Boston Properties (BXP) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 02, 2017
Entity Information [Line Items]
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
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		154,322,266
Boston Properties Limited Partnership
Entity Information [Line Items]
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
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

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,084,588 and $6,760,078 at September 30, 2017 and December 31, 2016, respectively)	$ 20,859,245	$ 20,147,263
Less: accumulated depreciation (amounts related to VIEs of $(825,390) and $(758,640) at September 30, 2017 and December 31, 2016, respectively)	(4,484,798)	(4,222,235)
Total real estate	16,374,447	15,925,028
Cash and cash equivalents (amounts related to VIEs of $285,089 and $253,999 at September 30, 2017 and December 31, 2016, respectively)	493,055	356,914
Cash held in escrows (amounts related to VIEs of $6,179 and $4,955 at September 30, 2017 and December 31, 2016, respectively)	83,779	63,174
Investments in securities	27,981	23,814
Tenant and other receivables (amounts related to VIEs of $19,891 and $23,525 at September 30, 2017 and December 31, 2016, respectively)	79,750	92,548
Accrued rental income (amounts related to VIEs of $232,336 and $224,185 at September 30, 2017 and December 31, 2016, respectively)	835,415	799,138
Deferred charges, net (amounts related to VIEs of $268,727 and $290,436 at September 30, 2017 and December 31, 2016, respectively)	657,474	686,163
Prepaid expenses and other assets (amounts related to VIEs of $68,330 and $42,718 at September 30, 2017 and December 31, 2016, respectively)	144,817	129,666
Investments in unconsolidated joint ventures	611,800	775,198
Total assets	19,308,518	18,851,643
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,941,550 and $2,018,483 at September 30, 2017 and December 31, 2016, respectively)	2,982,067	2,063,087
Unsecured senior notes, net	7,252,567	7,245,953
Unsecured line of credit	0	0
Unsecured term loan	0	0
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at September 30, 2017 and December 31, 2016, respectively)	0	307,093
Outside members’ notes payable (amounts related to VIEs of $0 and $180,000 at September 30, 2017 and December 31, 2016, respectively)	0	180,000
Accounts payable and accrued expenses (amounts related to VIEs of $106,772 and $110,457 at September 30, 2017 and December 31, 2016, respectively)	325,440	298,524
Dividends and distributions payable	130,434	130,308
Accrued interest payable (amounts related to VIEs of $6,800 and $162,226 at September 30, 2017 and December 31, 2016, respectively)	99,100	243,933
Other liabilities (amounts related to VIEs of $146,517 and $175,146 at September 30, 2017 and December 31, 2016, respectively)	419,215	450,821
Total liabilities	11,208,823	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, $.01 par value, 50,000,000 shares authorized
5.25% Series B cumulative redeemable preferred stock/unit, liquidation preference $2,500 per share/unit, 92,000 shares authorized, 80,000 shares/units issued and outstanding at September 30, 2017 and December 31, 2016	200,000	200,000
Common stock, $0.01 par value, 250,000,000 shares authorized, 154,401,166 and 153,869,075 issued and 154,322,266 and 153,790,175 outstanding at September 30, 2017 and December 31, 2016, respectively	1,543	1,538
Additional paid-in capital	6,370,932	6,333,424
Dividends in excess of earnings	(692,739)	(693,694)
Treasury common stock at cost, 78,900 shares at September 30, 2017 and December 31, 2016	(2,722)	(2,722)
Accumulated other comprehensive loss	(51,796)	(52,251)
Total stockholders’ equity attributable to Boston Properties, Inc.	5,825,218	5,786,295
Noncontrolling interests:
Common units of Boston Properties Limited Partnership	605,802	614,982
Property partnerships	1,668,675	1,530,647
Total equity / capital	8,099,695	7,931,924
Total liabilities and equity / capital	19,308,518	18,851,643
Boston Properties Limited Partnership
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $7,084,588 and $6,760,078 at September 30, 2017 and December 31, 2016, respectively)	20,447,767	19,733,872
Less: accumulated depreciation (amounts related to VIEs of $(825,390) and $(758,640) at September 30, 2017 and December 31, 2016, respectively)	(4,394,077)	(4,136,364)
Total real estate	16,053,690	15,597,508
Cash and cash equivalents (amounts related to VIEs of $285,089 and $253,999 at September 30, 2017 and December 31, 2016, respectively)	493,055	356,914
Cash held in escrows (amounts related to VIEs of $6,179 and $4,955 at September 30, 2017 and December 31, 2016, respectively)	83,779	63,174
Investments in securities	27,981	23,814
Tenant and other receivables (amounts related to VIEs of $19,891 and $23,525 at September 30, 2017 and December 31, 2016, respectively)	79,750	92,548
Accrued rental income (amounts related to VIEs of $232,336 and $224,185 at September 30, 2017 and December 31, 2016, respectively)	835,415	799,138
Deferred charges, net (amounts related to VIEs of $268,727 and $290,436 at September 30, 2017 and December 31, 2016, respectively)	657,474	686,163
Prepaid expenses and other assets (amounts related to VIEs of $68,330 and $42,718 at September 30, 2017 and December 31, 2016, respectively)	144,817	129,666
Investments in unconsolidated joint ventures	611,800	775,198
Total assets	18,987,761	18,524,123
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,941,550 and $2,018,483 at September 30, 2017 and December 31, 2016, respectively)	2,982,067	2,063,087
Unsecured senior notes, net	7,252,567	7,245,953
Unsecured line of credit	0	0
Unsecured term loan	0	0
Mezzanine notes payable (amounts related to VIEs of $0 and $307,093 at September 30, 2017 and December 31, 2016, respectively)	0	307,093
Outside members’ notes payable (amounts related to VIEs of $0 and $180,000 at September 30, 2017 and December 31, 2016, respectively)	0	180,000
Accounts payable and accrued expenses (amounts related to VIEs of $106,772 and $110,457 at September 30, 2017 and December 31, 2016, respectively)	325,440	298,524
Dividends and distributions payable	130,434	130,308
Accrued interest payable (amounts related to VIEs of $6,800 and $162,226 at September 30, 2017 and December 31, 2016, respectively)	99,100	243,933
Other liabilities (amounts related to VIEs of $146,517 and $175,146 at September 30, 2017 and December 31, 2016, respectively)	419,215	450,821
Total liabilities	11,208,823	10,919,719
Commitments and contingencies	0	0
Noncontrolling interest:
Redeemable partnership units—16,812,329 and 17,079,511 common units and 816,982 and 904,588 long term incentive units outstanding at redemption value at September 30, 2017 and December 31, 2016, respectively	2,166,290	2,262,040
Preferred stock, $.01 par value, 50,000,000 shares authorized
5.25% Series B cumulative redeemable preferred stock/unit, liquidation preference $2,500 per share/unit, 92,000 shares authorized, 80,000 shares/units issued and outstanding at September 30, 2017 and December 31, 2016	193,623	193,623
Accumulated other comprehensive loss	(60,346)	(60,853)
Noncontrolling interests:
Boston Properties Limited Partnership partners’ capital—1,719,516 and 1,717,743 general partner units and 152,602,750 and 152,072,432 limited partner units outstanding at September 30, 2017 and December 31, 2016, respectively	3,750,350	3,618,094
Noncontrolling interests in property partnerships	1,668,675	1,530,647
Total equity / capital	5,612,648	5,342,364
Total liabilities and equity / capital	$ 18,987,761	$ 18,524,123

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
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	154,401,166	153,869,075
Common stock, shares outstanding	154,322,266	153,790,175
Treasury common stock at cost, shares	78,900	78,900
General Partners' Capital Account, Units Outstanding	1,719,516
Limited Partners' Capital Account, Units Outstanding	152,602,750
Real Estate Investment Property, at Cost	$ 20,859,245	$ 20,147,263
Accumulated depreciation	(4,484,798)	(4,222,235)
Cash and Cash Equivalents	493,055	356,914
Cash held in escrow	83,779	63,174
Tenant and other receivables	79,750	92,548
Accrued rental income	835,415	799,138
Deferred Charges, net	657,474	686,163
Prepaid expense and other assets	144,817	129,666
Mortgage notes payable, net	2,982,067	2,063,087
Mezzanine notes payable	0	307,093
Accounts payable and accrued expenses	325,440	298,524
Accrued interest payable	99,100	243,933
Other Liabilities	$ 419,215	$ 450,821
Series B Cumulative Redeemable Preferred Stock [Member]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	92,000	92,000
Series B Dividend Rate Percentage	5.25%	5.25%
Series B, Liquidation Preference Per Share (dollars per share)	$ 2,500	$ 2,500
Series B, shares issued	80,000	80,000
Series B, Shares Outstanding (in shares)	80,000	80,000
Boston Properties Limited Partnership
NonControlling Interest Redeemable Partnership Units Common Units Shares Outstanding	16,812,329	17,079,511
NonControlling Interest Redeemable Partnership Units Common Units Long Term Incentive Units At Redemption Value Shares Outstanding	816,982	904,588
General Partners' Capital Account, Units Outstanding	1,719,516	1,717,743
Limited Partners' Capital Account, Units Outstanding	152,602,750	152,072,432
Real Estate Investment Property, at Cost	$ 20,447,767	$ 19,733,872
Accumulated depreciation	(4,394,077)	(4,136,364)
Cash and Cash Equivalents	493,055	356,914
Cash held in escrow	83,779	63,174
Tenant and other receivables	79,750	92,548
Accrued rental income	835,415	799,138
Deferred Charges, net	657,474	686,163
Prepaid expense and other assets	144,817	129,666
Mortgage notes payable, net	2,982,067	2,063,087
Mezzanine notes payable	0	307,093
Accounts payable and accrued expenses	325,440	298,524
Accrued interest payable	99,100	243,933
Other Liabilities	$ 419,215	$ 450,821
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock [Member]
Series B Dividend Rate Percentage	5.25%	5.25%
Series B, Liquidation Preference Per Share (dollars per share)	$ 2,500	$ 2,500
Series B, shares issued	80,000	80,000
Series B, Shares Outstanding (in shares)	80,000	80,000
VIE
Real Estate Investment Property, at Cost	$ 7,084,588	$ 6,760,078
Accumulated depreciation	(825,390)	(758,640)
Cash and Cash Equivalents	285,089	253,999
Cash held in escrow	6,179	4,955
Tenant and other receivables	19,891	23,525
Accrued rental income	232,336	224,185
Deferred Charges, net	268,727	290,436
Prepaid expense and other assets	68,330	42,718
Mortgage notes payable, net	2,941,550	2,018,483
Mezzanine notes payable	0	307,093
Outside member's notes payable	0	180,000
Accounts payable and accrued expenses	106,772	110,457
Accrued interest payable	6,800	162,226
Other Liabilities	146,517	175,146
VIE | Boston Properties Limited Partnership
Real Estate Investment Property, at Cost	7,084,588	6,760,078
Accumulated depreciation	(825,390)	(758,640)
Cash and Cash Equivalents	285,089	253,999
Cash held in escrow	6,179	4,955
Tenant and other receivables	19,891	23,525
Accrued rental income	232,336	224,185
Deferred Charges, net	268,727	290,436
Prepaid expense and other assets	68,330	42,718
Mortgage notes payable, net	2,941,550	2,018,483
Mezzanine notes payable	0	307,093
Outside member's notes payable	0	180,000
Accounts payable and accrued expenses	106,772	110,457
Accrued interest payable	6,800	162,226
Other Liabilities	$ 146,517	$ 175,146

