fourth and Harrison Land San Francisco, CA — — — 5,659 — — 5,659 — 5,659 — N/A N/A N/A North First Master Plan Land San Jose, CA — — — 3,018 — — 3,018 — 3,018 — N/A 2007 N/A Broad Run Business Park Land Loudoun County, VA — — — 2,367 — — 2,367 — 2,367 — N/A 1998 N/A Kendall Center Master Plan Land Cambridge, MA — — — 2,207 — — 2,207 — 2,207 — N/A N/A N/A Weston Quarry Land Weston, MA — — — 1,194 — — 1,194 — 1,194 — N/A 2001 N/A Reston Overlook Master Plan Land Reston, VA — — — 39 — — 39 — 39 — N/A 2000 N/A $ 2,979,281 (2 ) $ 4,762,002 $ 11,634,050 $ 4,662,662 $ 5,080,679 $ 14,503,772 $ 204,925 (3 ) $ 1,269,338 $ 21,058,714 $ 4,566,570 Note: Total Real Estate does not include Furniture, Fixtures and Equipment totaling approximately $37,928 . Accumulated Depreciation does not include approximately $23,064 of accumulated depreciation related to Furniture, Fixtures and Equipment. The aggregate cost and accumulated depreciation for tax purposes was approximately $17.3 billion and $3.6 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 unamortized deferred financing costs totaling approximately $(34.7) million . (3) Includes pre-development costs. Boston Properties, Inc. Real Estate and Accumulated Depreciation December 31, 2017 , 2016 and 2015 (dollars in thousands) A summary of activity for real estate and accumulated depreciation is as follows: 2017 2016 2015 Real Estate: Balance at the beginning of the year $ 20,114,576 $ 19,451,683 $ 19,208,417 Additions to/improvements of real estate 1,099,286 977,287 700,792 Assets sold/written-off (155,148 ) (314,394 ) $ (457,526 ) Balance at the end of the year $ 21,058,714 $ 20,114,576 $ 19,451,683 Accumulated Depreciation: Balance at the beginning of the year $ 4,201,891 $ 3,905,940 $ 3,529,978 Depreciation expense 497,059 560,024 486,450 Assets sold/written-off (132,380 ) (264,073 ) (110,488 ) Balance at the end of the year $ 4,566,570 $ 4,201,891 $ 3,905,940 Note: Real Estate and Accumulated Depreciation amounts do not include Furniture, Fixtures and Equipment.

Summary Of Significant Accoun31

Summary Of Significant Accounting Policies Summary Of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Real Estate	Real Estate Upon acquisitions of real estate, 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 tenants’ 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 an asset is not recoverable and exceeds its fair value. The evaluation of anticipated cash flows is highly subjective and is based in part on assumptions regarding anticipated hold period, future occupancy, rental rates and capital requirements that could differ materially from actual results in future periods. Because 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 an impairment has occurred, the affected assets must be reduced to their fair value, less cost to sell. Guidance in Accounting Standards Codification (“ASC”) 360 “Property Plant and Equipment” (“ASC 360”) 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. Discontinued operations presentation applies only to disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results (e.g., a disposal of a major geographical area, a major line of business, a major equity method investment or other major parts of an entity). The components of the property’s net income that are 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 Boston Properties, Inc.’s Board of Directors, or a committee thereof, and there are no known significant contingencies relating to the sale, such that a sale of the property 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 capitalizes acquisition costs that it incurs to effect an asset acquisition and expenses acquisition costs that it incurs to effect a business combination, including 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. Determination 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, involves a degree of judgment. The Company’s capitalization policy on development properties follows the 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 for 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, (2) occupied or held available for occupancy, and capitalizes only those costs associated with the portion under construction or (3) if activities necessary for the development of the property have been suspended. Interest costs capitalized for the years ended December 31, 2017 , 2016 and 2015 were $61.1 million , $39.2 million and $34.2 million , respectively. Salaries and related costs capitalized for the years ended December 31, 2017 , 2016 and 2015 were $13.2 million , $11.1 million and $10.4 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 “Business Combinations,” 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 .
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. Escrows also include cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties.
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 Boston Properties, Inc. 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, 2017 and 2016 , the Company had maintained approximately $29.2 million and $23.8 million , respectively, in a separate account, which is not restricted as to its use. The Company recognized gains (losses) of approximately $3.7 million , $2.3 million and $(0.7) million on its investments in the account associated with the Company’s deferred compensation plan during the years ended December 31, 2017 , 2016 and 2015 , 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 certain financing fees. Leasing costs include 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. Unamortized leasing costs are charged to expense upon the early termination of the lease. Fully amortized deferred leasing costs are removed from the books upon the expiration of the lease. Internal leasing salaries and related costs capitalized for the years ended December 31, 2017 , 2016 and 2015 were $5.0 million , $7.2 million and $5.5 million , respectively. Financing fees included in deferred charges consist of external fees and costs incurred to obtain the Company's revolving facility and if applicable, the delayed draw facility and construction financing arrangements where there are not sufficient amounts outstanding. Such financing costs have been deferred and are being amortized over the terms of the respective financing and included within interest expense. Unamortized financing costs are charged to expense upon the early repayment or significant modification of the financing. Fully amortized deferred financing costs are removed from the books upon the maturity of the debt. External fees and costs incurred to obtain mortgage financings and unsecured senior notes have been deferred and are presented as direct deductions from the carrying amounts of the corresponding debt liability. Such financing costs are being amortized over the terms of the respective financing and included within interest expense. Unamortized financing costs are charged to expense upon the early repayment or significant modification of the financing.
Investments in Unconsolidated Joint Ventures	Investments in Unconsolidated Joint Ventures The Company consolidates 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 substantive participating rights. 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 the right to receive the returns from the variable interest entity that could potentially be significant to the VIE. 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 noncontrolling 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. The ultimate realization of the investment in unconsolidated joint ventures is dependent on a number of factors, including the performance of each investment and market conditions. The Company will record an impairment charge if it determines that a decline in the value below the carrying value of an investment in an unconsolidated joint venture is other-than-temporary. 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. The combined summarized financial information of the unconsolidated joint ventures is disclosed in Note 5 .
Revenue Recognition	Revenue Recognition In general, the Company commences rental revenue recognition when the tenant takes possession of the leased space and the leased space is substantially ready for its intended use. 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 $54.8 million , $31.7 million and $80.0 million for the years ended December 31, 2017 , 2016 and 2015 , 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 acquired in-place “above-” and “below-market” leases at their fair values as rental revenue over the original term of the respective leases. The impact of the acquired in-place “above-” and “below-market” leases increased revenue by approximately $23.5 million , $30.2 million and $35.9 million for the years ended December 31, 2017 , 2016 and 2015 , 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 2018 $ 8,614 $ 32,152 2019 7,106 27,281 2020 5,394 10,736 2021 2,988 6,399 2022 315 5,669 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. 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 revenue is derived from room rentals and other sources such as charges to guests for telephone service, movie and vending commissions, meeting and banquet room revenue and laundry services. Hotel revenue is 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 records development fees as earned depending on the risk associated with each project. The Company recognizes development fees earned from joint venture projects equal to its cost plus profit 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 the 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 2114 . 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, 2017 , under non-cancelable ground leases which expire on various dates through 2114 , are as follows: Years Ending December 31, (in thousands) 2018 $ 11,349 2019 16,360 2020 25,552 2021 11,814 2022 8,894 Thereafter 576,315
Capital Leases	The following reflects the gross amount of assets recorded under capital leases by asset class at December 31, 2017 and December 31, 2016 (in thousands): December 31, 2017 2016 Buildings and improvements $ 23,636 $ 23,636 Construction in progress 28,962 — Total $ 52,598 $ 23,636 The future minimum lease payments, as of December 31, 2017, related to the three capital leases, through 2036 are as follows: Years Ending December 31, (in thousands) 2018 $ 913 2019 1,392 2020 2,097 2021 1,375 2022 930 Thereafter 74,185 Total expected minimum lease payments 80,892 Interest portion (29,296 ) Present value of expected net minimum lease payments $ 51,596
Earnings Per Share and Earnings Per Common Unit	Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income available to common shareholders, as adjusted for undistributed earnings (if any) of certain securities issued by Boston Properties Limited 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 Boston Properties Limited Partnership that are exchangeable for Common Stock. Earnings Per Common Unit Basic earnings per common unit is computed by dividing net income available to common unitholders, as adjusted for undistributed earnings (if any) of certain securities issued by Boston Properties Limited Partnership, by the weighted average number of common units outstanding during the year. Diluted earnings per common unit reflects the potential dilution that could occur from units issuable in connection with awards under Boston Properties, Inc.’s stock-based compensation plans, including upon the exercise of stock options, and conversion of preferred units of Boston Properties Limited Partnership.
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. Boston Properties Limited Partnership determines the fair value of its unsecured senior notes using market prices. The inputs used in determining the fair value of Boston Properties Limited Partnership’s unsecured senior notes is categorized at a Level 1 basis (as defined in ASC 820 "Fair Value Measurements and Disclosures", the accounting standards for Fair Value Measurements and Disclosures) due to the fact that it uses quoted market rates to value these instruments. However, the inputs used in determining the fair value could be categorized at a level 2 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) if trading volumes are low. The Company determines the fair value of its mortgage notes payable using discounted cash flow analysis by discounting the spread between the future contractual interest payments and hypothetical future interest payments on mortgage debt based on current market rates for similar securities. In determining the current market rates, the Company adds its estimates of market spreads to the quoted yields on federal government treasury securities with similar maturity dates to its debt. The inputs used in determining the fair value of the Company’s mortgage notes payable and mezzanine notes payable are categorized at a level 3 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) due to the fact that the Company considers the rates used in the valuation techniques to be unobservable inputs. To the extent that there are outstanding borrowings under the unsecured line of credit, the Company utilizes a discounted cash flow methodology in order to estimate the fair value. To the extent that credit spreads have changed since the origination, the net present value of the difference between future contractual interest payments and future interest payments based on the Company’s estimate of a current market rate would represent the difference between the book value and the fair value. The Company’s estimate of a current market rate is based upon the rate, considering current market conditions and the Company’s specific credit profile, at which it estimates it could obtain similar borrowings. To the extent there are outstanding borrowings, this current market rate is estimated and therefore would be primarily based upon a level 3 input. Because the Company’s valuations of its financial instruments are based on these types of estimates, the actual fair values of its financial instruments may differ materially if the Company’s estimates do not prove to be accurate, and the Company’s estimated fair values for these instruments as of the end of the applicable reporting period are not necessarily indicative of estimated or actual fair values in future reporting periods. The following table presents the aggregate carrying value of the Company’s mortgage notes payable, net, mezzanine notes payable, unsecured senior notes, net and unsecured line of credit and the Company’s corresponding estimate of fair value as of December 31, 2017 and December 31, 2016 (in thousands): December 31, 2017 December 31, 2016 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Mortgage notes payable, net $ 2,979,281 $ 3,042,920 $ 2,063,087 $ 2,092,237 Mezzanine notes payable — — 307,093 308,344 Unsecured senior notes, net 7,247,330 7,461,615 7,245,953 7,428,077 Unsecured line of credit 45,000 45,000 — — Total $ 10,271,611 $ 10,549,535 $ 9,616,133 $ 9,828,658 The Company uses interest rate swap agreements to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. To comply with the provisions of ASC 820, the Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. Although the Company determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. The Company assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and determined that the credit valuation adjustments were not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.
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.
Stock-Based Employee Compensation Plans	Stock-Based Employee Compensation Plans At December 31, 2017 , the Company has a stock-based employee compensation plan. The Company accounts for the plan under the guidance in 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	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 (“GAAP”) 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 May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). The objective of ASU 2014-09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most of the existing revenue recognition guidance, including industry-specific guidance. The core principle is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying ASU 2014-09, companies will perform a five-step analysis of transactions to determine when and how revenue is recognized. ASU 2014-09 applies to all contracts with customers except those that are within the scope of other topics in the FASB’s ASC. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date” (“ASU 2015-14”), which delayed the effective date of ASU 2014-09 by one year making it effective for the first interim period within annual reporting periods beginning after December 15, 2017. Early adoption is permitted as of the original effective date. In May 2016, the FASB issued ASU No. 2016-12, “Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients” (“ASU 2016-12”). ASU 2016-12 is intended to clarify and provide practical expedients for certain aspects of ASU 2014-09, which outlines a single comprehensive model for entities to use in accounting for revenues arising from contracts with customers and notes that lease contracts with customers are a scope exception. ASU 2014-09 is effective for the Company for reporting periods beginning after December 15, 2017. The Company adopted ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The Company expects that executory costs and certain non-lease components of revenue from leases may be impacted by the adoption of ASU 2014-09 (upon the adoption of ASU 2016-02). The adoption of ASU 2014-09 is expected to result in a change to the timing pattern of revenue recognized, but not the total revenue recognized over time for certain of the Company’s development services revenue. As a result, the modified retrospective approach is expected to result in the Company recognizing on January 1, 2018 the cumulative effect of adopting ASU 2014-09 reflecting the impact of applying the new guidance to certain of the Company’s outstanding development services contracts. ASU 2014-09 also updates the principal versus agent considerations and as a result the Company determined that amounts reimbursed for payroll and related costs received from third parties in connection with management services contracts should be reflected on a gross basis instead of on a net basis as the Company has determined that it is the principal under these arrangements. The adoption of ASU 2014-09 will not have a material impact on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. ASU 2016-02 supersedes previous leasing standards. ASU 2016-02 is effective for the Company for reporting periods beginning after December 15, 2018, with early adoption permitted. The Company will adopt ASU 2016-02 effective January 1, 2019 using the modified retrospective approach. The Company is in the pro cess of evaluating whether it will elect to apply the practical expedients. The Company is in the process of adopting ASU 2016-02, with its project team compiling an inventory of its leases that will be impacted by the adoption of ASU 2016-02. The Company continues to assess the impact of adopting ASU 2016-02. However, the Company will account for operating leases under which it is the lessor on its balance sheet in a manner similar to its current accounting with t he underlying leased asset recognized as real estate. In January 2018, the FASB issued a proposed ASU that would allow lessors to elect, as a practical expedient, not to allocate the total consideration to lease and non-lease components based on their relative standalone selling prices. If issued, this practical expedient will allow lessors to elect a combined single lease component presentation if (i) the timing and pattern of the revenue recognition of the combined single lease component is the same, and (ii) the related lease component and, the combined single lease component would be classified as an operating lease. If the practical expedient in the proposed ASU is issued, it could allow for tenant recoveries that qualify as non-lease components to be presented under a single lease component presentation. However, without the proposed practical expedient, tenant recoveries would be separated into lease and non-lease components. For leases in which the Company is the lessee, primarily consisting of ground leases, the Company will recognize a right-of-use asset and a lease liability equal to the present value of the minimum lease payments with rental payments being applied to the lease liability and to interest expense and the right-of-use asset being amortized to expense over the term of the lease. In addition, under ASU 2016-02, lessors will only capitalize incremental direct leasing costs. As a result, the Company will no longer be able to capitalize legal costs and internal leasing wages and instead will be required to expense these and other non-incremental costs as incurred. In March 2016, the FASB issued ASU 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”) . ASU 2016-09 is intended to improve the accounting for share-based payments and affects all organizations that issue share-based payment awards to their employees. Several aspects of the accounting for share-based payment awards are simplified with ASU 2016-09, including income tax consequences, classification of awards as equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for the Company for reporting periods beginning after December 15, 2016, with early adoption permitted. On January 1, 2017, the Company adopted ASU 2016-09 and elected to make an accounting policy change to its method of accounting for forfeitures on its awards of stock-based compensation including the issuance of shares of restricted common stock, LTIP Units and MYLTIP Units. The Company now accounts for forfeitures as they occur instead of estimating the number of forfeitures upon the issuance of such awards of stock-based compensation. The adoption resulted in the Company recognizing cumulative effect of a change in accounting principle adjustments to its consolidated balance sheets totaling approximately $0.3 million to Dividends in Excess of Earnings and Partners’ Capital for Boston Properties, Inc. and Boston Properties Limited Partnership, respectively, and approximately $1.8 million to noncontrolling interests - common units of Boston Properties Limited Partnership and noncontrolling interests - redeemable partnership units for Boston Properties, Inc. and Boston Properties Limited Partnership, respectively. In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2016-15”). ASU 2016-15 is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. The areas addressed in the new guidance related to debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned and bank-owned life insurance policies, distributions received from equity method investments, beneficial interest in securitization transactions, and separately identifiable cash flows and application of the predominance principle. ASU 2016-15 is effective for the Company for reporting periods beginning after December 15, 2017, with early adoption permitted (provided that all of the amendments are adopted in the same period), and will be applied retrospectively to all periods presented. The Company adopted ASU 2016-15 effective January 1, 2018. The adoption of ASU 2016-15 will result in the retrospective classification of debt prepayment costs as financing activities instead of operating activities in the Company's consolidated statements of cash flows. In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force)” (“ASU 2016-18”). ASU 2016-18 will require companies to include restricted cash and restricted cash equivalents with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 will require a disclosure of a reconciliation between the statement of financial position and the statement of cash flows when the statement of financial position includes more than one line item for cash, cash equivalents, restricted cash and restricted cash equivalents. Entities with material restricted cash and restricted cash equivalents balances will be required to disclose the nature of the restrictions. ASU 2016-18 is effective for reporting periods beginning after December 15, 2017, with early adoption permitted, and will be applied retrospectively to all periods presented. The Company adopted ASU 2016-18 effective January 1, 2018. The adoption of ASU 2016-18 will not have a material impact on the Company’s consolidated financial statements. In January 2017, the FASB issued ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business” (“ASU 2017-01”). ASU 2017-01 clarifies the framework for determining whether an integrated set of assets and activities meets the definition of a business. The revised framework establishes a screen for determining whether an integrated set of assets and activities is a business and narrows the definition of a business, which is expected to result in fewer transactions being accounted for as business combinations. Acquisitions of integrated sets of assets and activities that do not meet the definition of a business are accounted for as asset acquisitions. This update is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted for transactions that have not been reported in previously issued (or available to be issued) financial statements and shall be applied on a prospective basis. The Company early adopted ASU 2017-01 during the first quarter of 2017. The Company expects that acquisitions of real estate or in-substance real estate will not meet the revised definition of a business because substantially all of the fair value is concentrated in a single identifiable asset or group of similar identifiable assets (i.e. land, buildings, and related intangible assets) or because the acquisition does not include a substantive process in the form of an acquired workforce or an acquired contract that cannot be replaced without significant cost, effort or delay. In February 2017, the FASB issued ASU No. 2017-05, “Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets” (“ASU 2017-05”). ASU 2017-05 updates the definition of an “in substance nonfinancial asset” and clarifies the derecognition guidance for nonfinancial assets to conform with the new revenue recognition standard. The effective date and transition methods of ASU 2017-05 are aligned with ASU 2014-09 described above and are effective for the first interim period within annual reporting periods beginning after December 15, 2017. The Company adopted ASU 2017-05 effective January 1, 2018 using the modified retrospective approach. The adoption of ASU 2017-05 will not have a material impact on the Company's consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting” (“ASU 2017-09”). ASU 2017-09 is intended to provide clarity and reduce (1) diversity in practice, (2) cost and (3) complexity when applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award. ASU 2017-09 is effective for public entities for fiscal years and interim periods beginning after December 15, 2017. The Company adopted ASU 2017-09 effective January 1, 2018. The adoption of ASU 2017-09 will not have a material impact on the Company's consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities” (“ASU 2017-12”). ASU 2017-12 was issued with the objective of improving the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. ASU 2017-12 also makes certain targeted improvements to simplify the application of the hedge accounting guidance. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company early adopted ASU 2017-12 effective January 1, 2018. The adoption of ASU 2017-12 will not have a material impact on the Company's consolidated financial statements.
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 Boston Properties, Inc.’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, 2017 2016 2015 Per Share % Per Share % Per Share % Ordinary income $ 2.86 98.29 % $ 2.76 90.51 % $ 2.34 57.97 % Capital gain income 0.05 1.71 % 0.29 9.49 % 1.70 42.03 % Total $ 2.91 (1) 100.00 % $ 3.05 (2) 100.00 % $ 4.04 (3) 100.00 % _____________ (1) The fourth quarter 2017 regular quarterly dividend was $0.80 per common share of which approximately $0.47 per common share was allocable to 2017 and approximately $0.33 per common share is allocable to 2018. (2) The fourth quarter 2016 regular quarterly dividend was $0.75 per common share of which approximately $0.56 per common share was allocable to 2016 and approximately $0.19 per common share is allocable to 2017. (3) The fourth quarter 2015 dividend of $1.90 per common share consists of a $1.25 per common share special dividend and a $0.65 per common share regular quarterly dividend. Approximately $1.35 per common share was allocable to 2015 and approximately $0.55 per common share is allocable to 2016.
Income Taxes	Income Taxes Boston Properties, Inc. 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, it 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 (with certain adjustments). Boston Properties, Inc.’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 Boston Properties, Inc.’s consolidated taxable REIT subsidiaries. Boston Properties, Inc.’s taxable REIT subsidiaries did not have significant tax provisions or deferred income tax items. Boston Properties, Inc. has no uncertain tax positions recognized as of December 31, 2017 and 2016 . The Company owns a hotel property that is leased by a taxable REIT subsidiary and managed by Marriott International, Inc. The hotel taxable REIT subsidiary, a wholly owned subsidiary of Boston Properties Limited Partnership, is the lessee pursuant to the lease for the hotel property. As lessor, Boston Properties Limited 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, Boston Properties, Inc. has recorded a tax provision in its Consolidated Statements of Operations for the years ended December 31, 2017 , 2016 and 2015 . The net difference between the tax basis and the reported amounts of Boston Properties, Inc.’s assets and liabilities is approximately $1.8 billion and $1.7 billion as of December 31, 2017 and 2016 , respectively, which is primarily related to the difference in basis of contributed property and accrued rental income. Certain entities included in Boston Properties, Inc.’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 (unaudited): For the year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties, Inc. $ 462,439 $ 512,785 $ 583,106 Straight-line rent and net “above-” and “below-market” rent adjustments (77,801 ) (65,861 ) (92,483 ) Book/Tax differences from depreciation and amortization 142,234 235,819 307,115 Book/Tax differences from interest expense (18,136 ) (36,223 ) (43,349 ) Book/Tax differences on gains/(losses) from capital transactions 1,123 (70,880 ) (74,482 ) Book/Tax differences from stock-based compensation 37,990 33,463 22,008 Tangible Property Regulations (116,265 ) (104,783 ) (74,887 ) Other book/tax differences, net 33,411 (6,121 ) (15,259 ) Taxable income $ 464,995 $ 498,199 $ 611,769 Boston Properties Limited Partnership Income Taxes The partners are required to report their respective share of Boston Properties Limited Partnership’s taxable income or loss on their respective tax returns and are liable for any related taxes thereon. Accordingly, the only provision for federal income taxes in the accompanying consolidated financial statements relates to Boston Properties Limited Partnership’s consolidated taxable REIT subsidiaries. Boston Properties Limited Partnership’s taxable REIT subsidiaries did not have significant tax provisions or deferred income tax items. Boston Properties Limited Partnership has no uncertain tax positions recognized as of December 31, 2017 and 2016 . The Company owns a hotel property which is managed through a taxable REIT subsidiary. The hotel taxable REIT subsidiary, a wholly owned subsidiary Boston Properties Limited Partnership, is the lessee pursuant to the lease for the hotel property. As lessor, Boston Properties Limited 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, Boston Properties Limited Partnership has recorded a tax provision in its Consolidated Statements of Operations for the years ended December 31, 2017 , 2016 and 2015 . The net difference between the tax basis and the reported amounts of Boston Properties Limited Partnership’s assets and liabilities is approximately $2.9 billion and $2.7 billion as of December 31, 2017 and 2016 , respectively, which is primarily related to the difference in basis of contributed property and accrued rental income. Certain entities included in Boston Properties Limited Partnership’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 Limited Partnership to taxable income (unaudited): For the year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties Limited Partnership $ 523,366 $ 585,841 $ 659,248 Straight-line rent and net “above-” and “below-market” rent adjustments (86,773 ) (73,604 ) (103,227 ) Book/Tax differences from depreciation and amortization 144,436 245,239 329,629 Book/Tax differences from interest expense (20,227 ) (40,481 ) (48,385 ) Book/Tax differences on gains/(losses) from capital transactions 784 (69,683 ) (67,602 ) Book/Tax differences from stock-based compensation 42,371 37,397 24,565 Tangible Property Regulations (129,673 ) (117,102 ) (83,587 ) Other book/tax differences, net 37,607 (3,387 ) (14,561 ) Taxable income $ 511,891 $ 564,220 $ 696,080

Summary Of Significant Accoun32

Summary Of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
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
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 2018 $ 8,614 $ 32,152 2019 7,106 27,281 2020 5,394 10,736 2021 2,988 6,399 2022 315 5,669 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 2018 $ 33,651 2019 27,333 2020 14,464 2021 8,777 2022 4,758
Schedule Of Future Contractual Minimum Lease Payments Under Non-Cancelable Ground Leases [Table Text Block]	The future contractual minimum lease payments to be made by the Company as of December 31, 2017 , under non-cancelable ground leases which expire on various dates through 2114 , are as follows: Years Ending December 31, (in thousands) 2018 $ 11,349 2019 16,360 2020 25,552 2021 11,814 2022 8,894 Thereafter 576,315
Capital Leases in Financial Statements of Lessee Disclosure [Text Block]	The following reflects the gross amount of assets recorded under capital leases by asset class at December 31, 2017 and December 31, 2016 (in thousands): December 31, 2017 2016 Buildings and improvements $ 23,636 $ 23,636 Construction in progress 28,962 — Total $ 52,598 $ 23,636 The future minimum lease payments, as of December 31, 2017, related to the three capital leases, through 2036 are as follows: Years Ending December 31, (in thousands) 2018 $ 913 2019 1,392 2020 2,097 2021 1,375 2022 930 Thereafter 74,185 Total expected minimum lease payments 80,892 Interest portion (29,296 ) Present value of expected net minimum lease payments $ 51,596
Fair Value, by Balance Sheet Grouping [Table Text Block]	The following table presents the aggregate carrying value of the Company’s mortgage notes payable, net, mezzanine notes payable, unsecured senior notes, net and unsecured line of credit and the Company’s corresponding estimate of fair value as of December 31, 2017 and December 31, 2016 (in thousands): December 31, 2017 December 31, 2016 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Mortgage notes payable, net $ 2,979,281 $ 3,042,920 $ 2,063,087 $ 2,092,237 Mezzanine notes payable — — 307,093 308,344 Unsecured senior notes, net 7,247,330 7,461,615 7,245,953 7,428,077 Unsecured line of credit 45,000 45,000 — — Total $ 10,271,611 $ 10,549,535 $ 9,616,133 $ 9,828,658
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, 2017 2016 2015 Per Share % Per Share % Per Share % Ordinary income $ 2.86 98.29 % $ 2.76 90.51 % $ 2.34 57.97 % Capital gain income 0.05 1.71 % 0.29 9.49 % 1.70 42.03 % Total $ 2.91 (1) 100.00 % $ 3.05 (2) 100.00 % $ 4.04 (3) 100.00 % _____________ (1) The fourth quarter 2017 regular quarterly dividend was $0.80 per common share of which approximately $0.47 per common share was allocable to 2017 and approximately $0.33 per common share is allocable to 2018. (2) The fourth quarter 2016 regular quarterly dividend was $0.75 per common share of which approximately $0.56 per common share was allocable to 2016 and approximately $0.19 per common share is allocable to 2017. (3) The fourth quarter 2015 dividend of $1.90 per common share consists of a $1.25 per common share special dividend and a $0.65 per common share regular quarterly dividend. Approximately $1.35 per common share was allocable to 2015 and approximately $0.55 per common share is allocable to 2016.
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 (unaudited): For the year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties, Inc. $ 462,439 $ 512,785 $ 583,106 Straight-line rent and net “above-” and “below-market” rent adjustments (77,801 ) (65,861 ) (92,483 ) Book/Tax differences from depreciation and amortization 142,234 235,819 307,115 Book/Tax differences from interest expense (18,136 ) (36,223 ) (43,349 ) Book/Tax differences on gains/(losses) from capital transactions 1,123 (70,880 ) (74,482 ) Book/Tax differences from stock-based compensation 37,990 33,463 22,008 Tangible Property Regulations (116,265 ) (104,783 ) (74,887 ) Other book/tax differences, net 33,411 (6,121 ) (15,259 ) Taxable income $ 464,995 $ 498,199 $ 611,769
Boston Properties Limited Partnership
Summary Of Significant Accounting Policies [Line Items]
Gaap Reconciliation Of Net Income To Taxable Income, Table [Table Text Block]	The following table reconciles GAAP net income attributable to Boston Properties Limited Partnership to taxable income (unaudited): For the year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties Limited Partnership $ 523,366 $ 585,841 $ 659,248 Straight-line rent and net “above-” and “below-market” rent adjustments (86,773 ) (73,604 ) (103,227 ) Book/Tax differences from depreciation and amortization 144,436 245,239 329,629 Book/Tax differences from interest expense (20,227 ) (40,481 ) (48,385 ) Book/Tax differences on gains/(losses) from capital transactions 784 (69,683 ) (67,602 ) Book/Tax differences from stock-based compensation 42,371 37,397 24,565 Tangible Property Regulations (129,673 ) (117,102 ) (83,587 ) Other book/tax differences, net 37,607 (3,387 ) (14,561 ) Taxable income $ 511,891 $ 564,220 $ 696,080

Real Estate (Tables)

Real Estate (Tables)	12 Months Ended
	Dec. 31, 2017
Real Estate Properties [Line Items]
Schedule of Property Subject to or Available for Operating Lease	Boston Properties, Inc. Real estate consisted of the following at December 31, 2017 and December 31, 2016 (in thousands): 2017 2016 Land $ 5,080,679 $ 4,879,020 Land held for future development (1) 204,925 246,656 Buildings and improvements 12,284,164 11,890,626 Tenant improvements 2,219,608 2,060,315 Furniture, fixtures and equipment 37,928 32,687 Construction in progress 1,269,338 1,037,959 Total 21,096,642 20,147,263 Less: Accumulated depreciation (4,589,634 ) (4,222,235 ) $ 16,507,008 $ 15,925,028 _______________ (1) Includes pre-development costs. Boston Properties Limited Partnership Real estate consisted of the following at December 31, 2017 and December 31, 2016 (in thousands): 2017 2016 Land $ 4,976,303 $ 4,774,460 Land held for future development (1) 204,925 246,656 Buildings and improvements 11,977,062 11,581,795 Tenant improvements 2,219,608 2,060,315 Furniture, fixtures and equipment 37,928 32,687 Construction in progress 1,269,338 1,037,959 Total 20,685,164 19,733,872 Less: Accumulated depreciation (4,496,959 ) (4,136,364 ) $ 16,188,205 $ 15,597,508 _______________ (1) Includes pre-development costs.
103 Carnegie Center [Member]
Real Estate Properties [Line Items]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	Land $ 2,890 Building and improvements 11,229 Tenant improvements 871 In-place lease intangibles 2,389 Below-market lease intangible (1,426 ) Net assets acquired $ 15,953
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]	Acquired In-Place Lease Intangibles Acquired Below- Market Lease Intangibles Period from May 15, 2017 through December 31, 2017 $ 660 $ (248 ) 2018 590 (363 ) 2019 367 (337 ) 2020 243 (308 ) 2021 96 (105 )
MacArthur Station Residences
Real Estate Properties [Line Items]
Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block]	Period from June 29, 2017 through December 31, 2017 $ 5 2018 10 2019 10 2020 10 2021 13 Thereafter 38,778 Total expected minimum lease payments 38,826 Interest portion (9,864 ) Present value of expected net minimum lease payments $ 28,962

Deferred Charges (Tables)

Deferred Charges (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Charges [Abstract]
Deferred Charges	Deferred charges consisted of the following at December 31, 2017 and December 31, 2016 (in thousands): 2017 2016 Leasing costs, including lease related intangibles $ 1,147,181 $ 1,132,092 Financing costs 14,991 6,094 1,162,172 1,138,186 Less: Accumulated amortization (483,134 ) (452,023 ) $ 679,038 $ 686,163
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 2018 $ 8,614 $ 32,152 2019 7,106 27,281 2020 5,394 10,736 2021 2,988 6,399 2022 315 5,669 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 2018 $ 33,651 2019 27,333 2020 14,464 2021 8,777 2022 4,758

Investments in Unconsolidated35

Investments in Unconsolidated Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2017
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	The investments in unconsolidated joint ventures consist of the following at December 31, 2017 and 2016 : Carrying Value of Investment (1) Entity Properties Nominal % Ownership December 31, December 31, (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (8,258 ) $ (8,134 ) The Metropolitan Square Associates LLC Metropolitan Square 20.0 % 3,339 2,004 BP/CRF 901 New York Avenue LLC 901 New York Avenue 25.0 % (2) (13,811 ) (10,564 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 39,710 41,605 Annapolis Junction NFM, LLC Annapolis Junction 50.0 % (4) 18,381 20,539 540 Madison Venture LLC 540 Madison Avenue 60.0 % 66,179 67,816 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (3,876 ) (3,389 ) 501 K Street LLC 1001 6th Street 50.0 % (5) 42,657 42,528 Podium Developer LLC The Hub on Causeway 50.0 % 67,120 29,869 Residential Tower Developer LLC The Hub on Causeway - Residential 50.0 % (6) 28,212 20,803 Hotel Tower Developer LLC The Hub on Causeway - Hotel 50.0 % 1,690 933 1265 Main Office JV LLC 1265 Main Street 50.0 % 4,641 4,779 BNY Tower Holdings LLC Dock 72 at the Brooklyn Navy Yard 50.0 % 72,104 33,699 CA-Colorado Center Limited Partnership Colorado Center 50.0 % 254,440 510,623 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % (6) 21,452 N/A $ 593,980 $ 753,111 _______________ (1) Investments with deficit balances aggregating approximately $25.9 million and $22.1 million at December 31, 2017 and 2016 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets. (2) The Company’s economic ownership has increased based on the achievement of certain return thresholds. (3) The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project. (4) The joint venture owns four in-service buildings and two undeveloped land parcels. (5) Under the joint venture agreement for this land parcel, the partner will be entitled to up to two additional payments from the venture based on increases in total entitled square footage of the project above 520,000 square feet and achieving certain project returns at stabilization. (6) This entity is a VIE (See Note 2 ).
Schedule Of Balance Sheets Of The Unconsolidated Joint Ventures [Text Block]	The combined summarized balance sheets of the Company’s unconsolidated joint ventures are as follows: December 31, December 31, (in thousands) ASSETS Real estate and development in process, net $ 1,768,996 $ 1,519,217 Other assets 367,743 297,263 Total assets $ 2,136,739 $ 1,816,480 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 1,437,440 $ 865,665 Other liabilities 99,215 67,167 Members’/Partners’ equity 600,084 883,648 Total liabilities and members’/partners’ equity $ 2,136,739 $ 1,816,480 Company’s share of equity $ 286,495 $ 450,662 Basis differentials (1) 307,485 302,449 Carrying value of the Company’s investments in unconsolidated joint ventures (2) $ 593,980 $ 753,111 _______________ (1) This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At December 31, 2017 and 2016 , there was an aggregate basis differential of approximately $322.5 million and $328.8 million , respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities. (2) Investments with deficit balances aggregating approximately $25.9 million and $22.1 million at December 31, 2017 and 2016 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
Statements Of Operations Of The Joint Ventures	The combined summarized statements of operations of the Company’s unconsolidated joint ventures are as follows: For the year ended December 31, 2017 2016 2015 (in thousands) Total revenue (1) $ 222,517 $ 177,182 $ 155,642 Expenses Operating 90,542 76,741 65,093 Depreciation and amortization 57,079 44,989 36,057 Total expenses 147,621 121,730 101,150 Operating income 74,896 55,452 54,492 Other expense Interest expense (46,371 ) (34,016 ) (32,176 ) Net income $ 28,525 $ 21,436 $ 22,316 Company’s share of net income (2) $ 18,439 $ 9,873 $ 22,031 Basis differential (3) (7,207 ) (1,799 ) 739 Income from unconsolidated joint ventures $ 11,232 $ 8,074 $ 22,770 Gain on sale of investment in unconsolidated joint venture $ — $ 59,370 $ — _______________ (1) Includes straight-line rent adjustments of approximately $21.7 million , $18.1 million and $3.9 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. (2) During the year ended December 31, 2015, the Company received a distribution of approximately $24.5 million , which was generated from the excess loan proceeds from the refinancing of 901 New York Avenue’s mortgage loan to a new 10 -year mortgage loan totaling $225.0 million . The Company’s allocation of income and distributions for the year ended December 31, 2015 was not proportionate to its nominal ownership interest as a result of the achievement of specified investment return thresholds, as provided for in the joint venture agreement. (3) Includes straight-line rent adjustments of approximately $1.9 million and $1.4 million for the years ended December 31, 2017 and 2016, respectively. Also includes net above-/below-market rent adjustments of approximately $2.9 million and $0.9 million for the years ended December 31, 2017 and 2016, respectively.

Mortgage Notes Payable, Net, 36

Mortgage Notes Payable, Net, Mezzanine Notes Payable and Outside Members’ Notes Payable Schedule of Aggregate Principal Payments On Mortgage Notes (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 are as follows: Principal Payments (in thousands) 2018 $ 18,633 2019 19,670 2020 20,766 2021 40,182 2022 614,710 Thereafter 2,300,000 Total aggregate principal payments 3,013,961 Deferred financing costs, net (34,680 ) Total carrying value of mortgage notes payable, net $ 2,979,281

Derivative and Hedging Instru37

Derivative and Hedging Instruments Derivatives and Hedging Activities Notional Table (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]	767 Fifth Partners LLC’s interest rate swap contracts consisted of the following at December 31, 2016 (dollars in thousands): Derivative Instrument Aggregate Notional Amount Effective Date Maturity Date Strike Rate Range Balance Sheet Location Fair Value Low High Interest Rate Swaps $ 350,000 June 7, 2017 June 7, 2027 2.418 % - 2.950 % Other Liabilities $ (8,773 ) Interest Rate Swaps 100,000 June 7, 2017 June 7, 2027 2.336 % - 2.388 % Prepaid Expenses and Other Assets 509 $ 450,000 $ (8,264 )
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table presents the location in the financial statements of the losses recognized related to the Company’s cash flow hedges for the years ended December 31, 2017 , 2016 and 2015 : Year ended December 31, 2017 2016 2015 (in thousands) Amount of loss related to the effective portion recognized in other comprehensive loss $ (6,133 ) $ (47,144 ) $ (10,302 ) Amount of loss related to the effective portion subsequently reclassified to earnings (1) $ (6,033 ) $ (3,751 ) $ (2,510 ) Amount of loss related to the ineffective portion and amount excluded from effectiveness testing $ — $ (140 ) $ — ___________ (1) During the year ended December 31, 2016, the Company accelerated the reclassification of amounts in other comprehensive loss to earnings as a result of the hedged forecasted transactions becoming probable not to occur. The accelerated amounts were a loss of approximately $0.2 million and are included in the table above.
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Boston Properties, Inc. The following table reflects the changes in accumulated other comprehensive loss for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ (9,304 ) Effective portion of interest rate contracts (10,302 ) Amortization of interest rate contracts 2,510 Other comprehensive loss attributable to noncontrolling interests 2,982 Balance at December 31, 2015 (14,114 ) Effective portion of interest rate contracts (47,144 ) Amortization of interest rate contracts 3,751 Other comprehensive loss attributable to noncontrolling interests 5,256 Balance at December 31, 2016 (52,251 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 6,033 Other comprehensive loss attributable to noncontrolling interests 1,922 Balance at December 31, 2017 $ (50,429 )
Boston Properties Limited Partnership
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Boston Properties Limited Partnership The following table reflects the changes in accumulated other comprehensive loss for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ (12,973 ) Effective portion of interest rate contracts (10,302 ) Amortization of interest rate contracts 2,510 Other comprehensive loss attributable to noncontrolling interests in property partnership 2,428 Balance at December 31, 2015 (18,337 ) Effective portion of interest rate contracts (47,144 ) Amortization of interest rate contracts 3,751 Other comprehensive loss attributable to noncontrolling interests in property partnership 877 Balance at December 31, 2016 (60,853 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 6,033 Other comprehensive loss attributable to noncontrolling interests in property partnership 2,128 Balance at December 31, 2017 $ (58,825 )

Unsecured Senior Notes (Tables)

Unsecured Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Senior Notes	The following summarizes the unsecured senior notes outstanding as of December 31, 2017 (dollars in thousands): Coupon/ Stated Rate Effective Rate(1) Principal Amount Maturity Date(2) 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 11 Year Unsecured Senior Notes 3.850 % 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 3.800 % 3.916 % 700,000 February 1, 2024 7 Year Unsecured Senior Notes 3.200 % 3.350 % 850,000 January 15, 2025 10 Year Unsecured Senior Notes 3.650 % 3.766 % 1,000,000 February 1, 2026 10 Year Unsecured Senior Notes 2.750 % 3.495 % 1,000,000 October 1, 2026 Total principal 7,300,000 Net unamortized discount (17,894 ) Deferred financing costs, net (34,776 ) Total $ 7,247,330 _______________ (1) Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs. (2) No principal amounts are due prior to maturity.

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	12 Months Ended
	Dec. 31, 2017
Entity Information [Line Items]
Dividends Declared [Table Text Block]	The following table presents Boston Properties, Inc.’s dividends per share and Boston Properties Limited Partnership’s distributions per OP Unit and LTIP Unit paid or payable in 2017 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) December 29, 2017 January 30, 2018 $0.80 $0.80 September 29, 2017 October 31, 2017 0.75 0.75 June 30, 2017 July 31, 2017 0.75 0.75 March 31, 2017 April 28, 2017 0.75 0.75 December 31, 2016 January 30, 2017 0.75 0.75
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 entity for the year ended December 31, 2015 (in thousands): Balance at December 31, 2014 $ 104,692 Net loss (7 ) Distributions (2,900 ) Adjustment to reflect redeemable interest at redemption value 5,128 Acquisition of interest (106,913 ) Balance at December 31, 2015 $ —
Schedule Of Noncontrolling Interest Property Partnerships [Table Text Block]	The following table reflects the activity of the noncontrolling interests—property partnerships for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ 1,602,467 Capital contributions 3,758 Dissolution (4,082 ) Net income 144,734 Accumulated other comprehensive loss (2,428 ) Distributions (170,049 ) Balance at December 31, 2015 1,574,400 Capital contributions 10,756 Net loss (2,068 ) Accumulated other comprehensive loss (877 ) Distributions (51,564 ) Balance at December 31, 2016 1,530,647 Capital contributions (1) 161,585 Net loss 47,832 Accumulated other comprehensive loss (2,128 ) Distributions (54,176 ) Balance at December 31, 2017 $ 1,683,760
Boston Properties, Inc. [Member]
Entity Information [Line Items]
Schedule Of Redeemable Preferred Units of the Operating Partnership	The following table reflects the activity of the noncontrolling interests—redeemable preferred units for the year ended December 31, 2015 (in thousands): Balance at December 31, 2014 $ 633 Net income 6 Distributions (6 ) Redemption of redeemable preferred units (Series Four Preferred Units) (633 ) Balance at December 31, 2015 $ —
Boston Properties Limited Partnership
Entity Information [Line Items]
Schedule Of Redeemable Preferred Units of the Operating Partnership	Balance at December 31, 2014 $ 633 Net income 6 Distributions (6 ) Redemption of redeemable preferred units (Series Four Preferred Units) (633 ) Balance at December 31, 2015 $ —
Schedule Of Noncontrolling Interest Common Units [Table Text Block]	The following table reflects the activity of noncontrolling interests—redeemable common units of Boston Properties Limited Partnership for the years ended December 31, 2017 , 2016 and 2015 (in thousands): Balance at December 31, 2014 $ 2,310,046 Contributions 39,030 Net income 66,951 Distributions (69,447 ) Conversion of redeemable partnership units (14,343 ) Unearned compensation (4,579 ) Other comprehensive loss (554 ) Adjustment to reflect redeemable partnership units at redemption value (40,415 ) Balance at December 31, 2015 2,286,689 Contributions 31,395 Net income 59,260 Distributions (49,087 ) Conversion of redeemable partnership units (6,461 ) Unearned compensation (3,464 ) Other comprehensive loss (4,379 ) Adjustment to reflect redeemable partnership units at redemption value (51,913 ) Balance at December 31, 2016 2,262,040 Contributions 31,743 Net income 52,210 Distributions (54,494 ) Conversion of redeemable partnership units (16,916 ) Unearned compensation 1,650 Cumulative effect of a change in accounting principle (1,763 ) Other comprehensive income 206 Adjustment to reflect redeemable partnership units at redemption value 17,587 Balance at December 31, 2017 $ 2,292,263
Noncontrolling Interests [Member]
Entity Information [Line Items]
Dividends Declared [Table Text Block]	: Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit December 29, 2017 January 30, 2018 $0.80 $0.080 September 29, 2017 October 31, 2017 $0.75 $0.075 June 30, 2017 July 31, 2017 $0.75 $0.075 March 31, 2017 April 28, 2017 $0.75 $0.075 December 31, 2016 January 30, 2017 $0.75 $0.075

Stockholders' Equity _ Partne40

Stockholders' Equity / Partners' Capital Stockholders Equity / Partners Capital (Tables)	12 Months Ended
	Dec. 31, 2017
Class of Stock [Line Items]
Dividends Declared [Table Text Block]	The following table presents Boston Properties, Inc.’s dividends per share and Boston Properties Limited Partnership’s distributions per OP Unit and LTIP Unit paid or payable in 2017 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) December 29, 2017 January 30, 2018 $0.80 $0.80 September 29, 2017 October 31, 2017 0.75 0.75 June 30, 2017 July 31, 2017 0.75 0.75 March 31, 2017 April 28, 2017 0.75 0.75 December 31, 2016 January 30, 2017 0.75 0.75
Schedule Of Changes In Partners Capital Unit [Table Text Block]	The following table presents the changes in the issued and outstanding partners’ capital units since January 1, 2015 : General Partner Units Limited Partner Units Total Partners’ Outstanding at December 31, 2014 1,710,644 151,403,301 153,113,945 Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan 59 6,140 6,199 Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net 340 35,246 35,586 Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units 4,049 420,187 424,236 Outstanding at December 31, 2015 1,715,092 151,864,874 153,579,966 Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan 72 5,623 5,695 Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net 172 13,485 13,657 Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units 2,407 188,450 190,857 Outstanding at December 31, 2016 1,717,743 152,072,432 153,790,175 Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan 21 6,296 6,317 Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net 111 33,046 33,157 Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units 1,665 493,972 495,637 Outstanding at December 31, 2017 1,719,540 152,605,746 154,325,286
Schedule of changes in Series B Preferred Units [Table Text Block]	The following table reflects the activity of the Series B Preferred Units for the years ended December 31, 2017 , 2016 and 2015 (in thousands), which activity is included within Boston Properties Limited Partnership’s Consolidated Statements of Partners’ Capital: Balance at December 31, 2014 $ 193,623 Net income 10,500 Distributions (10,500 ) Balance at December 31, 2015 193,623 Net income 10,500 Distributions (10,500 ) Balance at December 31, 2016 193,623 Net income 10,500 Distributions (10,500 ) Balance at December 31, 2017 $ 193,623
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Dividends Declared [Table Text Block]	The following table presents Boston Properties Inc.’s dividends per share on its outstanding Series B Preferred Stock paid or payable in 2017 : Record Date Payment Date Dividend (Per Share) February 2, 2018 February 15, 2018 $32.8125 November 3, 2017 November 15, 2017 32.8125 August 4, 2017 August 15, 2017 32.8125 May 5, 2017 May 15, 2017 32.8125 February 3, 2017 February 15, 2017 32.8125

Future Minimum Rents (Tables)

Future Minimum Rents (Tables)	12 Months Ended
	Dec. 31, 2017
Future Minimum Rents [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	The future contractual minimum lease payments to be received (excluding operating expense reimbursements) by the Company as of December 31, 2017 , under non-cancelable operating leases which expire on various dates through 2046 , are as follows: Years Ending December 31, (in thousands) 2018 $ 1,962,841 2019 1,998,102 2020 1,920,002 2021 1,783,066 2022 1,596,719 Thereafter 11,160,780

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule Of Reconciliation Of Net Operating Income To Net Income	Boston Properties, Inc. Year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 451,939 $ 502,285 $ 572,606 Add: Preferred dividends 10,500 10,500 10,500 Noncontrolling interest—common units of the Operating Partnership 52,210 59,260 66,951 Noncontrolling interest—redeemable preferred units of the Operating Partnership — — 6 Noncontrolling interest in property partnerships 47,832 (2,068 ) 149,855 Losses from interest rate contracts — 140 — Interest expense 374,481 412,849 432,196 Depreciation and amortization expense 617,547 694,403 639,542 Impairment loss — 1,783 — Transaction costs 668 2,387 1,259 General and administrative expense 113,715 105,229 96,319 Less: Gains on sales of real estate 7,663 80,606 375,895 Gains (losses) from early extinguishments of debt 496 (371 ) (22,040 ) Gains (losses) from investments in securities 3,678 2,273 (653 ) Interest and other income 5,783 7,230 6,777 Gain on sale of investment in unconsolidated joint venture — 59,370 — Income from unconsolidated joint ventures 11,232 8,074 22,770 Development and management services income 34,605 28,284 22,554 Net Operating Income $ 1,605,435 $ 1,601,302 $ 1,563,931 Boston Properties Limited Partnership Year ended December 31, 2017 2016 2015 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 512,866 $ 575,341 $ 648,748 Add: Preferred distributions 10,500 10,500 10,500 Noncontrolling interest—redeemable preferred units — — 6 Noncontrolling interest in property partnerships 47,832 (2,068 ) 149,855 Losses from interest rate contracts — 140 — Interest expense 374,481 412,849 432,196 Depreciation and amortization expense 609,407 682,776 631,549 Impairment loss — 1,783 — Transaction costs 668 2,387 1,259 General and administrative expense 113,715 105,229 96,319 Less: Gains on sales of real estate 8,240 82,775 377,093 Gains (losses) from early extinguishments of debt 496 (371 ) (22,040 ) Gains (losses) from investments in securities 3,678 2,273 (653 ) Interest and other income 5,783 7,230 6,777 Gain on sale of investment in unconsolidated joint venture — 59,370 — Income from unconsolidated joint ventures 11,232 8,074 22,770 Development and management services income 34,605 28,284 22,554 Net Operating Income $ 1,605,435 $ 1,601,302 $ 1,563,931
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, 2017 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 776,279 $ 969,371 $ 345,519 $ 414,103 $ 2,505,272 Residential 4,745 — — 11,851 16,596 Hotel 45,603 — — — 45,603 Total 826,627 969,371 345,519 425,954 2,567,471 % of Grand Totals 32.20 % 37.75 % 13.46 % 16.59 % 100.00 % Rental Expenses: Office 301,097 372,810 105,253 144,515 923,675 Residential 2,044 — — 4,258 6,302 Hotel 32,059 — — — 32,059 Total 335,200 372,810 105,253 148,773 962,036 % of Grand Totals 34.84 % 38.76 % 10.94 % 15.46 % 100.00 % Net operating income $ 491,427 $ 596,561 $ 240,266 $ 277,181 $ 1,605,435 % of Grand Totals 30.61 % 37.15 % 14.97 % 17.27 % 100.00 % For the year ended December 31, 2016 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 727,265 $ 1,012,518 $ 318,609 $ 402,561 $ 2,460,953 Residential 4,812 — — 11,887 16,699 Hotel 44,884 — — — 44,884 Total 776,961 1,012,518 318,609 414,448 2,522,536 % of Grand Totals 30.80 % 40.14 % 12.63 % 16.43 % 100.00 % Rental Expenses: Office 282,827 363,188 100,787 135,890 882,692 Residential 2,708 — — 4,368 7,076 Hotel 31,466 — — — 31,466 Total 317,001 363,188 100,787 140,258 921,234 % of Grand Totals 34.41 % 39.42 % 10.94 % 15.23 % 100.00 % Net operating income $ 459,960 $ 649,330 $ 217,822 $ 274,190 $ 1,601,302 % of Grand Totals 28.73 % 40.55 % 13.60 % 17.12 % 100.00 % For the year ended December 31, 2015 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 716,246 $ 1,000,030 $ 302,434 $ 384,628 $ 2,403,338 Residential 4,801 — — 14,082 18,883 Hotel 46,046 — — — 46,046 Total 767,093 1,000,030 302,434 398,710 2,468,267 % of Grand Totals 31.08 % 40.52 % 12.25 % 16.15 % 100.00 % Rental Expenses: Office 287,341 346,897 98,206 131,581 864,025 Residential 2,006 — — 6,221 8,227 Hotel 32,084 — — — 32,084 Total 321,431 346,897 98,206 137,802 904,336 % of Grand Totals 35.54 % 38.36 % 10.86 % 15.24 % 100.00 % Net operating income $ 445,662 $ 653,133 $ 204,228 $ 260,908 $ 1,563,931 % of Grand Totals 28.50 % 41.76 % 13.06 % 16.68 % 100.00 %

Earnings Per Share _ Common U43

Earnings Per Share / Common Unit (Tables)	12 Months Ended
	Dec. 31, 2017
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share / Unit	For the Year Ended December 31, 2017 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 451,939 154,190 $ 2.93 Effect of Dilutive Securities: Stock Based Compensation — 200 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 451,939 154,390 $ 2.93 For the Year Ended December 31, 2016 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 502,285 153,715 $ 3.27 Allocation of undistributed earnings to participating securities (283 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 502,002 153,715 $ 3.27 Effect of Dilutive Securities: Stock Based Compensation — 262 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 502,002 153,977 $ 3.26 For the Year Ended December 31, 2015 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 572,606 153,471 $ 3.73 Effect of Dilutive Securities: Stock Based Compensation — 373 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 572,606 153,844 $ 3.72
Boston Properties Limited Partnership
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share / Unit	Included in the number of units (the denominator) below are approximately 17,471,000 , 17,646,000 and 17,668,000 redeemable common units for the years ended December 31, 2017 , 2016 and 2015 , respectively. For the Year Ended December 31, 2017 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 512,866 171,661 $ 2.99 Effect of Dilutive Securities: Stock Based Compensation — 200 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 512,866 171,861 $ 2.98 For the Year Ended December 31, 2016 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 575,341 171,361 $ 3.36 Allocation of undistributed earnings to participating securities (316 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 575,025 171,361 $ 3.36 Effect of Dilutive Securities: Stock Based Compensation — 262 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 575,025 171,623 $ 3.35 For the Year Ended December 31, 2015 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 648,748 171,139 $ 3.79 Effect of Dilutive Securities: Stock Based Compensation — 373 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 648,748 171,512 $ 3.78

Stock Option and Incentive Pl44

Stock Option and Incentive Plan Stock Option and Incentive Plan and Stock Purchase Plan (Tables)	12 Months Ended
	Dec. 31, 2017
Stock Option and Incentive Plan and Stock Purchase Plan [Abstract]
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	A summary of the status of Boston Properties, Inc.’s stock options as of December 31, 2017 , 2016 and 2015 and changes during the years then ended are presented below: Shares Weighted-Average Exercise Price Outstanding at December 31, 2014 553,312 $ 97.21 Exercised (11,447 ) $ 92.50 Special dividend adjustment 5,264 $ 96.38 Outstanding at December 31, 2015 547,129 $ 96.38 Exercised — $ — Outstanding at December 31, 2016 547,129 $ 96.38 Exercised (6,688 ) $ 99.15 Outstanding at December 31, 2017 540,441 $ 96.35
Schedule of Stock Options Outstanding [Table Text Block]	The following table summarizes information about Boston Properties, Inc.’s stock options outstanding at December 31, 2017 : Options Outstanding Options Exercisable Number Outstanding at 12/31/17 Weighted-Average Remaining Contractual Life Exercise Price Number Exercisable at 12/31/17 Exercise Price 118,502 3.1 years $ 86.86 118,502 $ 86.86 54,282 5.3 years $ 95.69 54,282 $ 95.69 202,030 5.1 years $ 98.46 202,030 $ 98.46 165,627 4.1 years $ 100.77 165,627 $ 100.77

Selected Interim Financial In45

Selected Interim Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Table Text Block]	Boston Properties, Inc. The tables below reflect Boston Properties, Inc.’s selected quarterly information for the years ended December 31, 2017 and 2016 . 2017 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per share amounts) Total revenue $ 632,228 $ 656,907 $ 657,712 $ 655,229 Income before gains on sales of real estate $ 115,431 $ 163,243 $ 144,813 $ 131,331 Net income attributable to Boston Properties, Inc. common shareholders $ 97,083 $ 133,709 $ 117,337 $ 103,829 Income attributable to Boston Properties, Inc. per share—basic $ 0.63 $ 0.87 $ 0.76 $ 0.67 Income attributable to Boston Properties, Inc. per share—diluted $ 0.63 $ 0.87 $ 0.76 $ 0.67 2016 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per share amounts) Total revenue $ 665,985 $ 623,546 $ 625,228 $ 636,061 Income before gains on sales of real estate $ 148,599 $ 117,357 $ 58,521 $ 164,894 Net income attributable to Boston Properties, Inc. common shareholders $ 181,747 $ 96,597 $ 76,753 $ 147,214 Income attributable to Boston Properties, Inc. per share—basic $ 1.18 $ 0.63 $ 0.50 $ 0.96 Income attributable to Boston Properties, Inc. per share—diluted $ 1.18 $ 0.63 $ 0.50 $ 0.96 Boston Properties Limited Partnership The tables below reflect Boston Properties Limited Partnership’s selected quarterly information for the years ended December 31, 2017 and 2016 . 2017 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per unit amounts) Total revenue $ 632,228 $ 656,907 $ 657,712 $ 655,229 Income before gains on sales of real estate $ 117,578 $ 165,328 $ 146,767 $ 133,285 Net income attributable to Boston Properties Limited Partnership common unitholders $ 110,662 $ 151,844 $ 132,693 $ 117,667 Income attributable to Boston Properties Limited Partnership per unit—basic $ 0.64 $ 0.88 $ 0.77 $ 0.69 Income attributable to Boston Properties Limited Partnership per unit—diluted $ 0.64 $ 0.88 $ 0.77 $ 0.68 2016 Quarter Ended March 31, June 30, September 30, December 31, (in thousands, except for per unit amounts) Total revenue $ 665,985 $ 623,546 $ 625,228 $ 636,061 Income before gains on sales of real estate $ 150,586 $ 119,341 $ 63,687 $ 167,384 Net income attributable to Boston Properties Limited Partnership common unitholders $ 207,296 $ 109,938 $ 91,306 $ 166,801 Income attributable to Boston Properties Limited Partnership per unit—basic $ 1.21 $ 0.64 $ 0.53 $ 0.97 Income attributable to Boston Properties Limited Partnership per unit—diluted $ 1.21 $ 0.64 $ 0.53 $ 0.97