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue
Base rent	$ 513,269	$ 489,312	$ 1,537,373	$ 1,518,826
Recoveries from tenants	94,476	92,560	272,803	267,852
Parking and other	26,092	24,638	78,164	75,576
Total rental revenue	633,837	606,510	1,888,340	1,862,254
Hotel revenue	13,064	12,354	33,859	33,919
Development and management services	10,811	6,364	24,648	18,586
Total revenue	657,712	625,228	1,946,847	1,914,759
Expenses
Rental	237,341	228,560	696,082	665,670
Hotel	8,447	8,118	23,942	23,730
General and administrative	25,792	25,165	84,319	79,936
Transaction costs	239	249	572	1,187
Impairment loss	0	1,783	0	1,783
Depreciation and amortization	152,164	203,748	463,288	516,371
Total expenses	423,983	467,623	1,268,203	1,288,677
Operating income	233,729	157,605	678,644	626,082
Other income (expense)
Income from unconsolidated joint ventures	843	1,464	7,035	5,489
Interest and other income	1,329	3,628	3,447	6,657
Gains from investments in securities	944	976	2,716	1,713
Gains (losses) from early extinguishments of debt	0	(371)	14,354	(371)
Losses from interest rate contracts	0	(140)	0	(140)
Interest expense	(92,032)	(104,641)	(282,709)	(314,953)
Income before gains on sales of real estate	144,813	58,521	423,487	324,477
Gains on sales of real estate	2,891	12,983	6,791	80,606
Net income	147,704	71,504	430,278	405,083
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships	(14,340)	17,225	(33,967)	(53)
Noncontrolling interest—common units of Boston Properties Limited Partnership	(13,402)	(9,387)	(40,350)	(42,120)
Net income attributable to the Company	119,962	79,342	355,961	362,910
Preferred dividends / distributions	(2,625)	(2,589)	(7,875)	(7,796)
Net income attributable to the Company's common shareholders / unitholders	$ 117,337	$ 76,753	$ 348,086	$ 355,114
Basic earnings per common share / unit attributable to the Company's common shareholders / unitholders
Net income (in dollars per share / unit)	$ 0.76	$ 0.50	$ 2.26	$ 2.31
Weighted average number of common shares / units outstanding	154,355	153,754	154,132	153,681
Diluted earnings per common share / unit attributable to the Company's common shareholders / unitholders
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 0.76	$ 0.50	$ 2.26	$ 2.31
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)	154,483	154,136	154,344	153,971
Dividends / Distributions, Per Share / Unit, Declared	$ 0.75	$ 0.65	$ 2.25	$ 1.95
Boston Properties Limited Partnership
Revenue
Base rent	$ 513,269	$ 489,312	$ 1,537,373	$ 1,518,826
Recoveries from tenants	94,476	92,560	272,803	267,852
Parking and other	26,092	24,638	78,164	75,576
Total rental revenue	633,837	606,510	1,888,340	1,862,254
Hotel revenue	13,064	12,354	33,859	33,919
Development and management services	10,811	6,364	24,648	18,586
Total revenue	657,712	625,228	1,946,847	1,914,759
Expenses
Rental	237,341	228,560	696,082	665,670
Hotel	8,447	8,118	23,942	23,730
General and administrative	25,792	25,165	84,319	79,936
Transaction costs	239	249	572	1,187
Impairment loss	0	1,783	0	1,783
Depreciation and amortization	150,210	198,582	457,102	507,234
Total expenses	422,029	462,457	1,262,017	1,279,540
Operating income	235,683	162,771	684,830	635,219
Other income (expense)
Income from unconsolidated joint ventures	843	1,464	7,035	5,489
Interest and other income	1,329	3,628	3,447	6,657
Gains from investments in securities	944	976	2,716	1,713
Gains (losses) from early extinguishments of debt	0	(371)	14,354	(371)
Losses from interest rate contracts	0	(140)	0	(140)
Interest expense	(92,032)	(104,641)	(282,709)	(314,953)
Income before gains on sales of real estate	146,767	63,687	429,673	333,614
Gains on sales of real estate	2,891	12,983	7,368	82,775
Net income	149,658	76,670	437,041	416,389
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships	(14,340)	17,225	(33,967)	(53)
Net income attributable to the Company	135,318	93,895	403,074	416,336
Preferred dividends / distributions	(2,625)	(2,589)	(7,875)	(7,796)
Net income attributable to the Company's common shareholders / unitholders	$ 132,693	$ 91,306	$ 395,199	$ 408,540
Basic earnings per common share / unit attributable to the Company's common shareholders / unitholders
Net income (in dollars per share / unit)	$ 0.77	$ 0.53	$ 2.30	$ 2.38
Weighted average number of common shares / units outstanding	171,691	171,379	171,649	171,353
Diluted earnings per common share / unit attributable to the Company's common shareholders / unitholders
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 0.77	$ 0.53	$ 2.30	$ 2.38
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)	171,819	171,761	171,861	171,643
Dividends / Distributions, Per Share / Unit, Declared	$ 0.75	$ 0.65	$ 2.25	$ 1.95

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net income		$ 147,704	$ 71,504	$ 430,278	$ 405,083
Other comprehensive income (loss):
Effective portion of interest rate contracts		0	5,712	(6,133)	(85,285)
Amortization of interest rate contracts	[1]	1,665	1,190	4,368	2,445
Other comprehensive income (loss)		1,665	6,902	(1,765)	(82,840)
Comprehensive income		149,369	78,406	428,513	322,243
Comprehensive income attributable to noncontrolling interests		(27,742)	7,838	(74,317)	(42,173)
Other comprehensive income (loss) attributable to noncontrolling interests		(300)	(1,097)	2,220	23,011
Comprehensive income attributable to the Company		121,327	85,147	356,416	303,081
Boston Properties Limited Partnership
Net income		149,658	76,670	437,041	416,389
Other comprehensive income (loss):
Effective portion of interest rate contracts		0	5,712	(6,133)	(85,285)
Amortization of interest rate contracts	[2]	1,665	1,190	4,368	2,445
Other comprehensive income (loss)		1,665	6,902	(1,765)	(82,840)
Comprehensive income		151,323	83,572	435,276	333,549
Comprehensive income attributable to noncontrolling interests		(14,484)	16,812	(31,695)	16,081
Comprehensive income attributable to the Company		$ 136,839	$ 100,384	$ 403,581	$ 349,630
[1]	Amounts reclassified from comprehensive income primarily to interest expense within the Boston Properties, Inc.’s Consolidated Statements of Operations.
[2]	Amounts reclassified from comprehensive income primarily to interest expense within the 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 (Income) Loss [Member]	Noncontrolling Interests [Member]
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]
Conversion of operating partnership units to Common Stock, shares		173,000
Conversion of operating partnership units to Common Stock, value	0	$ 2		5,879				(5,881)
Allocated net income for the year	405,083				362,910			42,173
Dividends/distributions declared	(342,980)				(307,480)			(35,500)
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		14,000
Net activity from stock option and incentive plan, value	24,290	$ 0		2,870				21,420
Sale of interests in property partnerships	0			1,320				(1,320)
Contributions from noncontrolling interests in property partnerships	6,737							6,737
Distributions to noncontrolling interests in property partnerships	(38,694)							(38,694)
Effective portion of interest rate contracts	(85,285)						(62,022)	(23,263)
Amortization of interest rate contracts	2,445						2,193	252
Reallocation of noncontrolling interest	0			10,094				(10,094)
Equity, value at Sep. 30, 2016	7,859,253	$ 1,538	200,000	6,326,580	(725,522)	(2,722)	(73,943)	2,133,322
Equity, shares at Sep. 30, 2016		153,773,000
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]
Conversion of operating partnership units to Common Stock, shares		492,000
Conversion of operating partnership units to Common Stock, value		$ 5		16,807				(16,812)
Allocated net income for the year	$ 430,278				355,961			74,317
Dividends/distributions declared	(395,026)				(354,734)			(40,292)
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	29,191			2,920				26,271
Cumulative effect of a change in accounting principle	(2,035)				(272)			(1,763)
Contributions from noncontrolling interests in property partnerships	147,772							147,772
Distributions to noncontrolling interests in property partnerships	(41,439)							(41,439)
Effective portion of interest rate contracts	(6,133)						(3,304)	(2,829)
Amortization of interest rate contracts	4,368						3,759	609
Reallocation of noncontrolling interest				16,986				(16,986)
Equity, value at Sep. 30, 2017	$ 8,099,695	$ 1,543	$ 200,000	$ 6,370,932	$ (692,739)	$ (2,722)	$ (51,796)	$ 2,274,477
Equity, shares at Sep. 30, 2017	154,322,266	154,322,000