Real Estate and Accumulated D46

Real Estate and Accumulated Depreciation Real Estate and Accumulated Depreciation (Tables)	12 Months Ended
	Dec. 31, 2017
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, By Property [Table Text Block]	Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 767 Fifth Avenue (the General Motors Building) Office New York, NY $ 2,267,041 $ 1,796,252 $ 1,532,654 $ 135,559 $ 1,796,252 $ 1,668,213 $ — $ — $ 3,464,465 $ 222,981 1968 2013 (1) Prudential Center Office Boston, MA — 92,077 948,357 501,709 115,638 1,426,505 — — 1,542,143 511,605 1965/1993/2002/2016-2017 1998/1999/2000 (1) Embarcadero Center Office San Francisco, CA — 179,697 847,410 366,780 195,987 1,197,900 — — 1,393,887 596,100 1970/1989 1998-1999 (1) 399 Park Avenue Office New York, NY — 339,200 700,358 181,418 354,107 866,869 — — 1,220,976 310,262 1961 2002 (1) 601 Lexington Avenue Office New York, NY 672,142 241,600 494,782 290,590 289,639 634,134 — 103,199 1,026,972 254,932 1977/1997 2001 (1) 200 Clarendon Street and Garage Office Boston, MA — 219,543 667,884 139,189 219,616 799,991 7,009 — 1,026,616 161,471 1976 2010 (1) 250 West 55th Street Office New York, NY — 285,263 603,167 43,296 285,263 646,463 — — 931,726 72,058 2014 2007 (1) Carnegie Center Office Princeton, NJ — 107,997 389,359 157,960 108,948 543,514 2,854 — 655,316 228,171 1983-2016 1998/1999/2000/2007/2014/2017 (1) 100 Federal Street Office Boston, MA — 131,067 435,954 79,035 131,067 514,989 — — 646,056 97,630 1971-1975/2017 2012 (1) Times Square Tower Office New York, NY — 165,413 380,438 87,050 169,193 463,708 — — 632,901 191,435 2004 2000 (1) Atlantic Wharf Office Boston, MA — 63,988 454,537 17,473 63,988 472,010 — — 535,998 101,525 2011 2007 (1) Fountain Square Office Reston, VA — 56,853 306,298 17,834 56,853 320,474 3,658 — 380,985 60,098 1986-1990 2012 (1) 510 Madison Avenue Office New York, NY — 103,000 253,665 23,875 103,000 277,540 — — 380,540 54,056 2012 2010 (1) 599 Lexington Avenue Office New York, NY — 81,040 100,507 165,350 87,852 259,045 — — 346,897 165,739 1986 1997 (1) 680 Folsom Street Office San Francisco, CA — 72,545 219,766 7,545 72,545 227,311 — — 299,856 30,577 2014 2012 (1) South of Market and Democracy Tower Office Reston, VA — 13,603 237,479 14,991 13,687 252,386 — — 266,073 87,711 2008-2009 2003 (1) 601 Massachusetts Avenue Office Washington, DC — 95,310 165,173 2,353 95,322 167,514 — — 262,836 12,177 2016 2008 (1) Bay Colony Corporate Center Office Waltham, MA — 18,789 148,451 73,418 18,789 221,869 — — 240,658 57,320 1985-1989 2011 (1) Gateway Center Office San Francisco, CA — 28,255 139,245 59,019 30,627 195,892 — — 226,519 102,634 1984/1986/2002 1999 (1) 535 Mission Street Office San Francisco, CA — 40,933 148,378 3,259 40,933 151,637 — — 192,570 14,637 2015 2013 (1) 2200 Pennsylvania Avenue Office Washington, DC — — 183,541 4,907 — 188,448 — — 188,448 46,780 2011 2008 (1) Mountain View Research Park Office Mountain View, CA — 95,066 68,373 8,136 95,066 76,509 — — 171,575 15,146 1977-1981/2007-2013 2013 (1) Reservoir Place Office Waltham, MA — 18,605 104,124 43,255 20,108 145,876 — — 165,984 66,230 1955/1987/2017 1997/1998 (1) 1330 Connecticut Avenue Office Washington, DC — 25,982 82,311 32,839 27,135 113,997 — — 141,132 22,530 1984 2004 (1) 1333 New Hampshire Avenue Office Washington, DC — 34,032 85,660 11,473 35,382 95,783 — — 131,165 40,499 1996 2003 (1) Kingstowne Towne Center Office Alexandria, VA — 18,021 109,038 1,371 18,062 110,368 — — 128,430 39,048 2003-2006 2007 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building One Freedom Square Office Reston, VA — 9,929 84,504 32,618 11,293 115,758 — — 127,051 50,313 2000 2003 (1) Capital Gallery Office Washington, DC — 4,725 29,565 89,514 8,662 115,142 — — 123,804 66,009 1981/2006 2007 (1) Weston Corporate Center Office Weston, MA — 25,753 92,312 (123 ) 25,854 92,088 — — 117,942 23,125 2010 2001 (1) Two Freedom Square Office Reston, VA — 13,930 77,739 23,379 15,420 99,628 — — 115,048 47,936 2001 2003 (1) One and Two Reston Overlook Office Reston, VA — 16,456 66,192 25,111 16,179 91,580 — — 107,759 44,626 1999 2000 (1) Discovery Square Office Reston, VA — 11,198 71,782 24,414 12,533 94,861 — — 107,394 43,184 2001 2003 (1) 140 Kendrick Street Office Needham, MA — 18,095 66,905 17,492 19,092 83,400 — — 102,492 29,013 2000 2004 (1) 355 Main Street Office Cambridge, MA — 18,863 53,346 27,450 21,173 78,486 — — 99,659 26,915 1981/1996/2013 2006 (1) 10 CityPoint Office Waltham, MA — 1,953 85,752 2,833 2,116 88,422 — — 90,538 4,673 2016 1997 (1) 90 Broadway Office Cambridge, MA — 19,104 52,078 17,180 20,785 67,577 — — 88,362 19,254 1983/1998/2013 2006 (1) 230 CityPoint Office Waltham, MA — 13,189 49,823 25,236 13,593 74,655 — — 88,248 26,562 1992 2005 (1) Waltham Weston Corporate Center Office Waltham, MA — 10,385 60,694 11,030 11,097 71,012 — — 82,109 30,036 2003 1999 (1) 77 CityPoint Office Waltham, MA — 13,847 60,383 5,703 13,873 66,060 — — 79,933 23,044 2008 2001 (1) 3625-3635 Peterson Way Office Santa Clara, CA — 63,206 14,879 138 63,206 14,879 138 — 78,223 5,120 1979 2016 (1) North First Business Park Office San Jose, CA — 58,402 13,069 4,416 23,377 16,600 35,910 — 75,887 15,839 1981 2007 (1) 300 Binney Street Office Cambridge, MA — 18,080 51,262 140 18,080 51,402 — — 69,482 7,755 2013 2009 (1) 2440 West El Camino Real Office Mountain View, CA — 16,741 51,285 1,287 16,741 52,572 — — 69,313 10,790 1987/2003 2011 (1) Wisconsin Place Office Chevy Chase, MD — — 53,349 14,907 — 68,256 — — 68,256 19,775 2009 2004 (1) Reston Corporate Center Office Reston, VA — 9,135 50,857 6,236 10,148 56,080 — — 66,228 26,769 1984 1998 (1) New Dominion Technology Park, Bldg. Two Office Herndon, VA — 5,584 51,868 4,157 6,510 55,099 — — 61,609 23,652 2004 1998 (1) 200 West Street Office Waltham, MA — 16,148 24,983 10,673 16,813 34,991 — — 51,804 21,140 1999 1997 (1) New Dominion Technology Park, Bldg. One Office Herndon, VA 32,691 3,880 43,227 3,882 4,583 46,406 — — 50,989 25,940 2001 1998 (1) Sumner Square Office Washington, DC — 624 28,745 19,000 1,478 46,891 — — 48,369 23,570 1985 1999 (1) 255 Main Street Office Cambridge, MA — 134 25,110 21,583 548 46,279 — — 46,827 28,250 1987 1997 (1) University Place Office Cambridge, MA 7,407 — 37,091 9,007 390 45,708 — — 46,098 26,295 1985 1998 (1) 2600 Tower Oaks Boulevard Office Rockville, MD — 4,243 31,125 9,867 4,785 40,450 — — 45,235 21,020 2001 1998 (1) Quorum Office Park Office Chelmsford, MA — 3,750 32,454 5,813 5,187 36,830 — — 42,017 16,594 2001 2000 (1) 500 E Street Office Washington, DC — 109 22,420 14,743 2,379 34,893 — — 37,272 23,781 1987 1997 (1) 150 Broadway Office Cambridge, MA — 850 25,042 8,540 1,323 33,109 — — 34,432 16,933 1999 1997 (1) 325 Main Street Office Cambridge, MA — 174 12,200 11,963 965 23,372 — — 24,337 12,852 1987/2013 1997 (1) 105 Broadway Office Cambridge, MA — 1,299 12,943 8,214 2,395 20,061 — — 22,456 13,493 1990 1997 (1) Lexington Office Park Office Lexington, MA — 998 1,426 18,219 1,264 19,379 — — 20,643 13,404 1982 1997 (1) 201 Spring Street Office Lexington, MA — 2,849 15,303 694 3,124 15,722 — — 18,846 7,931 1997 1997 (1) The Point Office Waltham, MA — 6,395 10,040 409 6,480 10,364 — — 16,844 714 2015 2007 (1) 92-100 Hayden Avenue Office Lexington, MA — 594 6,748 8,181 802 14,721 — — 15,523 12,495 1985 1997 (1) 91 Hartwell Avenue Office Lexington, MA — 784 6,464 8,269 941 14,576 — — 15,517 9,849 1985 1997 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 690 Folsom Street Office San Francisco, CA — 3,219 11,038 1,157 3,219 12,195 — — 15,414 1,295 2015 2012 (1) 181 Spring Street Office Lexington, MA — 1,066 9,520 2,318 1,160 11,744 — — 12,904 5,194 1999 1997 (1) 195 West Street Office Waltham, MA — 1,611 6,652 4,340 1,858 10,745 — — 12,603 7,963 1990 1997 (1) 33 Hayden Avenue Office Lexington, MA — 266 3,234 8,381 425 11,456 — — 11,881 8,211 1979 1997 (1) 7501 Boston Boulevard, Building Seven Office Springfield, VA — 665 9,273 819 791 9,966 — — 10,757 4,848 1997 1997 (1) 7435 Boston Boulevard, Building One Office Springfield, VA — 392 3,822 3,997 659 7,552 — — 8,211 5,510 1982 1997 (1) 250 Binney Street Office Cambridge, MA — 110 4,483 3,593 273 7,913 — — 8,186 5,066 1983 1997 (1) 8000 Grainger Court, Building Five Office Springfield, VA — 366 4,282 3,375 601 7,422 — — 8,023 5,644 1984 1997 (1) 7450 Boston Boulevard, Building Three Office Springfield, VA — 1,165 4,681 1,773 1,430 6,189 — — 7,619 3,451 1987 1998 (1) 453 Ravendale Drive Office Mountain View, CA — 5,477 1,090 408 5,477 1,498 — — 6,975 472 1977 2012 (1) 17 Hartwell Avenue Office Lexington, MA — 26 150 6,252 65 6,363 — — 6,428 1,098 1968 1997 (1) 7601 Boston Boulevard, Building Eight Office Springfield, VA — 200 878 5,052 551 5,579 — — 6,130 4,263 1986 1997 (1) 7300 Boston Boulevard, Building Thirteen Office Springfield, VA — 608 4,773 709 661 5,429 — — 6,090 2,785 2002 1997 (1) 7500 Boston Boulevard, Building Six Office Springfield, VA — 138 3,749 1,655 406 5,136 — — 5,542 3,965 1985 1997 (1) 8000 Corporate Court, Building Eleven Office Springfield, VA — 136 3,071 1,596 774 4,029 — — 4,803 2,909 1989 1997 (1) 7374 Boston Boulevard, Building Four Office Springfield, VA — 241 1,605 1,913 398 3,361 — — 3,759 2,578 1984 1997 (1) 7375 Boston Boulevard, Building Ten Office Springfield, VA — 23 2,685 938 93 3,553 — — 3,646 2,570 1988 1997 (1) 7451 Boston Boulevard, Building Two Office Springfield, VA — 249 1,542 1,659 613 2,837 — — 3,450 2,429 1982 1997 (1) 32 Hartwell Avenue Office Lexington, MA — 168 1,943 1,012 314 2,809 — — 3,123 1,974 1968/1979/1987 1997 (1) 164 Lexington Road Office Billerica, MA — 592 1,370 319 643 1,638 — — 2,281 868 1982 1997 (1) The Avant at Reston Town Center Residential Reston, VA — 20,350 91,995 830 20,350 92,825 — — 113,175 9,780 2014 2010 (1) The Lofts at Atlantic Wharf Residential Boston, MA — 3,529 54,891 1,768 3,529 56,659 — — 60,188 9,622 2011 2007 (1) Boston Marriott Cambridge Hotel Cambridge, MA — 478 37,918 38,799 1,201 75,994 — — 77,195 47,753 1986 1997 (1) Kendall Center Green Garage Garage Cambridge, MA — — 35,035 7,448 103 42,380 — — 42,483 10,779 1984 2006 (1) Kendall Center Yellow Garage Garage Cambridge, MA — 1,256 15,697 1,621 1,434 17,140 — — 18,574 5,181 2006 2004 (1) Kendall Center Blue Garage Garage Cambridge, MA — 1,163 11,633 2,283 1,579 13,500 — — 15,079 9,209 1990 1997 (1) Salesforce Tower Development San Francisco, CA — — — 947,106 200,349 55,318 — 691,439 947,106 116 N/A 2013 N/A Signature at Reston Development Reston, VA — — — 203,650 — — — 203,650 203,650 — N/A 2013 N/A Proto Kendall Square Development Cambridge, MA — — — 82,905 — — — 82,905 82,905 — N/A 2015 N/A 145 Broadway Development Cambridge, MA — 121 — 79,979 324 — — 79,776 80,100 — NA 1997 N/A 191 Spring Street Development Lexington, MA — 2,850 27,166 35,174 3,151 46,288 — 15,751 65,190 19,034 1971/1995 1997 (1) Boston Properties, Inc. Schedule III - Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Property Name Type Location Encumbrances Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Land Building 6595 Springfield Center Drive (TSA Headquarters) Development Springfield, VA — — — 41,918 — — — 41,918 41,918 — N/A 2007 N/A MacArthur Station Residences Development Oakland, CA — — — 37,644 — — — 37,644 37,644 — N/A N/A N/A 20 CityPoint Development Waltham, MA — — — 13,056 — — — 13,056 13,056 — N/A 2007 N/A Tower Oaks Master Plan Land Rockville, MD — — — 29,419 — — 29,419 — 29,419 — N/A 1998 N/A Plaza at Almaden Land San Jose, CA — — — 29,085 — — 29,085 — 29,085 — N/A 2006 N/A Springfield Metro Center Land Springfield, VA — — — 19,684 — — 19,684 — 19,684 — N/A 2007 N/A 214 Third Avenue Land Waltham, MA — — — 13,815 — — 13,815 — 13,815 — N/A 2006 N/A Reston Gateway Land Reston, VA — — — 13,730 — — 13,730 — 13,730 — N/A 1998 N/A 103 Fourth Avenue Land Waltham, MA — — — 12,115 — — 12,115 — 12,115 — N/A 2007 N/A Crane Meadow Land Marlborough, MA — — — 8,836 — — 8,836 — 8,836 — N/A 2000 N/A Washingtonian North Land Gaithersburg, MD — — — 7,645 — — 7,645 — 7,645 — N/A 1998 N/A 2100 Pennsylvania Avenue Land Washington, DC — — — 6,543 — — 6,543 — 6,543 — N/A N/A N/A Fourth and Harrison Land San Francisco, CA — — — 5,659 — — 5,659 — 5,659 — N/A N/A N/A North First Master Plan Land San Jose, CA — — — 3,018 — — 3,018 — 3,018 — N/A 2007 N/A Broad Run Business Park Land Loudoun County, VA — — — 2,367 — — 2,367 — 2,367 — N/A 1998 N/A Kendall Center Master Plan Land Cambridge, MA — — — 2,207 — — 2,207 — 2,207 — N/A N/A N/A Weston Quarry Land Weston, MA — — — 1,194 — — 1,194 — 1,194 — N/A 2001 N/A Reston Overlook Master Plan Land Reston, VA — — — 39 — — 39 — 39 — N/A 2000 N/A $ 2,979,281 (2 ) $ 4,762,002 $ 11,634,050 $ 4,662,662 $ 5,080,679 $ 14,503,772 $ 204,925 (3 ) $ 1,269,338 $ 21,058,714 $ 4,566,570 Note: Total Real Estate does not include Furniture, Fixtures and Equipment totaling approximately $37,928 . Accumulated Depreciation does not include approximately $23,064 of accumulated depreciation related to Furniture, Fixtures and Equipment. The aggregate cost and accumulated depreciation for tax purposes was approximately $17.3 billion and $3.6 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 unamortized deferred financing costs totaling approximately $(34.7) million . (3) Includes pre-development costs.
Activity of Real Estate and Accumulated Depreciation [Table Text Block]	A summary of activity for real estate and accumulated depreciation is as follows: 2017 2016 2015 Real Estate: Balance at the beginning of the year $ 20,114,576 $ 19,451,683 $ 19,208,417 Additions to/improvements of real estate 1,099,286 977,287 700,792 Assets sold/written-off (155,148 ) (314,394 ) $ (457,526 ) Balance at the end of the year $ 21,058,714 $ 20,114,576 $ 19,451,683 Accumulated Depreciation: Balance at the beginning of the year $ 4,201,891 $ 3,905,940 $ 3,529,978 Depreciation expense 497,059 560,024 486,450 Assets sold/written-off (132,380 ) (264,073 ) (110,488 ) Balance at the end of the year $ 4,566,570 $ 4,201,891 $ 3,905,940 Note: Real Estate and Accumulated Depreciation amounts do not include Furniture, Fixtures and Equipment.
Boston Properties Limited Partnership
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, By Property [Table Text Block]	Boston Properties Limited Partnership Schedule III—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building 767 Fifth Avenue (the General Motors Building) Office New York, NY $ 2,267,041 $ 1,796,252 $ 1,532,654 $ 135,559 $ 1,796,252 $ 1,668,213 $ — $ — $ 3,464,465 $ 222,981 1968 2013 (1) Prudential Center Office Boston, MA — 92,077 948,357 441,339 100,540 1,381,233 — — 1,481,773 497,960 1965/1993/2002/2016-2017 1998/1999/2000 (1) Embarcadero Center Office San Francisco, CA — 179,697 847,410 304,399 180,420 1,151,086 — — 1,331,506 581,932 1970/1989 1998-1999 (1) 399 Park Avenue Office New York, NY — 339,200 700,358 121,810 339,200 822,168 — — 1,161,368 296,763 1961 2002 (1) 200 Clarendon Street and Garage Office Boston, MA — 219,543 667,884 139,189 219,616 799,991 7,009 — 1,026,616 161,471 1976 2010 (1) 601 Lexington Avenue Office New York, NY 672,142 241,600 494,782 253,504 279,281 607,406 — 103,199 989,886 246,814 1977/1997 2001 (1) 250 West 55th Street Office New York, NY — 285,263 603,167 43,296 285,263 646,463 — — 931,726 72,058 2014 2007 (1) 100 Federal Street Office Boston, MA — 131,067 435,954 79,035 131,067 514,989 — — 646,056 97,630 1971-1975/2017 2012 (1) Carnegie Center Office Princeton, NJ — 107,997 389,359 140,642 104,617 530,527 2,854 — 637,998 224,256 1983-2016 1998/1999/2000/2007/2014/2017 (1) Times Square Tower Office New York, NY — 165,413 380,438 49,071 159,694 435,228 — — 594,922 182,850 2004 2000 (1) Atlantic Wharf Office Boston, MA — 63,988 454,537 17,473 63,988 472,010 — — 535,998 101,525 2011 2007 (1) Fountain Square Office Reston, VA — 56,853 306,298 17,834 56,853 320,474 3,658 — 380,985 60,098 1986-1990 2012 (1) 510 Madison Avenue Office New York, NY — 103,000 253,665 23,875 103,000 277,540 — — 380,540 54,056 2012 2010 (1) 599 Lexington Avenue Office New York, NY — 81,040 100,507 138,108 81,040 238,615 — — 319,655 159,586 1986 1997 (1) 680 Folsom Street Office San Francisco, CA — 72,545 219,766 7,545 72,545 227,311 — — 299,856 30,577 2014 2012 (1) South of Market and Democracy Tower Office Reston, VA — 13,603 237,479 14,655 13,603 252,134 — — 265,737 87,651 2008-2009 2003 (1) 601 Massachusetts Avenue Office Washington, DC — 95,310 165,173 2,341 95,310 167,514 — — 262,824 12,177 2016 2008 (1) Bay Colony Corporate Center Office Waltham, MA — 18,789 148,451 73,418 18,789 221,869 — — 240,658 57,320 1985-1989 2011 (1) Gateway Center Office San Francisco, CA — 28,255 139,245 52,630 29,029 191,101 — — 220,130 101,191 1984/1986/2002 1999 (1) 535 Mission Street Office San Francisco, CA — 40,933 148,378 3,259 40,933 151,637 — — 192,570 14,637 2015 2013 (1) 2200 Pennsylvania Avenue Office Washington, DC — — 183,541 4,907 — 188,448 — — 188,448 46,780 2011 2008 (1) Mountain View Research Park Office Mountain View, CA — 95,066 68,373 8,136 95,066 76,509 — — 171,575 15,146 1977-1981/2007-2013 2013 (1) Reservoir Place Office Waltham, MA — 18,605 104,124 39,180 19,089 142,820 — — 161,909 65,309 1955/1987/2017 1997/1998 (1) 1330 Connecticut Avenue Office Washington, DC — 25,982 82,311 28,226 25,982 110,537 — — 136,519 21,484 1984 2004 (1) Kingstowne Towne Center Office Alexandria, VA — 18,021 109,038 1,207 18,021 110,245 — — 128,266 39,018 2003-2006 2007 (1) 1333 New Hampshire Avenue Office Washington, DC — 34,032 85,660 6,079 34,032 91,739 — — 125,771 39,279 1996 2003 (1) One Freedom Square Office Reston, VA — 9,929 84,504 26,981 9,883 111,531 — — 121,414 49,037 2000 2003 (1) Weston Corporate Center Office Weston, MA — 25,753 92,312 (123 ) 25,854 92,088 — — 117,942 23,125 2010 2001 (1) Capital Gallery Office Washington, DC — 4,725 29,565 79,383 6,128 107,545 — — 113,673 63,717 1981/2006 2007 (1) Two Freedom Square Office Reston, VA — 13,930 77,739 17,167 13,866 94,970 — — 108,836 46,532 2001 2003 (1) One and Two Reston Overlook Office Reston, VA — 16,456 66,192 20,693 15,074 88,267 — — 103,341 43,627 1999 2000 (1) Boston Properties Limited Partnership Schedule 3—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building Discovery Square Office Reston, VA — 11,198 71,782 18,869 11,146 90,703 — — 101,849 41,928 2001 2003 (1) 355 Main Street Office Cambridge, MA — 18,863 53,346 27,152 21,098 78,263 — — 99,361 26,850 1981/1996/2013 2006 (1) 140 Kendrick Street Office Needham, MA — 18,095 66,905 13,502 18,095 80,407 — — 98,502 28,111 2000 2004 (1) 10 CityPoint Office Waltham, MA — 1,953 85,752 2,670 1,953 88,422 — — 90,375 4,673 2016 1997 (1) 90 Broadway Office Cambridge, MA — 19,104 52,078 17,001 20,741 67,442 — — 88,183 19,220 1983/1998/2013 2006 (1) 230 CityPoint Office Waltham, MA — 13,189 49,823 23,619 13,189 73,442 — — 86,631 26,200 1992 2005 (1) 77 CityPoint Office Waltham, MA — 13,847 60,383 5,598 13,847 65,981 — — 79,828 23,024 2008 2001 (1) Waltham Weston Corporate Center Office Waltham, MA — 10,385 60,694 8,043 10,350 68,772 — — 79,122 29,359 2003 1999 (1) 3625-3635 Peterson Way Office Santa Clara, CA — 63,206 14,879 138 63,206 14,879 138 — 78,223 5,120 1979 2016 (1) North First Business Park Office San Jose, CA — 58,402 13,069 4,393 23,371 16,583 35,910 — 75,864 15,839 1981 2007 (1) 300 Binney Street Office Cambridge, MA — 18,080 51,262 140 18,080 51,402 — — 69,482 7,755 2013 2009 (1) 2440 West El Camino Real Office Mountain View, CA — 16,741 51,285 1,287 16,741 52,572 — — 69,313 10,790 1987/2003 2011 (1) Wisconsin Place Office Chevy Chase, MD — — 53,349 14,907 — 68,256 — — 68,256 19,775 2009 2004 (1) Reston Corporate Center Office Reston, VA — 9,135 50,857 3,625 9,496 54,121 — — 63,617 26,178 1984 1998 (1) New Dominion Technology Park, Bldg. Two Office Herndon, VA — 5,584 51,868 412 5,574 52,290 — — 57,864 22,801 2004 1998 (1) 200 West Street Office Waltham, MA — 16,148 24,983 8,012 16,148 32,995 — — 49,143 20,538 1999 1997 (1) New Dominion Technology Park, Bldg. One Office Herndon, VA 32,691 3,880 43,227 1,072 3,880 44,299 — — 48,179 25,304 2001 1998 (1) Sumner Square Office Washington, DC — 624 28,745 16,920 958 45,331 — — 46,289 23,103 1985 1999 (1) 255 Main Street Office Cambridge, MA — 134 25,110 19,927 134 45,037 — — 45,171 27,878 1987 1997 (1) University Place Office Cambridge, MA 7,407 — 37,091 7,557 27 44,621 — — 44,648 25,971 1985 1998 (1) 2600 Tower Oaks Boulevard Office Rockville, MD — 4,243 31,125 7,704 4,244 38,828 — — 43,072 20,529 2001 1998 (1) Quorum Office Park Office Chelmsford, MA — 3,750 32,454 4,115 4,762 35,557 — — 40,319 16,211 2001 2000 (1) 500 E Street Office Washington, DC — 109 22,420 11,503 1,569 32,463 — — 34,032 23,051 1987 1997 (1) 150 Broadway Office Cambridge, MA — 850 25,042 6,535 822 31,605 — — 32,427 16,477 1999 1997 (1) 325 Main Street Office Cambridge, MA — 174 12,200 11,192 772 22,794 — — 23,566 12,675 1987/2013 1997 (1) 105 Broadway Office Cambridge, MA — 1,299 12,943 6,108 1,868 18,482 — — 20,350 13,015 1990 1997 (1) Lexington Office Park Office Lexington, MA — 998 1,426 17,455 1,073 18,806 — — 19,879 13,235 1982 1997 (1) 201 Spring Street Office Lexington, MA — 2,849 15,303 (405 ) 2,849 14,898 — — 17,747 7,681 1997 1997 (1) The Point Office Waltham, MA — 6,395 10,040 409 6,480 10,364 — — 16,844 714 2015 2007 (1) 690 Folsom Street Office San Francisco, CA — 3,219 11,038 1,157 3,219 12,195 — — 15,414 1,295 2015 2012 (1) 91 Hartwell Avenue Office Lexington, MA — 784 6,464 7,642 784 14,106 — — 14,890 9,705 1985 1997 (1) 92-100 Hayden Avenue Office Lexington, MA — 594 6,748 7,452 619 14,175 — — 14,794 12,329 1985 1997 (1) 181 Spring Street Office Lexington, MA — 1,066 9,520 1,941 1,066 11,461 — — 12,527 5,109 1999 1997 (1) 195 West Street Office Waltham, MA — 1,611 6,652 3,351 1,611 10,003 — — 11,614 7,736 1990 1997 (1) 33 Hayden Avenue Office Lexington, MA — 266 3,234 7,744 266 10,978 — — 11,244 8,067 1979 1997 (1) Boston Properties Limited Partnership Schedule 3—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building 7501 Boston Boulevard, Building Seven Office Springfield, VA — 665 9,273 314 665 9,587 — — 10,252 4,732 1997 1997 (1) 250 Binney Street Office Cambridge, MA — 110 4,483 2,939 110 7,422 — — 7,532 4,922 1983 1997 (1) 7435 Boston Boulevard, Building One Office Springfield, VA — 392 3,822 3,304 486 7,032 — — 7,518 5,354 1982 1997 (1) 8000 Grainger Court, Building Five Office Springfield, VA — 366 4,282 2,781 453 6,976 — — 7,429 5,511 1984 1997 (1) 7450 Boston Boulevard, Building Three Office Springfield, VA — 1,165 4,681 1,359 1,327 5,878 — — 7,205 3,354 1987 1998 (1) 453 Ravendale Drive Office Mountain View, CA — 5,477 1,090 408 5,477 1,498 — — 6,975 472 1977 2012 (1) 17 Hartwell Avenue Office Lexington, MA — 26 150 6,095 26 6,245 — — 6,271 1,062 1968 1997 (1) 7300 Boston Boulevard, Building Thirteen Office Springfield, VA — 608 4,773 497 608 5,270 — — 5,878 2,737 2002 1997 (1) 7601 Boston Boulevard, Building Eight Office Springfield, VA — 200 878 4,359 378 5,059 — — 5,437 4,107 1986 1997 (1) 7500 Boston Boulevard, Building Six Office Springfield, VA — 138 3,749 1,122 273 4,736 — — 5,009 3,845 1985 1997 (1) 8000 Corporate Court, Building Eleven Office Springfield, VA — 136 3,071 1,245 686 3,766 — — 4,452 2,826 1989 1997 (1) 7375 Boston Boulevard, Building Ten Office Springfield, VA — 23 2,685 757 47 3,418 — — 3,465 2,532 1988 1997 (1) 7374 Boston Boulevard, Building Four Office Springfield, VA — 241 1,605 1,530 303 3,073 — — 3,376 2,494 1984 1997 (1) 7451 Boston Boulevard, Building Two Office Springfield, VA — 249 1,542 1,346 535 2,602 — — 3,137 2,357 1982 1997 (1) 32 Hartwell Avenue Office Lexington, MA — 168 1,943 426 168 2,369 — — 2,537 1,840 1968/1979/1987 1997 (1) 164 Lexington Road Office Billerica, MA — 592 1,370 117 592 1,487 — — 2,079 819 1982 1997 (1) The Avant at Reston Town Center Residential Reston, VA — 20,350 91,995 830 20,350 92,825 — — 113,175 9,780 2014 2010 (1) The Lofts at Atlantic Wharf Residential Boston, MA — 3,529 54,891 1,768 3,529 56,659 — — 60,188 9,622 2011 2007 (1) Boston Marriott Cambridge Hotel Cambridge, MA — 478 37,918 35,908 478 73,826 — — 74,304 47,101 1986 1997 (1) Kendall Center Green Garage Garage Cambridge, MA — — 35,035 7,034 — 42,069 — — 42,069 10,687 1984 2006 (1) Kendall Center Yellow Garage Garage Cambridge, MA — 1,256 15,697 909 1,256 16,606 — — 17,862 5,024 2006 2004 (1) Kendall Center Blue Garage Garage Cambridge, MA — 1,163 11,633 618 1,163 12,251 — — 13,414 8,834 1990 1997 (1) Salesforce Tower Development San Francisco, CA — — — 947,106 200,349 55,318 — 691,439 947,106 116 N/A 2013 N/A Signature at Reston Development Reston, VA — — — 203,650 — — — 203,650 203,650 — N/A 2013 N/A Proto Kendall Square Development Cambridge, MA — — — 82,905 — — — 82,905 82,905 — N/A 2015 N/A 145 Broadway Development Cambridge, MA — 121 — 79,776 121 — — 79,776 79,897 — NA 1997 N/A 191 Spring Street Development Lexington, MA — 2,850 27,166 34,542 2,850 45,957 — 15,751 64,558 18,934 1971/1995 1997 (1) 6595 Springfield Center Drive (TSA Headquarters) Development Springfield, VA — — — 41,918 — — — 41,918 41,918 — N/A 2007 N/A Boston Properties Limited Partnership Schedule 3—Real Estate and Accumulated Depreciation December 31, 2017 (dollars in thousands) Original Costs Capitalized Subsequent to Acquisition Land and Improvements Building and Improvements Land Held for Development Development and Construction in Progress Total Accumulated Depreciation Year(s) Built/ Renovated Year(s) Acquired Depreciable Lives (Years) Property Name Type Location Encumbrances Land Building MacArthur Station Residences Development Oakland, CA — — — 37,644 — — — 37,644 37,644 — N/A N/A N/A 20 CityPoint Development Waltham, MA — — — 13,056 — — — 13,056 13,056 — N/A 2007 N/A Tower Oaks Master Plan Land Rockville, MD — — — 29,419 — — 29,419 — 29,419 — N/A 1998 N/A Plaza at Almaden Land San Jose, CA — — — 29,085 — — 29,085 — 29,085 — N/A 2006 N/A Springfield Metro Center Land Springfield, VA — — — 19,684 — — 19,684 — 19,684 — N/A 2007 N/A 214 Third Avenue Land Waltham, MA — — — 13,815 — — 13,815 — 13,815 — N/A 2006 N/A Reston Gateway Land Reston, VA — — — 13,730 — — 13,730 — 13,730 — N/A 1998 N/A 103 Fourth Avenue Land Waltham, MA — — — 12,115 — — 12,115 — 12,115 — N/A 2007 N/A Crane Meadow Land Marlborough, MA — — — 8,836 — — 8,836 — 8,836 — N/A 2000 N/A Washingtonian North Land Gaithersburg, MD — — — 7,645 — — 7,645 — 7,645 — N/A 1998 N/A 2100 Pennsylvania Avenue Land Washington, DC — — — 6,543 — — 6,543 — 6,543 — N/A N/A N/A Fourth and Harrison Land San Francisco, CA — — — 5,659 — — 5,659 — 5,659 — N/A N/A N/A North First Master Plan Land San Jose, CA — — — 3,018 — — 3,018 — 3,018 — N/A 2007 N/A Broad Run Business Park Land Loudoun County, VA — — — 2,367 — — 2,367 — 2,367 — N/A 1998 N/A Kendall Center Master Plan Land Cambridge, MA — — — 2,207 — — 2,207 — 2,207 — N/A N/A N/A Weston Quarry Land Weston, MA — — — 1,194 — — 1,194 — 1,194 — N/A 2001 N/A Reston Overlook Master Plan Land Reston, VA — — — 39 — — 39 — 39 — N/A 2000 N/A $ 2,979,281 (2 ) $ 4,762,002 $ 11,634,050 $ 4,251,184 $ 4,976,303 $ 14,196,670 $ 204,925 (3 ) $ 1,269,338 $ 20,647,236 $ 4,473,895 Note: Total Real Estate does not include Furniture, Fixtures and Equipment totaling approximately $37,928 . Accumulated Depreciation does not include approximately $23,064 of accumulated depreciation related to Furniture, Fixtures and Equipment. The aggregate cost and accumulated depreciation for tax purposes was approximately $19.3 billion and $4.1 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 unamortized deferred financing costs totaling approximately $(34.7) million . (3) Includes pre-development costs.
Activity of Real Estate and Accumulated Depreciation [Table Text Block]	A summary of activity for real estate and accumulated depreciation is as follows: 2017 2016 2015 Real Estate: Balance at the beginning of the year $ 19,701,185 $ 19,031,289 $ 18,786,572 Additions to/improvements of real estate 1,099,286 977,287 700,792 Assets sold/written-off (153,235 ) (307,391 ) (456,075 ) Balance at the end of the year $ 20,647,236 $ 19,701,185 $ 19,031,289 Accumulated Depreciation: Balance at the beginning of the year $ 4,116,020 $ 3,826,862 $ 3,458,640 Depreciation expense 488,919 548,397 478,457 Assets sold/written-off (131,044 ) (259,239 ) (110,235 ) Balance at the end of the year $ 4,473,895 $ 4,116,020 $ 3,826,862 Note: Real Estate and Accumulated Depreciation amounts do not include Furniture, Fixtures and Equipment.

Organization (Details)

Organization (Details) ft² in Millions	12 Months Ended
	Dec. 31, 2017ft²Real_Estate_Propertiesyrshares	Dec. 31, 2016shares
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.70%	89.50%
Restriction on redemption of OP units from date of issuance (years) | yr	1
One OP unit is equivalent to one share of Common Stock (in shares) | shares	1
OP unit conversion rate (in shares) | shares	1
Number Of series Of preferred units outstanding	1
Commercial Real Estate Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	179
Net Rentable Area | ft²	50.3
Total Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	12
Net Rentable Area | ft²	6.2
Total Office Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	167
Office Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	8
Hotel Property [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	1
Retail Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	5
Residential Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	6
Residential Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	4
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Real Estate Properties [Line Items]
Preferred stock / units, shares / units outstanding (in shares / units) | shares	80,000	80,000
Preferred Stock, Dividend Rate, Percentage	5.25%
Depositary shares of Series B Cumulative Redeemable Preferred [Member]
Real Estate Properties [Line Items]
Preferred stock / units, shares / units outstanding (in shares / units) | shares	8,000,000
Series B Preferred Units [Member]
Real Estate Properties [Line Items]
Preferred stock / units, shares / units outstanding (in shares / units) | shares	80,000

Summary Of Significant Accoun48

Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017USD ($)yr	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Entity Information [Line Items]
Probable Sale Term of Property After Classified As Held For Sale (Years) | yr	1
Maximum Period After Construction The Company Considers A Construction Project As Substantially Completed (In Years) | yr	1
Interest costs capitalized	$ 61,070,000	$ 39,237,000	$ 34,213,000
Salaries And Related Costs Capitalized	13,200,000	11,100,000	10,400,000
Cash FDIC Insured Limit	250,000
Separate Unrestricted Cash For Deferred Compensation Plan.	29,200,000	23,800,000
Gains (losses) from investments in securities	3,678,000	2,273,000	(653,000)
Internal Leasing Salaries And Related Costs Capitalized	5,000,000	7,200,000	5,500,000
Straight-line rent adjustments	(54,800,000)	(31,700,000)	(80,000,000)
Above and below market rent adjustments, net	$ 23,500,000	30,200,000	35,900,000
Ground Lease Expiration Date, Maximum	2,114
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.	$ 1,800,000,000	1,700,000,000
Debt Issuance Costs, Net	34,680,000
Cumulative effect of a change in accounting principle	2,035,000
Boston Properties Limited Partnership
Entity Information [Line Items]
Interest costs capitalized	61,070,000	39,237,000	34,213,000
Gains (losses) from investments in securities	3,678,000	2,273,000	$ (653,000)
Net Difference Between Tax Basis And Company's Assets And Liabilities.	2,900,000,000	$ 2,700,000,000
Debt Issuance Costs, Net	34,700,000
Cumulative effect of a change in accounting principle	272,000
Dividends In Excess Of Earnings [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	272,000
Noncontrolling Interests [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	1,763,000
Noncontrolling Interests [Member] | Boston Properties Limited Partnership
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	$ 1,763,000

Summary Of Significant Accoun49

Summary Of Significant Accounting Policies Schedule of Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2017
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	Shorter of useful life or terms of related 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 Accoun50

Summary Of Significant Accounting Policies Schedule of Finite Lived Intangible Assets Future Amortization Expense (Details) $ in Thousands	Dec. 31, 2017USD ($)
Finite-Lived Intangible Assets [Line Items]
2,018	$ 33,651
2,019	27,333
2,020	14,464
2,021	8,777
2,022	4,758
Acquired Above-Market Lease Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
2,018	8,614
2,019	7,106
2,020	5,394
2,021	2,988
2,022	315
Acquired Below-Market Lease Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
2,018	32,152
2,019	27,281
2,020	10,736
2,021	6,399
2,022	$ 5,669

Summary Of Significant Accoun51

Summary Of Significant Accounting Policies Schedule Of Future Contractual Minimum Lease Payments Under Non-Cancelable Ground Leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Summary of Significant Accounting Policies [Abstract]
2,018	$ 11,349
2,019	16,360
2,020	25,552
2,021	11,814
2,022	8,894
Thereafter	$ 576,315

Summary Of Significant Accoun52

Summary Of Significant Accounting Policies Capital lease disclosures (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Capital Leased Assets [Line Items]
Buildings and improvements	$ 12,284,164	$ 11,890,626
Construction in progress	1,269,338	1,037,959
2,018	913
2,019	1,392
2,020	2,097
2,021	1,375
2,022	930
Thereafter	74,185
Total expected minimum lease payments	80,892
Interest portion	(29,296)
Present value of expected net minimum lease payments	51,596
Capital Lease Obligations [Member]
Capital Leased Assets [Line Items]
Buildings and improvements	23,636	23,636
Construction in progress	28,962	0
Total	$ 52,598	$ 23,636

Summary Of Significant Accoun53

Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	$ 2,979,281	$ 2,063,087
Mezzanine notes payable	0	307,093
Unsecured senior notes, net	7,247,330	7,245,953
Unsecured line of credit	45,000	0
Total	3,013,961
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	2,979,281	2,063,087
Mezzanine notes payable	0	307,093
Unsecured senior notes, net	7,247,330	7,245,953
Unsecured line of credit	45,000
Total	10,271,611	9,616,133
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	3,042,920	2,092,237
Mezzanine notes payable	0	308,344
Unsecured senior notes, net	7,461,615	7,428,077
Unsecured line of credit	45,000
Total	$ 10,549,535	$ 9,828,658

Summary Of Significant Accoun54

Summary Of Significant Accounting Policies Schedule of Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015		Dec. 18, 2017
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Dividends Payable, Amount Per Share							$ 0.80
Special dividend (per share amount)					$ 1.25
Dividends Treatment For Federal Tax Purposes, Percentage	100.00%		100.00%		100.00%
Dividends treatment for federal tax purposes.	$ 2.91	[1]	$ 3.05	[2]	$ 4.04	[3]
Dividend Declared
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Dividends Payable, Amount Per Share	0.80		0.75		1.90
non-special dividend
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Dividends Payable, Amount Per Share					0.65
Allocated to fiscal 2015
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Special dividend (per share amount)					1.35
Allocated to fiscal 2016
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Special dividend (per share amount)			0.56		$ 0.55
Allocated to fiscal 2017
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Special dividend (per share amount)	0.47		$ 0.19
Allocated to fiscal two thousand and eighteen [Member]
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Special dividend (per share amount)	$ 0.33
Capital Gains Income
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Dividends Treatment For Federal Tax Purposes, Percentage	1.71%		9.49%		42.03%
Dividends treatment for federal tax purposes.	$ 0.05		$ 0.29		$ 1.70
Ordinary Income
Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes [Line Items]
Dividends Treatment For Federal Tax Purposes, Percentage	98.29%		90.51%		57.97%
Dividends treatment for federal tax purposes.	$ 2.86		$ 2.76		$ 2.34
[1]	The fourth quarter 2017 regular quarterly dividend was $0.80 per common share of which approximately $0.47 per common share was allocable to 2017 and approximately $0.33 per common share is allocable to 2018.
[2]	The fourth quarter 2016 regular quarterly dividend was $0.75 per common share of which approximately $0.56 per common share was allocable to 2016 and approximately $0.19 per common share is allocable to 2017.
[3]	The fourth quarter 2015 dividend of $1.90 per common share consists of a $1.25 per common share special dividend and a $0.65 per common share regular quarterly dividend. Approximately $1.35 per common share was allocable to 2015 and approximately $0.55 per common share is allocable to 2016.

Summary Of Significant Accoun55

Summary Of Significant Accounting Policies GAAP Reconciliation Of Net Income To Taxable Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Entity Information [Line Items]
Net income attributable to the Company	$ 103,829	$ 117,337	$ 133,709	$ 97,083	$ 147,214	$ 76,753	$ 96,597	$ 181,747	$ 462,439	$ 512,785	$ 583,106
Straight line rent and net above and below-market rent adjustments									(77,801)	(65,861)	(92,483)
Book/tax differences from depreciation and amortization									142,234	235,819	307,115
Book/Tax differences from interest expense									(18,136)	(36,223)	(43,349)
Book/tax differences on gains/(losses) from capital transactions									1,123	(70,880)	(74,482)
Book/tax differences from stock-based compensation									37,990	33,463	22,008
Tangible Property Regulations									(116,265)	(104,783)	(74,887)
Other book/tax differences, net									33,411	(6,121)	(15,259)
Taxable Income									464,995	498,199	611,769
Boston Properties Limited Partnership
Entity Information [Line Items]
Net income attributable to the Company	$ 117,667	$ 132,693	$ 151,844	$ 110,662	$ 166,801	$ 91,306	$ 109,938	$ 207,296	523,366	585,841	659,248
Straight line rent and net above and below-market rent adjustments									(86,773)	(73,604)	(103,227)
Book/tax differences from depreciation and amortization									144,436	245,239	329,629
Book/Tax differences from interest expense									(20,227)	(40,481)	(48,385)
Book/tax differences on gains/(losses) from capital transactions									784	(69,683)	(67,602)
Book/tax differences from stock-based compensation									42,371	37,397	24,565
Tangible Property Regulations									(129,673)	(117,102)	(83,587)
Other book/tax differences, net									37,607	(3,387)	(14,561)
Taxable Income									$ 511,891	$ 564,220	$ 696,080

Real Estate Schedule of Real Es

Real Estate Schedule of Real Estate Properties (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Real Estate Properties [Line Items]
Land		$ 5,080,679	$ 4,879,020
Land held for future development	[1]	204,925	246,656
Buildings and improvements		12,284,164	11,890,626
Tenant improvements		2,219,608	2,060,315
Furniture, fixtures and equipment		37,928	32,687
Construction in progress		1,269,338	1,037,959
Total		21,096,642	20,147,263
Less: accumulated depreciation		(4,589,634)	(4,222,235)
Total real estate		16,507,008	15,925,028
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Land		4,976,303	4,774,460
Land held for future development	[1]	204,925	246,656
Buildings and improvements		11,977,062	11,581,795
Tenant improvements		2,219,608	2,060,315
Furniture, fixtures and equipment		37,928	32,687
Construction in progress		1,269,338	1,037,959
Total		20,685,164	19,733,872
Less: accumulated depreciation		(4,496,959)	(4,136,364)
Total real estate		$ 16,188,205	$ 15,597,508
[1]	Includes pre-development costs.

Real Estate (Narrative) (Detail

Real Estate (Narrative) (Details)	Dec. 01, 2017ft²yr	Aug. 30, 2017USD ($)a	Jun. 13, 2017USD ($)ft²	Apr. 19, 2017USD ($)a	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Jun. 13, 2017USD ($)ft²	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Nov. 28, 2017ft²	Nov. 17, 2017ft²	Sep. 16, 2017ft²	Aug. 24, 2017ft²yr	Jun. 29, 2017USD ($)yrapartments	May 27, 2017ft²	May 15, 2017USD ($)ft²	Apr. 06, 2017ft²
Real Estate Properties [Line Items]
Revenues					$ 655,229,000	$ 657,712,000	$ 656,907,000	$ 632,228,000	$ 636,061,000	$ 625,228,000	$ 623,546,000	$ 665,985,000			$ 2,602,076,000	$ 2,550,820,000	$ 2,490,821,000
Operating Income (Loss)															908,110,000	825,784,000	849,365,000
Proceeds from sales of real estate															29,810,000	122,750,000	602,600,000
Gains on sales of real estate															7,663,000	80,606,000	375,895,000
Present value of expected net minimum lease payments					51,596,000									$ 51,596,000	51,596,000
30 Shattuck Road [Member]
Real Estate Properties [Line Items]
Contractual Sales Price				$ 5,000,000
Proceeds from sales of real estate				5,000,000
Gains on sales of real estate				$ 3,700,000
Area of Land | a				9.5
40 Shattuck Road [Member]
Real Estate Properties [Line Items]
Net Rentable Area | ft²			122,000										122,000
Operating Income (Loss)													$ (28,000)			(50,000)	300,000
Contractual Sales Price			$ 12,000,000										$ 12,000,000
Proceeds from sales of real estate			11,900,000
Gains on sales of real estate			28,000
Reston Eastgate [Member]
Real Estate Properties [Line Items]
Contractual Sales Price		$ 14,000,000
Proceeds from sales of real estate		13,200,000
Gains on sales of real estate		$ 2,800,000
Area of Land | a		21.7
145 Broadway
Real Estate Properties [Line Items]
Net Rentable Area | ft²																									485,000
Reservoir Place North [Member]
Real Estate Properties [Line Items]
Net Rentable Area | ft²																							73,000
103 Carnegie Center [Member] | 103 Carnegie Center [Member]
Real Estate Properties [Line Items]
Aggregate purchase price																								$ 15,800,000
Net Rentable Area | ft²																								96,000
Revenues														1,700,000
Operating Income (Loss)														$ (300,000)
6595 Springfield Center Drive (TSA Headquarters)
Real Estate Properties [Line Items]
Net Rentable Area | ft²																					634,000
Term of Lease Signed (in years) | yr																					15
888 Boylston Street [Member]
Real Estate Properties [Line Items]
Net Rentable Area | ft²																				417,000
191 Spring Street
Real Estate Properties [Line Items]
Net Rentable Area | ft²																			171,000
20 CityPoint
Real Estate Properties [Line Items]
Net Rentable Area | ft²																		211,000
2100 Pennsylvania Avenue [Member]
Real Estate Properties [Line Items]
Net Rentable Area | ft²	469,000
Ground Lease Term (in years) | yr	75
Term of Lease Signed (in years) | yr	16
Square Footage Of Signed Lease | ft²	288,000
MacArthur Transit Center [Member]
Real Estate Properties [Line Items]
Term of Lease Signed (in years) | yr																						99
Number of apartment units | apartments																						402
Present value of expected net minimum lease payments																						$ 28,962,000
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Revenues					$ 655,229,000	$ 657,712,000	$ 656,907,000	$ 632,228,000	$ 636,061,000	$ 625,228,000	$ 623,546,000	$ 665,985,000			2,602,076,000	2,550,820,000	2,490,821,000
Operating Income (Loss)															916,250,000	837,411,000	857,358,000
Proceeds from sales of real estate															29,810,000	122,750,000	602,600,000
Gains on sales of real estate															$ 8,240,000	$ 82,775,000	$ 377,093,000
Boston Properties Limited Partnership | 40 Shattuck Road [Member]
Real Estate Properties [Line Items]
Gains on sales of real estate			$ 600,000
Consolidated Properties [Member] | Salesforce Tower [Member]
Real Estate Properties [Line Items]
Net Rentable Area | ft²	1,400,000
Ownership Percentage by Parent	95.00%

Real Estate Future minimum paym

Real Estate Future minimum payments for MacArthur Transit capital lease (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 29, 2017
Capital Leased Assets [Line Items]
2,018	$ 1,392
2,019	2,097
2,020	1,375
2,021	930
Thereafter	74,185
Total expected minimum lease payments	80,892
Interest portion	29,296
Present value of expected net minimum lease payments	$ 51,596
MacArthur Transit Center [Member]
Capital Leased Assets [Line Items]
Period from June 29, 2017 through December 31, 2017		$ 5
2,018		10
2,019		10
2,020		10
2,021		13
Thereafter		38,778
Total expected minimum lease payments		38,826
Interest portion		9,864
Present value of expected net minimum lease payments		$ 28,962

Real Estate Real Estate Activit

Real Estate Real Estate Activity Purchase Price Allocation (Details) - 103 Carnegie Center [Member] $ in Thousands	May 15, 2017USD ($)
Business Acquisition [Line Items]
Land	$ 2,890
Building and improvements	11,229
Tenant Improvements	871
In-place lease Intangibles	2,389
Below-market lease intangible	(1,426)
Net assets acquired	$ 15,953

Real Estate Real Estate Intangi

Real Estate Real Estate Intangible Assets Amortization Table (Details) - USD ($) $ in Thousands	Dec. 31, 2017	May 15, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
2,018	$ 27,333
2,019	14,464
2,020	8,777
2,021	$ 4,758
103 Carnegie Center [Member] | Acquired in-place lease intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Period from May 15, 2017 through December 31, 2017		$ 660
2,018		590
2,019		367
2,020		243
2,021		96
103 Carnegie Center [Member] | Acquired below-mark lease intangible
Acquired Finite-Lived Intangible Assets [Line Items]
Period from May 15, 2017 through December 31, 2017		(248)
2,018		(363)
2,019		(337)
2,020		(308)
2,021		$ (105)

Deferred Charges (Details)

Deferred Charges (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Charges [Abstract]
Leasing costs, including lease related intangibles	$ 1,147,181	$ 1,132,092
Financing costs	14,991	6,094
Deferred charges, gross	1,162,172	1,138,186
Less: Accumulated amortization	(483,134)	(452,023)
Deferred charges, total	$ 679,038	$ 686,163

Deferred Charges Schedule of Ac

Deferred Charges Schedule of Acquired In-Place Lease Intangibles (Details) $ in Thousands	Dec. 31, 2017USD ($)
Deferred Charges [Abstract]
2,018	$ 33,651
2,019	27,333
2,020	14,464
2,021	8,777
2,022	$ 4,758

Investments in Unconsolidated63

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2017USD ($)ft²Land_ParcelsBuildingspayments	Sep. 06, 2017	Dec. 31, 2016USD ($)
Schedule of Equity Method Investments [Line Items]
Other Liabilities		$ 443,980		$ 450,821
Investments in unconsolidated joint ventures		619,925		775,198
Investments In Affiliates Subsidiaries Associates And Joint Ventures net	[1]	593,980		753,111
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Other Liabilities		$ 25,900		22,100
Square 407 Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Market Square North
Ownership Percentage		50.00%
Other Liabilities	[1]	$ 8,258		8,134
The Metropolitan Square Associates LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Metropolitan Square
Ownership Percentage		20.00%
Investments in unconsolidated joint ventures	[1]	$ 3,339		2,004
BP/CRF 901 New York Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		901 New York Avenue
Ownership Percentage	[2]	25.00%
Other Liabilities	[1]	$ 13,811		10,564
WP Project Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Wisconsin Place Land and Infrastructure
Ownership Percentage	[3]	33.30%
Investments in unconsolidated joint ventures	[1]	$ 39,710		41,605
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Annapolis Junction
Ownership Percentage	[4]	50.00%
Investments in unconsolidated joint ventures	[1]	$ 18,381		20,539
Number of real estate properties | Buildings		4
Parcels of undeveloped land | Land_Parcels		2
540 Madison Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		540 Madison Avenue
Ownership Percentage		60.00%
Investments in unconsolidated joint ventures	[1]	$ 66,179		67,816
500 North Capitol Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		500 North Capitol Street, NW
Ownership Percentage		30.00%
Other Liabilities	[1]	$ 3,876		3,389
501 K Street LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		1001 6th Street
Ownership Percentage	[5]	50.00%
Investments in unconsolidated joint ventures	[1]	$ 42,657		42,528
Potential additonal payments to joint venture partner | payments		2
Minimum square footage to make a potential additional payment to joint venture partner (in sqft) | ft²		520,000
Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		The Hub on Causeway
Ownership Percentage		50.00%	50.00%
Investments in unconsolidated joint ventures	[1]	$ 67,120		29,869
Residential Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		The Hub on Causeway - Residential
Ownership Percentage	[6]	50.00%
Investments in unconsolidated joint ventures	[1]	$ 28,212		20,803
Hotel Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		The Hub on Causeway - Hotel
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 1,690		933
Entity Owning Land And Infrastructure Of Project [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		33.30%
1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		1265 Main Street
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 4,641		4,779
BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Dock 72 at the Brooklyn Navy Yard
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 72,104		33,699
CA-Colorado Center Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Colorado Center
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 254,440		$ 510,623
7750 Wisconsin Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		7750 Wisconsin Avenue
Ownership Percentage	[6]	50.00%
Investments in unconsolidated joint ventures	[1]	$ 21,452
[1]	Investments with deficit balances aggregating approximately $25.9 million and $22.1 million at December 31, 2017 and 2016, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[2]	The Company’s economic ownership has increased based on the achievement of certain return thresholds.
[3]	The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.
[4]	The joint venture owns four in-service buildings and two undeveloped land parcels.
[5]	Under the joint venture agreement for this land parcel, the partner will be entitled to up to two additional payments from the venture based on increases in total entitled square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.
[6]	This entity is a VIE (See Note 2).

Investments in Unconsolidated64

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
ASSETS
Real estate and development in process, net		$ 16,507,008	$ 15,925,028
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable, net		2,979,281	2,063,087
Other Liabilities		443,980	450,821
Total liabilities and equity / capital		19,372,233	18,851,643
Carying value of the Company's investment in unconsolidated joint ventures		619,925	775,198
Unconsolidated Joint Ventures [Member]
ASSETS
Real estate and development in process, net		1,768,996	1,519,217
Other assets		367,743	297,263
Total assets		2,136,739	1,816,480
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable, net		1,437,440	865,665
Other Liabilities		99,215	67,167
Members'/Partners' equity		600,084	883,648
Total liabilities and equity / capital		2,136,739	1,816,480
Company's share of equity		286,495	450,662
Basis differentials	[1]	307,485	302,449
Carying value of the Company's investment in unconsolidated joint ventures	[2]	593,980	753,111
Colorado Center [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Basis differentials		322,500	328,800
Unconsolidated Joint Ventures [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Other Liabilities		$ 25,900	$ 22,100
[1]	This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At December 31, 2017 and 2016, there was an aggregate basis differential of approximately $322.5 million and $328.8 million, respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities.
[2]	Investments with deficit balances aggregating approximately $25.9 million and $22.1 million at December 31, 2017 and 2016, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

Investments in Unconsolidated65

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 655,229	$ 657,712	$ 656,907	$ 632,228	$ 636,061	$ 625,228	$ 623,546	$ 665,985	$ 2,602,076		$ 2,550,820		$ 2,490,821
Expenses
Depreciation and amortization										617,547		694,403		639,542
Total expenses										1,693,966		1,725,036		1,641,456
Operating income										908,110		825,784		849,365
Other income (expense)
Interest expense										(374,481)		(412,849)		(432,196)
Net income										562,481		569,977		799,918
Income from unconsolidated joint ventures										11,232		8,074		22,770
Gain on sale of investment in unconsolidated joint venture										0		59,370		0
Straight-line rent adjustments										54,800		31,700		80,000
Mortgage and notes payable, net		2,979,281				2,063,087				2,979,281		2,063,087
Above and below market rent adjustments, net										23,500		30,200		35,900
Gain on sale of investment in unconsolidated joint venture										0		55,707		0
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]									222,517		177,182		155,642
Expenses
Operating										90,542		76,741		65,093
Depreciation and amortization										57,079		44,989		36,057
Total expenses										147,621		121,730		101,150
Operating income										74,896		55,452		54,492
Other income (expense)
Interest expense										(46,371)		(34,016)		(32,176)
Net income										28,525		21,436		22,316
Company's share of net income										18,439		9,873		22,031	[2]
Basis differential										(7,207)	[3]	(1,799)	[3]	739
Income from unconsolidated joint ventures										11,232		8,074		22,770
Straight-line rent adjustments										21,700		18,100		3,900
Mortgage and notes payable, net		$ 1,437,440				$ 865,665				1,437,440		865,665
BP/CRF 901 New York Avenue LLC [Member]
Other income (expense)
Mortgage and notes payable, net														225,000
Gain on sale of investment in unconsolidated joint venture														$ 24,500
Colorado Center [Member]
Other income (expense)
Straight-line rent adjustments										1,900		1,400
Above and below market rent adjustments, net										$ 2,900		$ 900
[1]	Includes straight-line rent adjustments of approximately $21.7 million, $18.1 million and $3.9 million for the years ended December 31, 2017, 2016 and 2015, respectively.
[2]	During the year ended December 31, 2015, the Company received a distribution of approximately $24.5 million, which was generated from the excess loan proceeds from the refinancing of 901 New York Avenue’s mortgage loan to a new 10-year mortgage loan totaling $225.0 million. The Company’s allocation of income and distributions for the year ended December 31, 2015 was not proportionate to its nominal ownership interest as a result of the achievement of specified investment return thresholds, as provided for in the joint venture agreement.
[3]	Includes straight-line rent adjustments of approximately $1.9 million and $1.4 million for the years ended December 31, 2017 and 2016, respectively. Also includes net above-/below-market rent adjustments of approximately $2.9 million and $0.9 million for the years ended December 31, 2017 and 2016, respectively.

Investment in unconsolidated Jo

Investment in unconsolidated Joint Ventures (Narrative) (Details) $ in Thousands	Sep. 06, 2017USD ($)ft²	Aug. 07, 2017USD ($)ft²yr	Jul. 28, 2017USD ($)ft²aVehiclesBuildings	Jul. 10, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 01, 2017ft²apartments
Schedule of Equity Method Investments [Line Items]
Proceeds from Issuance of Secured Debt					$ 2,300,000	$ 0	$ 0
Payments to Acquire Equity Method Investments					109,015	575,795	38,207
Capital distributions from unconsolidated joint ventures					251,000	20,440	24,527
Restricted Cash and Cash Equivalents, Current					$ 70,602	63,174
Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area | ft²	385,000
Ownership Percentage	50.00%				50.00%
Colorado Center [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area | ft²			1,118,000
Vehicles In Structured Parking | Vehicles			3,100
Ownership Percentage				50.00%
number of buildings | Buildings			6
Area of Land | a			15
7750 Wisconsin Avenue [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area | ft²		733,000
Term of Lease Signed (in years) | yr		20
Ownership Percentage		50.00%
Payments and improvements for equity method investments		$ 20,800
Restricted Cash and Cash Equivalents, Current		25,000
The Hub on Causeway - Residential [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area | ft²								320,000
Ownership Percentage								50.00%
Number of apartment units | apartments								440
Boston Properties Limited Partnership
Schedule of Equity Method Investments [Line Items]
Proceeds from Issuance of Secured Debt					$ 2,300,000	0	0
Payments to Acquire Equity Method Investments					109,015	575,795	38,207
Capital distributions from unconsolidated joint ventures					251,000	20,440	$ 24,527
Restricted Cash and Cash Equivalents, Current					$ 70,602	$ 63,174
Joint venture partner [Member] | 7750 Wisconsin Avenue [Member]
Schedule of Equity Method Investments [Line Items]
Contribution of Property		72,000
Payments and improvements for equity method investments		4,900
Capital distributions from unconsolidated joint ventures		$ 11,000
Secured Debt [Member] | Colorado Center [Member]
Schedule of Equity Method Investments [Line Items]
Coupon/Stated Rate			3.56%
Proceeds from Issuance of Secured Debt			$ 550,000
Capital distributions from unconsolidated joint ventures			502,000
Secured Debt [Member] | Boston Properties Limited Partnership | Colorado Center [Member]
Schedule of Equity Method Investments [Line Items]
Capital distributions from unconsolidated joint ventures			$ 251,000
Secured Debt [Member] | Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Construction Loan Facility Borrowing Capacity	$ 204,600
Debt Instrument, Basis Spread on Variable Rate	2.25%
Number of extensions	2
Extension Option (in years)	1
Colorado Center [Member] | Colorado Center [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage				0.20%
Payments to Acquire Equity Method Investments				$ 2,100

Mortgage Notes Payable, Net, 67

Mortgage Notes Payable, Net, Mezzanine Notes Payable and Outside Members’ Notes Payable Schedule Of Aggregate Principal Payments On Mortgage Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Mortgage Notes Payable [Abstract]
2,018	$ 18,633
2,019	19,670
2,020	20,766
2,021	40,182
2,022	614,710
Thereafter	2,300,000
Total	3,013,961
Deferred finance costs, net	(34,680)
Total carrying value of mortgage notes payable, net	$ 2,979,281	$ 2,063,087

Mortgage Notes Payable, Net, 68

Mortgage Notes Payable, Net, Mezzanine Notes Payable and Outside Members’ Notes Payable (Narrative) (Details) $ in Thousands	Jun. 07, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2008USD ($)	Jun. 06, 2017USD ($)	Apr. 24, 2017USD ($)
Mortgage Notes Payable [Line Items]
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)		$ 2,979,281	$ 2,063,087
Proceeds from Issuance of Secured Debt		2,300,000	0	$ 0
Repayments of Secured Debt		1,317,653	1,326,865	54,801
Repayments of Subordinated Debt		306,000	0	0
Other Notes Payable		0	180,000
Interest Payable		83,646	243,933
Gains (losses) from early extinguishments of debt		$ 496	$ (371)	(22,040)
Number Of Mortgage Loans Accounted For Fair Value		0	1
Mortgage Loans Accounted For At Fair Value Upon Assumption			$ 1,300,000
Interest Expense Decrease Due To Recording Mortgage Loans At Fair Value		$ 19,600	46,400	$ 55,000
Cumulative Liability Related to the Fair Value of Debt Adjustment			$ 33,800
Minimum [Member]
Mortgage Notes Payable [Line Items]
Coupon/Stated Rate		3.43%	4.75%
Number Real Estate Assets Used For Mortgage Loan Collateral		1
Maximum [Member]
Mortgage Notes Payable [Line Items]
Coupon/Stated Rate		7.69%	7.69%
Fixed Rate Mortgages [Member]
Mortgage Notes Payable [Line Items]
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)		$ 3,000,000	$ 2,100,000
Debt, Weighted Average Interest Rate		3.78%	5.59%
Variable Rate Mortgages [Member]
Mortgage Notes Payable [Line Items]
Number of variable rate mortgage loans		0	0
767 Fifth Avenue (the general motors building) [Member]
Mortgage Notes Payable [Line Items]
Gains (losses) from early extinguishments of debt	$ 14,600
767 Fifth Avenue (the general motors building) [Member] | Notes Payable, Other Payables [Member]
Mortgage Notes Payable [Line Items]
Repayment of a portion of members loans accrued interest and principal balance	176,100
767 Fifth Avenue (the general motors building) [Member] | Secured Debt [Member]
Mortgage Notes Payable [Line Items]
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)							$ 2,300,000
Coupon/Stated Rate							3.43%
Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member]
Mortgage Notes Payable [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity	$ 273,900
Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member] | Junior Subordinated Debt [Member]
Mortgage Notes Payable [Line Items]
Coupon/Stated Rate	6.02%
Other Long-term Debt	$ 294,000
Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member] | Notes Payable, Other Payables [Member]
Mortgage Notes Payable [Line Items]
Coupon/Stated Rate	11.00%
Other Notes Payable	$ 450,000
Interest Payable	$ 425,000
Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member] | Secured Debt [Member]
Mortgage Notes Payable [Line Items]
Ownership Percentage by Parent	60.00%
Proceeds from Issuance of Secured Debt	$ 2,300,000
Coupon/Stated Rate	3.43%					5.95%
Repayments of Secured Debt	$ 1,300,000
Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member] | Subordinated Debt [Member]
Mortgage Notes Payable [Line Items]
Coupon/Stated Rate	6.02%
Repayments of Subordinated Debt	$ 306,000
Consolidated Properties [Member] | 767 Fifth Avenue (the general motors building) [Member]
Mortgage Notes Payable [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity						$ 273,900
Ownership Percentage by Parent						60.00%
Consolidation, Eliminations [Member] | 767 Fifth Avenue (the general motors building) [Member] | Junior Subordinated Debt [Member]
Mortgage Notes Payable [Line Items]
Repayments of Other Long-term Debt					$ 263,100
Consolidation, Eliminations [Member] | Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member]
Mortgage Notes Payable [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity	164,400
Consolidation, Eliminations [Member] | Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member] | Notes Payable, Other Payables [Member]
Mortgage Notes Payable [Line Items]
Other Notes Payable	270,000
Interest Payable	255,000
Consolidation, Eliminations [Member] | Consolidated Properties [Member] | 767 Fifth Avenue (the general motors building) [Member]
Mortgage Notes Payable [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity						$ 164,400
Boston Properties, Inc. [Member] | Consolidated Entities [Member] | 767 Fifth Avenue (the general motors building) [Member] | Notes Payable, Other Payables [Member]
Mortgage Notes Payable [Line Items]
Other Notes Payable	180,000
Interest Payable	$ 170,000

Derivative and Hedging Instru69

Derivative and Hedging Instruments (Details) $ in Thousands	Apr. 24, 2017USD ($)	Aug. 17, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)yrswaps	Dec. 31, 2015USD ($)
Derivative [Line Items]
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)			$ 2,979,281	$ 2,063,087
Other liabilities			(44,914)	(106,022)	$ (34,005)
Losses from interest rate contracts			$ 0	$ (140)	0
Boston Properties Limited Partnership | Interest Rate Swap [Member]
Derivative [Line Items]
Number of interest rate swap agreements entered into | swaps				17
Term of anticipated mortgage loan (in years) | yr				10
Derivative, Average Fixed Interest Rate				2.423%
Derivative, Notional Amount				$ 550,000
767 Fifth Partners LLC [Member]
Derivative [Line Items]
Ownership Percentage by Parent			60.00%
767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Number of interest rate swap agreements entered into | swaps				16
Derivative, Average Fixed Interest Rate				2.619%
Derivative, Notional Amount				$ 450,000
Derivative Asset, Notional Amount				100,000
Derivative Liability, Notional Amount				350,000
Other liabilities	$ 14,400
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	14,400
Derivative instrument, yearly amount reclassed to interest expense	1,400
Boston Properties Limited Partnership
Derivative [Line Items]
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)			$ 2,979,281	2,063,087
Other liabilities			(44,914)	(106,022)	(34,005)
Losses from interest rate contracts			$ 0	$ (140)	$ 0
Boston Properties Limited Partnership | Interest Rate Swap [Member]
Derivative [Line Items]
Other liabilities		$ 49,300
Losses from interest rate contracts		(100)
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion		49,200
Derivative instrument, yearly amount reclassed to interest expense		$ 4,900
Unsecured Senior Note 3.495% | Senior Notes [Member] | Boston Properties Limited Partnership
Derivative [Line Items]
Coupon/Stated Rate		2.75%	2.75%
767 Fifth Avenue (the general motors building) [Member] | Secured Debt [Member]
Derivative [Line Items]
Mortgage notes payable, net (amounts related to VIEs of $2,939,183 and $2,018,483 at December 31, 2017 and 2016, respectively)	$ 2,300,000
Coupon/Stated Rate	3.43%

Derivative and Hedging Instru70

Derivative and Hedging Instruments Derivative Instrument and Hedging Activities Notional Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value	$ (6,133)	$ (47,144)	$ (10,302)
Boston Properties Limited Partnership | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount		550,000
767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Liability, Notional Amount		350,000
Derivative Asset, Notional Amount		100,000
Derivative, Notional Amount		450,000
Fair Value		(8,264)
Other Liabilities [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value		$ (8,773)
Other Liabilities [Member] | Minimum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fixed Interest Rate		2.418%
Other Liabilities [Member] | Maximum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fixed Interest Rate		2.95%
Prepaid Expenses and Other Assets [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value		$ 509
Prepaid Expenses and Other Assets [Member] | Minimum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fixed Interest Rate		2.336%
Prepaid Expenses and Other Assets [Member] | Maximum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fixed Interest Rate		2.388%

Derivative and Hedging Instru71

Derivative and Hedging Instruments Derivative Instruments and Hedging Activities Gain or Loss Recognized Related to Cash Flow Hedges (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Losses from interest rate contracts		$ 0	$ (140)	$ 0
Amount of loss related to the effective portion recognized in other comprehensive loss		(6,133)	(47,144)	(10,302)
Amount of loss related to the effective portion subsequently reclassified to earnings (1)	[1]	(6,033)	(3,751)	(2,510)
Amount of loss related to the ineffective portion and amount excluded from effectiveness testing		$ 0	(140)	$ 0
Prior hedge program [Member]
Derivative [Line Items]
Losses from interest rate contracts			$ (200)
[1]	During the year ended December 31, 2016, the Company accelerated the reclassification of amounts in other comprehensive loss to earnings as a result of the hedged forecasted transactions becoming probable not to occur. The accelerated amounts were a loss of approximately $0.2 million and are included in the table above.

Derivative and Hedging Instru72

Derivative and Hedging Instruments Derivative Instruments and Hedging Activities Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Beginning Balance		$ (52,251)	$ (14,114)	$ (9,304)
Effective portion of interest rate contracts		(6,133)	(47,144)	(10,302)
Amortization of interest rate contracts	[1]	6,033	3,751	2,510
Other comprehensive loss attributable to noncontrolling interests		1,922	5,256	2,982
Ending Balance		(50,429)	(52,251)	(14,114)
Boston Properties Limited Partnership
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Beginning Balance		(60,853)	(18,337)	(12,973)
Effective portion of interest rate contracts		(6,133)	(47,144)	(10,302)
Amortization of interest rate contracts	[2]	6,033	3,751	2,510
Other comprehensive loss attributable to noncontrolling interests		2,128	877	2,428
Ending Balance		$ (58,825)	$ (60,853)	$ (18,337)
[1]	Amounts reclassified from comprehensive income primarily to interest expense within Boston Properties, Inc.’s Consolidated Statements of Operations
[2]	Amounts reclassified from comprehensive income primarily to interest expense within Boston Properties Limited Partnership's Consolidated Statements of Operations.

Unsecured Senior Notes Schedule

Unsecured Senior Notes Schedule of Unsecured Senior Notes (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 04, 2017	Dec. 31, 2016	Aug. 17, 2016
Debt Instrument [Line Items]
Deferred finance costs, net		$ (34,680)
Total		7,247,330			$ 7,245,953
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Deferred finance costs, net		(34,700)
Total		7,247,330			$ 7,245,953
Boston Properties Limited Partnership | Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount		7,300,000
Net unamortized discount		(17,894)
Deferred finance costs, net		(34,776)
Total		$ 7,247,330
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 5.967%
Debt Instrument [Line Items]
Coupon/Stated Rate		5.875%
Effective Rate	[1]	5.967%
Principal Amount		$ 700,000
Maturity date	[2]	Oct. 15, 2019
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 5.708%
Debt Instrument [Line Items]
Coupon/Stated Rate		5.625%
Effective Rate	[1]	5.708%
Principal Amount		$ 700,000
Maturity date	[2]	Nov. 15, 2020
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 4.289%
Debt Instrument [Line Items]
Coupon/Stated Rate		4.125%
Effective Rate	[1]	4.289%
Principal Amount		$ 850,000
Maturity date	[2]	May 15, 2021
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 3.954%
Debt Instrument [Line Items]
Coupon/Stated Rate		3.85%
Effective Rate	[1]	3.954%
Principal Amount		$ 1,000,000
Maturity date	[2]	Feb. 1, 2023
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 3.279%
Debt Instrument [Line Items]
Coupon/Stated Rate		3.125%
Effective Rate	[1]	3.279%
Principal Amount		$ 500,000
Maturity date	[2]	Sep. 1, 2023
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 3.916%
Debt Instrument [Line Items]
Coupon/Stated Rate		3.80%
Effective Rate	[1]	3.916%
Principal Amount		$ 700,000
Maturity date	[2]	Feb. 1, 2024
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 3.35% [Member]
Debt Instrument [Line Items]
Coupon/Stated Rate		3.20%		3.20%
Effective Rate		3.35%	[1]	3.35%
Principal Amount		$ 850,000
Maturity date	[2]	Jan. 15, 2025
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Note 3.766%
Debt Instrument [Line Items]
Coupon/Stated Rate		3.65%
Effective Rate	[1]	3.766%
Principal Amount		$ 1,000,000
Maturity date	[2]	Feb. 1, 2026
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Note 3.495%
Debt Instrument [Line Items]
Coupon/Stated Rate		2.75%				2.75%
Effective Rate	[1]	3.495%
Principal Amount		$ 1,000,000
Maturity date	[2]	Oct. 1, 2026
[1]	Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs.
[2]	No principal amounts are due prior to maturity.

Unsecured Senior Notes Unsecure

Unsecured Senior Notes Unsecured Senior Notes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 17, 2017	Dec. 04, 2017	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Loss on Extinguishment of Debt			$ (496)		$ 371	$ 22,040
Repayments of Unsecured Debt			848,020		0	0
Proceeds from unsecured senior notes			$ 847,935		1,989,790	0
Senior Notes [Member]
Debt Instrument [Line Items]
Maximum Leverage Ratio			60.00%
Maximum Secured Debt Leverage Ratio			50.00%
Minimum Interest Coverage Ratio			1.50
Minimum Unencumbered Asset Value Percentage Of Unsecured Debt			150.00%
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Loss on Extinguishment of Debt			$ (496)		371	22,040
Repayments of Unsecured Debt			848,020		0	0
Proceeds from unsecured senior notes			847,935		$ 1,989,790	$ 0
Boston Properties Limited Partnership | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 7,300,000
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 3.35% [Member]
Debt Instrument [Line Items]
Coupon/Stated Rate		3.20%	3.20%
Senior Notes Pricing		99.757%
Effective Rate		3.35%	3.35%	[1]
Proceeds from unsecured senior notes		$ 841,100
Debt Instrument, Face Amount		$ 850,000
Long-term Debt, Gross			$ 850,000
Boston Properties Limited Partnership | Senior Notes [Member] | Unsecured Senior Notes 3.853%
Debt Instrument [Line Items]
Debt Instrument, Increase, Accrued Interest	$ 2,800
Debt Instrument, Redemption Price, Percentage	101.49%
Loss on Extinguishment of Debt	$ 13,900
Redemption Premium	$ 12,700
Coupon/Stated Rate	3.70%
Repayments of Unsecured Debt	$ 865,500
Debt Instrument, Face Amount	$ 850,000
[1]	Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs.

Unsecured Credit Facility (Deta

Unsecured Credit Facility (Details) $ in Thousands	Apr. 24, 2017USD ($)mo	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)yr	Apr. 23, 2017USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding		$ 45,000	$ 45,000		$ 0
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 1,500,000			$ 1,000,000
Competitive bid quote	65.00%
Maximum Leverage Ratio		60.00%
Leverage Ratio Maximum Increasing Limit		65.00%
Leverage Ratio Reduction Limit		60.00%
Leverage Ratio Reduction Period, Years | yr			1
Maximum Secured Debt Leverage Ratio		55.00%
Fixed Charge Coverage Ratio Minimum.		1.40	1.40
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		1.75	1
Delayed Draw Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 500,000			$ 500,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.15%
Line of Credit Facility, Frequency of Commitment Fee Payment	4
minimum borrowing amount	$ 50,000
Maximum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.30%
Minimum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.10%
Current credit rating [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.15%
Interest Rate Based on LIBOR or CDOR [Member] | Maximum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	1.55%
Interest Rate Based on LIBOR or CDOR [Member] | Maximum [Member] | Delayed Draw Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	1.75%
Interest Rate Based on LIBOR or CDOR [Member] | Minimum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	0.775%
Interest Rate Based on LIBOR or CDOR [Member] | Minimum [Member] | Delayed Draw Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	0.85%
Interest Rate Based on LIBOR or CDOR [Member] | Current credit rating [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate		0.875%	0.875%
Interest Rate Based on LIBOR or CDOR [Member] | Current credit rating [Member] | Delayed Draw Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate		0.95%	0.95%
Alternative Base Interest Rate Calculation [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Amount added to Federal Funds Rate to Calculate Interest Rate	0.50%
LIBOR Period Used to Calculate Interest Rate (in months) | mo	1
Amount added to LIBOR to Calculate Interest Rate	1.00%
Alternative Base Interest Rate Calculation [Member] | Maximum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	0.55%
Alternative Base Interest Rate Calculation [Member] | Maximum [Member] | Delayed Draw Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	0.75%
Alternative Base Interest Rate Calculation [Member] | Minimum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	0.00%
Alternative Base Interest Rate Calculation [Member] | Minimum [Member] | Delayed Draw Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate	0.00%
Alternative Base Interest Rate Calculation [Member] | Current credit rating [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate		0.00%	0.00%
Alternative Base Interest Rate Calculation [Member] | Current credit rating [Member] | Delayed Draw Facility [Member]
Line of Credit Facility [Line Items]
Margin added to Calculated Interest Rate		0.00%	0.00%

Commitments And Contingencies (

Commitments And Contingencies (Details) - USD ($) $ in Millions	2 Months Ended	10 Months Ended	12 Months Ended
	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2009	Dec. 31, 2016	Dec. 31, 2015	Sep. 18, 2014	Jan. 10, 2014
Commitments And Contingencies [Line Items]
Letter of credit and performance obligations		$ 9.1	$ 9.1
Property insurance program per occurrence limits		1,000	1,000
Per occurrence limit for NBCR Coverage			1,000
Value of program trigger		140	$ 140
Coinsurance of program trigger			17.00%
Deductible in insurance as a percentage of the value of the affected property, San Francisco and Los Angeles			3.00%
Per occurrence limit of the earthquake insurance which covers San Francisco and Los Angeles regions	$ 170	240
Annual aggregate limit of the earthquake insurance which covers San Francisco and Los Angeles regions	170	240
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco and Los Angeles			$ 20
Earthquake Coverage Included In Builders Risk Policy For Below Grade improvements for Salesforce Tower	$ 60
767 Venture, LLC [Member]
Commitments And Contingencies [Line Items]
Maximum funding obligation		193.4	193.4
Property insurance program per occurrence limits		1,625	1,625
Lehman [Member]
Commitments And Contingencies [Line Items]
Bankruptcy claim, amount filed by general creditor				$ 45.3
Bankruptcy claim amount allowed by court to creditor								$ 45.2
Bankruptcy Claims, Amount of Claims Settled		0.4	0.4		$ 1.4	$ 8.1	$ 7.7
Bankruptcy remaining claim amount allowed by court to creditor		$ 27.6	27.6
601 Lexington Avenue
Commitments And Contingencies [Line Items]
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP			$ 250
767 Fifth Partners LLC [Member]
Commitments And Contingencies [Line Items]
Ownership Percentage by Parent		60.00%	60.00%
Boston Properties Limited Partnership
Commitments And Contingencies [Line Items]
Operating partnership guarantee to cover liabilities of IXP		$ 20	$ 20

Noncontrolling Interests (Narra

Noncontrolling Interests (Narrative) (Details)	Dec. 31, 2017shares
Noncontrolling Interest [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operating Partnership (OP) Units (in shares)	16,810,378
Boston Properties Limited Partnership | Noncontrolling Interest [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Long-Term Incentive Plan (LTIP) Units (in shares)	818,343
Boston Properties Limited Partnership | 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)	118,067
Boston Properties Limited Partnership | MYLTIP 2013
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP	85,405
Boston Properties Limited Partnership | MYLTIP 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP	25,107
Boston Properties Limited Partnership | MYLTIP 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIP	366,618
Boston Properties Limited Partnership | MYLTIP 2016 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIP	473,360
Boston Properties Limited Partnership | MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP	400,000

Noncontrolling Interests (Redee

Noncontrolling Interests (Redeemable Preferred Units) (Narrative) (Details) - Series Four Preferred Units [Member] - Noncontrolling Interest [Member] $ / shares in Units, $ in Millions	Jun. 25, 2015USD ($)$ / sharesshares
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Series Four Preferred Units Redeemed | shares	12,667
Redemption of Series Four Preferred Units | $	$ 0.6
Series Four Preferred Units Annual Dividend Payable Rate	2.00%
Preferred Units Liquidation Preference | $ / shares	$ 50

Noncontrolling Interests (Red79

Noncontrolling Interests (Redeemable Preferred Units) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	$ 0	$ 0	$ 6
Redemption of redeemable preferred units (Series Four Preferred Units)	$ 0	0	(633)
Redeemable Preferred Units [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning Balance		$ 0	633
Net income			6
Distributions			(6)
Redemption of redeemable preferred units (Series Four Preferred Units)			(633)
Ending Balance			$ 0

Noncontrolling Interests Redeem

Noncontrolling Interests Redeemable interest in property partnerships (narrative) (Details) - USD ($) $ in Thousands	Sep. 15, 2015	Aug. 06, 2015	Oct. 04, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Payments for Repurchase of Redeemable Noncontrolling Interest				$ 0	$ 0	$ 108,499
Fountain Square
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Aggregate purchase price			$ 385,000
Debt recorded upon consolidation			$ 211,300
Ownership Percentage	50.00%	50.00%	50.00%
Fixed Price to Acquire Remaining Portion of Joint venture		$ 100,900
Consideration paid			$ 87,000
Ownership Percentage by Parent			50.00%
Future Fixed Price to Acquire Remaining Portion of Joint venture			$ 102,000
Payments for Repurchase of Redeemable Noncontrolling Interest	$ 100,900
Mortgage debt assumed upon acquisition of noncontrolling interest	$ 105,600

Noncontrolling Interests Rede81

Noncontrolling Interests Redeemable Property Partnerships (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning Balance	$ 104,692
Net Loss	(7)
Distributions	(2,900)
Adjustment to reflect redeemable partnership units at redemption value	5,128
Acquisition of interest	(106,913)
Ending Balance	$ 0

(Common Units) (Narrative) (Det

(Common Units) (Narrative) (Details) $ / shares in Units, $ in Millions	Feb. 03, 2017USD ($)shares	Feb. 04, 2016USD ($)shares	Feb. 06, 2015USD ($)shares	Dec. 31, 2017USD ($)yrshares	Dec. 31, 2016shares	Dec. 29, 2017$ / shares	May 02, 2016shares
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Conversion of LTIP Units to OP Units (in units)							625,043
MYLTIP 2,014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target	27.70%
Value of MYLTIP Awards | $	$ 3.5
MYLTIP Units forfeited	447,386
2012 OPP and 2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Conversion of LTIP Units to OP Units (in units)							32,349
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)				495,637	190,857
Redemption of OP units issued on conversion of LTIP Units (in shares)				36,486	103,847
MYLTIP Units distribution as percentage of OP Unit distribution prior to measurement date				10.00%
Restriction on redemption of OP Unit to Common Stock (in years) | yr				1
Redemption of OP Unit equivalence to Common Stock (in shares)				1
Common units of operating partnership if converted value | $				$ 2,300
Closing price of common stock (in dollars per share) | $ / shares						$ 130.03
MYLTIP 2,013
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target		109.50%
Value of MYLTIP Awards | $		$ 13.5
MYLTIP Units forfeited		205,762
OPP Units 2012 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards earned | $			$ 32.1
Potential maximum amount of Outperformance Awards earned (percent)			80.00%
Potential Awards Earned | $			$ 40
2012 OPP Units forfeited			174,549
Boston Properties Limited Partnership | MYLTIP 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP				25,107
Boston Properties Limited Partnership | MYLTIP 2016 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIP				473,360
Boston Properties Limited Partnership | MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP				400,000
Boston Properties Limited Partnership | MYLTIP 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIP				366,618

Noncontrolling Interests Common

Noncontrolling Interests Common Units Distributions (Details) - Boston Properties Limited Partnership - $ / shares	Oct. 31, 2017	Jul. 31, 2017	Apr. 28, 2017	Jan. 30, 2017	Dec. 18, 2017
Noncontrolling Interest [Line Items]
Distributions Declared To OP And LTIP Units Per Unit					$ 0.80
Distributions Declared To MYLTIP Units Per Unit					$ 0.080
Distributions made to OP and LTIP units per unit (in dollars per share)	$ 0.75	$ 0.75	$ 0.75	$ 0.75
Distributions Made To MYLTIP Units Per Unit	$ 0.075	$ 0.075	$ 0.075	$ 0.075

Noncontrolling Interests Rede84

Noncontrolling Interests Redeemable common units of Boston Properties Limited Partnership (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Conversion of redeemable partnership units	$ 0	$ 0	$ 0
Cumulative effect of a change in accounting principle	(2,035)
Adjustment to reflect redeemable partnership units at redemption value			5,128
Boston Properties Limited Partnership
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Cumulative effect of a change in accounting principle	(272)
Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Conversion of redeemable partnership units	(22,879)	(15,374)	(17,137)
Cumulative effect of a change in accounting principle	(1,763)
Noncontrolling Interest [Member] | Boston Properties Limited Partnership
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning Balance	2,262,040	2,286,689	2,310,046
Contributions	31,743	31,395	39,030
Net income	52,210	59,260	66,951
Distributions	(54,494)	(49,087)	(69,447)
Conversion of redeemable partnership units	(16,916)	(6,461)	(14,343)
Unearned compensation	1,650	(3,464)	(4,579)
Cumulative effect of a change in accounting principle	(1,763)
Other Comprehensive Loss,	206	(4,379)	(554)
Adjustment to reflect redeemable partnership units at redemption value	17,587	(51,913)	(40,415)
Ending Balance	$ 2,292,263	$ 2,262,040	$ 2,286,689

Noncontrolling Interests (Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) $ in Thousands	May 12, 2016	Sep. 18, 2015USD ($)ft²	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jun. 06, 2017USD ($)	Dec. 10, 2015USD ($)
Noncontrolling Interest [Line Items]
Property partnerships			$ 1,683,760	$ 1,530,647
Proceeds from sales of real estate			29,810	122,750	$ 602,600
Gains on sales of real estate			7,663	80,606	375,895
505 9th Street [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Ownership Percentage by Parent		50.00%
Sale Price Of Sold Property		$ 318,000
Mortgage Loan Related to Property Sales		$ 117,000
Net Rentable Area | ft²		322,000
Proceeds from sales of real estate		$ 194,600
Gains on sales of real estate		199,500
Noncontroling interest for a dissolved entity relcassed to accounts payable and and accrued expenses				200			$ 4,100
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | 505 9th Street [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Proceeds from sales of real estate		97,300
Gains on sales of real estate		101,100
Boston Properties Limited Partnership
Noncontrolling Interest [Line Items]
Property partnerships			1,683,760	1,530,647
Proceeds from sales of real estate			29,810	122,750	602,600
Gains on sales of real estate			8,240	$ 82,775	$ 377,093
Boston Properties Limited Partnership | 505 9th Street [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Gains on sales of real estate		$ 199,700
Salesforce Tower | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Ownership Percentage	5.00%
Portion of project costs covered by a construction loan	50.00%
Portion of costs funded (in percentage)	50.00%
Debt Instrument, Basis Spread on Variable Rate	3.00%
Salesforce Tower | Boston Properties, Inc. [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Costs funded (in percentage)	2.50%
Preferred equity funded			$ 16,400
767 Fifth Avenue (the general motors building) [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Ownership Percentage by Parent						60.00%
Unpaid principal balance of the members' notes payable contributed to equity						$ 273,900
Property partnerships						109,600
Consolidation, Eliminations [Member] | 767 Fifth Avenue (the general motors building) [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity						$ 164,400

Noncontrolling Interests noncon

Noncontrolling Interests noncontrolling interests—property partnerships table (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Beginning Balance	$ 1,530,647,000
Capital contributions	161,585,000		$ 11,951,000	$ 2,705,000
Dissolution				(4,082,000)
Net income (loss)	47,832,000		(2,068,000)	149,855,000
Accumulated other comprehensive loss	(1,922,000)		(5,256,000)	(2,982,000)
Ending Balance	1,683,760,000		1,530,647,000
Property Partnerships Member
Noncontrolling Interest [Line Items]
Beginning Balance	1,530,647,000		1,574,400,000	1,602,467,000
Capital contributions	161,585,000	[1]	10,756,000	3,758,000
Dissolution				(4,082,000)
Net income (loss)	47,832,000		(2,068,000)	144,734,000
Accumulated other comprehensive loss	(2,128,000)		(877,000)	(2,428,000)
Distributions	(54,176,000)		(51,564,000)	(170,049,000)
Ending Balance	1,683,760,000		$ 1,530,647,000	$ 1,574,400,000
767 Fifth Avenue (the general motors building) [Member] | Property Partnerships Member
Noncontrolling Interest [Line Items]
Ending Balance	$ 109,576
[1]	Includes the contribution of the remaining unpaid principal balance of the members’ notes payable totaling $109,576 to equity in the consolidated entity that owns 767 Fifth Avenue (the General Motors Building).