Consolidated Statement of Partn

Consolidated Statement of Partners' Capital Statement - USD ($) $ in Thousands	Total	Boston Properties Limited Partnership
Beginning Balance at Dec. 31, 2015		$ 3,684,522
Contributions		3,269
Net income allocable to general and limited partner units		374,216
Distributions		(307,480)
Accumulated other comprehensive income (loss)		(59,829)
Unearned compensation		1,651
Conversion of redeemable partnership units		5,881
Adjustment to reflect redeemable partnership units at redemption value		(151,545)
Ending Balance at Sep. 30, 2016		3,550,685
Beginning Balance at Dec. 31, 2016		3,811,717
Contributions		4,937
Net income allocable to general and limited partner units		362,724
Distributions		(354,734)
Accumulated other comprehensive income (loss)		455
Cumulative effect of a change in accounting principle	$ (2,035)	(272)
Unearned compensation		(1,222)
Conversion of redeemable partnership units		16,812
Adjustment to reflect redeemable partnership units at redemption value		103,556
Ending Balance at Sep. 30, 2017		$ 3,943,973

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 430,278	$ 405,083
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	463,288	516,371
Impairment loss	0	1,783
Non-cash compensation expense	27,260	25,290
Income from unconsolidated joint ventures	(7,035)	(5,489)
Distributions of net cash flow from operations of unconsolidated joint ventures	8,563	11,645
Gains from investments in securities	(2,716)	(1,713)
(Gains) losses from early extinguishments of debt	(14,444)	371
Non-cash portion of interest expense	(6,667)	(27,386)
Gains on sales of real estate	(6,791)	(80,606)
Change in assets and liabilities:
Cash held in escrows	7,795	1,675
Tenant and other receivables, net	12,528	22,135
Accrued rental income, net	(36,012)	(14,618)
Prepaid expenses and other assets	(13,633)	4,883
Accounts payable and accrued expenses	7,861	16,852
Accrued interest payable	(144,833)	44,242
Other liabilities	(65,031)	(114,321)
Tenant leasing costs	(67,699)	(62,412)
Total adjustments	162,434	338,702
Net cash provided by operating activities	592,712	743,785
Cash flows from investing activities:
Acquisitions of real estate	(15,953)	(78,000)
Construction in progress	(452,283)	(359,716)
Building and other capital improvements	(162,395)	(81,842)
Tenant improvements	(152,749)	(167,762)
Proceeds from sales of real estate	29,810	122,750
Proceeds from sales of real estate placed in escrow	(29,810)	(122,647)
Proceeds from sales of real estate released from escrow	16,640	122,647
Cash released from escrow for investing activities	9,638	6,694
Cash released from escrow for land sale contracts	0	1,403
Cash placed in escrow for investment in unconsolidated joint venture	(25,000)	0
Capital contributions to unconsolidated joint ventures	(89,874)	(546,982)
Capital distributions from unconsolidated joint ventures	251,000	0
Investments in securities, net	(1,451)	(929)
Net cash used in investing activities	(622,427)	(1,104,384)
Cash flows from financing activities:
Proceeds from mortgage notes payable	2,300,000	0
Repayments of mortgage notes payable	(1,313,890)	(1,323,284)
Proceeds from unsecured senior notes	0	1,989,790
Borrowings on unsecured line of credit	470,000	0
Repayments of unsecured line of credit	(470,000)	0
Repayments of mezzanine notes payable	(306,000)	0
Repayments of outside members’ notes payable	(70,424)	0
Payments on capital lease obligations	(373)	0
Payments on real estate financing transactions	(1,306)	(4,712)
Deposit on mortgage note payable interest rate lock	(23,200)	0
Return of deposit on mortgage note payable interest rate lock	23,200	0
Deferred financing costs	(44,083)	(16,101)
Net proceeds from equity transactions	241	(270)
Dividends and distributions	(394,900)	(557,262)
Contributions from noncontrolling interests in property partnerships	38,196	6,737
Distributions to noncontrolling interests in property partnerships	(41,605)	(38,694)
Net cash provided by financing activities	165,856	56,204
Net increase (decrease) in cash and cash equivalents	136,141	(304,395)
Cash and cash equivalents, beginning of period	356,914	723,718
Cash and cash equivalents, end of period	493,055	419,323
Supplemental disclosures:
Cash paid for interest	477,189	327,053
Interest capitalized	43,286	28,956
Non-cash investing and financing activities:
Write off of fully depreciated real estate	(103,972)	(168,861)
Additions to real estate included in accounts payable and accrued expenses	36,609	11,864
Real estate acquired through capital lease	28,962	0
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	109,576	0
Dividends and distributions declared but not paid	130,434	113,038
Conversions of noncontrolling interests to stockholders’ equity	16,812	5,881
Issuance of restricted securities to employees	35,711	33,711
Boston Properties Limited Partnership
Cash flows from operating activities:
Net income	437,041	416,389
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	457,102	507,234
Impairment loss	0	1,783
Non-cash compensation expense	27,260	25,290
Income from unconsolidated joint ventures	(7,035)	(5,489)
Distributions of net cash flow from operations of unconsolidated joint ventures	8,563	11,645
Gains from investments in securities	(2,716)	(1,713)
(Gains) losses from early extinguishments of debt	(14,444)	371
Non-cash portion of interest expense	(6,667)	(27,386)
Gains on sales of real estate	(7,368)	(82,775)
Change in assets and liabilities:
Cash held in escrows	7,795	1,675
Tenant and other receivables, net	12,528	22,135
Accrued rental income, net	(36,012)	(14,618)
Prepaid expenses and other assets	(13,633)	4,883
Accounts payable and accrued expenses	7,861	16,852
Accrued interest payable	(144,833)	44,242
Other liabilities	(65,031)	(114,321)
Tenant leasing costs	(67,699)	(62,412)
Total adjustments	155,671	327,396
Net cash provided by operating activities	592,712	743,785
Cash flows from investing activities:
Acquisitions of real estate	(15,953)	(78,000)
Construction in progress	(452,283)	(359,716)
Building and other capital improvements	(162,395)	(81,842)
Tenant improvements	(152,749)	(167,762)
Proceeds from sales of real estate	29,810	122,750
Proceeds from sales of real estate placed in escrow	(29,810)	(122,647)
Proceeds from sales of real estate released from escrow	16,640	122,647
Cash released from escrow for investing activities	9,638	6,694
Cash released from escrow for land sale contracts	0	1,403
Cash placed in escrow for investment in unconsolidated joint venture	(25,000)	0
Capital contributions to unconsolidated joint ventures	(89,874)	(546,982)
Capital distributions from unconsolidated joint ventures	251,000	0
Investments in securities, net	(1,451)	(929)
Net cash used in investing activities	(622,427)	(1,104,384)
Cash flows from financing activities:
Proceeds from mortgage notes payable	2,300,000	0
Repayments of mortgage notes payable	(1,313,890)	(1,323,284)
Proceeds from unsecured senior notes	0	1,989,790
Borrowings on unsecured line of credit	470,000	0
Repayments of unsecured line of credit	(470,000)	0
Repayments of mezzanine notes payable	(306,000)	0
Repayments of outside members’ notes payable	(70,424)	0
Payments on capital lease obligations	(373)	0
Payments on real estate financing transactions	(1,306)	(4,712)
Deposit on mortgage note payable interest rate lock	(23,200)	0
Return of deposit on mortgage note payable interest rate lock	23,200	0
Deferred financing costs	(44,083)	(16,101)
Net proceeds from equity transactions	241	(270)
Dividends and distributions	(394,900)	(557,262)
Contributions from noncontrolling interests in property partnerships	38,196	6,737
Distributions to noncontrolling interests in property partnerships	(41,605)	(38,694)
Net cash provided by financing activities	165,856	56,204
Net increase (decrease) in cash and cash equivalents	136,141	(304,395)
Cash and cash equivalents, beginning of period	356,914	723,718
Cash and cash equivalents, end of period	493,055	419,323
Supplemental disclosures:
Cash paid for interest	477,189	327,053
Interest capitalized	43,286	28,956
Non-cash investing and financing activities:
Write off of fully depreciated real estate	(102,795)	(164,528)
Additions to real estate included in accounts payable and accrued expenses	36,609	11,864
Real estate acquired through capital lease	28,962	0
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	109,576	0
Dividends and distributions declared but not paid	130,434	113,038
Conversions of noncontrolling interests to stockholders’ equity	16,812	5,881
Issuance of restricted securities to employees	$ 35,711	$ 33,711

Organization

Organization	9 Months Ended
	Sep. 30, 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 September 30, 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 such OP Unit for one share of Common Stock. Because the number of shares of Common Stock outstanding at all times equals the number of OP Units that Boston Properties, Inc. owns, one share of Common Stock is generally the economic equivalent of one OP Unit, and the quarterly distribution that may be paid to the holder of an OP Unit equals the quarterly dividend that may be paid to the holder of a share of Common Stock. 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 8 , 9 and 11 ). At September 30, 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 9 ). Properties At September 30, 2017 , the Company owned or had interests in a portfolio of 177 commercial real estate properties (the “Properties”) aggregating approximately 49.8 million net rentable square feet of primarily Class A office properties, including ten properties under construction/redevelopment totaling approximately 5.7 million net rentable square feet. At September 30, 2017 , the Properties consisted of: • 166 Office properties (including seven properties under construction/redevelopment); • one hotel; • five retail properties; and • five residential properties (including three properties under construction). 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 And Summa

Basis Of Presentation And Summary Of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis Of Presentation And Summary Of Significant Accounting Policies	2. Basis of Presentation and Summary of Significant Accounting Policies Boston Properties, Inc. does not have any other significant assets, liabilities or operations, other than its investment in 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. The accompanying interim financial statements are unaudited; however, the financial statements have been prepared in accordance with generally accepted accounting principles (“GAAP”) for interim financial information and in conjunction with the rules and regulations of the Securities and Exchange Commission. Accordingly, they do not include all of the disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting solely of normal recurring matters) necessary for a fair statement of the financial statements for these interim periods have been included. The results of operations for the interim periods are not necessarily indicative of the results to be obtained for other interim periods or for the full fiscal year. The year-end consolidated balance sheet data was derived from audited financial statements, but does not include all disclosure required by GAAP. These financial statements should be read in conjunction with the Company’s financial statements and notes thereto contained in the Company’s Annual Report in the Company’s Form 10-K for its fiscal year ended December 31, 2016 . Fair Value of Financial Instruments The Company determines the fair value of its unsecured senior notes using market prices. The inputs used in determining the fair value of the Company’s unsecured senior notes are categorized at a level 1 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) due to the fact that the Company uses quoted market rates to value these instruments. However, the inputs used in determining the fair value could be categorized at a level 2 basis (as defined in the accounting standards for Fair Value Measurements and Disclosures) if trading volumes are low. The Company determines the fair value of its mortgage notes payable using discounted cash flow 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 internally 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 and unsecured senior notes, net and the Company’s corresponding estimate of fair value as of September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 December 31, 2016 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Mortgage notes payable, net $ 2,982,067 $ 3,049,617 $ 2,063,087 $ 2,092,237 Mezzanine notes payable — — 307,093 308,344 Unsecured senior notes, net 7,252,567 7,533,164 7,245,953 7,428,077 Total $ 10,234,634 $ 10,582,781 $ 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 Accounting Standards Codification (“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 has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. The Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. Variable Interest Entities (VIEs) 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 September 30, 2017 , Boston Properties, Inc. has identified seven consolidated VIEs, including Boston Properties Limited Partnership. The VIEs own (1) the following five in-service properties: 767 Fifth Avenue (the General Motors Building), Times Square Tower, 601 Lexington Avenue, Atlantic Wharf Office Building and 100 Federal Street and (2) Salesforce Tower, which is currently under development. 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 interest in property partnerships in the accompanying Consolidated Financial Statements (See Note 8 ). In addition, Boston Properties, Inc.’s 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. All of Boston Properties, Inc.’s debt is an obligation of Boston Properties Limited Partnership. Variable Interest Entities Not Consolidated The Company has determined that its BNY Tower Holdings LLC joint venture, which owns Dock 72 at the Brooklyn Navy Yard, and its 7750 Wisconsin Avenue LLC joint venture, which owns 7750 Wisconsin Avenue, are VIEs. The Company does not consolidate these entities because the Company does not have the power to direct the activities that, when taken together, most significantly impact each VIE’s performance and, therefore, the Company is not considered to be the primary beneficiary. Recent Accounting Pronouncements In May 2014, the Financial Standards Accounting Board (“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 will adopt ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The Company’s project team has completed the compilation of the inventory of the sources of revenue that will be impacted by the adoption of ASU 2014-09. The Company expects that executory costs and certain non-lease components of revenue from leases (upon the adoption of ASU 2016-02), certain of its development and management services revenue and gains on sales of real estate may be impacted by the adoption of ASU 2014-09, although the Company anticipates that the impact will be to the pattern of revenue recognition and not the total revenue recognized over time. The Company is progressing with its analysis and evaluation of the impact that the adoption of ASU 2014-09 will have on the recognition pattern of each of its sources of revenue and is nearing completion of its assessment of the overall impact of adopting ASU 2014-09. The Company does not expect that the adoption of ASU 2014-09 will have a material impact on its 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 process 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 the underlying leased asset re cognized as real estate. The Company expects that executory costs and certain other non-lease components will need to be accounted for separately from the lease component of the lease with the lease component continuing to be recognized on a straight-line basis over the lease term and the executory costs and certain other non-lease components being accounted for under the new revenue recognition guidance in ASU 2014-09. 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 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 is currently assessing the potential impact that the adoption of ASU 2017-05 will have on its 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 is currently assessing the potential impact that the adoption of ASU 2017-09 will have on its 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 is currently assessing the potential impact that the adoption of ASU 2017-12 will have on its consolidated financial statements.

Real Estate

Real Estate	9 Months Ended
	Sep. 30, 2017
Real Estate [Abstract]
Real Estate	3. Real Estate Boston Properties, Inc. Real estate consisted of the following at September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 December 31, 2016 Land $ 4,880,331 $ 4,879,020 Land held for future development (1) 212,585 246,656 Buildings and improvements 12,155,126 11,890,626 Tenant improvements 2,186,953 2,060,315 Furniture, fixtures and equipment 37,612 32,687 Construction in progress 1,386,638 1,037,959 Total 20,859,245 20,147,263 Less: Accumulated depreciation (4,484,798 ) (4,222,235 ) $ 16,374,447 $ 15,925,028 _______________ (1) Includes pre-development costs. Boston Properties Limited Partnership Real estate consisted of the following at September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 December 31, 2016 Land $ 4,775,955 $ 4,774,460 Land held for future development (1) 212,585 246,656 Buildings and improvements 11,848,024 11,581,795 Tenant improvements 2,186,953 2,060,315 Furniture, fixtures and equipment 37,612 32,687 Construction in progress 1,386,638 1,037,959 Total 20,447,767 19,733,872 Less: Accumulated depreciation (4,394,077 ) (4,136,364 ) $ 16,053,690 $ 15,597,508 _______________ (1) Includes pre-development costs. Development On April 6, 2017, the Company commenced the development 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 approximately 623,000 net rentable square feet of Class A office space 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. 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, 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 obligations 38,826 Interest portion (9,864 ) Present value of net expected minimum 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 $1.1 million of revenue and approximately ( $0.1 million ) of earnings to the Company for the period from May 15, 2017 through September 30, 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 $(33,000) and $(18,000) of net loss to the Company for the three and nine months ended September 30, 2016, 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.

Investments in Unconsolidated J

Investments in Unconsolidated Joint Ventures	9 Months Ended
	Sep. 30, 2017
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	4. Investments in Unconsolidated Joint Ventures The investments in unconsolidated joint ventures consist of the following at September 30, 2017 and December 31, 2016 : Nominal % Ownership Carrying Value of Investment (1) Entity Properties September 30, 2017 December 31, 2016 (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (8,474 ) $ (8,134 ) The Metropolitan Square Associates LLC Metropolitan Square 20.0 % 2,537 2,004 BP/CRF 901 New York Avenue LLC 901 New York Avenue 25.0 % (2) (10,747 ) (10,564 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 40,158 41,605 Annapolis Junction NFM, LLC Annapolis Junction 50.0 % (4) 18,771 20,539 540 Madison Venture LLC 540 Madison Avenue 60.0 % 67,046 67,816 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (3,642 ) (3,389 ) 501 K Street LLC 1001 6th Street 50.0 % (5) 42,442 42,528 Podium Developer LLC The Hub on Causeway 50.0 % 55,917 29,869 Residential Tower Developer LLC The Hub on Causeway - Residential 50.0 % 25,811 20,803 Hotel Tower Developer LLC The Hub on Causeway - Hotel 50.0 % 1,596 933 1265 Main Office JV LLC 1265 Main Street 50.0 % 4,686 4,779 BNY Tower Holdings LLC Dock 72 at the Brooklyn Navy Yard 50.0 % (6) 67,901 33,699 CA-Colorado Center Limited Partnership Colorado Center 50.0 % 263,834 510,623 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % (6) 21,101 N/A $ 588,937 $ 753,111 _______________ (1) Investments with deficit balances aggregating approximately $22.9 million and $22.1 million at September 30, 2017 and December 31, 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 entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking garage and infrastructure of the project. (4) The joint venture owns 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) The 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 exception, 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: September 30, 2017 December 31, 2016 (in thousands) ASSETS Real estate and development in process, net $ 1,716,447 $ 1,519,217 Other assets 374,484 297,263 Total assets $ 2,090,931 $ 1,816,480 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 1,411,401 $ 865,665 Other liabilities 86,971 67,167 Members’/Partners’ equity 592,559 883,648 Total liabilities and members’/partners’ equity $ 2,090,931 $ 1,816,480 Company’s share of equity $ 291,029 $ 450,662 Basis differentials (1) 297,908 302,449 Carrying value of the Company’s investments in unconsolidated joint ventures (2) $ 588,937 $ 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 September 30, 2017 and December 31, 2016 , there was an aggregate basis differential of approximately $324.4 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 $22.9 million and $22.1 million at September 30, 2017 and December 31, 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: Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Total revenue (1) $ 55,516 $ 49,002 $ 166,139 $ 125,039 Expenses Operating 23,128 21,753 67,310 54,779 Depreciation and amortization 16,440 12,038 44,973 30,306 Total expenses 39,568 33,791 112,283 85,085 Operating income 15,948 15,211 53,856 39,954 Other expense Interest expense 13,088 8,400 31,815 25,172 Net income $ 2,860 $ 6,811 $ 22,041 $ 14,782 Company’s share of net income $ 2,909 $ 3,179 $ 11,576 $ 6,830 Basis differential (2) (2,066 ) (1,715 ) (4,541 ) (1,341 ) Income from unconsolidated joint ventures $ 843 $ 1,464 $ 7,035 $ 5,489 _______________ (1) Includes straight-line rent adjustments of approximately $5.1 million and $5.2 million for the three months ended September 30, 2017 and 2016 , respectively, and $16.4 million and $11.0 million for the nine months ended September 30, 2017 and 2016 , respectively. (2) Includes straight-line rent adjustments of approximately $0.7 million and $0.7 million for the three months ended September 30, 2017 and 2016, respectively, and $2.2 million and $0.7 million for the nine months ended September 30, 2017 and 2016, respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.5 million for the three months ended September 30, 2017 and 2016, respectively, and $1.3 million and $0.5 million for the nine months ended September 30, 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 722,000 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 7 . 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. As of September 30, 2017, the venture had not drawn any funds under the loan. 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 guaranty 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 guaranty.