Stockholders' Equity _ Partne87

Stockholders' Equity / Partners' Capital (Details) $ / shares in Units, $ in Millions	Jun. 02, 2017USD ($)yr	Dec. 31, 2017$ / sharesshares	Dec. 31, 2016$ / sharesshares	Dec. 31, 2015shares	Mar. 27, 2018$ / shares	Jun. 03, 2014USD ($)
Class of Stock [Line Items]
General Partners' Capital Account, Units Outstanding (in units)		1,719,540
Limited Partners' Capital Account, Units Outstanding		152,605,746
Common stock, shares outstanding		154,325,286	153,790,175
Shares of Common Stock issued upon the exercise of options to purchase Common Stock by certain employees		6,688	0	11,447
Shares of its Common Stock issued in connection with the redemption of an equal number of OP Units		495,637	190,857
ATM Program [Member]
Class of Stock [Line Items]
At the market stock offering program, aggregate value of common stock | $	$ 600					$ 600
At Market Stock Offering Program Maximum Length Of Sale In Years | yr	3
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding		80,000	80,000
Preferred Stock, Dividend Rate, Percentage		5.25%
Series B Liquidation Preference Per Share | $ / shares		$ 2,500	$ 2,500		$ 2,500
Depositary shares of Series B Cumulative Redeemable Preferred [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding		8,000,000
Series B Liquidation Preference Per Share | $ / shares		$ 25			$ 25
Boston Properties Limited Partnership
Class of Stock [Line Items]
General Partners' Capital Account, Units Outstanding (in units)		1,719,540	1,717,743
Limited Partners' Capital Account, Units Outstanding		152,605,746	152,072,432
Shares of its Common Stock issued in connection with the redemption of an equal number of OP Units		495,637	190,857	424,236
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding		80,000	80,000
Series B Liquidation Preference Per Share | $ / shares		$ 2,500	$ 2,500

Stockholders' Equity _ Partne88

Stockholders' Equity / Partners' Capital Dividends / Distributions (Details) - $ / shares	Nov. 15, 2017	Oct. 31, 2017	Aug. 15, 2017	Jul. 31, 2017	May 15, 2017	Apr. 28, 2017	Feb. 15, 2017	Jan. 30, 2017	Dec. 18, 2017	Dec. 31, 2015
Dividends / Distributions [Line Items]
Special dividend / distribution (per share / common unit amount)										$ 1.25
Common Stock / Unit, Dividends / Distributions, Per Share / Unit, Cash Paid		$ 0.75		$ 0.75		$ 0.75		$ 0.75
Dividends Payable, Amount Per Share / Unit									$ 0.80
Boston Properties Limited Partnership
Dividends / Distributions [Line Items]
Common Stock / Unit, Dividends / Distributions, Per Share / Unit, Cash Paid		$ 0.75		$ 0.75		$ 0.75		$ 0.75
Dividends Payable, Amount Per Share / Unit									0.80
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Dividends / Distributions [Line Items]
Common Stock / Unit, Dividends / Distributions, Per Share / Unit, Cash Paid	$ 32.8125		$ 32.8125		$ 32.8125		$ 32.8125
Dividends Payable, Amount Per Share / Unit									$ 32.8125

Stockholders' Equity _ Partne89

Stockholders' Equity / Partners' Capital Partners' Capital Changes in Issued and Outstanding Partners' Capital Units (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Limited Partners' Capital Account [Line Items]
Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units	495,637	190,857
Limited Partners' Ending Balance	152,605,746
General Partners' Ending Balance	1,719,540
Boston Properties Limited Partnership
Limited Partners' Capital Account [Line Items]
General Partners' Beginning Balance	1,717,743
Limited Partners Beginning Balance	152,072,432
Partners' Capital Beginning Balance	153,790,175	153,579,966	153,113,945
Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan	6,317	5,695	6,199
Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net	33,157	13,657	35,586
Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units	495,637	190,857	424,236
Limited Partners' Ending Balance	152,605,746	152,072,432
Partners' Capital Ending Balance	154,325,286	153,790,175	153,579,966
General Partners' Ending Balance	1,719,540	1,717,743
Boston Properties Limited Partnership | General Partner [Member]
Limited Partners' Capital Account [Line Items]
General Partners' Beginning Balance	1,717,743	1,715,092	1,710,644
Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan	21	72	59
Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net	111	172	340
Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units	1,665	2,407	4,049
General Partners' Ending Balance	1,719,540	1,717,743	1,715,092
Boston Properties Limited Partnership | Limited Partner [Member]
Limited Partners' Capital Account [Line Items]
Limited Partners Beginning Balance	152,072,432	151,864,874	151,403,301
Units issued to Boston Properties, Inc. related to Common Stock issued under the Employee Stock Purchase Plan	6,296	5,623	6,140
Units issued to Boston Properties, Inc. related to Common Stock issued under the Stock Option and Incentive Plan, net	33,046	13,485	35,246
Units issued to Boston Properties, Inc. related to Common Stock issued in exchange for OP Units	493,972	188,450	420,187
Limited Partners' Ending Balance	152,605,746	152,072,432	151,864,874

Stockholders' Equity _ Partne90

Stockholders' Equity / Partners' Capital Partners' Capital Change in Series B Preferred Units (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Entity Information [Line Items]
Beginning Balance	$ 200,000
Ending Balance	200,000	$ 200,000
Boston Properties Limited Partnership
Entity Information [Line Items]
Beginning Balance	193,623	193,623	$ 193,623
Net Income	10,500	10,500	10,500
Distributions	(10,500)	(10,500)	(10,500)
Ending Balance	$ 193,623	$ 193,623	$ 193,623

Future Minimum Rents Narrative

Future Minimum Rents Narrative (Details) - tenants	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Future Minimum Rent [Line Items]
Number Of Tenants Above Concentration Amount.	0	0	0
Concentration Risk, Percentage	10.00%	10.00%	10.00%
Maximum [Member]
Future Minimum Rent [Line Items]
Initial Term Lease Expiration Date	2,046

Future Minimum Rents Future min

Future Minimum Rents Future minimum rent under non-cancelable operating leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Future minimum rent [Abstract]
2,018	$ 1,962,841
2,019	1,998,102
2,020	1,920,002
2,021	1,783,066
2,022	1,596,719
Thereafter	$ 11,160,780

Segment Information (Schedule O

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income attributable to the Company's common shareholders / unitholders	$ 451,939	$ 502,285	$ 572,606
Preferred dividends / distributions	(10,500)	(10,500)	(10,500)
Noncontrolling interest-common units of the Operating Partnership	(52,210)	(59,260)	(66,951)
Noncontrolling interest - redeemable preferred units	0	0	(6)
Noncontrolling interest in property partnerships	(47,832)	2,068	(149,855)
Losses from interest rate contracts	0	(140)	0
Interest expense	(374,481)	(412,849)	(432,196)
Depreciation and amortization expense	(617,547)	(694,403)	(639,542)
Impairment loss	0	(1,783)	0
Transaction costs	(668)	(2,387)	(1,259)
General and administrative expense	(113,715)	(105,229)	(96,319)
Gains (losses) from early extinguishments of debt	(496)	371	22,040
Gains (losses) from investments in securities	(3,678)	(2,273)	653
Interest and other income	(5,783)	(7,230)	(6,777)
Gain on sale of investment in unconsolidated joint venture	0	(59,370)	0
Income from unconsolidated joint ventures	(11,232)	(8,074)	(22,770)
Development and management services income	(34,605)	(28,284)	(22,554)
Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income attributable to the Company's common shareholders / unitholders	451,939	502,285	572,606
Preferred dividends / distributions	10,500	10,500	10,500
Noncontrolling interest-common units of the Operating Partnership	52,210	59,260	66,951
Noncontrolling interest - redeemable preferred units	0	0	6
Noncontrolling interest in property partnerships	47,832	(2,068)	149,855
Losses from interest rate contracts	0	140	0
Interest expense	374,481	412,849	432,196
Depreciation and amortization expense	617,547	694,403	639,542
Impairment loss	0	1,783	0
Transaction costs	668	2,387	1,259
General and administrative expense	113,715	105,229	96,319
Gains on sales of real estate	7,663	80,606	375,895
Gains (losses) from early extinguishments of debt	496	(371)	(22,040)
Gains (losses) from investments in securities	3,678	2,273	(653)
Interest and other income	5,783	7,230	6,777
Gain on sale of investment in unconsolidated joint venture	0	59,370	0
Income from unconsolidated joint ventures	11,232	8,074	22,770
Development and management services income	34,605	28,284	22,554
Net Operating Income	1,605,435	1,601,302	1,563,931
Boston Properties Limited Partnership
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income attributable to the Company's common shareholders / unitholders	512,866	575,341	648,748
Preferred dividends / distributions	(10,500)	(10,500)	(10,500)
Noncontrolling interest - redeemable preferred units	0	0	(6)
Noncontrolling interest in property partnerships	(47,832)	2,068	(149,855)
Losses from interest rate contracts	0	(140)	0
Interest expense	(374,481)	(412,849)	(432,196)
Depreciation and amortization expense	(609,407)	(682,776)	(631,549)
Impairment loss	0	(1,783)	0
Transaction costs	(668)	(2,387)	(1,259)
General and administrative expense	(113,715)	(105,229)	(96,319)
Gains (losses) from early extinguishments of debt	(496)	371	22,040
Gains (losses) from investments in securities	(3,678)	(2,273)	653
Interest and other income	(5,783)	(7,230)	(6,777)
Gain on sale of investment in unconsolidated joint venture	0	(59,370)	0
Income from unconsolidated joint ventures	(11,232)	(8,074)	(22,770)
Development and management services income	(34,605)	(28,284)	(22,554)
Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income attributable to the Company's common shareholders / unitholders	512,866	575,341	648,748
Preferred dividends / distributions	10,500	10,500	10,500
Noncontrolling interest - redeemable preferred units	0	0	6
Noncontrolling interest in property partnerships	47,832	(2,068)	149,855
Losses from interest rate contracts	0	140	0
Interest expense	374,481	412,849	432,196
Depreciation and amortization expense	609,407	682,776	631,549
Impairment loss	0	1,783	0
Transaction costs	668	2,387	1,259
General and administrative expense	113,715	105,229	96,319
Gains on sales of real estate	8,240	82,775	377,093
Gains (losses) from early extinguishments of debt	496	(371)	(22,040)
Gains (losses) from investments in securities	3,678	2,273	(653)
Interest and other income	5,783	7,230	6,777
Gain on sale of investment in unconsolidated joint venture	0	59,370	0
Income from unconsolidated joint ventures	11,232	8,074	22,770
Development and management services income	34,605	28,284	22,554
Net Operating Income	$ 1,605,435	$ 1,601,302	$ 1,563,931

Segment Information (Schedule94

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	$ 2,505,272	$ 2,460,953	$ 2,403,338
Rental Revenue: Residential	16,596	16,699	18,883
Rental Revenue: Hotel	45,603	44,884	46,046
Rental Revenue Total	$ 2,567,471	$ 2,522,536	$ 2,468,267
Rental Revenue: % of Grand Totals	100.00%	100.00%	100.00%
Rental Expenses: Class A Office	$ 923,675	$ 882,692	$ 864,025
Rental Expenses: Residential	6,302	7,076	8,227
Rental Expenses: Hotel	32,059	31,466	32,084
Rental Expenses: Total	$ 962,036	$ 921,234	$ 904,336
Rental Expenses: % Of Grand Totals	100.00%	100.00%	100.00%
Net operating Income	$ 1,605,435	$ 1,601,302	$ 1,563,931
Net operating Income: % of Grand Totals	100.00%	100.00%	100.00%
Boston [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	$ 776,279	$ 727,265	$ 716,246
Rental Revenue: Residential	4,745	4,812	4,801
Rental Revenue: Hotel	45,603	44,884	46,046
Rental Revenue Total	$ 826,627	$ 776,961	$ 767,093
Rental Revenue: % of Grand Totals	32.20%	30.80%	31.08%
Rental Expenses: Class A Office	$ 301,097	$ 282,827	$ 287,341
Rental Expenses: Residential	2,044	2,708	2,006
Rental Expenses: Hotel	32,059	31,466	32,084
Rental Expenses: Total	$ 335,200	$ 317,001	$ 321,431
Rental Expenses: % Of Grand Totals	34.84%	34.41%	35.54%
Net operating Income	$ 491,427	$ 459,960	$ 445,662
Net operating Income: % of Grand Totals	30.61%	28.73%	28.50%
New York [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	$ 969,371	$ 1,012,518	$ 1,000,030
Rental Revenue: Residential	0	0	0
Rental Revenue: Hotel	0	0	0
Rental Revenue Total	$ 969,371	$ 1,012,518	$ 1,000,030
Rental Revenue: % of Grand Totals	37.75%	40.14%	40.52%
Rental Expenses: Class A Office	$ 372,810	$ 363,188	$ 346,897
Rental Expenses: Residential	0	0	0
Rental Expenses: Hotel	0	0	0
Rental Expenses: Total	$ 372,810	$ 363,188	$ 346,897
Rental Expenses: % Of Grand Totals	38.76%	39.42%	38.36%
Net operating Income	$ 596,561	$ 649,330	$ 653,133
Net operating Income: % of Grand Totals	37.15%	40.55%	41.76%
San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	$ 345,519	$ 318,609	$ 302,434
Rental Revenue: Residential	0	0	0
Rental Revenue: Hotel	0	0	0
Rental Revenue Total	$ 345,519	$ 318,609	$ 302,434
Rental Revenue: % of Grand Totals	13.46%	12.63%	12.25%
Rental Expenses: Class A Office	$ 105,253	$ 100,787	$ 98,206
Rental Expenses: Residential	0	0	0
Rental Expenses: Hotel	0	0	0
Rental Expenses: Total	$ 105,253	$ 100,787	$ 98,206
Rental Expenses: % Of Grand Totals	10.94%	10.94%	10.86%
Net operating Income	$ 240,266	$ 217,822	$ 204,228
Net operating Income: % of Grand Totals	14.97%	13.60%	13.06%
Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	$ 414,103	$ 402,561	$ 384,628
Rental Revenue: Residential	11,851	11,887	14,082
Rental Revenue: Hotel	0	0	0
Rental Revenue Total	$ 425,954	$ 414,448	$ 398,710
Rental Revenue: % of Grand Totals	16.59%	16.43%	16.15%
Rental Expenses: Class A Office	$ 144,515	$ 135,890	$ 131,581
Rental Expenses: Residential	4,258	4,368	6,221
Rental Expenses: Hotel	0	0	0
Rental Expenses: Total	$ 148,773	$ 140,258	$ 137,802
Rental Expenses: % Of Grand Totals	15.46%	15.23%	15.24%
Net operating Income	$ 277,181	$ 274,190	$ 260,908
Net operating Income: % of Grand Totals	17.27%	17.12%	16.68%

Earnings Per Share _ Common U95

Earnings Per Share / Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic Earnings:
Net income attributable to the Company's shareholders/unitholders (Numerator)									$ 451,939	$ 502,285	$ 572,606
Net income attributable to the Company in Shares / Units (Denominator)									154,190,000	153,715,000	153,471,000
Net income attributable to the Company's shareholders/unitholders (in dollars per share / unit)									$ 2.93	$ 3.27	$ 3.73
Allocation of undistributed earnings to participating securities (Numerator)										$ (283)
Allocation of undistributed earnings to participating securities (in shares) (Denominator)										0
Allocation of undistributed earnings to participating securities (in dollars per share / unit)										$ 0
Net income attributable to the Company Per Share / Unit Amount (in dollars per share / unit)	$ 0.67	$ 0.76	$ 0.87	$ 0.63	$ 0.96	$ 0.50	$ 0.63	$ 1.18	$ 2.93	$ 3.27	$ 3.73
Net Income Available To Common Stockholders After Allocation of Undistributed Earnings to Participating Securities Basic										$ 502,002
Weighted Average Number Of Shares Outstanding After Allocation of Undistributed Earnings to Participating Securities Basic (in shares)										153,715,000
Earnings Per Share After Allccation of Undistributed Earnings to Particiapting Securities Basic (dollars per share)										$ 3.27
Effect of Dilutive Securities:
Stock Based Compensation (Numerator)									$ 0	$ 0	$ 0
Stock Based Compensation, Shares / Units (Denominator)									200,000	262,000	373,000
Stock Based Compensation Per Share / Unit Amount									$ 0	$ (0.01)	$ (0.01)
Diluted Earnings:
Diluted Earnings: Net income attributable to the Company's shareholders/unitholdersIncome (Numerator)									$ 451,939	$ 502,002	$ 572,606
Diluted Earnings Net income attributable to the Company's shareholders/unitholders Shares / Units (Denominator)									154,390,000	153,977,000	153,844,000
Diluted Earnings: Net income, Per Share / Unit Amount (in dollars per share / unit)	0.67	0.76	0.87	0.63	0.96	0.50	0.63	1.18	$ 2.93	$ 3.26	$ 3.72
Boston Properties Limited Partnership
Redeemable Common Units									17,471,000	17,646,000	17,668,000
Basic Earnings:
Net income attributable to the Company's shareholders/unitholders (Numerator)									$ 512,866	$ 575,341	$ 648,748
Net income attributable to the Company in Shares / Units (Denominator)									171,661,000	171,361,000	171,139,000
Net income attributable to the Company's shareholders/unitholders (in dollars per share / unit)									$ 2.99	$ 3.36	$ 3.79
Allocation of undistributed earnings to participating securities (Numerator)										$ (316)
Allocation of undistributed earnings to participating securities (in shares) (Denominator)										0
Allocation of undistributed earnings to participating securities (in dollars per share / unit)										$ 0
Net income attributable to the Company Per Share / Unit Amount (in dollars per share / unit)	0.69	0.77	0.88	0.64	0.97	0.53	0.64	1.21	$ 2.99	$ 3.36	$ 3.79
Effect of Dilutive Securities:
Stock Based Compensation (Numerator)									$ 0	$ 0	$ 0
Stock Based Compensation, Shares / Units (Denominator)									200,000	262,000	373,000
Stock Based Compensation Per Share / Unit Amount									$ (0.01)	$ (0.01)	$ (0.01)
Diluted Earnings:
Diluted Earnings: Net income attributable to the Company's shareholders/unitholdersIncome (Numerator)									$ 512,866	$ 575,025	$ 648,748
Diluted Earnings Net income attributable to the Company's shareholders/unitholders Shares / Units (Denominator)									171,861,000	171,623,000	171,512,000
Diluted Earnings: Net income, Per Share / Unit Amount (in dollars per share / unit)	$ 0.68	$ 0.77	$ 0.88	$ 0.64	$ 0.97	$ 0.53	$ 0.64	$ 1.21	$ 2.98	$ 3.35	$ 3.78

Employee Benefit Plans (Details

Employee Benefit Plans (Details)	12 Months Ended			192 Months Ended	216 Months Ended
	Dec. 31, 2017USD ($)mo	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2016USD ($)yrage	Dec. 31, 2017USD ($)
Employee Benefit Plans [Abstract]
Eligibility Period For 401K Savings Plan In Months | mo	3
Employer Matching Contribution, Percent of Match					200.00%
Employer Matching Contribution, Percent of Employees' Gross Pay					3.00%
Maximum Eligible Earnings As Established By IRS For Matching Contributions	$ 270,000	$ 265,000	$ 265,000
Employer Contribution Amount	4,100,000	4,000,000	3,700,000
Years Of Service For Supplemental Retirement Contribution | yr				10
Age Of Employee For Supplemental Retirement Contribution | age				40
Annual Supplemental Retirement Contribution And Credit Total.	18,000	21,000	$ 42,000
Separate Unrestricted Cash For Deferred Compensation Plan.	29,200,000	23,800,000		$ 23,800,000	$ 29,200,000
Deferred Compensation Liability	$ 29,200,000	$ 23,800,000		$ 23,800,000	$ 29,200,000

Stock Option and Incentive Pl97

Stock Option and Incentive Plan (Narrative) (Details)	Feb. 03, 2017USD ($)shares	Jan. 25, 2017USD ($)yrtiers	Feb. 04, 2016USD ($)shares	Feb. 06, 2015USD ($)shares	May 15, 2012yrshares	Jan. 01, 2015USD ($)
MYLTIP 2,013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards			$ 13,500,000
MYLTIP Units forfeited | shares			205,762
Final awards percentage of target			109.50%
OPP Units 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned				$ 40,000,000
Outperformance awards earned				$ 32,100,000
Potential maximum amount of Outperformance Awards earned (percent)				80.00%
2012 OPP Units forfeited | shares				174,549
2012 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Additional Shares Authorized | shares					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 | yr					10
MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Tiers | tiers		4
TSR measurement (in years) | yr		3
Distributions percent before measurement date		10.00%
Indices Used to Compare TSR		2
Threshold Tier		$ 10,700,000
Target Tier		21,300,000
High Tier		32,000,000
Exceptional Tier		$ 42,700,000
Percentage of annualized TSR 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%
Value of MYLTIP Awards		$ 17,700,000
MYLTIP Value Amortized Into Earnings, Years | yr		4
MYLTIP 2,014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards	$ 3,500,000
MYLTIP Units forfeited | shares	447,386
Final awards percentage of target	27.70%
Minimum [Member] | MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		$ 0
Maximum [Member] | MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		$ 42,700,000
Board of Directors Chairman [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash Payment Related to Transition Agreement						$ 6,700,000
Target Equity Award Compensation Associated with Transition Agreement						$ 11,100,000
Cohen & Steers Realty Majors Portfolio Index [Member] | MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
NAREIT Office Index adjusted [Member] | MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
MYLTIP vesting 2020 [Member] | MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%
MYLTIP vesting 2021 | MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%

Stock Option and Incentive Pl98

Stock Option and Incentive Plan (Restricted Stock) (Narrative) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)VestingInstallmentsd$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	May 17, 2016shares	Jan. 01, 2015shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued	154,404,186	153,869,075		1,507
Stock-based compensation associated with restricted stock, non-qualified options, LTIP Units, 2012 OPP Units and 2013-2017 MYLTIP Units | $	$ 33,200	$ 30,600	$ 26,900
Value of shares of common stock | $	1,543	$ 1,538
Exercisable, Weighted Average Exercise Price | $ / shares		$ 96.32	$ 96.10
Total intrinsic value of the outstanding and exercisable stock options | $	$ 18,200
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued	37,414	22,067	34,150
Employee and director payment per share (in dollars per share) | $ / shares	$ 0.01
Value of shares of common stock | $	$ 4,900	$ 2,500	$ 4,800
Employee's weighted average cost per share (in dollars per share) | $ / shares	$ 130.32	$ 113.51	$ 140.88
LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of LTIP units issued | $	$ 13,600	$ 15,400	$ 13,500
Per unit fair value weighted-average (in dollars per share) | $ / shares	$ 119.41	$ 103.83	$ 128.94
Expected life assumed to calculate per unit fair value per LTIP unit (years)	5 years 8 months 12 days	5 years 8 months 12 days	5 years 8 months 12 days
Risk-free rate	2.14%	1.61%	1.47%
Expected price volatility	28.00%	33.00%	26.00%
Unvested Restricted stock, LTIP and 2013 - 2014 MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses | $	$ 19,200
LTIPs And Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting annual installments | VestingInstallments	4
Unvested 2015 - 2017 MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses | $	$ 21,000
Weighted-average period (years)	2 years 3 months 18 days
LTIPs, OPP and MYLTIP Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee and director payment per share (in dollars per share) | $ / shares	$ 0.25
MYLTIP 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued			375,000
MYLTIP 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued		475,004
Non-Qualified Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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 | d	10
Shares issued	6,317	5,695	6,199
Shares issued, weighted-average purchase price per share | $ / shares	$ 105.97	$ 109.27	$ 108.73
Boston Properties Limited Partnership | LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP units issued (in shares)	113,918	147,872	190,563
Boston Properties Limited Partnership | MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued	400,000
Boston Properties Limited Partnership | Non-executive Chairman of the Board of Directors [Member] | LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP units issued (in shares)					85,962

Stock Option and Incentive Pl99

Stock Option and Incentive Plan Schedule of Stock Options Status (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Outstanding, Shares	547,129	547,129	553,312
Beginning Oustanding, Weighted Average Exercise Price	$ 96.38	$ 96.38	$ 97.21
Exercised, Shares	(6,688)	0	(11,447)
Exercised, Weighted Averge Exercise Price	$ 99.15	$ 0	$ 92.50
Special dividend adjustment (shares)			5,264
Special dividend adjustment weighted average exercise price			$ 96.38
Ending Outstanding, Shares	540,441	547,129	547,129
Ending Oustanding, Weighted Average Exercise Pric	$ 96.35	$ 96.38	$ 96.38

Stock Option and Incentive P100

Stock Option and Incentive Plan Schedule of Stock Options Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number Outstanding at period end	540,441	547,129	547,129	553,312
Outstanding, Weighted Average Exercise Price	$ 96.35	$ 96.38	$ 96.38	$ 97.21
Number Exercisable		514,360	465,371
Exercisable, Weighted Average Exercise Price		$ 96.32	$ 96.10
Exercise Price of $86.86 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Remaining Contractual Life (Years)	3 years 1 month 6 days
Number Outstanding at period end	118,502
Outstanding, Weighted Average Exercise Price	$ 86.86
Number Exercisable	118,502
Exercisable, Weighted Average Exercise Price	$ 86.86
Exercise Price of $95.69 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Remaining Contractual Life (Years)	5 years 3 months 18 days
Number Outstanding at period end	54,282
Outstanding, Weighted Average Exercise Price	$ 95.69
Number Exercisable	54,282
Exercisable, Weighted Average Exercise Price	$ 95.69
Exercise Price of $98.46 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Remaining Contractual Life (Years)	5 years 1 month 6 days
Number Outstanding at period end	202,030
Outstanding, Weighted Average Exercise Price	$ 98.46
Number Exercisable	202,030
Exercisable, Weighted Average Exercise Price	$ 98.46
Exercise Price of $100.77 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Remaining Contractual Life (Years)	4 years 1 month 6 days
Number Outstanding at period end	165,627
Outstanding, Weighted Average Exercise Price	$ 100.77
Number Exercisable	165,627
Exercisable, Weighted Average Exercise Price	$ 100.77
Unvested 2015 - 2017 MYLTIP Units [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted-average period (years)	2 years 3 months 18 days

Related Party Transactions (Det

Related Party Transactions (Details)	12 Months Ended
	Dec. 31, 2017USD ($)nonemployeedirectorsshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)	May 17, 2016shares
Related Party Transaction [Line Items]
Number Of Non Employee Directors Electing To Receive Deferred Stock Units | nonemployeedirectors	5
Shares issued | shares	154,404,186	153,869,075		1,507
Deferred Stock Units Outstanding	105,479	99,035
Executive Vice President and New York regional manager [Member]
Related Party Transaction [Line Items]
Aggregate leasing commissions paid to related parties	$ 22,000	$ 315,000	$ 616,000
Brother of Senior Executive Vice President [Member]
Related Party Transaction [Line Items]
Aggregate leasing commissions paid to related parties	$ 368,000	$ 374,000	$ 384,000

Selected Interim Financial I102

Selected Interim Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total revenue	$ 655,229	$ 657,712	$ 656,907	$ 632,228	$ 636,061	$ 625,228	$ 623,546	$ 665,985	$ 2,602,076	$ 2,550,820	$ 2,490,821
Income before gains on sales of real estate	131,331	144,813	163,243	115,431	164,894	58,521	117,357	148,599	554,818	489,371	424,023
Net income attributable to the Company	$ 103,829	$ 117,337	$ 133,709	$ 97,083	$ 147,214	$ 76,753	$ 96,597	$ 181,747	$ 462,439	$ 512,785	$ 583,106
Income attributable to the Company (in dollars per share / unit) - Basic	$ 0.67	$ 0.76	$ 0.87	$ 0.63	$ 0.96	$ 0.50	$ 0.63	$ 1.18	$ 2.93	$ 3.27	$ 3.73
Income attributable to the Company (in dollars per share / unit) - Diluted	$ 0.67	$ 0.76	$ 0.87	$ 0.63	$ 0.96	$ 0.50	$ 0.63	$ 1.18	$ 2.93	$ 3.26	$ 3.72
Boston Properties Limited Partnership
Total revenue	$ 655,229	$ 657,712	$ 656,907	$ 632,228	$ 636,061	$ 625,228	$ 623,546	$ 665,985	$ 2,602,076	$ 2,550,820	$ 2,490,821
Income before gains on sales of real estate	133,285	146,767	165,328	117,578	167,384	63,687	119,341	150,586	562,958	500,998	432,016
Net income attributable to the Company	$ 117,667	$ 132,693	$ 151,844	$ 110,662	$ 166,801	$ 91,306	$ 109,938	$ 207,296	$ 523,366	$ 585,841	$ 659,248
Income attributable to the Company (in dollars per share / unit) - Basic	$ 0.69	$ 0.77	$ 0.88	$ 0.64	$ 0.97	$ 0.53	$ 0.64	$ 1.21	$ 2.99	$ 3.36	$ 3.79
Income attributable to the Company (in dollars per share / unit) - Diluted	$ 0.68	$ 0.77	$ 0.88	$ 0.64	$ 0.97	$ 0.53	$ 0.64	$ 1.21	$ 2.98	$ 3.35	$ 3.78

Subsequent Events subsequent Ev

Subsequent Events subsequent Events (Details)	Feb. 23, 2018ft²	Feb. 06, 2018USD ($)yrindicesshares	Feb. 04, 2018USD ($)shares	Feb. 02, 2018shares	Jan. 31, 2018ft²apartments	Jan. 24, 2018ft²	Jan. 09, 2018USD ($)ft²	Dec. 31, 2017shares	Dec. 31, 2016shares	May 17, 2016shares
Subsequent Event [Line Items]
Common stock, shares issued | shares								154,404,186	153,869,075	1,507
Subsequent Event [Member] | MYLTIP 2015 [Member]
Subsequent Event [Line Items]
Final awards percentage of target			22.00%
Value of MYLTIP Awards			$ 3,600,000
MYLTIP Units forfeited | shares			337,847
Subsequent Event [Member] | MYLTIPS 2018 [Member]
Subsequent Event [Line Items]
Target Tier		$ 16,200,000
Indices Used to Compare TSR | indices		2
Percentage of annualized TSR for Reduction of Earned Awards		0.00%
Percentage to Cause Some Awards to be Earned Even if on a Relative Basis it Would Not Result in any Earned Awards		12.00%
Distributions percent before measurement date		10.00%
Value of MYLTIP Awards		$ 13,300,000
MYLTIP Value Amortized Into Earnings, Years | yr		4
TSR measurement (in years) | yr		3
Subsequent Event [Member] | MYLTIPS 2018 [Member] | Cohen & Steers Realty Majors Portfolio Index [Member]
Subsequent Event [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
Subsequent Event [Member] | MYLTIPS 2018 [Member] | NAREIT Office Index adjusted [Member]
Subsequent Event [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
Subsequent Event [Member] | Minimum [Member] | MYLTIPS 2018 [Member]
Subsequent Event [Line Items]
Potential Awards Earned		$ 0
Subsequent Event [Member] | Maximum [Member] | MYLTIPS 2018 [Member]
Subsequent Event [Line Items]
Potential Awards Earned		$ 32,300,000
Subsequent Event [Member] | MYLTIP vesting 2021 | MYLTIPS 2018 [Member]
Subsequent Event [Line Items]
Vesting Percentage		50.00%
Subsequent Event [Member] | MYLTIP vesting 2022 | MYLTIPS 2018 [Member]
Subsequent Event [Line Items]
Vesting Percentage		50.00%
Subsequent Event [Member] | Restricted Stock [Member]
Subsequent Event [Line Items]
Common stock, shares issued | shares				18,226
Boston Properties Limited Partnership | Subsequent Event [Member] | LTIP Units [Member]
Subsequent Event [Line Items]
LTIP units issued (in shares) | shares		195,546
500 E Street | Subsequent Event [Member]
Subsequent Event [Line Items]
Net Contractual Sales Price							$ 118,600,000
Net Rentable Area | ft²							262,000
17Fifty Presidents Street [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Net Rentable Area | ft²						276,000
Signature at Reston | Subsequent Event [Member]
Subsequent Event [Line Items]
Net Rentable Area | ft²					515,000
Number of apartment units | apartments					508
Reston Gateway | Subsequent Event [Member]
Subsequent Event [Line Items]
Net Rentable Area | ft²	1,000,000
Square Footage Of Signed Lease | ft²	850,000