Debt (Notes)

Debt (Notes)	9 Months Ended
	Sep. 30, 2017
Debt [Abstract]
Debt Disclosure [Text Block]	5. Debt Mortgage Notes Payable, Net, Mezzanine Notes Payable and Outside Members ’ Notes Payable 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 8 ). 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. 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 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 current 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. 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.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities (Notes)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities [Text Block]	6. 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 nine months ended September 30, 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 5 ). 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 September 30, 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 gains (losses) recognized related to the Company’s cash flow hedges for the three and nine months ended September 30, 2017 and 2016 : Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Amount of gain (loss) related to the effective portion recognized in other comprehensive loss $ — $ 5,712 $ (6,133 ) $ (85,285 ) Amount of loss related to the effective portion subsequently reclassified to earnings $ (1,665 ) $ (1,190 ) $ (4,368 ) $ (2,445 ) Amount of loss related to the ineffective portion and amount excluded from effectiveness testing $ — $ (140 ) $ — $ (140 ) Boston Properties, Inc. The following table reflects the changes in accumulated other comprehensive loss for the nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ (52,251 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 4,368 Other comprehensive loss attributable to noncontrolling interests 2,220 Balance at September 30, 2017 $ (51,796 ) Balance at December 31, 2015 $ (14,114 ) Effective portion of interest rate contracts (85,285 ) Amortization of interest rate contracts 2,445 Other comprehensive loss attributable to noncontrolling interests 23,011 Balance at September 30, 2016 $ (73,943 ) Boston Properties Limited Partnership The following table reflects the changes in accumulated other comprehensive loss for the nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ (60,853 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 4,368 Other comprehensive loss attributable to noncontrolling interests 2,272 Balance at September 30, 2017 $ (60,346 ) Balance at December 31, 2015 $ (18,337 ) Effective portion of interest rate contracts (85,285 ) Amortization of interest rate contracts 2,445 Other comprehensive loss attributable to noncontrolling interests 16,134 Balance at September 30, 2016 $ (85,043 )

Commitments And Contingencies

Commitments And Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	7. Commitments and Contingencies General In the normal course of business, the Company guarantees its performance of services or indemnifies third parties against its negligence. In addition, in the normal course of business, the Company guarantees to certain tenants the obligations of its subsidiaries for the payment of tenant improvement allowances and brokerage commissions in connection with their leases and limited costs arising from delays in delivery of their premises. The Company has letter of credit and performance obligations 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 8. 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 September 30, 2017, the maximum funding obligation under the guarantee was approximately $222.7 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 September 30, 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 September 30, 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 4. 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 and 2015, the Company received distributions of approximately $7.7 million and $8.1 million , respectively. On July 5, 2016, the Company received a fourth interim distribution totaling approximately $1.4 million . On May 19, 2017, the Company received a fifth interim distribution totaling approximately $0.4 million , 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 September 30, 2017 . 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 our portfolio, including 767 Fifth Avenue, but excluding certain other properties owned in joint ventures with third parties or which the Company manages. The per occurrence limit for NBCR Coverage is $1.0 billion . Under TRIA, after the payment of the required deductible and coinsurance, the NBCR Coverage provided by IXP is backstopped by the Federal Government if the aggregate industry insured losses resulting from a certified act of terrorism exceed a “program trigger.” In 2017, the program trigger is $140 million and the coinsurance is 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.

Noncontrolling Interests

Noncontrolling Interests	9 Months Ended
	Sep. 30, 2017
Noncontrolling Interest [Abstract]
Noncontrolling Interests	8. 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 September 30, 2017 , the noncontrolling interests in Boston Properties Limited Partnership consisted of 16,812,329 OP Units, 816,982 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—Common Units During the nine months ended September 30, 2017 , 492,617 OP Units were presented by the holders for redemption (including 33,466 OP Units 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. At September 30, 2017 , Boston Properties Limited Partnership had outstanding 366,618 2015 MYLTIP Units, 473,360 2016 MYLTIP Units and 400,000 2017 MYLTIP Units. Prior to the applicable measurement date (February 4, 2018 for 2015 MYLTIP Units, 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 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 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 September 30, 2017 was approximately $2.2 billion based on the last reported price of a share of Common Stock on the New York Stock Exchange of $122.88 per share on September 30, 2017 . Boston Properties Limited Partnership The following table reflects the activity of noncontrolling interests—redeemable partnership units of Boston Properties Limited Partnership for the nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ 2,262,040 Contributions 31,465 Net income 40,350 Distributions (40,292 ) Conversion of redeemable partnership units (16,812 ) Unearned compensation (5,194 ) Cumulative effect of a change in accounting principle (1,763 ) Accumulated other comprehensive income 52 Adjustment to reflect redeemable partnership units at redemption value (103,556 ) Balance at September 30, 2017 $ 2,166,290 Balance at December 31, 2015 $ 2,286,689 Contributions 31,492 Net income 42,120 Distributions (35,500 ) Conversion of redeemable partnership units (5,881 ) Unearned compensation (10,072 ) Accumulated other comprehensive loss (6,877 ) Adjustment to reflect redeemable partnership units at redemption value 151,545 Balance at September 30, 2016 $ 2,453,516 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 at September 30, 2017 and $1.5 billion at December 31, 2016 , are included in Noncontrolling Interests—Property Partnerships in the accompanying Consolidated Balance Sheets. 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 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 have 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 September 30, 2017 , the Company had contributed an aggregate of approximately $15.2 million of preferred equity to the venture. Also, under the agreement, (1) the partner has the right to cause the Company to purchase the partner’s interest after the defined stabilization date and (2) the Company has the right to acquire the partner’s interest on the third anniversary of the stabilization date, in each case at an agreed upon purchase price or appraised value; provided, however, if certain return thresholds are achieved the partner will be entitled to an additional promoted interest. 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 5 ). 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 in property partnerships for the nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ 1,530,647 Capital contributions (1) 147,772 Net income 33,967 Accumulated other comprehensive loss (2,272 ) Distributions (41,439 ) Balance at September 30, 2017 $ 1,668,675 Balance at December 31, 2015 $ 1,574,400 Capital contributions 5,417 Net income 53 Accumulated other comprehensive loss (16,134 ) Distributions (38,694 ) Balance at September 30, 2016 $ 1,525,042 _______________ (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	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Stockholders' Equity / Partners' Capital	9. Stockholders’ Equity / Partners’ Capital As of September 30, 2017 , Boston Properties, Inc. had 154,322,266 shares of Common Stock outstanding. As of September 30, 2017 , Boston Properties, Inc. owned 1,719,516 general partnership units and 152,602,750 limited partnership units of Boston Properties Limited Partnership. 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 replaces 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 nine months ended September 30, 2017 , Boston Properties, Inc. issued 492,617 shares of Common Stock 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 in 2017 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) 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 September 30, 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 during 2017 : Record Date Payment Date Dividend (Per Share) 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

Earnings Per Share _ Common Uni

Earnings Per Share / Common Unit	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Share / Common Unit	10. 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 also participating securities. As such, unvested restricted common stock of the Company, LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic EPS of the Company using the two -class method. Participating securities are included in the computation of diluted EPS of the Company using the if-converted method if the impact is dilutive. Because the 2012 OPP Units, 2013 MYLTIP Units and 2014 MYLTIP Units required, and the 2015-2017 MYLTIP Units require, the Company to outperform absolute and relative return thresholds, unless such thresholds have been met by the end of the applicable reporting period, the Company excludes such units from the diluted EPS calculation. Other potentially dilutive common shares, including stock options, restricted stock and other securities of Boston Properties Limited Partnership that are exchangeable for the Boston Properties, Inc.’s Common Stock, and the related impact on earnings, are considered when calculating diluted EPS. Three months ended September 30, 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 $ 117,337 154,355 $ 0.76 Allocation of undistributed earnings to participating securities (7 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 117,330 154,355 $ 0.76 Effect of Dilutive Securities: Stock Based Compensation — 128 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 117,330 154,483 $ 0.76 Three months ended September 30, 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 $ 76,753 153,754 $ 0.50 Effect of Dilutive Securities: Stock Based Compensation — 382 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 76,753 154,136 $ 0.50 Nine months ended September 30, 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 $ 348,086 154,132 $ 2.26 Allocation of undistributed earnings to participating securities (15 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 348,071 154,132 $ 2.26 Effect of Dilutive Securities: Stock Based Compensation — 212 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 348,071 154,344 $ 2.26 Nine months ended September 30, 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 $ 355,114 153,681 $ 2.31 Allocation of undistributed earnings to participating securities (189 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 354,925 153,681 $ 2.31 Effect of Dilutive Securities: Stock Based Compensation — 290 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 354,925 153,971 $ 2.31 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 also 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 17,336,000 and 17,625,000 redeemable common units for the three months ended September 30, 2017 and 2016 , respectively, and 17,517,000 and 17,672,000 redeemable common units for the nine months ended September 30, 2017 and 2016 , respectively. Three months ended September 30, 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 $ 132,693 171,691 $ 0.77 Allocation of undistributed earnings to participating securities (8 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 132,685 171,691 $ 0.77 Effect of Dilutive Securities: Stock Based Compensation — 128 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 132,685 171,819 $ 0.77 Three months ended September 30, 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 $ 91,306 171,379 $ 0.53 Effect of Dilutive Securities: Stock Based Compensation — 382 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 91,306 171,761 $ 0.53 Nine months ended September 30, 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 $ 395,199 171,649 $ 2.30 Allocation of undistributed earnings to participating securities (17 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 395,182 171,649 $ 2.30 Effect of Dilutive Securities: Stock Based Compensation — 212 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 395,182 171,861 $ 2.30 Nine months ended September 30, 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 $ 408,540 171,353 $ 2.38 Allocation of undistributed earnings to participating securities (210 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 408,330 171,353 $ 2.38 Effect of Dilutive Securities: Stock Based Compensation — 290 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 408,330 171,643 $ 2.38

Stock Option and Incentive Plan

Stock Option and Incentive Plan	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	11. Stock Option and Incentive Plan On January 25, 2017, Boston Properties, Inc.’s Compensation Committee approved the 2017 MYLTIP awards under Boston Properties, Inc.’s 2012 Stock Option and Incentive Plan (the “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. During the nine months ended September 30, 2017 , Boston Properties, Inc. issued 37,414 shares of restricted common stock and Boston Properties Limited Partnership issued 111,488 LTIP Units and 400,000 2017 MYLTIP Units to employees and non-employee directors under the 2012 Plan. Employees and non-employee directors paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit and 2017 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. The shares of restricted stock granted during the nine months ended September 30, 2017 were valued at approximately $4.9 million ( $130.32 per share weighted-average). The LTIP Units granted were valued at approximately $13.3 million (approximately $119.52 per unit weighted-average fair value) using a Monte Carlo simulation method model. The per unit fair values of the LTIP Units granted were estimated on the dates of grant and for a substantial majority of such units were valued using the following assumptions: an expected life of 5.7 years , a risk-free interest rate of 2.14% and an expected price volatility of 28.0% . As the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units and 2017 MYLTIP Units are subject to both a service condition and a market condition, the Company recognizes the compensation expense related to the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units and 2017 MYLTIP Units under the graded vesting attribution method. Under the graded vesting attribution method, each portion of the award that vests at a different date is accounted for as a separate award and recognized over the period appropriate to that portion so that the compensation cost for each portion should be recognized in full by the time that portion vests. 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 $7.5 million and $7.1 million for the three months ended September 30, 2017 and 2016 , respectively, and $25.6 million and $23.6 million for the nine months ended September 30, 2017 and 2016 , respectively. At September 30, 2017 , there was (1) an aggregate of approximately $22.8 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 $24.7 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 2.5 years.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Information	12. 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 three and nine months ended September 30, 2017 and 2016 . Boston Properties, Inc. Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 117,337 $ 76,753 $ 348,086 $ 355,114 Add: Preferred dividends 2,625 2,589 7,875 7,796 Noncontrolling interest—common units of Boston Properties Limited Partnership 13,402 9,387 40,350 42,120 Noncontrolling interests in property partnerships 14,340 (17,225 ) 33,967 53 Interest expense 92,032 104,641 282,709 314,953 Losses from interest rate contracts — 140 — 140 Depreciation and amortization expense 152,164 203,748 463,288 516,371 Impairment loss — 1,783 — 1,783 Transaction costs 239 249 572 1,187 General and administrative expense 25,792 25,165 84,319 79,936 Less: Gains on sales of real estate 2,891 12,983 6,791 80,606 Gains (losses) from early extinguishments of debt — (371 ) 14,354 (371 ) Gains from investments in securities 944 976 2,716 1,713 Interest and other income 1,329 3,628 3,447 6,657 Income from unconsolidated joint ventures 843 1,464 7,035 5,489 Development and management services revenue 10,811 6,364 24,648 18,586 Net Operating Income $ 401,113 $ 382,186 $ 1,202,175 $ 1,206,773 Boston Properties Limited Partnership Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 132,693 $ 91,306 $ 395,199 $ 408,540 Add: Preferred distributions 2,625 2,589 7,875 7,796 Noncontrolling interests in property partnerships 14,340 (17,225 ) 33,967 53 Interest expense 92,032 104,641 282,709 314,953 Losses from interest rate contracts — 140 — 140 Depreciation and amortization expense 150,210 198,582 457,102 507,234 Impairment loss — 1,783 — 1,783 Transaction costs 239 249 572 1,187 General and administrative expense 25,792 25,165 84,319 79,936 Less: Gains on sales of real estate 2,891 12,983 7,368 82,775 Gains (losses) from early extinguishments of debt — (371 ) 14,354 (371 ) Gains from investments in securities 944 976 2,716 1,713 Interest and other income 1,329 3,628 3,447 6,657 Income from unconsolidated joint ventures 843 1,464 7,035 5,489 Development and management services revenue 10,811 6,364 24,648 18,586 Net Operating Income $ 401,113 $ 382,186 $ 1,202,175 $ 1,206,773 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, the most directly comparable GAAP financial measures, plus (1) preferred dividends/distributions, noncontrolling interests, interest expense, losses from interest rate contracts, depreciation and amortization expense, 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 from investments in securities, interest and other income, 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 financial condition and results of operations 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 or 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., for other investment activity). In addition, because of historical cost accounting and useful life estimates, depreciation and amortization 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, gains on sales of real estate, interest expense, losses from interest rate contracts, gains (losses) from early extinguishments of debt, gains from investments in securities, interest and other income, income from unconsolidated joint ventures, depreciation and amortization expense, impairment loss, transaction costs, general and administrative expenses and development and management services revenue are not included in Net Operating Income 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. Information by geographic area and property type (dollars in thousands): For the three months ended September 30, 2017 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 196,687 $ 242,071 $ 87,162 $ 103,622 $ 629,542 Residential 1,228 — — 3,067 4,295 Hotel 13,064 — — — 13,064 Total 210,979 242,071 87,162 106,689 646,901 % of Grand Totals 32.61 % 37.43 % 13.47 % 16.49 % 100.00 % Rental Expenses: Office 76,086 95,775 26,792 37,111 235,764 Residential 512 — — 1,065 1,577 Hotel 8,447 — — — 8,447 Total 85,045 95,775 26,792 38,176 245,788 % of Grand Totals 34.60 % 38.97 % 10.90 % 15.53 % 100.00 % Net operating income $ 125,934 $ 146,296 $ 60,370 $ 68,513 $ 401,113 % of Grand Totals 31.40 % 36.47 % 15.05 % 17.08 % 100.00 % For the three months ended September 30, 2016 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 183,975 $ 237,262 $ 80,235 $ 100,666 $ 602,138 Residential 1,227 — — 3,145 4,372 Hotel 12,354 — — — 12,354 Total 197,556 237,262 80,235 103,811 618,864 % of Grand Totals 31.92 % 38.34 % 12.96 % 16.78 % 100.00 % Rental Expenses: Office 71,254 95,073 26,037 33,973 226,337 Residential 1,141 — — 1,082 2,223 Hotel 8,118 — — — 8,118 Total 80,513 95,073 26,037 35,055 236,678 % of Grand Totals 34.02 % 40.17 % 11.00 % 14.81 % 100.00 % Net operating income $ 117,043 $ 142,189 $ 54,198 $ 68,756 $ 382,186 % of Grand Totals 30.62 % 37.21 % 14.18 % 17.99 % 100.00 % For the nine months ended September 30, 2017 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 573,883 $ 735,485 $ 257,286 $ 309,225 $ 1,875,879 Residential 3,520 — — 8,941 12,461 Hotel 33,859 — — — 33,859 Total 611,262 735,485 257,286 318,166 1,922,199 % of Grand Totals 31.80 % 38.27 % 13.38 % 16.55 % 100.00 % Rental Expenses: Office 225,502 280,569 77,204 108,044 691,319 Residential 1,552 — — 3,211 4,763 Hotel 23,942 — — — 23,942 Total 250,996 280,569 77,204 111,255 720,024 % of Grand Totals 34.86 % 38.97 % 10.72 % 15.45 % 100.00 % Net operating income $ 360,266 $ 454,916 $ 180,082 $ 206,911 $ 1,202,175 % of Grand Totals 29.97 % 37.84 % 14.98 % 17.21 % 100.00 % For the nine months ended September 30, 2016 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 540,850 $ 773,077 $ 235,076 $ 300,742 $ 1,849,745 Residential 3,578 — — 8,931 12,509 Hotel 33,919 — — — 33,919 Total 578,347 773,077 235,076 309,673 1,896,173 % of Grand Totals 30.50 % 40.77 % 12.40 % 16.33 % 100.00 % Rental Expenses: Office 210,695 272,620 75,412 101,514 660,241 Residential 2,174 — — 3,255 5,429 Hotel 23,730 — — — 23,730 Total 236,599 272,620 75,412 104,769 689,400 % of Grand Totals 34.32 % 39.54 % 10.94 % 15.20 % 100.00 % Net operating income $ 341,748 $ 500,457 $ 159,664 $ 204,904 $ 1,206,773 % of Grand Totals 28.32 % 41.47 % 13.23 % 16.98 % 100.00 %