Real Estate and Accumulated 104

Real Estate and Accumulated Depreciation Schedule of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[1]	$ 2,979,281
Original Land		4,762,002
Original Building		11,634,050
Costs Capitalized Subsequent to Acquisition		4,662,662
Land and improvements		5,080,679
Buildings and Improvements		14,503,772
Land Held for Development	[2]	204,925
Development and Construction in Progress		1,269,338
Total		21,058,714
Accumulated Depreciation		4,566,570
Furniture, fixtures and equipment		37,928	$ 32,687
Furniture, fixtures and equipment accumulated depreciation		23,064
Real Estate Aggregate Cost For Tax Purposes		17,300,000
Real Estate Aggregate Accumulated Depreciation For Tax Purposes		$ 3,600,000
Real Estate and Accumulated Depreciation, Life Used for Depreciation		40 years
Unamortized deferred finance costs		$ (34,680)
767 Fifth Avenue (the General Motors Building)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		767 Fifth Avenue (the General Motors Building)
Type		Office
Location		New York, NY
Encumbrances		$ 2,267,041
Original Land		1,796,252
Original Building		1,532,654
Costs Capitalized Subsequent to Acquisition		135,559
Land and improvements		1,796,252
Buildings and Improvements		1,668,213
Land Held for Development		0
Development and Construction in Progress		0
Total		3,464,465
Accumulated Depreciation		$ 222,981
Year(s) Built / Renovated		1,968
Year(s) Acquired		2,013
Depreciable Lives (Years)	[3]	(1)
Prudential Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Prudential Center
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		92,077
Original Building		948,357
Costs Capitalized Subsequent to Acquisition		501,709
Land and improvements		115,638
Buildings and Improvements		1,426,505
Land Held for Development		0
Development and Construction in Progress		0
Total		1,542,143
Accumulated Depreciation		$ 511,605
Year(s) Built / Renovated		1965/1993/2002/2016-2017
Year(s) Acquired		1998/1999/2000
Depreciable Lives (Years)	[3]	(1)
Embarcadero Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Embarcadero Center
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		179,697
Original Building		847,410
Costs Capitalized Subsequent to Acquisition		366,780
Land and improvements		195,987
Buildings and Improvements		1,197,900
Land Held for Development		0
Development and Construction in Progress		0
Total		1,393,887
Accumulated Depreciation		$ 596,100
Year(s) Built / Renovated		1970/1989
Year(s) Acquired		1998-1999
Depreciable Lives (Years)	[3]	(1)
399 Park Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		399 Park Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		339,200
Original Building		700,358
Costs Capitalized Subsequent to Acquisition		181,418
Land and improvements		354,107
Buildings and Improvements		866,869
Land Held for Development		0
Development and Construction in Progress		0
Total		1,220,976
Accumulated Depreciation		$ 310,262
Year(s) Built / Renovated		1,961
Year(s) Acquired		2,002
Depreciable Lives (Years)	[3]	(1)
601 Lexington Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		601 Lexington Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 672,142
Original Land		241,600
Original Building		494,782
Costs Capitalized Subsequent to Acquisition		290,590
Land and improvements		289,639
Buildings and Improvements		634,134
Land Held for Development		0
Development and Construction in Progress		103,199
Total		1,026,972
Accumulated Depreciation		$ 254,932
Year(s) Built / Renovated		1977/1997
Year(s) Acquired		2,001
Depreciable Lives (Years)	[3]	(1)
200 Clarendon Street and Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		200 Clarendon Street and Garage
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		219,543
Original Building		667,884
Costs Capitalized Subsequent to Acquisition		139,189
Land and improvements		219,616
Buildings and Improvements		799,991
Land Held for Development		7,009
Development and Construction in Progress		0
Total		1,026,616
Accumulated Depreciation		$ 161,471
Year(s) Built / Renovated		1,976
Year(s) Acquired		2,010
Depreciable Lives (Years)	[3]	(1)
250 West 55th Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		250 West 55th Street
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		285,263
Original Building		603,167
Costs Capitalized Subsequent to Acquisition		43,296
Land and improvements		285,263
Buildings and Improvements		646,463
Land Held for Development		0
Development and Construction in Progress		0
Total		931,726
Accumulated Depreciation		$ 72,058
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
Carnegie Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Carnegie Center
Type		Office
Location		Princeton, NJ
Encumbrances		$ 0
Original Land		107,997
Original Building		389,359
Costs Capitalized Subsequent to Acquisition		157,960
Land and improvements		108,948
Buildings and Improvements		543,514
Land Held for Development		2,854
Development and Construction in Progress		0
Total		655,316
Accumulated Depreciation		$ 228,171
Year(s) Built / Renovated		1983-2016
Year(s) Acquired		1998/1999/2000/2007/2014/2017
Depreciable Lives (Years)	[3]	(1)
100 Federal Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		100 Federal Street
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		131,067
Original Building		435,954
Costs Capitalized Subsequent to Acquisition		79,035
Land and improvements		131,067
Buildings and Improvements		514,989
Land Held for Development		0
Development and Construction in Progress		0
Total		646,056
Accumulated Depreciation		$ 97,630
Year(s) Built / Renovated		1971-1975/2017
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
Times Square Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Times Square Tower
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		165,413
Original Building		380,438
Costs Capitalized Subsequent to Acquisition		87,050
Land and improvements		169,193
Buildings and Improvements		463,708
Land Held for Development		0
Development and Construction in Progress		0
Total		632,901
Accumulated Depreciation		$ 191,435
Year(s) Built / Renovated		2,004
Year(s) Acquired		2,000
Depreciable Lives (Years)	[3]	(1)
Atlantic Wharf
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Atlantic Wharf
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		63,988
Original Building		454,537
Costs Capitalized Subsequent to Acquisition		17,473
Land and improvements		63,988
Buildings and Improvements		472,010
Land Held for Development		0
Development and Construction in Progress		0
Total		535,998
Accumulated Depreciation		$ 101,525
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
Fountain Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Fountain Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		56,853
Original Building		306,298
Costs Capitalized Subsequent to Acquisition		17,834
Land and improvements		56,853
Buildings and Improvements		320,474
Land Held for Development		3,658
Development and Construction in Progress		0
Total		380,985
Accumulated Depreciation		$ 60,098
Year(s) Built / Renovated		1986-1990
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
510 Madison Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		510 Madison Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		103,000
Original Building		253,665
Costs Capitalized Subsequent to Acquisition		23,875
Land and improvements		103,000
Buildings and Improvements		277,540
Land Held for Development		0
Development and Construction in Progress		0
Total		380,540
Accumulated Depreciation		$ 54,056
Year(s) Built / Renovated		2,012
Year(s) Acquired		2,010
Depreciable Lives (Years)	[3]	(1)
599 Lexington Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		599 Lexington Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		81,040
Original Building		100,507
Costs Capitalized Subsequent to Acquisition		165,350
Land and improvements		87,852
Buildings and Improvements		259,045
Land Held for Development		0
Development and Construction in Progress		0
Total		346,897
Accumulated Depreciation		$ 165,739
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
680 Folsom Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		680 Folsom Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		72,545
Original Building		219,766
Costs Capitalized Subsequent to Acquisition		7,545
Land and improvements		72,545
Buildings and Improvements		227,311
Land Held for Development		0
Development and Construction in Progress		0
Total		299,856
Accumulated Depreciation		$ 30,577
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
South of Market and Democracy Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		South of Market and Democracy Tower
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		13,603
Original Building		237,479
Costs Capitalized Subsequent to Acquisition		14,991
Land and improvements		13,687
Buildings and Improvements		252,386
Land Held for Development		0
Development and Construction in Progress		0
Total		266,073
Accumulated Depreciation		$ 87,711
Year(s) Built / Renovated		2008-2009
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
601 Massachusetts Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		601 Massachusetts Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		95,310
Original Building		165,173
Costs Capitalized Subsequent to Acquisition		2,353
Land and improvements		95,322
Buildings and Improvements		167,514
Land Held for Development		0
Development and Construction in Progress		0
Total		262,836
Accumulated Depreciation		$ 12,177
Year(s) Built / Renovated		2,016
Year(s) Acquired		2,008
Depreciable Lives (Years)	[3]	(1)
Bay Colony Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Bay Colony Corporate Center
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		18,789
Original Building		148,451
Costs Capitalized Subsequent to Acquisition		73,418
Land and improvements		18,789
Buildings and Improvements		221,869
Land Held for Development		0
Development and Construction in Progress		0
Total		240,658
Accumulated Depreciation		$ 57,320
Year(s) Built / Renovated		1985-1989
Year(s) Acquired		2,011
Depreciable Lives (Years)	[3]	(1)
Gateway Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Gateway Center
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		28,255
Original Building		139,245
Costs Capitalized Subsequent to Acquisition		59,019
Land and improvements		30,627
Buildings and Improvements		195,892
Land Held for Development		0
Development and Construction in Progress		0
Total		226,519
Accumulated Depreciation		$ 102,634
Year(s) Built / Renovated		1984/1986/2002
Year(s) Acquired		1,999
Depreciable Lives (Years)	[3]	(1)
535 Mission Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		535 Mission Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		40,933
Original Building		148,378
Costs Capitalized Subsequent to Acquisition		3,259
Land and improvements		40,933
Buildings and Improvements		151,637
Land Held for Development		0
Development and Construction in Progress		0
Total		192,570
Accumulated Depreciation		$ 14,637
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,013
Depreciable Lives (Years)	[3]	(1)
2200 Pennsylvania Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2200 Pennsylvania Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		0
Original Building		183,541
Costs Capitalized Subsequent to Acquisition		4,907
Land and improvements		0
Buildings and Improvements		188,448
Land Held for Development		0
Development and Construction in Progress		0
Total		188,448
Accumulated Depreciation		$ 46,780
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,008
Depreciable Lives (Years)	[3]	(1)
Mountain View Research Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Mountain View Research Park
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		95,066
Original Building		68,373
Costs Capitalized Subsequent to Acquisition		8,136
Land and improvements		95,066
Buildings and Improvements		76,509
Land Held for Development		0
Development and Construction in Progress		0
Total		171,575
Accumulated Depreciation		$ 15,146
Year(s) Built / Renovated		1977-1981/2007-2013
Year(s) Acquired		2,013
Depreciable Lives (Years)	[3]	(1)
Reservoir Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reservoir Place
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		18,605
Original Building		104,124
Costs Capitalized Subsequent to Acquisition		43,255
Land and improvements		20,108
Buildings and Improvements		145,876
Land Held for Development		0
Development and Construction in Progress		0
Total		165,984
Accumulated Depreciation		$ 66,230
Year(s) Built / Renovated		1955/1987/2017
Year(s) Acquired		1997/1998
Depreciable Lives (Years)	[3]	(1)
1330 Connecticut Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		1330 Connecticut Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		25,982
Original Building		82,311
Costs Capitalized Subsequent to Acquisition		32,839
Land and improvements		27,135
Buildings and Improvements		113,997
Land Held for Development		0
Development and Construction in Progress		0
Total		141,132
Accumulated Depreciation		$ 22,530
Year(s) Built / Renovated		1,984
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
1333 New Hampshire Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		1333 New Hampshire Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		34,032
Original Building		85,660
Costs Capitalized Subsequent to Acquisition		11,473
Land and improvements		35,382
Buildings and Improvements		95,783
Land Held for Development		0
Development and Construction in Progress		0
Total		131,165
Accumulated Depreciation		$ 40,499
Year(s) Built / Renovated		1,996
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
Kingstowne Towne Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kingstowne Towne Center
Type		Office
Location		Alexandria, VA
Encumbrances		$ 0
Original Land		18,021
Original Building		109,038
Costs Capitalized Subsequent to Acquisition		1,371
Land and improvements		18,062
Buildings and Improvements		110,368
Land Held for Development		0
Development and Construction in Progress		0
Total		128,430
Accumulated Depreciation		$ 39,048
Year(s) Built / Renovated		2003-2006
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
One Freedom Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		One Freedom Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		9,929
Original Building		84,504
Costs Capitalized Subsequent to Acquisition		32,618
Land and improvements		11,293
Buildings and Improvements		115,758
Land Held for Development		0
Development and Construction in Progress		0
Total		127,051
Accumulated Depreciation		$ 50,313
Year(s) Built / Renovated		2,000
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
Capital Gallery
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Capital Gallery
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		4,725
Original Building		29,565
Costs Capitalized Subsequent to Acquisition		89,514
Land and improvements		8,662
Buildings and Improvements		115,142
Land Held for Development		0
Development and Construction in Progress		0
Total		123,804
Accumulated Depreciation		$ 66,009
Year(s) Built / Renovated		1981/2006
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
Weston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Weston Corporate Center
Type		Office
Location		Weston, MA
Encumbrances		$ 0
Original Land		25,753
Original Building		92,312
Costs Capitalized Subsequent to Acquisition		(123)
Land and improvements		25,854
Buildings and Improvements		92,088
Land Held for Development		0
Development and Construction in Progress		0
Total		117,942
Accumulated Depreciation		$ 23,125
Year(s) Built / Renovated		2,010
Year(s) Acquired		2,001
Depreciable Lives (Years)	[3]	(1)
Two Freedom Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Two Freedom Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		13,930
Original Building		77,739
Costs Capitalized Subsequent to Acquisition		23,379
Land and improvements		15,420
Buildings and Improvements		99,628
Land Held for Development		0
Development and Construction in Progress		0
Total		115,048
Accumulated Depreciation		$ 47,936
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
One and Two Reston Overlook
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		One and Two Reston Overlook
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		16,456
Original Building		66,192
Costs Capitalized Subsequent to Acquisition		25,111
Land and improvements		16,179
Buildings and Improvements		91,580
Land Held for Development		0
Development and Construction in Progress		0
Total		107,759
Accumulated Depreciation		$ 44,626
Year(s) Built / Renovated		1,999
Year(s) Acquired		2,000
Depreciable Lives (Years)	[3]	(1)
Discovery Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Discovery Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		11,198
Original Building		71,782
Costs Capitalized Subsequent to Acquisition		24,414
Land and improvements		12,533
Buildings and Improvements		94,861
Land Held for Development		0
Development and Construction in Progress		0
Total		107,394
Accumulated Depreciation		$ 43,184
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
140 Kendrick Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		140 Kendrick Street
Type		Office
Location		Needham, MA
Encumbrances		$ 0
Original Land		18,095
Original Building		66,905
Costs Capitalized Subsequent to Acquisition		17,492
Land and improvements		19,092
Buildings and Improvements		83,400
Land Held for Development		0
Development and Construction in Progress		0
Total		102,492
Accumulated Depreciation		$ 29,013
Year(s) Built / Renovated		2,000
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
355 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		355 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		18,863
Original Building		53,346
Costs Capitalized Subsequent to Acquisition		27,450
Land and improvements		21,173
Buildings and Improvements		78,486
Land Held for Development		0
Development and Construction in Progress		0
Total		99,659
Accumulated Depreciation		$ 26,915
Year(s) Built / Renovated		1981/1996/2013
Year(s) Acquired		2,006
Depreciable Lives (Years)	[3]	(1)
10 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		10 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		1,953
Original Building		85,752
Costs Capitalized Subsequent to Acquisition		2,833
Land and improvements		2,116
Buildings and Improvements		88,422
Land Held for Development		0
Development and Construction in Progress		0
Total		90,538
Accumulated Depreciation		$ 4,673
Year(s) Built / Renovated		2,016
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
90 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		90 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		19,104
Original Building		52,078
Costs Capitalized Subsequent to Acquisition		17,180
Land and improvements		20,785
Buildings and Improvements		67,577
Land Held for Development		0
Development and Construction in Progress		0
Total		88,362
Accumulated Depreciation		$ 19,254
Year(s) Built / Renovated		1983/1998/2013
Year(s) Acquired		2,006
Depreciable Lives (Years)	[3]	(1)
230 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		230 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		13,189
Original Building		49,823
Costs Capitalized Subsequent to Acquisition		25,236
Land and improvements		13,593
Buildings and Improvements		74,655
Land Held for Development		0
Development and Construction in Progress		0
Total		88,248
Accumulated Depreciation		$ 26,562
Year(s) Built / Renovated		1,992
Year(s) Acquired		2,005
Depreciable Lives (Years)	[3]	(1)
Waltham Weston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Waltham Weston Corporate Center
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		10,385
Original Building		60,694
Costs Capitalized Subsequent to Acquisition		11,030
Land and improvements		11,097
Buildings and Improvements		71,012
Land Held for Development		0
Development and Construction in Progress		0
Total		82,109
Accumulated Depreciation		$ 30,036
Year(s) Built / Renovated		2,003
Year(s) Acquired		1,999
Depreciable Lives (Years)	[3]	(1)
77 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		77 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		13,847
Original Building		60,383
Costs Capitalized Subsequent to Acquisition		5,703
Land and improvements		13,873
Buildings and Improvements		66,060
Land Held for Development		0
Development and Construction in Progress		0
Total		79,933
Accumulated Depreciation		$ 23,044
Year(s) Built / Renovated		2,008
Year(s) Acquired		2,001
Depreciable Lives (Years)	[3]	(1)
3625-3635 Peterson Way
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		3625-3635 Peterson Way
Type		Office
Location		Santa Clara, CA
Encumbrances		$ 0
Original Land		63,206
Original Building		14,879
Costs Capitalized Subsequent to Acquisition		138
Land and improvements		63,206
Buildings and Improvements		14,879
Land Held for Development		138
Development and Construction in Progress		0
Total		78,223
Accumulated Depreciation		$ 5,120
Year(s) Built / Renovated		1,979
Year(s) Acquired		2,016
Depreciable Lives (Years)	[3]	(1)
North First Business Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		North First Business Park
Type		Office
Location		San Jose, CA
Encumbrances		$ 0
Original Land		58,402
Original Building		13,069
Costs Capitalized Subsequent to Acquisition		4,416
Land and improvements		23,377
Buildings and Improvements		16,600
Land Held for Development		35,910
Development and Construction in Progress		0
Total		75,887
Accumulated Depreciation		$ 15,839
Year(s) Built / Renovated		1,981
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
300 Binney Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		300 Binney Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		18,080
Original Building		51,262
Costs Capitalized Subsequent to Acquisition		140
Land and improvements		18,080
Buildings and Improvements		51,402
Land Held for Development		0
Development and Construction in Progress		0
Total		69,482
Accumulated Depreciation		$ 7,755
Year(s) Built / Renovated		2,013
Year(s) Acquired		2,009
Depreciable Lives (Years)	[3]	(1)
2440 West El Camino Real
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2440 West El Camino Real
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		16,741
Original Building		51,285
Costs Capitalized Subsequent to Acquisition		1,287
Land and improvements		16,741
Buildings and Improvements		52,572
Land Held for Development		0
Development and Construction in Progress		0
Total		69,313
Accumulated Depreciation		$ 10,790
Year(s) Built / Renovated		1987/2003
Year(s) Acquired		2,011
Depreciable Lives (Years)	[3]	(1)
Wisconsin Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Wisconsin Place
Type		Office
Location		Chevy Chase, MD
Encumbrances		$ 0
Original Land		0
Original Building		53,349
Costs Capitalized Subsequent to Acquisition		14,907
Land and improvements		0
Buildings and Improvements		68,256
Land Held for Development		0
Development and Construction in Progress		0
Total		68,256
Accumulated Depreciation		$ 19,775
Year(s) Built / Renovated		2,009
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
Reston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Corporate Center
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		9,135
Original Building		50,857
Costs Capitalized Subsequent to Acquisition		6,236
Land and improvements		10,148
Buildings and Improvements		56,080
Land Held for Development		0
Development and Construction in Progress		0
Total		66,228
Accumulated Depreciation		$ 26,769
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
New Dominion Technology Park, Bldg. Two
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		New Dominion Technology Park, Bldg. Two
Type		Office
Location		Herndon, VA
Encumbrances		$ 0
Original Land		5,584
Original Building		51,868
Costs Capitalized Subsequent to Acquisition		4,157
Land and improvements		6,510
Buildings and Improvements		55,099
Land Held for Development		0
Development and Construction in Progress		0
Total		61,609
Accumulated Depreciation		$ 23,652
Year(s) Built / Renovated		2,004
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
200 West Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		200 West Street
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		16,148
Original Building		24,983
Costs Capitalized Subsequent to Acquisition		10,673
Land and improvements		16,813
Buildings and Improvements		34,991
Land Held for Development		0
Development and Construction in Progress		0
Total		51,804
Accumulated Depreciation		$ 21,140
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
New Dominion Technology Park, Bldg. One
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		New Dominion Technology Park, Bldg. One
Type		Office
Location		Herndon, VA
Encumbrances		$ 32,691
Original Land		3,880
Original Building		43,227
Costs Capitalized Subsequent to Acquisition		3,882
Land and improvements		4,583
Buildings and Improvements		46,406
Land Held for Development		0
Development and Construction in Progress		0
Total		50,989
Accumulated Depreciation		$ 25,940
Year(s) Built / Renovated		2,001
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
Sumner Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Sumner Square
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		624
Original Building		28,745
Costs Capitalized Subsequent to Acquisition		19,000
Land and improvements		1,478
Buildings and Improvements		46,891
Land Held for Development		0
Development and Construction in Progress		0
Total		48,369
Accumulated Depreciation		$ 23,570
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,999
Depreciable Lives (Years)	[3]	(1)
255 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		255 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		134
Original Building		25,110
Costs Capitalized Subsequent to Acquisition		21,583
Land and improvements		548
Buildings and Improvements		46,279
Land Held for Development		0
Development and Construction in Progress		0
Total		46,827
Accumulated Depreciation		$ 28,250
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
University Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		University Place
Type		Office
Location		Cambridge, MA
Encumbrances		$ 7,407
Original Land		0
Original Building		37,091
Costs Capitalized Subsequent to Acquisition		9,007
Land and improvements		390
Buildings and Improvements		45,708
Land Held for Development		0
Development and Construction in Progress		0
Total		46,098
Accumulated Depreciation		$ 26,295
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
2600 Tower Oaks Boulevard
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2600 Tower Oaks Boulevard
Type		Office
Location		Rockville, MD
Encumbrances		$ 0
Original Land		4,243
Original Building		31,125
Costs Capitalized Subsequent to Acquisition		9,867
Land and improvements		4,785
Buildings and Improvements		40,450
Land Held for Development		0
Development and Construction in Progress		0
Total		45,235
Accumulated Depreciation		$ 21,020
Year(s) Built / Renovated		2,001
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
Quorum Office Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Quorum Office Park
Type		Office
Location		Chelmsford, MA
Encumbrances		$ 0
Original Land		3,750
Original Building		32,454
Costs Capitalized Subsequent to Acquisition		5,813
Land and improvements		5,187
Buildings and Improvements		36,830
Land Held for Development		0
Development and Construction in Progress		0
Total		42,017
Accumulated Depreciation		$ 16,594
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,000
Depreciable Lives (Years)	[3]	(1)
500 E Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		500 E Street
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		109
Original Building		22,420
Costs Capitalized Subsequent to Acquisition		14,743
Land and improvements		2,379
Buildings and Improvements		34,893
Land Held for Development		0
Development and Construction in Progress		0
Total		37,272
Accumulated Depreciation		$ 23,781
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
150 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		150 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		850
Original Building		25,042
Costs Capitalized Subsequent to Acquisition		8,540
Land and improvements		1,323
Buildings and Improvements		33,109
Land Held for Development		0
Development and Construction in Progress		0
Total		34,432
Accumulated Depreciation		$ 16,933
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
325 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		325 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		174
Original Building		12,200
Costs Capitalized Subsequent to Acquisition		11,963
Land and improvements		965
Buildings and Improvements		23,372
Land Held for Development		0
Development and Construction in Progress		0
Total		24,337
Accumulated Depreciation		$ 12,852
Year(s) Built / Renovated		1987/2013
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
105 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		105 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,299
Original Building		12,943
Costs Capitalized Subsequent to Acquisition		8,214
Land and improvements		2,395
Buildings and Improvements		20,061
Land Held for Development		0
Development and Construction in Progress		0
Total		22,456
Accumulated Depreciation		$ 13,493
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
Lexington Office Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Lexington Office Park
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		998
Original Building		1,426
Costs Capitalized Subsequent to Acquisition		18,219
Land and improvements		1,264
Buildings and Improvements		19,379
Land Held for Development		0
Development and Construction in Progress		0
Total		20,643
Accumulated Depreciation		$ 13,404
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
201 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		201 Spring Street
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		2,849
Original Building		15,303
Costs Capitalized Subsequent to Acquisition		694
Land and improvements		3,124
Buildings and Improvements		15,722
Land Held for Development		0
Development and Construction in Progress		0
Total		18,846
Accumulated Depreciation		$ 7,931
Year(s) Built / Renovated		1,997
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
The Point
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Point
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		6,395
Original Building		10,040
Costs Capitalized Subsequent to Acquisition		409
Land and improvements		6,480
Buildings and Improvements		10,364
Land Held for Development		0
Development and Construction in Progress		0
Total		16,844
Accumulated Depreciation		$ 714
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
92-100 Hayden Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		92-100 Hayden Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		594
Original Building		6,748
Costs Capitalized Subsequent to Acquisition		8,181
Land and improvements		802
Buildings and Improvements		14,721
Land Held for Development		0
Development and Construction in Progress		0
Total		15,523
Accumulated Depreciation		$ 12,495
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
91 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		91 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		784
Original Building		6,464
Costs Capitalized Subsequent to Acquisition		8,269
Land and improvements		941
Buildings and Improvements		14,576
Land Held for Development		0
Development and Construction in Progress		0
Total		15,517
Accumulated Depreciation		$ 9,849
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
690 Folsom Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		690 Folsom Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		3,219
Original Building		11,038
Costs Capitalized Subsequent to Acquisition		1,157
Land and improvements		3,219
Buildings and Improvements		12,195
Land Held for Development		0
Development and Construction in Progress		0
Total		15,414
Accumulated Depreciation		$ 1,295
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
181 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		181 Spring Street
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		1,066
Original Building		9,520
Costs Capitalized Subsequent to Acquisition		2,318
Land and improvements		1,160
Buildings and Improvements		11,744
Land Held for Development		0
Development and Construction in Progress		0
Total		12,904
Accumulated Depreciation		$ 5,194
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
195 West Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		195 West Street
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		1,611
Original Building		6,652
Costs Capitalized Subsequent to Acquisition		4,340
Land and improvements		1,858
Buildings and Improvements		10,745
Land Held for Development		0
Development and Construction in Progress		0
Total		12,603
Accumulated Depreciation		$ 7,963
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
33 Hayden Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		33 Hayden Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		266
Original Building		3,234
Costs Capitalized Subsequent to Acquisition		8,381
Land and improvements		425
Buildings and Improvements		11,456
Land Held for Development		0
Development and Construction in Progress		0
Total		11,881
Accumulated Depreciation		$ 8,211
Year(s) Built / Renovated		1,979
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7501 Boston Boulevard, Building Seven
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7501 Boston Boulevard, Building Seven
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		665
Original Building		9,273
Costs Capitalized Subsequent to Acquisition		819
Land and improvements		791
Buildings and Improvements		9,966
Land Held for Development		0
Development and Construction in Progress		0
Total		10,757
Accumulated Depreciation		$ 4,848
Year(s) Built / Renovated		1,997
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7435 Boston Boulevard, Building One
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7435 Boston Boulevard, Building One
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		392
Original Building		3,822
Costs Capitalized Subsequent to Acquisition		3,997
Land and improvements		659
Buildings and Improvements		7,552
Land Held for Development		0
Development and Construction in Progress		0
Total		8,211
Accumulated Depreciation		$ 5,510
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
250 Binney Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		250 Binney Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		110
Original Building		4,483
Costs Capitalized Subsequent to Acquisition		3,593
Land and improvements		273
Buildings and Improvements		7,913
Land Held for Development		0
Development and Construction in Progress		0
Total		8,186
Accumulated Depreciation		$ 5,066
Year(s) Built / Renovated		1,983
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
8000 Grainger Court, Building Five
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		8000 Grainger Court, Building Five
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		366
Original Building		4,282
Costs Capitalized Subsequent to Acquisition		3,375
Land and improvements		601
Buildings and Improvements		7,422
Land Held for Development		0
Development and Construction in Progress		0
Total		8,023
Accumulated Depreciation		$ 5,644
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7450 Boston Boulevard, Building Three
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7450 Boston Boulevard, Building Three
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		1,165
Original Building		4,681
Costs Capitalized Subsequent to Acquisition		1,773
Land and improvements		1,430
Buildings and Improvements		6,189
Land Held for Development		0
Development and Construction in Progress		0
Total		7,619
Accumulated Depreciation		$ 3,451
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
453 Ravendale Drive
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		453 Ravendale Drive
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		5,477
Original Building		1,090
Costs Capitalized Subsequent to Acquisition		408
Land and improvements		5,477
Buildings and Improvements		1,498
Land Held for Development		0
Development and Construction in Progress		0
Total		6,975
Accumulated Depreciation		$ 472
Year(s) Built / Renovated		1,977
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
17 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		17 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		26
Original Building		150
Costs Capitalized Subsequent to Acquisition		6,252
Land and improvements		65
Buildings and Improvements		6,363
Land Held for Development		0
Development and Construction in Progress		0
Total		6,428
Accumulated Depreciation		$ 1,098
Year(s) Built / Renovated		1,968
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7601 Boston Boulevard, Building Eight
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7601 Boston Boulevard, Building Eight
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		200
Original Building		878
Costs Capitalized Subsequent to Acquisition		5,052
Land and improvements		551
Buildings and Improvements		5,579
Land Held for Development		0
Development and Construction in Progress		0
Total		6,130
Accumulated Depreciation		$ 4,263
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7300 Boston Boulevard, Building Thirteen
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7300 Boston Boulevard, Building Thirteen
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		608
Original Building		4,773
Costs Capitalized Subsequent to Acquisition		709
Land and improvements		661
Buildings and Improvements		5,429
Land Held for Development		0
Development and Construction in Progress		0
Total		6,090
Accumulated Depreciation		$ 2,785
Year(s) Built / Renovated		2,002
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7500 Boston Boulevard, Building Six
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7500 Boston Boulevard, Building Six
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		138
Original Building		3,749
Costs Capitalized Subsequent to Acquisition		1,655
Land and improvements		406
Buildings and Improvements		5,136
Land Held for Development		0
Development and Construction in Progress		0
Total		5,542
Accumulated Depreciation		$ 3,965
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
8000 Corporate Court, Building Eleven
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		8000 Corporate Court, Building Eleven
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		136
Original Building		3,071
Costs Capitalized Subsequent to Acquisition		1,596
Land and improvements		774
Buildings and Improvements		4,029
Land Held for Development		0
Development and Construction in Progress		0
Total		4,803
Accumulated Depreciation		$ 2,909
Year(s) Built / Renovated		1,989
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7374 Boston Boulevard, Building Four
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7374 Boston Boulevard, Building Four
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		241
Original Building		1,605
Costs Capitalized Subsequent to Acquisition		1,913
Land and improvements		398
Buildings and Improvements		3,361
Land Held for Development		0
Development and Construction in Progress		0
Total		3,759
Accumulated Depreciation		$ 2,578
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7375 Boston Boulevard, Building Ten
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7375 Boston Boulevard, Building Ten
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		23
Original Building		2,685
Costs Capitalized Subsequent to Acquisition		938
Land and improvements		93
Buildings and Improvements		3,553
Land Held for Development		0
Development and Construction in Progress		0
Total		3,646
Accumulated Depreciation		$ 2,570
Year(s) Built / Renovated		1,988
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7451 Boston Boulevard, Building Two
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7451 Boston Boulevard, Building Two
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		249
Original Building		1,542
Costs Capitalized Subsequent to Acquisition		1,659
Land and improvements		613
Buildings and Improvements		2,837
Land Held for Development		0
Development and Construction in Progress		0
Total		3,450
Accumulated Depreciation		$ 2,429
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
32 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		32 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		168
Original Building		1,943
Costs Capitalized Subsequent to Acquisition		1,012
Land and improvements		314
Buildings and Improvements		2,809
Land Held for Development		0
Development and Construction in Progress		0
Total		3,123
Accumulated Depreciation		$ 1,974
Year(s) Built / Renovated		1968/1979/1987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
164 Lexington Road
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		164 Lexington Road
Type		Office
Location		Billerica, MA
Encumbrances		$ 0
Original Land		592
Original Building		1,370
Costs Capitalized Subsequent to Acquisition		319
Land and improvements		643
Buildings and Improvements		1,638
Land Held for Development		0
Development and Construction in Progress		0
Total		2,281
Accumulated Depreciation		$ 868
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
The Avant at Reston Town Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Avant at Reston Town Center
Type		Residential
Location		Reston, VA
Encumbrances		$ 0
Original Land		20,350
Original Building		91,995
Costs Capitalized Subsequent to Acquisition		830
Land and improvements		20,350
Buildings and Improvements		92,825
Land Held for Development		0
Development and Construction in Progress		0
Total		113,175
Accumulated Depreciation		$ 9,780
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,010
Depreciable Lives (Years)	[3]	(1)
The Lofts at Atlantic Wharf
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Lofts at Atlantic Wharf
Type		Residential
Location		Boston, MA
Encumbrances		$ 0
Original Land		3,529
Original Building		54,891
Costs Capitalized Subsequent to Acquisition		1,768
Land and improvements		3,529
Buildings and Improvements		56,659
Land Held for Development		0
Development and Construction in Progress		0
Total		60,188
Accumulated Depreciation		$ 9,622
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
Boston Marriott Cambridge
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Boston Marriott Cambridge
Type		Hotel
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		478
Original Building		37,918
Costs Capitalized Subsequent to Acquisition		38,799
Land and improvements		1,201
Buildings and Improvements		75,994
Land Held for Development		0
Development and Construction in Progress		0
Total		77,195
Accumulated Depreciation		$ 47,753
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
Kendall Center Green Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Green Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		35,035
Costs Capitalized Subsequent to Acquisition		7,448
Land and improvements		103
Buildings and Improvements		42,380
Land Held for Development		0
Development and Construction in Progress		0
Total		42,483
Accumulated Depreciation		$ 10,779
Year(s) Built / Renovated		1,984
Year(s) Acquired		2,006
Depreciable Lives (Years)	[3]	(1)
Kendall Center Yellow Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Yellow Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,256
Original Building		15,697
Costs Capitalized Subsequent to Acquisition		1,621
Land and improvements		1,434
Buildings and Improvements		17,140
Land Held for Development		0
Development and Construction in Progress		0
Total		18,574
Accumulated Depreciation		$ 5,181
Year(s) Built / Renovated		2,006
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
Kendall Center Blue Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Blue Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,163
Original Building		11,633
Costs Capitalized Subsequent to Acquisition		2,283
Land and improvements		1,579
Buildings and Improvements		13,500
Land Held for Development		0
Development and Construction in Progress		0
Total		15,079
Accumulated Depreciation		$ 9,209
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
Salesforce Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Salesforce Tower
Type		Development
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		947,106
Land and improvements		200,349
Buildings and Improvements		55,318
Land Held for Development		0
Development and Construction in Progress		691,439
Total		947,106
Accumulated Depreciation		$ 116
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,013
Depreciable Lives (Years)		N/A
Signature at Reston
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Signature at Reston
Type		Development
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		203,650
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		203,650
Total		203,650
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,013
Depreciable Lives (Years)		N/A
Proto Kendall Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Proto Kendall Square
Type		Development
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		82,905
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		82,905
Total		82,905
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,015
Depreciable Lives (Years)		N/A
145 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		145 Broadway
Type		Development
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		121
Original Building		0
Costs Capitalized Subsequent to Acquisition		79,979
Land and improvements		324
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		79,776
Total		80,100
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		NA
Year(s) Acquired		1,997
Depreciable Lives (Years)		N/A
191 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		191 Spring Street
Type		Development
Location		Lexington, MA
Encumbrances		$ 0
Original Land		2,850
Original Building		27,166
Costs Capitalized Subsequent to Acquisition		35,174
Land and improvements		3,151
Buildings and Improvements		46,288
Land Held for Development		0
Development and Construction in Progress		15,751
Total		65,190
Accumulated Depreciation		$ 19,034
Year(s) Built / Renovated		1971/1995
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
6595 Springfield Center Drive (TSA Headquarters)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		6595 Springfield Center Drive (TSA Headquarters)
Type		Development
Location		Springfield, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		41,918
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		41,918
Total		41,918
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
MacArthur Station Residences
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		MacArthur Station Residences
Type		Development
Location		Oakland, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		37,644
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		37,644
Total		37,644
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
20 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		20 CityPoint
Type		Development
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,056
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		13,056
Total		13,056
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Tower Oaks Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Tower Oaks Master Plan
Type		Land
Location		Rockville, MD
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		29,419
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		29,419
Development and Construction in Progress		0
Total		29,419
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Plaza at Almaden
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Plaza at Almaden
Type		Land
Location		San Jose, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		29,085
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		29,085
Development and Construction in Progress		0
Total		29,085
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,006
Depreciable Lives (Years)		N/A
Springfield Metro Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Springfield Metro Center
Type		Land
Location		Springfield, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		19,684
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		19,684
Development and Construction in Progress		0
Total		19,684
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
214 Third Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		214 Third Avenue
Type		Land
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,815
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		13,815
Development and Construction in Progress		0
Total		13,815
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,006
Depreciable Lives (Years)		N/A
Reston Gateway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Gateway
Type		Land
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,730
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		13,730
Development and Construction in Progress		0
Total		13,730
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
103 Fourth Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		103 Fourth Avenue
Type		Land
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		12,115
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		12,115
Development and Construction in Progress		0
Total		12,115
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Crane Meadow
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Crane Meadow
Type		Land
Location		Marlborough, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		8,836
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		8,836
Development and Construction in Progress		0
Total		8,836
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,000
Depreciable Lives (Years)		N/A
Washingtonian North
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Washingtonian North
Type		Land
Location		Gaithersburg, MD
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		7,645
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		7,645
Development and Construction in Progress		0
Total		7,645
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
2100 Pennsylvania Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2100 Pennsylvania Avenue
Type		Land
Location		Washington, DC
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		6,543
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		6,543
Development and Construction in Progress		0
Total		6,543
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Fourth and Harrison
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Fourth and Harrison
Type		Land
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		5,659
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		5,659
Development and Construction in Progress		0
Total		5,659
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
North First Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		North First Master Plan
Type		Land
Location		San Jose, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		3,018
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		3,018
Development and Construction in Progress		0
Total		3,018
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Broad Run Business Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Broad Run Business Park
Type		Land
Location		Loudoun County, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		2,367
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		2,367
Development and Construction in Progress		0
Total		2,367
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Kendall Center Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Master Plan
Type		Land
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		2,207
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		2,207
Development and Construction in Progress		0
Total		2,207
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Weston Quarry
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Weston Quarry
Type		Land
Location		Weston, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		1,194
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		1,194
Development and Construction in Progress		0
Total		1,194
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,001
Depreciable Lives (Years)		N/A
Reston Overlook Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Overlook Master Plan
Type		Land
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		39
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		39
Development and Construction in Progress		0
Total		39
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,000
Depreciable Lives (Years)		N/A
Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life Used for Depreciation		life of the lease
[1]	Includes unamortized deferred financing costs totaling approximately $(34.7) million.
[2]	Includes pre-development costs.
[3]	Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.

Real Estate and Accumulated 105

Real Estate and Accumulated Depreciation Activity of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Real Estate, Balance at the beginning of the year	$ 20,114,576	$ 19,451,683	$ 19,208,417
Real Estate, Additions to / improvements of real estate	1,099,286	977,287	700,792
Real Estate, Assets sold / written off	(155,148)	(314,394)	(457,526)
Real Estate, Balance at the end of the year	21,058,714	20,114,576	19,451,683
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Accumulated depreciation, Balance at beginning of the year	4,201,891	3,905,940	3,529,978
Accumulated depreciation, Depreciation expense	497,059	560,024	486,450
Accumulated depreciation, Assets sold / written off	(132,380)	(264,073)	(110,488)
Accumulated depreciation, Balance at end of the year	$ 4,566,570	$ 4,201,891	$ 3,905,940