Basis Of Presentation And Sum21

Basis Of Presentation And Summary Of Significant Accounting Policies Recent Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2017
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncement [Policy Text Block]	Recent Accounting Pronouncements In May 2014, the Financial Standards Accounting Board (“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 will adopt ASU 2014-09 effective January 1, 2018 using the modified retrospective approach. The Company’s project team has completed the compilation of the inventory of the sources of revenue that will be impacted by the adoption of ASU 2014-09. The Company expects that executory costs and certain non-lease components of revenue from leases (upon the adoption of ASU 2016-02), certain of its development and management services revenue and gains on sales of real estate may be impacted by the adoption of ASU 2014-09, although the Company anticipates that the impact will be to the pattern of revenue recognition and not the total revenue recognized over time. The Company is progressing with its analysis and evaluation of the impact that the adoption of ASU 2014-09 will have on the recognition pattern of each of its sources of revenue and is nearing completion of its assessment of the overall impact of adopting ASU 2014-09. The Company does not expect that the adoption of ASU 2014-09 will have a material impact on its 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 process 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 the underlying leased asset re cognized as real estate. The Company expects that executory costs and certain other non-lease components will need to be accounted for separately from the lease component of the lease with the lease component continuing to be recognized on a straight-line basis over the lease term and the executory costs and certain other non-lease components being accounted for under the new revenue recognition guidance in ASU 2014-09. 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 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 is currently assessing the potential impact that the adoption of ASU 2017-05 will have on its 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 is currently assessing the potential impact that the adoption of ASU 2017-09 will have on its 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 is currently assessing the potential impact that the adoption of ASU 2017-12 will have on its consolidated financial statements.

Basis Of Presentation And Sum22

Basis Of Presentation And Summary Of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value	The following table presents the aggregate carrying value of the Company’s mortgage notes payable, net, mezzanine notes payable and unsecured senior notes, net and the Company’s corresponding estimate of fair value as of September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 December 31, 2016 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Mortgage notes payable, net $ 2,982,067 $ 3,049,617 $ 2,063,087 $ 2,092,237 Mezzanine notes payable — — 307,093 308,344 Unsecured senior notes, net 7,252,567 7,533,164 7,245,953 7,428,077 Total $ 10,234,634 $ 10,582,781 $ 9,616,133 $ 9,828,658

Real Estate Real Estate (Tables

Real Estate Real Estate (Tables)	9 Months Ended
	Sep. 30, 2017
Entity Information [Line Items]
Schedule of Real Estate Properties [Table Text Block]	Boston Properties, Inc. Real estate consisted of the following at September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 December 31, 2016 Land $ 4,880,331 $ 4,879,020 Land held for future development (1) 212,585 246,656 Buildings and improvements 12,155,126 11,890,626 Tenant improvements 2,186,953 2,060,315 Furniture, fixtures and equipment 37,612 32,687 Construction in progress 1,386,638 1,037,959 Total 20,859,245 20,147,263 Less: Accumulated depreciation (4,484,798 ) (4,222,235 ) $ 16,374,447 $ 15,925,028 _______________ (1) Includes pre-development costs.
Boston Properties Limited Partnership
Entity Information [Line Items]
Schedule of Real Estate Properties [Table Text Block]	Boston Properties Limited Partnership Real estate consisted of the following at September 30, 2017 and December 31, 2016 (in thousands): September 30, 2017 December 31, 2016 Land $ 4,775,955 $ 4,774,460 Land held for future development (1) 212,585 246,656 Buildings and improvements 11,848,024 11,581,795 Tenant improvements 2,186,953 2,060,315 Furniture, fixtures and equipment 37,612 32,687 Construction in progress 1,386,638 1,037,959 Total 20,447,767 19,733,872 Less: Accumulated depreciation (4,394,077 ) (4,136,364 ) $ 16,053,690 $ 15,597,508 _______________ (1) Includes pre-development costs.
MacArthur Transit Center [Member]
Entity Information [Line Items]
Capital Leases in Financial Statements of Lessee Disclosure [Text Block]	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 obligations 38,826 Interest portion (9,864 ) Present value of net expected minimum payments $ 28,962
103 Carnegie Center [Member]
Entity Information [Line Items]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	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
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]	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 )

Investments in Unconsolidated24

Investments in Unconsolidated Joint Ventures (Tables)	9 Months Ended
	Sep. 30, 2017
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	The investments in unconsolidated joint ventures consist of the following at September 30, 2017 and December 31, 2016 : Nominal % Ownership Carrying Value of Investment (1) Entity Properties September 30, 2017 December 31, 2016 (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (8,474 ) $ (8,134 ) The Metropolitan Square Associates LLC Metropolitan Square 20.0 % 2,537 2,004 BP/CRF 901 New York Avenue LLC 901 New York Avenue 25.0 % (2) (10,747 ) (10,564 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 40,158 41,605 Annapolis Junction NFM, LLC Annapolis Junction 50.0 % (4) 18,771 20,539 540 Madison Venture LLC 540 Madison Avenue 60.0 % 67,046 67,816 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (3,642 ) (3,389 ) 501 K Street LLC 1001 6th Street 50.0 % (5) 42,442 42,528 Podium Developer LLC The Hub on Causeway 50.0 % 55,917 29,869 Residential Tower Developer LLC The Hub on Causeway - Residential 50.0 % 25,811 20,803 Hotel Tower Developer LLC The Hub on Causeway - Hotel 50.0 % 1,596 933 1265 Main Office JV LLC 1265 Main Street 50.0 % 4,686 4,779 BNY Tower Holdings LLC Dock 72 at the Brooklyn Navy Yard 50.0 % (6) 67,901 33,699 CA-Colorado Center Limited Partnership Colorado Center 50.0 % 263,834 510,623 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % (6) 21,101 N/A $ 588,937 $ 753,111 _______________ (1) Investments with deficit balances aggregating approximately $22.9 million and $22.1 million at September 30, 2017 and December 31, 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 entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking garage and infrastructure of the project. (4) The joint venture owns 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) The 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: September 30, 2017 December 31, 2016 (in thousands) ASSETS Real estate and development in process, net $ 1,716,447 $ 1,519,217 Other assets 374,484 297,263 Total assets $ 2,090,931 $ 1,816,480 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 1,411,401 $ 865,665 Other liabilities 86,971 67,167 Members’/Partners’ equity 592,559 883,648 Total liabilities and members’/partners’ equity $ 2,090,931 $ 1,816,480 Company’s share of equity $ 291,029 $ 450,662 Basis differentials (1) 297,908 302,449 Carrying value of the Company’s investments in unconsolidated joint ventures (2) $ 588,937 $ 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 September 30, 2017 and December 31, 2016 , there was an aggregate basis differential of approximately $324.4 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 $22.9 million and $22.1 million at September 30, 2017 and December 31, 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: Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Total revenue (1) $ 55,516 $ 49,002 $ 166,139 $ 125,039 Expenses Operating 23,128 21,753 67,310 54,779 Depreciation and amortization 16,440 12,038 44,973 30,306 Total expenses 39,568 33,791 112,283 85,085 Operating income 15,948 15,211 53,856 39,954 Other expense Interest expense 13,088 8,400 31,815 25,172 Net income $ 2,860 $ 6,811 $ 22,041 $ 14,782 Company’s share of net income $ 2,909 $ 3,179 $ 11,576 $ 6,830 Basis differential (2) (2,066 ) (1,715 ) (4,541 ) (1,341 ) Income from unconsolidated joint ventures $ 843 $ 1,464 $ 7,035 $ 5,489 _______________ (1) Includes straight-line rent adjustments of approximately $5.1 million and $5.2 million for the three months ended September 30, 2017 and 2016 , respectively, and $16.4 million and $11.0 million for the nine months ended September 30, 2017 and 2016 , respectively. (2) Includes straight-line rent adjustments of approximately $0.7 million and $0.7 million for the three months ended September 30, 2017 and 2016, respectively, and $2.2 million and $0.7 million for the nine months ended September 30, 2017 and 2016, respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.5 million for the three months ended September 30, 2017 and 2016, respectively, and $1.3 million and $0.5 million for the nine months ended September 30, 2017 and 2016, respectively.