Real Estate and Accumulated 106

Real Estate and Accumulated Depreciation Schedule of Real Estate and Accumulated Depreciation (BPLP) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[1]	$ 2,979,281
Original Land		4,762,002
Original Building		11,634,050
Costs Capitalized Subsequent to Acquisition		4,662,662
Land and improvements		5,080,679
Buildings and Improvements		14,503,772
Land Held for Development	[2]	204,925
Development and Construction in Progress		1,269,338
Total		21,058,714
Accumulated Depreciation		4,566,570
Furniture, fixtures and equipment		37,928	$ 32,687
Furniture, fixtures and equipment accumulated depreciation		23,064
Real Estate Aggregate Cost For Tax Purposes		17,300,000
Real Estate Aggregate Accumulated Depreciation For Tax Purposes		$ 3,600,000
Real Estate and Accumulated Depreciation, Life Used for Depreciation		40 years
Unamortized deferred finance costs		$ (34,680)
767 Fifth Avenue (the General Motors Building)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		767 Fifth Avenue (the General Motors Building)
Type		Office
Location		New York, NY
Encumbrances		$ 2,267,041
Original Land		1,796,252
Original Building		1,532,654
Costs Capitalized Subsequent to Acquisition		135,559
Land and improvements		1,796,252
Buildings and Improvements		1,668,213
Land Held for Development		0
Development and Construction in Progress		0
Total		3,464,465
Accumulated Depreciation		$ 222,981
Year(s) Built / Renovated		1,968
Year(s) Acquired		2,013
Depreciable Lives (Years)	[3]	(1)
Prudential Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Prudential Center
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		92,077
Original Building		948,357
Costs Capitalized Subsequent to Acquisition		501,709
Land and improvements		115,638
Buildings and Improvements		1,426,505
Land Held for Development		0
Development and Construction in Progress		0
Total		1,542,143
Accumulated Depreciation		$ 511,605
Year(s) Built / Renovated		1965/1993/2002/2016-2017
Year(s) Acquired		1998/1999/2000
Depreciable Lives (Years)	[3]	(1)
Embarcadero Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Embarcadero Center
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		179,697
Original Building		847,410
Costs Capitalized Subsequent to Acquisition		366,780
Land and improvements		195,987
Buildings and Improvements		1,197,900
Land Held for Development		0
Development and Construction in Progress		0
Total		1,393,887
Accumulated Depreciation		$ 596,100
Year(s) Built / Renovated		1970/1989
Year(s) Acquired		1998-1999
Depreciable Lives (Years)	[3]	(1)
399 Park Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		399 Park Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		339,200
Original Building		700,358
Costs Capitalized Subsequent to Acquisition		181,418
Land and improvements		354,107
Buildings and Improvements		866,869
Land Held for Development		0
Development and Construction in Progress		0
Total		1,220,976
Accumulated Depreciation		$ 310,262
Year(s) Built / Renovated		1,961
Year(s) Acquired		2,002
Depreciable Lives (Years)	[3]	(1)
200 Clarendon Street and Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		200 Clarendon Street and Garage
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		219,543
Original Building		667,884
Costs Capitalized Subsequent to Acquisition		139,189
Land and improvements		219,616
Buildings and Improvements		799,991
Land Held for Development		7,009
Development and Construction in Progress		0
Total		1,026,616
Accumulated Depreciation		$ 161,471
Year(s) Built / Renovated		1,976
Year(s) Acquired		2,010
Depreciable Lives (Years)	[3]	(1)
601 Lexington Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		601 Lexington Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 672,142
Original Land		241,600
Original Building		494,782
Costs Capitalized Subsequent to Acquisition		290,590
Land and improvements		289,639
Buildings and Improvements		634,134
Land Held for Development		0
Development and Construction in Progress		103,199
Total		1,026,972
Accumulated Depreciation		$ 254,932
Year(s) Built / Renovated		1977/1997
Year(s) Acquired		2,001
Depreciable Lives (Years)	[3]	(1)
250 West 55th Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		250 West 55th Street
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		285,263
Original Building		603,167
Costs Capitalized Subsequent to Acquisition		43,296
Land and improvements		285,263
Buildings and Improvements		646,463
Land Held for Development		0
Development and Construction in Progress		0
Total		931,726
Accumulated Depreciation		$ 72,058
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
100 Federal Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		100 Federal Street
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		131,067
Original Building		435,954
Costs Capitalized Subsequent to Acquisition		79,035
Land and improvements		131,067
Buildings and Improvements		514,989
Land Held for Development		0
Development and Construction in Progress		0
Total		646,056
Accumulated Depreciation		$ 97,630
Year(s) Built / Renovated		1971-1975/2017
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
Carnegie Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Carnegie Center
Type		Office
Location		Princeton, NJ
Encumbrances		$ 0
Original Land		107,997
Original Building		389,359
Costs Capitalized Subsequent to Acquisition		157,960
Land and improvements		108,948
Buildings and Improvements		543,514
Land Held for Development		2,854
Development and Construction in Progress		0
Total		655,316
Accumulated Depreciation		$ 228,171
Year(s) Built / Renovated		1983-2016
Year(s) Acquired		1998/1999/2000/2007/2014/2017
Depreciable Lives (Years)	[3]	(1)
Times Square Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Times Square Tower
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		165,413
Original Building		380,438
Costs Capitalized Subsequent to Acquisition		87,050
Land and improvements		169,193
Buildings and Improvements		463,708
Land Held for Development		0
Development and Construction in Progress		0
Total		632,901
Accumulated Depreciation		$ 191,435
Year(s) Built / Renovated		2,004
Year(s) Acquired		2,000
Depreciable Lives (Years)	[3]	(1)
Atlantic Wharf
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Atlantic Wharf
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		63,988
Original Building		454,537
Costs Capitalized Subsequent to Acquisition		17,473
Land and improvements		63,988
Buildings and Improvements		472,010
Land Held for Development		0
Development and Construction in Progress		0
Total		535,998
Accumulated Depreciation		$ 101,525
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
Fountain Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Fountain Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		56,853
Original Building		306,298
Costs Capitalized Subsequent to Acquisition		17,834
Land and improvements		56,853
Buildings and Improvements		320,474
Land Held for Development		3,658
Development and Construction in Progress		0
Total		380,985
Accumulated Depreciation		$ 60,098
Year(s) Built / Renovated		1986-1990
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
510 Madison Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		510 Madison Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		103,000
Original Building		253,665
Costs Capitalized Subsequent to Acquisition		23,875
Land and improvements		103,000
Buildings and Improvements		277,540
Land Held for Development		0
Development and Construction in Progress		0
Total		380,540
Accumulated Depreciation		$ 54,056
Year(s) Built / Renovated		2,012
Year(s) Acquired		2,010
Depreciable Lives (Years)	[3]	(1)
599 Lexington Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		599 Lexington Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		81,040
Original Building		100,507
Costs Capitalized Subsequent to Acquisition		165,350
Land and improvements		87,852
Buildings and Improvements		259,045
Land Held for Development		0
Development and Construction in Progress		0
Total		346,897
Accumulated Depreciation		$ 165,739
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
680 Folsom Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		680 Folsom Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		72,545
Original Building		219,766
Costs Capitalized Subsequent to Acquisition		7,545
Land and improvements		72,545
Buildings and Improvements		227,311
Land Held for Development		0
Development and Construction in Progress		0
Total		299,856
Accumulated Depreciation		$ 30,577
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
South of Market and Democracy Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		South of Market and Democracy Tower
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		13,603
Original Building		237,479
Costs Capitalized Subsequent to Acquisition		14,991
Land and improvements		13,687
Buildings and Improvements		252,386
Land Held for Development		0
Development and Construction in Progress		0
Total		266,073
Accumulated Depreciation		$ 87,711
Year(s) Built / Renovated		2008-2009
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
601 Massachusetts Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		601 Massachusetts Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		95,310
Original Building		165,173
Costs Capitalized Subsequent to Acquisition		2,353
Land and improvements		95,322
Buildings and Improvements		167,514
Land Held for Development		0
Development and Construction in Progress		0
Total		262,836
Accumulated Depreciation		$ 12,177
Year(s) Built / Renovated		2,016
Year(s) Acquired		2,008
Depreciable Lives (Years)	[3]	(1)
Bay Colony Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Bay Colony Corporate Center
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		18,789
Original Building		148,451
Costs Capitalized Subsequent to Acquisition		73,418
Land and improvements		18,789
Buildings and Improvements		221,869
Land Held for Development		0
Development and Construction in Progress		0
Total		240,658
Accumulated Depreciation		$ 57,320
Year(s) Built / Renovated		1985-1989
Year(s) Acquired		2,011
Depreciable Lives (Years)	[3]	(1)
Gateway Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Gateway Center
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		28,255
Original Building		139,245
Costs Capitalized Subsequent to Acquisition		59,019
Land and improvements		30,627
Buildings and Improvements		195,892
Land Held for Development		0
Development and Construction in Progress		0
Total		226,519
Accumulated Depreciation		$ 102,634
Year(s) Built / Renovated		1984/1986/2002
Year(s) Acquired		1,999
Depreciable Lives (Years)	[3]	(1)
535 Mission Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		535 Mission Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		40,933
Original Building		148,378
Costs Capitalized Subsequent to Acquisition		3,259
Land and improvements		40,933
Buildings and Improvements		151,637
Land Held for Development		0
Development and Construction in Progress		0
Total		192,570
Accumulated Depreciation		$ 14,637
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,013
Depreciable Lives (Years)	[3]	(1)
2200 Pennsylvania Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2200 Pennsylvania Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		0
Original Building		183,541
Costs Capitalized Subsequent to Acquisition		4,907
Land and improvements		0
Buildings and Improvements		188,448
Land Held for Development		0
Development and Construction in Progress		0
Total		188,448
Accumulated Depreciation		$ 46,780
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,008
Depreciable Lives (Years)	[3]	(1)
Mountain View Research Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Mountain View Research Park
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		95,066
Original Building		68,373
Costs Capitalized Subsequent to Acquisition		8,136
Land and improvements		95,066
Buildings and Improvements		76,509
Land Held for Development		0
Development and Construction in Progress		0
Total		171,575
Accumulated Depreciation		$ 15,146
Year(s) Built / Renovated		1977-1981/2007-2013
Year(s) Acquired		2,013
Depreciable Lives (Years)	[3]	(1)
Reservoir Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reservoir Place
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		18,605
Original Building		104,124
Costs Capitalized Subsequent to Acquisition		43,255
Land and improvements		20,108
Buildings and Improvements		145,876
Land Held for Development		0
Development and Construction in Progress		0
Total		165,984
Accumulated Depreciation		$ 66,230
Year(s) Built / Renovated		1955/1987/2017
Year(s) Acquired		1997/1998
Depreciable Lives (Years)	[3]	(1)
1330 Connecticut Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		1330 Connecticut Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		25,982
Original Building		82,311
Costs Capitalized Subsequent to Acquisition		32,839
Land and improvements		27,135
Buildings and Improvements		113,997
Land Held for Development		0
Development and Construction in Progress		0
Total		141,132
Accumulated Depreciation		$ 22,530
Year(s) Built / Renovated		1,984
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
Kingstowne Towne Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kingstowne Towne Center
Type		Office
Location		Alexandria, VA
Encumbrances		$ 0
Original Land		18,021
Original Building		109,038
Costs Capitalized Subsequent to Acquisition		1,371
Land and improvements		18,062
Buildings and Improvements		110,368
Land Held for Development		0
Development and Construction in Progress		0
Total		128,430
Accumulated Depreciation		$ 39,048
Year(s) Built / Renovated		2003-2006
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
1333 New Hampshire Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		1333 New Hampshire Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		34,032
Original Building		85,660
Costs Capitalized Subsequent to Acquisition		11,473
Land and improvements		35,382
Buildings and Improvements		95,783
Land Held for Development		0
Development and Construction in Progress		0
Total		131,165
Accumulated Depreciation		$ 40,499
Year(s) Built / Renovated		1,996
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
One Freedom Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		One Freedom Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		9,929
Original Building		84,504
Costs Capitalized Subsequent to Acquisition		32,618
Land and improvements		11,293
Buildings and Improvements		115,758
Land Held for Development		0
Development and Construction in Progress		0
Total		127,051
Accumulated Depreciation		$ 50,313
Year(s) Built / Renovated		2,000
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
Weston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Weston Corporate Center
Type		Office
Location		Weston, MA
Encumbrances		$ 0
Original Land		25,753
Original Building		92,312
Costs Capitalized Subsequent to Acquisition		(123)
Land and improvements		25,854
Buildings and Improvements		92,088
Land Held for Development		0
Development and Construction in Progress		0
Total		117,942
Accumulated Depreciation		$ 23,125
Year(s) Built / Renovated		2,010
Year(s) Acquired		2,001
Depreciable Lives (Years)	[3]	(1)
Capital Gallery
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Capital Gallery
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		4,725
Original Building		29,565
Costs Capitalized Subsequent to Acquisition		89,514
Land and improvements		8,662
Buildings and Improvements		115,142
Land Held for Development		0
Development and Construction in Progress		0
Total		123,804
Accumulated Depreciation		$ 66,009
Year(s) Built / Renovated		1981/2006
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
Two Freedom Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Two Freedom Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		13,930
Original Building		77,739
Costs Capitalized Subsequent to Acquisition		23,379
Land and improvements		15,420
Buildings and Improvements		99,628
Land Held for Development		0
Development and Construction in Progress		0
Total		115,048
Accumulated Depreciation		$ 47,936
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
One and Two Reston Overlook
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		One and Two Reston Overlook
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		16,456
Original Building		66,192
Costs Capitalized Subsequent to Acquisition		25,111
Land and improvements		16,179
Buildings and Improvements		91,580
Land Held for Development		0
Development and Construction in Progress		0
Total		107,759
Accumulated Depreciation		$ 44,626
Year(s) Built / Renovated		1,999
Year(s) Acquired		2,000
Depreciable Lives (Years)	[3]	(1)
Discovery Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Discovery Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		11,198
Original Building		71,782
Costs Capitalized Subsequent to Acquisition		24,414
Land and improvements		12,533
Buildings and Improvements		94,861
Land Held for Development		0
Development and Construction in Progress		0
Total		107,394
Accumulated Depreciation		$ 43,184
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,003
Depreciable Lives (Years)	[3]	(1)
355 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		355 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		18,863
Original Building		53,346
Costs Capitalized Subsequent to Acquisition		27,450
Land and improvements		21,173
Buildings and Improvements		78,486
Land Held for Development		0
Development and Construction in Progress		0
Total		99,659
Accumulated Depreciation		$ 26,915
Year(s) Built / Renovated		1981/1996/2013
Year(s) Acquired		2,006
Depreciable Lives (Years)	[3]	(1)
140 Kendrick Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		140 Kendrick Street
Type		Office
Location		Needham, MA
Encumbrances		$ 0
Original Land		18,095
Original Building		66,905
Costs Capitalized Subsequent to Acquisition		17,492
Land and improvements		19,092
Buildings and Improvements		83,400
Land Held for Development		0
Development and Construction in Progress		0
Total		102,492
Accumulated Depreciation		$ 29,013
Year(s) Built / Renovated		2,000
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
10 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		10 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		1,953
Original Building		85,752
Costs Capitalized Subsequent to Acquisition		2,833
Land and improvements		2,116
Buildings and Improvements		88,422
Land Held for Development		0
Development and Construction in Progress		0
Total		90,538
Accumulated Depreciation		$ 4,673
Year(s) Built / Renovated		2,016
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
90 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		90 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		19,104
Original Building		52,078
Costs Capitalized Subsequent to Acquisition		17,180
Land and improvements		20,785
Buildings and Improvements		67,577
Land Held for Development		0
Development and Construction in Progress		0
Total		88,362
Accumulated Depreciation		$ 19,254
Year(s) Built / Renovated		1983/1998/2013
Year(s) Acquired		2,006
Depreciable Lives (Years)	[3]	(1)
230 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		230 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		13,189
Original Building		49,823
Costs Capitalized Subsequent to Acquisition		25,236
Land and improvements		13,593
Buildings and Improvements		74,655
Land Held for Development		0
Development and Construction in Progress		0
Total		88,248
Accumulated Depreciation		$ 26,562
Year(s) Built / Renovated		1,992
Year(s) Acquired		2,005
Depreciable Lives (Years)	[3]	(1)
77 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		77 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		13,847
Original Building		60,383
Costs Capitalized Subsequent to Acquisition		5,703
Land and improvements		13,873
Buildings and Improvements		66,060
Land Held for Development		0
Development and Construction in Progress		0
Total		79,933
Accumulated Depreciation		$ 23,044
Year(s) Built / Renovated		2,008
Year(s) Acquired		2,001
Depreciable Lives (Years)	[3]	(1)
Waltham Weston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Waltham Weston Corporate Center
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		10,385
Original Building		60,694
Costs Capitalized Subsequent to Acquisition		11,030
Land and improvements		11,097
Buildings and Improvements		71,012
Land Held for Development		0
Development and Construction in Progress		0
Total		82,109
Accumulated Depreciation		$ 30,036
Year(s) Built / Renovated		2,003
Year(s) Acquired		1,999
Depreciable Lives (Years)	[3]	(1)
3625-3635 Peterson Way
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		3625-3635 Peterson Way
Type		Office
Location		Santa Clara, CA
Encumbrances		$ 0
Original Land		63,206
Original Building		14,879
Costs Capitalized Subsequent to Acquisition		138
Land and improvements		63,206
Buildings and Improvements		14,879
Land Held for Development		138
Development and Construction in Progress		0
Total		78,223
Accumulated Depreciation		$ 5,120
Year(s) Built / Renovated		1,979
Year(s) Acquired		2,016
Depreciable Lives (Years)	[3]	(1)
North First Business Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		North First Business Park
Type		Office
Location		San Jose, CA
Encumbrances		$ 0
Original Land		58,402
Original Building		13,069
Costs Capitalized Subsequent to Acquisition		4,416
Land and improvements		23,377
Buildings and Improvements		16,600
Land Held for Development		35,910
Development and Construction in Progress		0
Total		75,887
Accumulated Depreciation		$ 15,839
Year(s) Built / Renovated		1,981
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
300 Binney Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		300 Binney Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		18,080
Original Building		51,262
Costs Capitalized Subsequent to Acquisition		140
Land and improvements		18,080
Buildings and Improvements		51,402
Land Held for Development		0
Development and Construction in Progress		0
Total		69,482
Accumulated Depreciation		$ 7,755
Year(s) Built / Renovated		2,013
Year(s) Acquired		2,009
Depreciable Lives (Years)	[3]	(1)
2440 West El Camino Real
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2440 West El Camino Real
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		16,741
Original Building		51,285
Costs Capitalized Subsequent to Acquisition		1,287
Land and improvements		16,741
Buildings and Improvements		52,572
Land Held for Development		0
Development and Construction in Progress		0
Total		69,313
Accumulated Depreciation		$ 10,790
Year(s) Built / Renovated		1987/2003
Year(s) Acquired		2,011
Depreciable Lives (Years)	[3]	(1)
Wisconsin Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Wisconsin Place
Type		Office
Location		Chevy Chase, MD
Encumbrances		$ 0
Original Land		0
Original Building		53,349
Costs Capitalized Subsequent to Acquisition		14,907
Land and improvements		0
Buildings and Improvements		68,256
Land Held for Development		0
Development and Construction in Progress		0
Total		68,256
Accumulated Depreciation		$ 19,775
Year(s) Built / Renovated		2,009
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
Reston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Corporate Center
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		9,135
Original Building		50,857
Costs Capitalized Subsequent to Acquisition		6,236
Land and improvements		10,148
Buildings and Improvements		56,080
Land Held for Development		0
Development and Construction in Progress		0
Total		66,228
Accumulated Depreciation		$ 26,769
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
New Dominion Technology Park, Bldg. Two
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		New Dominion Technology Park, Bldg. Two
Type		Office
Location		Herndon, VA
Encumbrances		$ 0
Original Land		5,584
Original Building		51,868
Costs Capitalized Subsequent to Acquisition		4,157
Land and improvements		6,510
Buildings and Improvements		55,099
Land Held for Development		0
Development and Construction in Progress		0
Total		61,609
Accumulated Depreciation		$ 23,652
Year(s) Built / Renovated		2,004
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
200 West Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		200 West Street
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		16,148
Original Building		24,983
Costs Capitalized Subsequent to Acquisition		10,673
Land and improvements		16,813
Buildings and Improvements		34,991
Land Held for Development		0
Development and Construction in Progress		0
Total		51,804
Accumulated Depreciation		$ 21,140
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
New Dominion Technology Park, Bldg. One
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		New Dominion Technology Park, Bldg. One
Type		Office
Location		Herndon, VA
Encumbrances		$ 32,691
Original Land		3,880
Original Building		43,227
Costs Capitalized Subsequent to Acquisition		3,882
Land and improvements		4,583
Buildings and Improvements		46,406
Land Held for Development		0
Development and Construction in Progress		0
Total		50,989
Accumulated Depreciation		$ 25,940
Year(s) Built / Renovated		2,001
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
Sumner Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Sumner Square
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		624
Original Building		28,745
Costs Capitalized Subsequent to Acquisition		19,000
Land and improvements		1,478
Buildings and Improvements		46,891
Land Held for Development		0
Development and Construction in Progress		0
Total		48,369
Accumulated Depreciation		$ 23,570
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,999
Depreciable Lives (Years)	[3]	(1)
255 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		255 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		134
Original Building		25,110
Costs Capitalized Subsequent to Acquisition		21,583
Land and improvements		548
Buildings and Improvements		46,279
Land Held for Development		0
Development and Construction in Progress		0
Total		46,827
Accumulated Depreciation		$ 28,250
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
University Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		University Place
Type		Office
Location		Cambridge, MA
Encumbrances		$ 7,407
Original Land		0
Original Building		37,091
Costs Capitalized Subsequent to Acquisition		9,007
Land and improvements		390
Buildings and Improvements		45,708
Land Held for Development		0
Development and Construction in Progress		0
Total		46,098
Accumulated Depreciation		$ 26,295
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
2600 Tower Oaks Boulevard
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2600 Tower Oaks Boulevard
Type		Office
Location		Rockville, MD
Encumbrances		$ 0
Original Land		4,243
Original Building		31,125
Costs Capitalized Subsequent to Acquisition		9,867
Land and improvements		4,785
Buildings and Improvements		40,450
Land Held for Development		0
Development and Construction in Progress		0
Total		45,235
Accumulated Depreciation		$ 21,020
Year(s) Built / Renovated		2,001
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
Quorum Office Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Quorum Office Park
Type		Office
Location		Chelmsford, MA
Encumbrances		$ 0
Original Land		3,750
Original Building		32,454
Costs Capitalized Subsequent to Acquisition		5,813
Land and improvements		5,187
Buildings and Improvements		36,830
Land Held for Development		0
Development and Construction in Progress		0
Total		42,017
Accumulated Depreciation		$ 16,594
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,000
Depreciable Lives (Years)	[3]	(1)
500 E Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		500 E Street
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		109
Original Building		22,420
Costs Capitalized Subsequent to Acquisition		14,743
Land and improvements		2,379
Buildings and Improvements		34,893
Land Held for Development		0
Development and Construction in Progress		0
Total		37,272
Accumulated Depreciation		$ 23,781
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
150 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		150 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		850
Original Building		25,042
Costs Capitalized Subsequent to Acquisition		8,540
Land and improvements		1,323
Buildings and Improvements		33,109
Land Held for Development		0
Development and Construction in Progress		0
Total		34,432
Accumulated Depreciation		$ 16,933
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
325 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		325 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		174
Original Building		12,200
Costs Capitalized Subsequent to Acquisition		11,963
Land and improvements		965
Buildings and Improvements		23,372
Land Held for Development		0
Development and Construction in Progress		0
Total		24,337
Accumulated Depreciation		$ 12,852
Year(s) Built / Renovated		1987/2013
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
105 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		105 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,299
Original Building		12,943
Costs Capitalized Subsequent to Acquisition		8,214
Land and improvements		2,395
Buildings and Improvements		20,061
Land Held for Development		0
Development and Construction in Progress		0
Total		22,456
Accumulated Depreciation		$ 13,493
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
Lexington Office Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Lexington Office Park
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		998
Original Building		1,426
Costs Capitalized Subsequent to Acquisition		18,219
Land and improvements		1,264
Buildings and Improvements		19,379
Land Held for Development		0
Development and Construction in Progress		0
Total		20,643
Accumulated Depreciation		$ 13,404
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
201 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		201 Spring Street
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		2,849
Original Building		15,303
Costs Capitalized Subsequent to Acquisition		694
Land and improvements		3,124
Buildings and Improvements		15,722
Land Held for Development		0
Development and Construction in Progress		0
Total		18,846
Accumulated Depreciation		$ 7,931
Year(s) Built / Renovated		1,997
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
The Point
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Point
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		6,395
Original Building		10,040
Costs Capitalized Subsequent to Acquisition		409
Land and improvements		6,480
Buildings and Improvements		10,364
Land Held for Development		0
Development and Construction in Progress		0
Total		16,844
Accumulated Depreciation		$ 714
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
690 Folsom Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		690 Folsom Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		3,219
Original Building		11,038
Costs Capitalized Subsequent to Acquisition		1,157
Land and improvements		3,219
Buildings and Improvements		12,195
Land Held for Development		0
Development and Construction in Progress		0
Total		15,414
Accumulated Depreciation		$ 1,295
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
91 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		91 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		784
Original Building		6,464
Costs Capitalized Subsequent to Acquisition		8,269
Land and improvements		941
Buildings and Improvements		14,576
Land Held for Development		0
Development and Construction in Progress		0
Total		15,517
Accumulated Depreciation		$ 9,849
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
92-100 Hayden Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		92-100 Hayden Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		594
Original Building		6,748
Costs Capitalized Subsequent to Acquisition		8,181
Land and improvements		802
Buildings and Improvements		14,721
Land Held for Development		0
Development and Construction in Progress		0
Total		15,523
Accumulated Depreciation		$ 12,495
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
181 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		181 Spring Street
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		1,066
Original Building		9,520
Costs Capitalized Subsequent to Acquisition		2,318
Land and improvements		1,160
Buildings and Improvements		11,744
Land Held for Development		0
Development and Construction in Progress		0
Total		12,904
Accumulated Depreciation		$ 5,194
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
195 West Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		195 West Street
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		1,611
Original Building		6,652
Costs Capitalized Subsequent to Acquisition		4,340
Land and improvements		1,858
Buildings and Improvements		10,745
Land Held for Development		0
Development and Construction in Progress		0
Total		12,603
Accumulated Depreciation		$ 7,963
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
33 Hayden Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		33 Hayden Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		266
Original Building		3,234
Costs Capitalized Subsequent to Acquisition		8,381
Land and improvements		425
Buildings and Improvements		11,456
Land Held for Development		0
Development and Construction in Progress		0
Total		11,881
Accumulated Depreciation		$ 8,211
Year(s) Built / Renovated		1,979
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7501 Boston Boulevard, Building Seven
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7501 Boston Boulevard, Building Seven
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		665
Original Building		9,273
Costs Capitalized Subsequent to Acquisition		819
Land and improvements		791
Buildings and Improvements		9,966
Land Held for Development		0
Development and Construction in Progress		0
Total		10,757
Accumulated Depreciation		$ 4,848
Year(s) Built / Renovated		1,997
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
250 Binney Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		250 Binney Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		110
Original Building		4,483
Costs Capitalized Subsequent to Acquisition		3,593
Land and improvements		273
Buildings and Improvements		7,913
Land Held for Development		0
Development and Construction in Progress		0
Total		8,186
Accumulated Depreciation		$ 5,066
Year(s) Built / Renovated		1,983
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7435 Boston Boulevard, Building One
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7435 Boston Boulevard, Building One
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		392
Original Building		3,822
Costs Capitalized Subsequent to Acquisition		3,997
Land and improvements		659
Buildings and Improvements		7,552
Land Held for Development		0
Development and Construction in Progress		0
Total		8,211
Accumulated Depreciation		$ 5,510
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
8000 Grainger Court, Building Five
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		8000 Grainger Court, Building Five
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		366
Original Building		4,282
Costs Capitalized Subsequent to Acquisition		3,375
Land and improvements		601
Buildings and Improvements		7,422
Land Held for Development		0
Development and Construction in Progress		0
Total		8,023
Accumulated Depreciation		$ 5,644
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7450 Boston Boulevard, Building Three
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7450 Boston Boulevard, Building Three
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		1,165
Original Building		4,681
Costs Capitalized Subsequent to Acquisition		1,773
Land and improvements		1,430
Buildings and Improvements		6,189
Land Held for Development		0
Development and Construction in Progress		0
Total		7,619
Accumulated Depreciation		$ 3,451
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,998
Depreciable Lives (Years)	[3]	(1)
453 Ravendale Drive
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		453 Ravendale Drive
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		5,477
Original Building		1,090
Costs Capitalized Subsequent to Acquisition		408
Land and improvements		5,477
Buildings and Improvements		1,498
Land Held for Development		0
Development and Construction in Progress		0
Total		6,975
Accumulated Depreciation		$ 472
Year(s) Built / Renovated		1,977
Year(s) Acquired		2,012
Depreciable Lives (Years)	[3]	(1)
17 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		17 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		26
Original Building		150
Costs Capitalized Subsequent to Acquisition		6,252
Land and improvements		65
Buildings and Improvements		6,363
Land Held for Development		0
Development and Construction in Progress		0
Total		6,428
Accumulated Depreciation		$ 1,098
Year(s) Built / Renovated		1,968
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7300 Boston Boulevard, Building Thirteen
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7300 Boston Boulevard, Building Thirteen
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		608
Original Building		4,773
Costs Capitalized Subsequent to Acquisition		709
Land and improvements		661
Buildings and Improvements		5,429
Land Held for Development		0
Development and Construction in Progress		0
Total		6,090
Accumulated Depreciation		$ 2,785
Year(s) Built / Renovated		2,002
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7601 Boston Boulevard, Building Eight
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7601 Boston Boulevard, Building Eight
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		200
Original Building		878
Costs Capitalized Subsequent to Acquisition		5,052
Land and improvements		551
Buildings and Improvements		5,579
Land Held for Development		0
Development and Construction in Progress		0
Total		6,130
Accumulated Depreciation		$ 4,263
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7500 Boston Boulevard, Building Six
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7500 Boston Boulevard, Building Six
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		138
Original Building		3,749
Costs Capitalized Subsequent to Acquisition		1,655
Land and improvements		406
Buildings and Improvements		5,136
Land Held for Development		0
Development and Construction in Progress		0
Total		5,542
Accumulated Depreciation		$ 3,965
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
8000 Corporate Court, Building Eleven
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		8000 Corporate Court, Building Eleven
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		136
Original Building		3,071
Costs Capitalized Subsequent to Acquisition		1,596
Land and improvements		774
Buildings and Improvements		4,029
Land Held for Development		0
Development and Construction in Progress		0
Total		4,803
Accumulated Depreciation		$ 2,909
Year(s) Built / Renovated		1,989
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7375 Boston Boulevard, Building Ten
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7375 Boston Boulevard, Building Ten
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		23
Original Building		2,685
Costs Capitalized Subsequent to Acquisition		938
Land and improvements		93
Buildings and Improvements		3,553
Land Held for Development		0
Development and Construction in Progress		0
Total		3,646
Accumulated Depreciation		$ 2,570
Year(s) Built / Renovated		1,988
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7374 Boston Boulevard, Building Four
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7374 Boston Boulevard, Building Four
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		241
Original Building		1,605
Costs Capitalized Subsequent to Acquisition		1,913
Land and improvements		398
Buildings and Improvements		3,361
Land Held for Development		0
Development and Construction in Progress		0
Total		3,759
Accumulated Depreciation		$ 2,578
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
7451 Boston Boulevard, Building Two
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7451 Boston Boulevard, Building Two
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		249
Original Building		1,542
Costs Capitalized Subsequent to Acquisition		1,659
Land and improvements		613
Buildings and Improvements		2,837
Land Held for Development		0
Development and Construction in Progress		0
Total		3,450
Accumulated Depreciation		$ 2,429
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
32 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		32 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		168
Original Building		1,943
Costs Capitalized Subsequent to Acquisition		1,012
Land and improvements		314
Buildings and Improvements		2,809
Land Held for Development		0
Development and Construction in Progress		0
Total		3,123
Accumulated Depreciation		$ 1,974
Year(s) Built / Renovated		1968/1979/1987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
164 Lexington Road
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		164 Lexington Road
Type		Office
Location		Billerica, MA
Encumbrances		$ 0
Original Land		592
Original Building		1,370
Costs Capitalized Subsequent to Acquisition		319
Land and improvements		643
Buildings and Improvements		1,638
Land Held for Development		0
Development and Construction in Progress		0
Total		2,281
Accumulated Depreciation		$ 868
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
The Avant at Reston Town Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Avant at Reston Town Center
Type		Residential
Location		Reston, VA
Encumbrances		$ 0
Original Land		20,350
Original Building		91,995
Costs Capitalized Subsequent to Acquisition		830
Land and improvements		20,350
Buildings and Improvements		92,825
Land Held for Development		0
Development and Construction in Progress		0
Total		113,175
Accumulated Depreciation		$ 9,780
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,010
Depreciable Lives (Years)	[3]	(1)
The Lofts at Atlantic Wharf
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Lofts at Atlantic Wharf
Type		Residential
Location		Boston, MA
Encumbrances		$ 0
Original Land		3,529
Original Building		54,891
Costs Capitalized Subsequent to Acquisition		1,768
Land and improvements		3,529
Buildings and Improvements		56,659
Land Held for Development		0
Development and Construction in Progress		0
Total		60,188
Accumulated Depreciation		$ 9,622
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,007
Depreciable Lives (Years)	[3]	(1)
Boston Marriott Cambridge
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Boston Marriott Cambridge
Type		Hotel
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		478
Original Building		37,918
Costs Capitalized Subsequent to Acquisition		38,799
Land and improvements		1,201
Buildings and Improvements		75,994
Land Held for Development		0
Development and Construction in Progress		0
Total		77,195
Accumulated Depreciation		$ 47,753
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
Kendall Center Green Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Green Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		35,035
Costs Capitalized Subsequent to Acquisition		7,448
Land and improvements		103
Buildings and Improvements		42,380
Land Held for Development		0
Development and Construction in Progress		0
Total		42,483
Accumulated Depreciation		$ 10,779
Year(s) Built / Renovated		1,984
Year(s) Acquired		2,006
Depreciable Lives (Years)	[3]	(1)
Kendall Center Yellow Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Yellow Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,256
Original Building		15,697
Costs Capitalized Subsequent to Acquisition		1,621
Land and improvements		1,434
Buildings and Improvements		17,140
Land Held for Development		0
Development and Construction in Progress		0
Total		18,574
Accumulated Depreciation		$ 5,181
Year(s) Built / Renovated		2,006
Year(s) Acquired		2,004
Depreciable Lives (Years)	[3]	(1)
Kendall Center Blue Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Blue Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,163
Original Building		11,633
Costs Capitalized Subsequent to Acquisition		2,283
Land and improvements		1,579
Buildings and Improvements		13,500
Land Held for Development		0
Development and Construction in Progress		0
Total		15,079
Accumulated Depreciation		$ 9,209
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
Salesforce Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Salesforce Tower
Type		Development
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		947,106
Land and improvements		200,349
Buildings and Improvements		55,318
Land Held for Development		0
Development and Construction in Progress		691,439
Total		947,106
Accumulated Depreciation		$ 116
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,013
Depreciable Lives (Years)		N/A
Signature at Reston
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Signature at Reston
Type		Development
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		203,650
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		203,650
Total		203,650
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,013
Depreciable Lives (Years)		N/A
Proto Kendall Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Proto Kendall Square
Type		Development
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		82,905
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		82,905
Total		82,905
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,015
Depreciable Lives (Years)		N/A
145 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		145 Broadway
Type		Development
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		121
Original Building		0
Costs Capitalized Subsequent to Acquisition		79,979
Land and improvements		324
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		79,776
Total		80,100
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		NA
Year(s) Acquired		1,997
Depreciable Lives (Years)		N/A
191 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		191 Spring Street
Type		Development
Location		Lexington, MA
Encumbrances		$ 0
Original Land		2,850
Original Building		27,166
Costs Capitalized Subsequent to Acquisition		35,174
Land and improvements		3,151
Buildings and Improvements		46,288
Land Held for Development		0
Development and Construction in Progress		15,751
Total		65,190
Accumulated Depreciation		$ 19,034
Year(s) Built / Renovated		1971/1995
Year(s) Acquired		1,997
Depreciable Lives (Years)	[3]	(1)
6595 Springfield Center Drive (TSA Headquarters)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		6595 Springfield Center Drive (TSA Headquarters)
Type		Development
Location		Springfield, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		41,918
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		41,918
Total		41,918
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
MacArthur Station Residences
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		MacArthur Station Residences
Type		Development
Location		Oakland, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		37,644
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		37,644
Total		37,644
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
20 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		20 CityPoint
Type		Development
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,056
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		13,056
Total		13,056
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Tower Oaks Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Tower Oaks Master Plan
Type		Land
Location		Rockville, MD
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		29,419
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		29,419
Development and Construction in Progress		0
Total		29,419
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Plaza at Almaden
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Plaza at Almaden
Type		Land
Location		San Jose, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		29,085
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		29,085
Development and Construction in Progress		0
Total		29,085
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,006
Depreciable Lives (Years)		N/A
Springfield Metro Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Springfield Metro Center
Type		Land
Location		Springfield, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		19,684
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		19,684
Development and Construction in Progress		0
Total		19,684
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
214 Third Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		214 Third Avenue
Type		Land
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,815
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		13,815
Development and Construction in Progress		0
Total		13,815
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,006
Depreciable Lives (Years)		N/A
Reston Gateway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Gateway
Type		Land
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,730
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		13,730
Development and Construction in Progress		0
Total		13,730
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
103 Fourth Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		103 Fourth Avenue
Type		Land
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		12,115
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		12,115
Development and Construction in Progress		0
Total		12,115
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Crane Meadow
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Crane Meadow
Type		Land
Location		Marlborough, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		8,836
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		8,836
Development and Construction in Progress		0
Total		8,836
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,000
Depreciable Lives (Years)		N/A
Washingtonian North
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Washingtonian North
Type		Land
Location		Gaithersburg, MD
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		7,645
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		7,645
Development and Construction in Progress		0
Total		7,645
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
2100 Pennsylvania Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2100 Pennsylvania Avenue
Type		Land
Location		Washington, DC
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		6,543
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		6,543
Development and Construction in Progress		0
Total		6,543
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Fourth and Harrison
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Fourth and Harrison
Type		Land
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		5,659
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		5,659
Development and Construction in Progress		0
Total		5,659
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
North First Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		North First Master Plan
Type		Land
Location		San Jose, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		3,018
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		3,018
Development and Construction in Progress		0
Total		3,018
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Broad Run Business Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Broad Run Business Park
Type		Land
Location		Loudoun County, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		2,367
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		2,367
Development and Construction in Progress		0
Total		2,367
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Kendall Center Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Master Plan
Type		Land
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		2,207
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		2,207
Development and Construction in Progress		0
Total		2,207
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Weston Quarry
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Weston Quarry
Type		Land
Location		Weston, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		1,194
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		1,194
Development and Construction in Progress		0
Total		1,194
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,001
Depreciable Lives (Years)		N/A
Reston Overlook Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Overlook Master Plan
Type		Land
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		39
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		39
Development and Construction in Progress		0
Total		39
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,000
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[4]	$ 2,979,281
Original Land		4,762,002
Original Building		11,634,050
Costs Capitalized Subsequent to Acquisition		4,251,184
Land and improvements		4,976,303
Buildings and Improvements		14,196,670
Land Held for Development	[5]	204,925
Development and Construction in Progress		1,269,338
Total		20,647,236
Accumulated Depreciation		4,473,895
Furniture, fixtures and equipment		37,928	$ 32,687
Furniture, fixtures and equipment accumulated depreciation		23,064
Real Estate Aggregate Cost For Tax Purposes		19,300,000
Real Estate Aggregate Accumulated Depreciation For Tax Purposes		$ 4,100,000
Real Estate and Accumulated Depreciation, Life Used for Depreciation		40 years
Unamortized deferred finance costs		$ (34,700)
Boston Properties Limited Partnership | 767 Fifth Avenue (the General Motors Building)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		767 Fifth Avenue (the General Motors Building)
Type		Office
Location		New York, NY
Encumbrances		$ 2,267,041
Original Land		1,796,252
Original Building		1,532,654
Costs Capitalized Subsequent to Acquisition		135,559
Land and improvements		1,796,252
Buildings and Improvements		1,668,213
Land Held for Development		0
Development and Construction in Progress		0
Total		3,464,465
Accumulated Depreciation		$ 222,981
Year(s) Built / Renovated		1,968
Year(s) Acquired		2,013
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Prudential Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Prudential Center
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		92,077
Original Building		948,357
Costs Capitalized Subsequent to Acquisition		441,339
Land and improvements		100,540
Buildings and Improvements		1,381,233
Land Held for Development		0
Development and Construction in Progress		0
Total		1,481,773
Accumulated Depreciation		$ 497,960
Year(s) Built / Renovated		1965/1993/2002/2016-2017
Year(s) Acquired		1998/1999/2000
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Embarcadero Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Embarcadero Center
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		179,697
Original Building		847,410
Costs Capitalized Subsequent to Acquisition		304,399
Land and improvements		180,420
Buildings and Improvements		1,151,086
Land Held for Development		0
Development and Construction in Progress		0
Total		1,331,506
Accumulated Depreciation		$ 581,932
Year(s) Built / Renovated		1970/1989
Year(s) Acquired		1998-1999
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 399 Park Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		399 Park Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		339,200
Original Building		700,358
Costs Capitalized Subsequent to Acquisition		121,810
Land and improvements		339,200
Buildings and Improvements		822,168
Land Held for Development		0
Development and Construction in Progress		0
Total		1,161,368
Accumulated Depreciation		$ 296,763
Year(s) Built / Renovated		1,961
Year(s) Acquired		2,002
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 200 Clarendon Street and Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		200 Clarendon Street and Garage
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		219,543
Original Building		667,884
Costs Capitalized Subsequent to Acquisition		139,189
Land and improvements		219,616
Buildings and Improvements		799,991
Land Held for Development		7,009
Development and Construction in Progress		0
Total		1,026,616
Accumulated Depreciation		$ 161,471
Year(s) Built / Renovated		1,976
Year(s) Acquired		2,010
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 601 Lexington Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		601 Lexington Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 672,142
Original Land		241,600
Original Building		494,782
Costs Capitalized Subsequent to Acquisition		253,504
Land and improvements		279,281
Buildings and Improvements		607,406
Land Held for Development		0
Development and Construction in Progress		103,199
Total		989,886
Accumulated Depreciation		$ 246,814
Year(s) Built / Renovated		1977/1997
Year(s) Acquired		2,001
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 250 West 55th Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		250 West 55th Street
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		285,263
Original Building		603,167
Costs Capitalized Subsequent to Acquisition		43,296
Land and improvements		285,263
Buildings and Improvements		646,463
Land Held for Development		0
Development and Construction in Progress		0
Total		931,726
Accumulated Depreciation		$ 72,058
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 100 Federal Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		100 Federal Street
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		131,067
Original Building		435,954
Costs Capitalized Subsequent to Acquisition		79,035
Land and improvements		131,067
Buildings and Improvements		514,989
Land Held for Development		0
Development and Construction in Progress		0
Total		646,056
Accumulated Depreciation		$ 97,630
Year(s) Built / Renovated		1971-1975/2017
Year(s) Acquired		2,012
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Carnegie Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Carnegie Center
Type		Office
Location		Princeton, NJ
Encumbrances		$ 0
Original Land		107,997
Original Building		389,359
Costs Capitalized Subsequent to Acquisition		140,642
Land and improvements		104,617
Buildings and Improvements		530,527
Land Held for Development		2,854
Development and Construction in Progress		0
Total		637,998
Accumulated Depreciation		$ 224,256
Year(s) Built / Renovated		1983-2016
Year(s) Acquired		1998/1999/2000/2007/2014/2017
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Times Square Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Times Square Tower
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		165,413
Original Building		380,438
Costs Capitalized Subsequent to Acquisition		49,071
Land and improvements		159,694
Buildings and Improvements		435,228
Land Held for Development		0
Development and Construction in Progress		0
Total		594,922
Accumulated Depreciation		$ 182,850
Year(s) Built / Renovated		2,004
Year(s) Acquired		2,000
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Atlantic Wharf
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Atlantic Wharf
Type		Office
Location		Boston, MA
Encumbrances		$ 0
Original Land		63,988
Original Building		454,537
Costs Capitalized Subsequent to Acquisition		17,473
Land and improvements		63,988
Buildings and Improvements		472,010
Land Held for Development		0
Development and Construction in Progress		0
Total		535,998
Accumulated Depreciation		$ 101,525
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Fountain Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Fountain Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		56,853
Original Building		306,298
Costs Capitalized Subsequent to Acquisition		17,834
Land and improvements		56,853
Buildings and Improvements		320,474
Land Held for Development		3,658
Development and Construction in Progress		0
Total		380,985
Accumulated Depreciation		$ 60,098
Year(s) Built / Renovated		1986-1990
Year(s) Acquired		2,012
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 510 Madison Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		510 Madison Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		103,000
Original Building		253,665
Costs Capitalized Subsequent to Acquisition		23,875
Land and improvements		103,000
Buildings and Improvements		277,540
Land Held for Development		0
Development and Construction in Progress		0
Total		380,540
Accumulated Depreciation		$ 54,056
Year(s) Built / Renovated		2,012
Year(s) Acquired		2,010
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 599 Lexington Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		599 Lexington Avenue
Type		Office
Location		New York, NY
Encumbrances		$ 0
Original Land		81,040
Original Building		100,507
Costs Capitalized Subsequent to Acquisition		138,108
Land and improvements		81,040
Buildings and Improvements		238,615
Land Held for Development		0
Development and Construction in Progress		0
Total		319,655
Accumulated Depreciation		$ 159,586
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 680 Folsom Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		680 Folsom Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		72,545
Original Building		219,766
Costs Capitalized Subsequent to Acquisition		7,545
Land and improvements		72,545
Buildings and Improvements		227,311
Land Held for Development		0
Development and Construction in Progress		0
Total		299,856
Accumulated Depreciation		$ 30,577
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,012
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | South of Market and Democracy Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		South of Market and Democracy Tower
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		13,603
Original Building		237,479
Costs Capitalized Subsequent to Acquisition		14,655
Land and improvements		13,603
Buildings and Improvements		252,134
Land Held for Development		0
Development and Construction in Progress		0
Total		265,737
Accumulated Depreciation		$ 87,651
Year(s) Built / Renovated		2008-2009
Year(s) Acquired		2,003
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 601 Massachusetts Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		601 Massachusetts Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		95,310
Original Building		165,173
Costs Capitalized Subsequent to Acquisition		2,341
Land and improvements		95,310
Buildings and Improvements		167,514
Land Held for Development		0
Development and Construction in Progress		0
Total		262,824
Accumulated Depreciation		$ 12,177
Year(s) Built / Renovated		2,016
Year(s) Acquired		2,008
Depreciable Lives (Years)		(1)
Boston Properties Limited Partnership | Bay Colony Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Bay Colony Corporate Center
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		18,789
Original Building		148,451
Costs Capitalized Subsequent to Acquisition		73,418
Land and improvements		18,789
Buildings and Improvements		221,869
Land Held for Development		0
Development and Construction in Progress		0
Total		240,658
Accumulated Depreciation		$ 57,320
Year(s) Built / Renovated		1985-1989
Year(s) Acquired		2,011
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Gateway Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Gateway Center
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		28,255
Original Building		139,245
Costs Capitalized Subsequent to Acquisition		52,630
Land and improvements		29,029
Buildings and Improvements		191,101
Land Held for Development		0
Development and Construction in Progress		0
Total		220,130
Accumulated Depreciation		$ 101,191
Year(s) Built / Renovated		1984/1986/2002
Year(s) Acquired		1,999
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 535 Mission Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		535 Mission Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		40,933
Original Building		148,378
Costs Capitalized Subsequent to Acquisition		3,259
Land and improvements		40,933
Buildings and Improvements		151,637
Land Held for Development		0
Development and Construction in Progress		0
Total		192,570
Accumulated Depreciation		$ 14,637
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,013
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 2200 Pennsylvania Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2200 Pennsylvania Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		0
Original Building		183,541
Costs Capitalized Subsequent to Acquisition		4,907
Land and improvements		0
Buildings and Improvements		188,448
Land Held for Development		0
Development and Construction in Progress		0
Total		188,448
Accumulated Depreciation		$ 46,780
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,008
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Mountain View Research Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Mountain View Research Park
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		95,066
Original Building		68,373
Costs Capitalized Subsequent to Acquisition		8,136
Land and improvements		95,066
Buildings and Improvements		76,509
Land Held for Development		0
Development and Construction in Progress		0
Total		171,575
Accumulated Depreciation		$ 15,146
Year(s) Built / Renovated		1977-1981/2007-2013
Year(s) Acquired		2,013
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Reservoir Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reservoir Place
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		18,605
Original Building		104,124
Costs Capitalized Subsequent to Acquisition		39,180
Land and improvements		19,089
Buildings and Improvements		142,820
Land Held for Development		0
Development and Construction in Progress		0
Total		161,909
Accumulated Depreciation		$ 65,309
Year(s) Built / Renovated		1955/1987/2017
Year(s) Acquired		1997/1998
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 1330 Connecticut Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		1330 Connecticut Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		25,982
Original Building		82,311
Costs Capitalized Subsequent to Acquisition		28,226
Land and improvements		25,982
Buildings and Improvements		110,537
Land Held for Development		0
Development and Construction in Progress		0
Total		136,519
Accumulated Depreciation		$ 21,484
Year(s) Built / Renovated		1,984
Year(s) Acquired		2,004
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Kingstowne Towne Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kingstowne Towne Center
Type		Office
Location		Alexandria, VA
Encumbrances		$ 0
Original Land		18,021
Original Building		109,038
Costs Capitalized Subsequent to Acquisition		1,207
Land and improvements		18,021
Buildings and Improvements		110,245
Land Held for Development		0
Development and Construction in Progress		0
Total		128,266
Accumulated Depreciation		$ 39,018
Year(s) Built / Renovated		2003-2006
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 1333 New Hampshire Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		1333 New Hampshire Avenue
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		34,032
Original Building		85,660
Costs Capitalized Subsequent to Acquisition		6,079
Land and improvements		34,032
Buildings and Improvements		91,739
Land Held for Development		0
Development and Construction in Progress		0
Total		125,771
Accumulated Depreciation		$ 39,279
Year(s) Built / Renovated		1,996
Year(s) Acquired		2,003
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | One Freedom Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		One Freedom Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		9,929
Original Building		84,504
Costs Capitalized Subsequent to Acquisition		26,981
Land and improvements		9,883
Buildings and Improvements		111,531
Land Held for Development		0
Development and Construction in Progress		0
Total		121,414
Accumulated Depreciation		$ 49,037
Year(s) Built / Renovated		2,000
Year(s) Acquired		2,003
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Weston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Weston Corporate Center
Type		Office
Location		Weston, MA
Encumbrances		$ 0
Original Land		25,753
Original Building		92,312
Costs Capitalized Subsequent to Acquisition		(123)
Land and improvements		25,854
Buildings and Improvements		92,088
Land Held for Development		0
Development and Construction in Progress		0
Total		117,942
Accumulated Depreciation		$ 23,125
Year(s) Built / Renovated		2,010
Year(s) Acquired		2,001
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Capital Gallery
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Capital Gallery
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		4,725
Original Building		29,565
Costs Capitalized Subsequent to Acquisition		79,383
Land and improvements		6,128
Buildings and Improvements		107,545
Land Held for Development		0
Development and Construction in Progress		0
Total		113,673
Accumulated Depreciation		$ 63,717
Year(s) Built / Renovated		1981/2006
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Two Freedom Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Two Freedom Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		13,930
Original Building		77,739
Costs Capitalized Subsequent to Acquisition		17,167
Land and improvements		13,866
Buildings and Improvements		94,970
Land Held for Development		0
Development and Construction in Progress		0
Total		108,836
Accumulated Depreciation		$ 46,532
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,003
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | One and Two Reston Overlook
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		One and Two Reston Overlook
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		16,456
Original Building		66,192
Costs Capitalized Subsequent to Acquisition		20,693
Land and improvements		15,074
Buildings and Improvements		88,267
Land Held for Development		0
Development and Construction in Progress		0
Total		103,341
Accumulated Depreciation		$ 43,627
Year(s) Built / Renovated		1,999
Year(s) Acquired		2,000
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Discovery Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Discovery Square
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		11,198
Original Building		71,782
Costs Capitalized Subsequent to Acquisition		18,869
Land and improvements		11,146
Buildings and Improvements		90,703
Land Held for Development		0
Development and Construction in Progress		0
Total		101,849
Accumulated Depreciation		$ 41,928
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,003
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 355 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		355 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		18,863
Original Building		53,346
Costs Capitalized Subsequent to Acquisition		27,152
Land and improvements		21,098
Buildings and Improvements		78,263
Land Held for Development		0
Development and Construction in Progress		0
Total		99,361
Accumulated Depreciation		$ 26,850
Year(s) Built / Renovated		1981/1996/2013
Year(s) Acquired		2,006
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 140 Kendrick Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		140 Kendrick Street
Type		Office
Location		Needham, MA
Encumbrances		$ 0
Original Land		18,095
Original Building		66,905
Costs Capitalized Subsequent to Acquisition		13,502
Land and improvements		18,095
Buildings and Improvements		80,407
Land Held for Development		0
Development and Construction in Progress		0
Total		98,502
Accumulated Depreciation		$ 28,111
Year(s) Built / Renovated		2,000
Year(s) Acquired		2,004
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 10 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		10 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		1,953
Original Building		85,752
Costs Capitalized Subsequent to Acquisition		2,670
Land and improvements		1,953
Buildings and Improvements		88,422
Land Held for Development		0
Development and Construction in Progress		0
Total		90,375
Accumulated Depreciation		$ 4,673
Year(s) Built / Renovated		2,016
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 90 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		90 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		19,104
Original Building		52,078
Costs Capitalized Subsequent to Acquisition		17,001
Land and improvements		20,741
Buildings and Improvements		67,442
Land Held for Development		0
Development and Construction in Progress		0
Total		88,183
Accumulated Depreciation		$ 19,220
Year(s) Built / Renovated		1983/1998/2013
Year(s) Acquired		2,006
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 230 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		230 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		13,189
Original Building		49,823
Costs Capitalized Subsequent to Acquisition		23,619
Land and improvements		13,189
Buildings and Improvements		73,442
Land Held for Development		0
Development and Construction in Progress		0
Total		86,631
Accumulated Depreciation		$ 26,200
Year(s) Built / Renovated		1,992
Year(s) Acquired		2,005
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 77 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		77 CityPoint
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		13,847
Original Building		60,383
Costs Capitalized Subsequent to Acquisition		5,598
Land and improvements		13,847
Buildings and Improvements		65,981
Land Held for Development		0
Development and Construction in Progress		0
Total		79,828
Accumulated Depreciation		$ 23,024
Year(s) Built / Renovated		2,008
Year(s) Acquired		2,001
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Waltham Weston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Waltham Weston Corporate Center
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		10,385
Original Building		60,694
Costs Capitalized Subsequent to Acquisition		8,043
Land and improvements		10,350
Buildings and Improvements		68,772
Land Held for Development		0
Development and Construction in Progress		0
Total		79,122
Accumulated Depreciation		$ 29,359
Year(s) Built / Renovated		2,003
Year(s) Acquired		1,999
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 3625-3635 Peterson Way
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		3625-3635 Peterson Way
Type		Office
Location		Santa Clara, CA
Encumbrances		$ 0
Original Land		63,206
Original Building		14,879
Costs Capitalized Subsequent to Acquisition		138
Land and improvements		63,206
Buildings and Improvements		14,879
Land Held for Development		138
Development and Construction in Progress		0
Total		78,223
Accumulated Depreciation		$ 5,120
Year(s) Built / Renovated		1,979
Year(s) Acquired		2,016
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | North First Business Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		North First Business Park
Type		Office
Location		San Jose, CA
Encumbrances		$ 0
Original Land		58,402
Original Building		13,069
Costs Capitalized Subsequent to Acquisition		4,393
Land and improvements		23,371
Buildings and Improvements		16,583
Land Held for Development		35,910
Development and Construction in Progress		0
Total		75,864
Accumulated Depreciation		$ 15,839
Year(s) Built / Renovated		1,981
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 300 Binney Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		300 Binney Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		18,080
Original Building		51,262
Costs Capitalized Subsequent to Acquisition		140
Land and improvements		18,080
Buildings and Improvements		51,402
Land Held for Development		0
Development and Construction in Progress		0
Total		69,482
Accumulated Depreciation		$ 7,755
Year(s) Built / Renovated		2,013
Year(s) Acquired		2,009
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 2440 West El Camino Real
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2440 West El Camino Real
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		16,741
Original Building		51,285
Costs Capitalized Subsequent to Acquisition		1,287
Land and improvements		16,741
Buildings and Improvements		52,572
Land Held for Development		0
Development and Construction in Progress		0
Total		69,313
Accumulated Depreciation		$ 10,790
Year(s) Built / Renovated		1987/2003
Year(s) Acquired		2,011
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Wisconsin Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Wisconsin Place
Type		Office
Location		Chevy Chase, MD
Encumbrances		$ 0
Original Land		0
Original Building		53,349
Costs Capitalized Subsequent to Acquisition		14,907
Land and improvements		0
Buildings and Improvements		68,256
Land Held for Development		0
Development and Construction in Progress		0
Total		68,256
Accumulated Depreciation		$ 19,775
Year(s) Built / Renovated		2,009
Year(s) Acquired		2,004
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Reston Corporate Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Corporate Center
Type		Office
Location		Reston, VA
Encumbrances		$ 0
Original Land		9,135
Original Building		50,857
Costs Capitalized Subsequent to Acquisition		3,625
Land and improvements		9,496
Buildings and Improvements		54,121
Land Held for Development		0
Development and Construction in Progress		0
Total		63,617
Accumulated Depreciation		$ 26,178
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,998
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | New Dominion Technology Park, Bldg. Two
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		New Dominion Technology Park, Bldg. Two
Type		Office
Location		Herndon, VA
Encumbrances		$ 0
Original Land		5,584
Original Building		51,868
Costs Capitalized Subsequent to Acquisition		412
Land and improvements		5,574
Buildings and Improvements		52,290
Land Held for Development		0
Development and Construction in Progress		0
Total		57,864
Accumulated Depreciation		$ 22,801
Year(s) Built / Renovated		2,004
Year(s) Acquired		1,998
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 200 West Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		200 West Street
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		16,148
Original Building		24,983
Costs Capitalized Subsequent to Acquisition		8,012
Land and improvements		16,148
Buildings and Improvements		32,995
Land Held for Development		0
Development and Construction in Progress		0
Total		49,143
Accumulated Depreciation		$ 20,538
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | New Dominion Technology Park, Bldg. One
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		New Dominion Technology Park, Bldg. One
Type		Office
Location		Herndon, VA
Encumbrances		$ 32,691
Original Land		3,880
Original Building		43,227
Costs Capitalized Subsequent to Acquisition		1,072
Land and improvements		3,880
Buildings and Improvements		44,299
Land Held for Development		0
Development and Construction in Progress		0
Total		48,179
Accumulated Depreciation		$ 25,304
Year(s) Built / Renovated		2,001
Year(s) Acquired		1,998
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Sumner Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Sumner Square
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		624
Original Building		28,745
Costs Capitalized Subsequent to Acquisition		16,920
Land and improvements		958
Buildings and Improvements		45,331
Land Held for Development		0
Development and Construction in Progress		0
Total		46,289
Accumulated Depreciation		$ 23,103
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,999
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 255 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		255 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		134
Original Building		25,110
Costs Capitalized Subsequent to Acquisition		19,927
Land and improvements		134
Buildings and Improvements		45,037
Land Held for Development		0
Development and Construction in Progress		0
Total		45,171
Accumulated Depreciation		$ 27,878
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | University Place
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		University Place
Type		Office
Location		Cambridge, MA
Encumbrances		$ 7,407
Original Land		0
Original Building		37,091
Costs Capitalized Subsequent to Acquisition		7,557
Land and improvements		27
Buildings and Improvements		44,621
Land Held for Development		0
Development and Construction in Progress		0
Total		44,648
Accumulated Depreciation		$ 25,971
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,998
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 2600 Tower Oaks Boulevard
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2600 Tower Oaks Boulevard
Type		Office
Location		Rockville, MD
Encumbrances		$ 0
Original Land		4,243
Original Building		31,125
Costs Capitalized Subsequent to Acquisition		7,704
Land and improvements		4,244
Buildings and Improvements		38,828
Land Held for Development		0
Development and Construction in Progress		0
Total		43,072
Accumulated Depreciation		$ 20,529
Year(s) Built / Renovated		2,001
Year(s) Acquired		1,998
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Quorum Office Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Quorum Office Park
Type		Office
Location		Chelmsford, MA
Encumbrances		$ 0
Original Land		3,750
Original Building		32,454
Costs Capitalized Subsequent to Acquisition		4,115
Land and improvements		4,762
Buildings and Improvements		35,557
Land Held for Development		0
Development and Construction in Progress		0
Total		40,319
Accumulated Depreciation		$ 16,211
Year(s) Built / Renovated		2,001
Year(s) Acquired		2,000
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 500 E Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		500 E Street
Type		Office
Location		Washington, DC
Encumbrances		$ 0
Original Land		109
Original Building		22,420
Costs Capitalized Subsequent to Acquisition		11,503
Land and improvements		1,569
Buildings and Improvements		32,463
Land Held for Development		0
Development and Construction in Progress		0
Total		34,032
Accumulated Depreciation		$ 23,051
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 150 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		150 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		850
Original Building		25,042
Costs Capitalized Subsequent to Acquisition		6,535
Land and improvements		822
Buildings and Improvements		31,605
Land Held for Development		0
Development and Construction in Progress		0
Total		32,427
Accumulated Depreciation		$ 16,477
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 325 Main Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		325 Main Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		174
Original Building		12,200
Costs Capitalized Subsequent to Acquisition		11,192
Land and improvements		772
Buildings and Improvements		22,794
Land Held for Development		0
Development and Construction in Progress		0
Total		23,566
Accumulated Depreciation		$ 12,675
Year(s) Built / Renovated		1987/2013
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 105 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		105 Broadway
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,299
Original Building		12,943
Costs Capitalized Subsequent to Acquisition		6,108
Land and improvements		1,868
Buildings and Improvements		18,482
Land Held for Development		0
Development and Construction in Progress		0
Total		20,350
Accumulated Depreciation		$ 13,015
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Lexington Office Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Lexington Office Park
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		998
Original Building		1,426
Costs Capitalized Subsequent to Acquisition		17,455
Land and improvements		1,073
Buildings and Improvements		18,806
Land Held for Development		0
Development and Construction in Progress		0
Total		19,879
Accumulated Depreciation		$ 13,235
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 201 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		201 Spring Street
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		2,849
Original Building		15,303
Costs Capitalized Subsequent to Acquisition		(405)
Land and improvements		2,849
Buildings and Improvements		14,898
Land Held for Development		0
Development and Construction in Progress		0
Total		17,747
Accumulated Depreciation		$ 7,681
Year(s) Built / Renovated		1,997
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | The Point
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Point
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		6,395
Original Building		10,040
Costs Capitalized Subsequent to Acquisition		409
Land and improvements		6,480
Buildings and Improvements		10,364
Land Held for Development		0
Development and Construction in Progress		0
Total		16,844
Accumulated Depreciation		$ 714
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 690 Folsom Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		690 Folsom Street
Type		Office
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		3,219
Original Building		11,038
Costs Capitalized Subsequent to Acquisition		1,157
Land and improvements		3,219
Buildings and Improvements		12,195
Land Held for Development		0
Development and Construction in Progress		0
Total		15,414
Accumulated Depreciation		$ 1,295
Year(s) Built / Renovated		2,015
Year(s) Acquired		2,012
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 91 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		91 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		784
Original Building		6,464
Costs Capitalized Subsequent to Acquisition		7,642
Land and improvements		784
Buildings and Improvements		14,106
Land Held for Development		0
Development and Construction in Progress		0
Total		14,890
Accumulated Depreciation		$ 9,705
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 92-100 Hayden Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		92-100 Hayden Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		594
Original Building		6,748
Costs Capitalized Subsequent to Acquisition		7,452
Land and improvements		619
Buildings and Improvements		14,175
Land Held for Development		0
Development and Construction in Progress		0
Total		14,794
Accumulated Depreciation		$ 12,329
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 181 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		181 Spring Street
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		1,066
Original Building		9,520
Costs Capitalized Subsequent to Acquisition		1,941
Land and improvements		1,066
Buildings and Improvements		11,461
Land Held for Development		0
Development and Construction in Progress		0
Total		12,527
Accumulated Depreciation		$ 5,109
Year(s) Built / Renovated		1,999
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 195 West Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		195 West Street
Type		Office
Location		Waltham, MA
Encumbrances		$ 0
Original Land		1,611
Original Building		6,652
Costs Capitalized Subsequent to Acquisition		3,351
Land and improvements		1,611
Buildings and Improvements		10,003
Land Held for Development		0
Development and Construction in Progress		0
Total		11,614
Accumulated Depreciation		$ 7,736
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 33 Hayden Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		33 Hayden Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		266
Original Building		3,234
Costs Capitalized Subsequent to Acquisition		7,744
Land and improvements		266
Buildings and Improvements		10,978
Land Held for Development		0
Development and Construction in Progress		0
Total		11,244
Accumulated Depreciation		$ 8,067
Year(s) Built / Renovated		1,979
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7501 Boston Boulevard, Building Seven
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7501 Boston Boulevard, Building Seven
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		665
Original Building		9,273
Costs Capitalized Subsequent to Acquisition		314
Land and improvements		665
Buildings and Improvements		9,587
Land Held for Development		0
Development and Construction in Progress		0
Total		10,252
Accumulated Depreciation		$ 4,732
Year(s) Built / Renovated		1,997
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 250 Binney Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		250 Binney Street
Type		Office
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		110
Original Building		4,483
Costs Capitalized Subsequent to Acquisition		2,939
Land and improvements		110
Buildings and Improvements		7,422
Land Held for Development		0
Development and Construction in Progress		0
Total		7,532
Accumulated Depreciation		$ 4,922
Year(s) Built / Renovated		1,983
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7435 Boston Boulevard, Building One
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7435 Boston Boulevard, Building One
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		392
Original Building		3,822
Costs Capitalized Subsequent to Acquisition		3,304
Land and improvements		486
Buildings and Improvements		7,032
Land Held for Development		0
Development and Construction in Progress		0
Total		7,518
Accumulated Depreciation		$ 5,354
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 8000 Grainger Court, Building Five
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		8000 Grainger Court, Building Five
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		366
Original Building		4,282
Costs Capitalized Subsequent to Acquisition		2,781
Land and improvements		453
Buildings and Improvements		6,976
Land Held for Development		0
Development and Construction in Progress		0
Total		7,429
Accumulated Depreciation		$ 5,511
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7450 Boston Boulevard, Building Three
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7450 Boston Boulevard, Building Three
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		1,165
Original Building		4,681
Costs Capitalized Subsequent to Acquisition		1,359
Land and improvements		1,327
Buildings and Improvements		5,878
Land Held for Development		0
Development and Construction in Progress		0
Total		7,205
Accumulated Depreciation		$ 3,354
Year(s) Built / Renovated		1,987
Year(s) Acquired		1,998
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 453 Ravendale Drive
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		453 Ravendale Drive
Type		Office
Location		Mountain View, CA
Encumbrances		$ 0
Original Land		5,477
Original Building		1,090
Costs Capitalized Subsequent to Acquisition		408
Land and improvements		5,477
Buildings and Improvements		1,498
Land Held for Development		0
Development and Construction in Progress		0
Total		6,975
Accumulated Depreciation		$ 472
Year(s) Built / Renovated		1,977
Year(s) Acquired		2,012
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 17 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		17 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		26
Original Building		150
Costs Capitalized Subsequent to Acquisition		6,095
Land and improvements		26
Buildings and Improvements		6,245
Land Held for Development		0
Development and Construction in Progress		0
Total		6,271
Accumulated Depreciation		$ 1,062
Year(s) Built / Renovated		1,968
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7300 Boston Boulevard, Building Thirteen
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7300 Boston Boulevard, Building Thirteen
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		608
Original Building		4,773
Costs Capitalized Subsequent to Acquisition		497
Land and improvements		608
Buildings and Improvements		5,270
Land Held for Development		0
Development and Construction in Progress		0
Total		5,878
Accumulated Depreciation		$ 2,737
Year(s) Built / Renovated		2,002
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7601 Boston Boulevard, Building Eight
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7601 Boston Boulevard, Building Eight
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		200
Original Building		878
Costs Capitalized Subsequent to Acquisition		4,359
Land and improvements		378
Buildings and Improvements		5,059
Land Held for Development		0
Development and Construction in Progress		0
Total		5,437
Accumulated Depreciation		$ 4,107
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7500 Boston Boulevard, Building Six
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7500 Boston Boulevard, Building Six
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		138
Original Building		3,749
Costs Capitalized Subsequent to Acquisition		1,122
Land and improvements		273
Buildings and Improvements		4,736
Land Held for Development		0
Development and Construction in Progress		0
Total		5,009
Accumulated Depreciation		$ 3,845
Year(s) Built / Renovated		1,985
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 8000 Corporate Court, Building Eleven
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		8000 Corporate Court, Building Eleven
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		136
Original Building		3,071
Costs Capitalized Subsequent to Acquisition		1,245
Land and improvements		686
Buildings and Improvements		3,766
Land Held for Development		0
Development and Construction in Progress		0
Total		4,452
Accumulated Depreciation		$ 2,826
Year(s) Built / Renovated		1,989
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7375 Boston Boulevard, Building Ten
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7375 Boston Boulevard, Building Ten
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		23
Original Building		2,685
Costs Capitalized Subsequent to Acquisition		757
Land and improvements		47
Buildings and Improvements		3,418
Land Held for Development		0
Development and Construction in Progress		0
Total		3,465
Accumulated Depreciation		$ 2,532
Year(s) Built / Renovated		1,988
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7374 Boston Boulevard, Building Four
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7374 Boston Boulevard, Building Four
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		241
Original Building		1,605
Costs Capitalized Subsequent to Acquisition		1,530
Land and improvements		303
Buildings and Improvements		3,073
Land Held for Development		0
Development and Construction in Progress		0
Total		3,376
Accumulated Depreciation		$ 2,494
Year(s) Built / Renovated		1,984
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 7451 Boston Boulevard, Building Two
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		7451 Boston Boulevard, Building Two
Type		Office
Location		Springfield, VA
Encumbrances		$ 0
Original Land		249
Original Building		1,542
Costs Capitalized Subsequent to Acquisition		1,346
Land and improvements		535
Buildings and Improvements		2,602
Land Held for Development		0
Development and Construction in Progress		0
Total		3,137
Accumulated Depreciation		$ 2,357
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 32 Hartwell Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		32 Hartwell Avenue
Type		Office
Location		Lexington, MA
Encumbrances		$ 0
Original Land		168
Original Building		1,943
Costs Capitalized Subsequent to Acquisition		426
Land and improvements		168
Buildings and Improvements		2,369
Land Held for Development		0
Development and Construction in Progress		0
Total		2,537
Accumulated Depreciation		$ 1,840
Year(s) Built / Renovated		1968/1979/1987
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 164 Lexington Road
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		164 Lexington Road
Type		Office
Location		Billerica, MA
Encumbrances		$ 0
Original Land		592
Original Building		1,370
Costs Capitalized Subsequent to Acquisition		117
Land and improvements		592
Buildings and Improvements		1,487
Land Held for Development		0
Development and Construction in Progress		0
Total		2,079
Accumulated Depreciation		$ 819
Year(s) Built / Renovated		1,982
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | The Avant at Reston Town Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Avant at Reston Town Center
Type		Residential
Location		Reston, VA
Encumbrances		$ 0
Original Land		20,350
Original Building		91,995
Costs Capitalized Subsequent to Acquisition		830
Land and improvements		20,350
Buildings and Improvements		92,825
Land Held for Development		0
Development and Construction in Progress		0
Total		113,175
Accumulated Depreciation		$ 9,780
Year(s) Built / Renovated		2,014
Year(s) Acquired		2,010
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | The Lofts at Atlantic Wharf
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		The Lofts at Atlantic Wharf
Type		Residential
Location		Boston, MA
Encumbrances		$ 0
Original Land		3,529
Original Building		54,891
Costs Capitalized Subsequent to Acquisition		1,768
Land and improvements		3,529
Buildings and Improvements		56,659
Land Held for Development		0
Development and Construction in Progress		0
Total		60,188
Accumulated Depreciation		$ 9,622
Year(s) Built / Renovated		2,011
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Boston Marriott Cambridge
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Boston Marriott Cambridge
Type		Hotel
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		478
Original Building		37,918
Costs Capitalized Subsequent to Acquisition		35,908
Land and improvements		478
Buildings and Improvements		73,826
Land Held for Development		0
Development and Construction in Progress		0
Total		74,304
Accumulated Depreciation		$ 47,101
Year(s) Built / Renovated		1,986
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Kendall Center Green Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Green Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		35,035
Costs Capitalized Subsequent to Acquisition		7,034
Land and improvements		0
Buildings and Improvements		42,069
Land Held for Development		0
Development and Construction in Progress		0
Total		42,069
Accumulated Depreciation		$ 10,687
Year(s) Built / Renovated		1,984
Year(s) Acquired		2,006
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Kendall Center Yellow Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Yellow Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,256
Original Building		15,697
Costs Capitalized Subsequent to Acquisition		909
Land and improvements		1,256
Buildings and Improvements		16,606
Land Held for Development		0
Development and Construction in Progress		0
Total		17,862
Accumulated Depreciation		$ 5,024
Year(s) Built / Renovated		2,006
Year(s) Acquired		2,004
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Kendall Center Blue Garage
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Blue Garage
Type		Garage
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		1,163
Original Building		11,633
Costs Capitalized Subsequent to Acquisition		618
Land and improvements		1,163
Buildings and Improvements		12,251
Land Held for Development		0
Development and Construction in Progress		0
Total		13,414
Accumulated Depreciation		$ 8,834
Year(s) Built / Renovated		1,990
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | Salesforce Tower
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Salesforce Tower
Type		Development
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		947,106
Land and improvements		200,349
Buildings and Improvements		55,318
Land Held for Development		0
Development and Construction in Progress		691,439
Total		947,106
Accumulated Depreciation		$ 116
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,013
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Signature at Reston
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Signature at Reston
Type		Development
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		203,650
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		203,650
Total		203,650
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,013
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Proto Kendall Square
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Proto Kendall Square
Type		Development
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		82,905
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		82,905
Total		82,905
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,015
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 145 Broadway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		145 Broadway
Type		Development
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		121
Original Building		0
Costs Capitalized Subsequent to Acquisition		79,776
Land and improvements		121
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		79,776
Total		79,897
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		NA
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	N/A
Boston Properties Limited Partnership | 191 Spring Street
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		191 Spring Street
Type		Development
Location		Lexington, MA
Encumbrances		$ 0
Original Land		2,850
Original Building		27,166
Costs Capitalized Subsequent to Acquisition		34,542
Land and improvements		2,850
Buildings and Improvements		45,957
Land Held for Development		0
Development and Construction in Progress		15,751
Total		64,558
Accumulated Depreciation		$ 18,934
Year(s) Built / Renovated		1971/1995
Year(s) Acquired		1,997
Depreciable Lives (Years)	[6]	(1)
Boston Properties Limited Partnership | 6595 Springfield Center Drive (TSA Headquarters)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		6595 Springfield Center Drive (TSA Headquarters)
Type		Development
Location		Springfield, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		41,918
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		41,918
Total		41,918
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)	[6]	N/A
Boston Properties Limited Partnership | MacArthur Station Residences
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		MacArthur Station Residences
Type		Development
Location		Oakland, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		37,644
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		37,644
Total		37,644
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 20 CityPoint
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		20 CityPoint
Type		Development
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,056
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		0
Development and Construction in Progress		13,056
Total		13,056
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Tower Oaks Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Tower Oaks Master Plan
Type		Land
Location		Rockville, MD
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		29,419
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		29,419
Development and Construction in Progress		0
Total		29,419
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Plaza at Almaden
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Plaza at Almaden
Type		Land
Location		San Jose, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		29,085
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		29,085
Development and Construction in Progress		0
Total		29,085
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,006
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Springfield Metro Center
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Springfield Metro Center
Type		Land
Location		Springfield, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		19,684
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		19,684
Development and Construction in Progress		0
Total		19,684
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 214 Third Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		214 Third Avenue
Type		Land
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,815
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		13,815
Development and Construction in Progress		0
Total		13,815
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,006
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Reston Gateway
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Gateway
Type		Land
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,730
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		13,730
Development and Construction in Progress		0
Total		13,730
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 103 Fourth Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		103 Fourth Avenue
Type		Land
Location		Waltham, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		12,115
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		12,115
Development and Construction in Progress		0
Total		12,115
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Crane Meadow
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Crane Meadow
Type		Land
Location		Marlborough, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		8,836
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		8,836
Development and Construction in Progress		0
Total		8,836
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,000
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Washingtonian North
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Washingtonian North
Type		Land
Location		Gaithersburg, MD
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		7,645
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		7,645
Development and Construction in Progress		0
Total		7,645
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 2100 Pennsylvania Avenue
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		2100 Pennsylvania Avenue
Type		Land
Location		Washington, DC
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		6,543
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		6,543
Development and Construction in Progress		0
Total		6,543
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Fourth and Harrison
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Fourth and Harrison
Type		Land
Location		San Francisco, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		5,659
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		5,659
Development and Construction in Progress		0
Total		5,659
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | North First Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		North First Master Plan
Type		Land
Location		San Jose, CA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		3,018
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		3,018
Development and Construction in Progress		0
Total		3,018
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,007
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Broad Run Business Park
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Broad Run Business Park
Type		Land
Location		Loudoun County, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		2,367
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		2,367
Development and Construction in Progress		0
Total		2,367
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		1,998
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Kendall Center Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Kendall Center Master Plan
Type		Land
Location		Cambridge, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		2,207
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		2,207
Development and Construction in Progress		0
Total		2,207
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		N/A
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Weston Quarry
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Weston Quarry
Type		Land
Location		Weston, MA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		1,194
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		1,194
Development and Construction in Progress		0
Total		1,194
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,001
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Reston Overlook Master Plan
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Name		Reston Overlook Master Plan
Type		Land
Location		Reston, VA
Encumbrances		$ 0
Original Land		0
Original Building		0
Costs Capitalized Subsequent to Acquisition		39
Land and improvements		0
Buildings and Improvements		0
Land Held for Development		39
Development and Construction in Progress		0
Total		39
Accumulated Depreciation		$ 0
Year(s) Built / Renovated		N/A
Year(s) Acquired		2,000
Depreciable Lives (Years)		N/A
Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life Used for Depreciation		life of the lease
Minimum [Member] | Boston Properties Limited Partnership
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life Used for Depreciation		life of the lease
[1]	Includes unamortized deferred financing costs totaling approximately $(34.7) million.
[2]	Includes pre-development costs.
[3]	Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.
[4]	Includes unamortized deferred financing costs totaling approximately $(34.7) million.
[5]	Includes pre-development costs.
[6]	Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.

Real Estate and Accumulated 107

Real Estate and Accumulated Depreciation Activity of Real Estate and Accumulated Depreciation (BPLP) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Real Estate, Balance at the beginning of the year	$ 20,114,576	$ 19,451,683	$ 19,208,417
Real Estate, Additions to / improvements of real estate	1,099,286	977,287	700,792
Real Estate, Assets sold / written off	(155,148)	(314,394)	(457,526)
Real Estate, Balance at the end of the year	21,058,714	20,114,576	19,451,683
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Accumulated depreciation, Balance at beginning of the year	4,201,891	3,905,940	3,529,978
Accumulated depreciation, Depreciation expense	497,059	560,024	486,450
Accumulated depreciation, Assets sold / written off	(132,380)	(264,073)	(110,488)
Accumulated depreciation, Balance at end of the year	4,566,570	4,201,891	3,905,940
Boston Properties Limited Partnership
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Real Estate, Balance at the beginning of the year	19,701,185	19,031,289	18,786,572
Real Estate, Additions to / improvements of real estate	1,099,286	977,287	700,792
Real Estate, Assets sold / written off	(153,235)	(307,391)	(456,075)
Real Estate, Balance at the end of the year	20,647,236	19,701,185	19,031,289
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Accumulated depreciation, Balance at beginning of the year	4,116,020	3,826,862	3,458,640
Accumulated depreciation, Depreciation expense	488,919	548,397	478,457
Accumulated depreciation, Assets sold / written off	(131,044)	(259,239)	(110,235)
Accumulated depreciation, Balance at end of the year	$ 4,473,895	$ 4,116,020	$ 3,826,862