Derivative Instruments and He25

Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]	At September 30, 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 )
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 gains (losses) recognized related to the Company’s cash flow hedges for the three and nine months ended September 30, 2017 and 2016 : Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Amount of gain (loss) related to the effective portion recognized in other comprehensive loss $ — $ 5,712 $ (6,133 ) $ (85,285 ) Amount of loss related to the effective portion subsequently reclassified to earnings $ (1,665 ) $ (1,190 ) $ (4,368 ) $ (2,445 ) Amount of loss related to the ineffective portion and amount excluded from effectiveness testing $ — $ (140 ) $ — $ (140 )
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 nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ (52,251 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 4,368 Other comprehensive loss attributable to noncontrolling interests 2,220 Balance at September 30, 2017 $ (51,796 ) Balance at December 31, 2015 $ (14,114 ) Effective portion of interest rate contracts (85,285 ) Amortization of interest rate contracts 2,445 Other comprehensive loss attributable to noncontrolling interests 23,011 Balance at September 30, 2016 $ (73,943 ) Boston Properties Limited Partnership The following table reflects the changes in accumulated other comprehensive loss for the nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ (60,853 ) Effective portion of interest rate contracts (6,133 ) Amortization of interest rate contracts 4,368 Other comprehensive loss attributable to noncontrolling interests 2,272 Balance at September 30, 2017 $ (60,346 ) Balance at December 31, 2015 $ (18,337 ) Effective portion of interest rate contracts (85,285 ) Amortization of interest rate contracts 2,445 Other comprehensive loss attributable to noncontrolling interests 16,134 Balance at September 30, 2016 $ (85,043 )

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	9 Months Ended
	Sep. 30, 2017
Noncontrolling Interest [Line Items]
Distributions Declared to OP, LTIP, OPP and MYLTIP Units [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 in 2017 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) 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 Noncontrolling Interest Common Units [Table Text Block]	The following table reflects the activity of noncontrolling interests—redeemable partnership units of Boston Properties Limited Partnership for the nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ 2,262,040 Contributions 31,465 Net income 40,350 Distributions (40,292 ) Conversion of redeemable partnership units (16,812 ) Unearned compensation (5,194 ) Cumulative effect of a change in accounting principle (1,763 ) Accumulated other comprehensive income 52 Adjustment to reflect redeemable partnership units at redemption value (103,556 ) Balance at September 30, 2017 $ 2,166,290 Balance at December 31, 2015 $ 2,286,689 Contributions 31,492 Net income 42,120 Distributions (35,500 ) Conversion of redeemable partnership units (5,881 ) Unearned compensation (10,072 ) Accumulated other comprehensive loss (6,877 ) Adjustment to reflect redeemable partnership units at redemption value 151,545 Balance at September 30, 2016 $ 2,453,516
Schedule Of Noncontrolling Interest Property Partnerships [Table Text Block]	The following table reflects the activity of the noncontrolling interests in property partnerships for the nine months ended September 30, 2017 and 2016 (in thousands): Balance at December 31, 2016 $ 1,530,647 Capital contributions (1) 147,772 Net income 33,967 Accumulated other comprehensive loss (2,272 ) Distributions (41,439 ) Balance at September 30, 2017 $ 1,668,675 Balance at December 31, 2015 $ 1,574,400 Capital contributions 5,417 Net income 53 Accumulated other comprehensive loss (16,134 ) Distributions (38,694 ) Balance at September 30, 2016 $ 1,525,042
Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Distributions Declared to OP, LTIP, OPP and MYLTIP Units [Table Text Block]	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 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 _ Partne27

Stockholders' Equity / Partners' Capital Tables (Tables)	9 Months Ended
	Sep. 30, 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 in 2017 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) 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
Series B Cumulative Redeemable 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 during 2017 : Record Date Payment Date Dividend (Per Share) 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

Earnings Per Share _ Common U28

Earnings Per Share / Common Unit (Tables)	9 Months Ended
	Sep. 30, 2017
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share	Three months ended September 30, 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 $ 117,337 154,355 $ 0.76 Allocation of undistributed earnings to participating securities (7 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 117,330 154,355 $ 0.76 Effect of Dilutive Securities: Stock Based Compensation — 128 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 117,330 154,483 $ 0.76 Three months ended September 30, 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 $ 76,753 153,754 $ 0.50 Effect of Dilutive Securities: Stock Based Compensation — 382 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 76,753 154,136 $ 0.50 Nine months ended September 30, 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 $ 348,086 154,132 $ 2.26 Allocation of undistributed earnings to participating securities (15 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 348,071 154,132 $ 2.26 Effect of Dilutive Securities: Stock Based Compensation — 212 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 348,071 154,344 $ 2.26 Nine months ended September 30, 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 $ 355,114 153,681 $ 2.31 Allocation of undistributed earnings to participating securities (189 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 354,925 153,681 $ 2.31 Effect of Dilutive Securities: Stock Based Compensation — 290 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 354,925 153,971 $ 2.31
Boston Properties Limited Partnership
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share	Three months ended September 30, 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 $ 132,693 171,691 $ 0.77 Allocation of undistributed earnings to participating securities (8 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 132,685 171,691 $ 0.77 Effect of Dilutive Securities: Stock Based Compensation — 128 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 132,685 171,819 $ 0.77 Three months ended September 30, 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 $ 91,306 171,379 $ 0.53 Effect of Dilutive Securities: Stock Based Compensation — 382 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 91,306 171,761 $ 0.53 Nine months ended September 30, 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 $ 395,199 171,649 $ 2.30 Allocation of undistributed earnings to participating securities (17 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 395,182 171,649 $ 2.30 Effect of Dilutive Securities: Stock Based Compensation — 212 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 395,182 171,861 $ 2.30 Nine months ended September 30, 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 $ 408,540 171,353 $ 2.38 Allocation of undistributed earnings to participating securities (210 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 408,330 171,353 $ 2.38 Effect of Dilutive Securities: Stock Based Compensation — 290 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 408,330 171,643 $ 2.38

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Schedule Of Reconciliation Of Net Operating Income To Net Income	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 three and nine months ended September 30, 2017 and 2016 . Boston Properties, Inc. Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 117,337 $ 76,753 $ 348,086 $ 355,114 Add: Preferred dividends 2,625 2,589 7,875 7,796 Noncontrolling interest—common units of Boston Properties Limited Partnership 13,402 9,387 40,350 42,120 Noncontrolling interests in property partnerships 14,340 (17,225 ) 33,967 53 Interest expense 92,032 104,641 282,709 314,953 Losses from interest rate contracts — 140 — 140 Depreciation and amortization expense 152,164 203,748 463,288 516,371 Impairment loss — 1,783 — 1,783 Transaction costs 239 249 572 1,187 General and administrative expense 25,792 25,165 84,319 79,936 Less: Gains on sales of real estate 2,891 12,983 6,791 80,606 Gains (losses) from early extinguishments of debt — (371 ) 14,354 (371 ) Gains from investments in securities 944 976 2,716 1,713 Interest and other income 1,329 3,628 3,447 6,657 Income from unconsolidated joint ventures 843 1,464 7,035 5,489 Development and management services revenue 10,811 6,364 24,648 18,586 Net Operating Income $ 401,113 $ 382,186 $ 1,202,175 $ 1,206,773 Boston Properties Limited Partnership Three months ended September 30, Nine months ended September 30, 2017 2016 2017 2016 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 132,693 $ 91,306 $ 395,199 $ 408,540 Add: Preferred distributions 2,625 2,589 7,875 7,796 Noncontrolling interests in property partnerships 14,340 (17,225 ) 33,967 53 Interest expense 92,032 104,641 282,709 314,953 Losses from interest rate contracts — 140 — 140 Depreciation and amortization expense 150,210 198,582 457,102 507,234 Impairment loss — 1,783 — 1,783 Transaction costs 239 249 572 1,187 General and administrative expense 25,792 25,165 84,319 79,936 Less: Gains on sales of real estate 2,891 12,983 7,368 82,775 Gains (losses) from early extinguishments of debt — (371 ) 14,354 (371 ) Gains from investments in securities 944 976 2,716 1,713 Interest and other income 1,329 3,628 3,447 6,657 Income from unconsolidated joint ventures 843 1,464 7,035 5,489 Development and management services revenue 10,811 6,364 24,648 18,586 Net Operating Income $ 401,113 $ 382,186 $ 1,202,175 $ 1,206,773
Schedule Of Segment Information By Geographic Area And Property Type	Information by geographic area and property type (dollars in thousands): For the three months ended September 30, 2017 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 196,687 $ 242,071 $ 87,162 $ 103,622 $ 629,542 Residential 1,228 — — 3,067 4,295 Hotel 13,064 — — — 13,064 Total 210,979 242,071 87,162 106,689 646,901 % of Grand Totals 32.61 % 37.43 % 13.47 % 16.49 % 100.00 % Rental Expenses: Office 76,086 95,775 26,792 37,111 235,764 Residential 512 — — 1,065 1,577 Hotel 8,447 — — — 8,447 Total 85,045 95,775 26,792 38,176 245,788 % of Grand Totals 34.60 % 38.97 % 10.90 % 15.53 % 100.00 % Net operating income $ 125,934 $ 146,296 $ 60,370 $ 68,513 $ 401,113 % of Grand Totals 31.40 % 36.47 % 15.05 % 17.08 % 100.00 % For the three months ended September 30, 2016 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 183,975 $ 237,262 $ 80,235 $ 100,666 $ 602,138 Residential 1,227 — — 3,145 4,372 Hotel 12,354 — — — 12,354 Total 197,556 237,262 80,235 103,811 618,864 % of Grand Totals 31.92 % 38.34 % 12.96 % 16.78 % 100.00 % Rental Expenses: Office 71,254 95,073 26,037 33,973 226,337 Residential 1,141 — — 1,082 2,223 Hotel 8,118 — — — 8,118 Total 80,513 95,073 26,037 35,055 236,678 % of Grand Totals 34.02 % 40.17 % 11.00 % 14.81 % 100.00 % Net operating income $ 117,043 $ 142,189 $ 54,198 $ 68,756 $ 382,186 % of Grand Totals 30.62 % 37.21 % 14.18 % 17.99 % 100.00 % For the nine months ended September 30, 2017 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 573,883 $ 735,485 $ 257,286 $ 309,225 $ 1,875,879 Residential 3,520 — — 8,941 12,461 Hotel 33,859 — — — 33,859 Total 611,262 735,485 257,286 318,166 1,922,199 % of Grand Totals 31.80 % 38.27 % 13.38 % 16.55 % 100.00 % Rental Expenses: Office 225,502 280,569 77,204 108,044 691,319 Residential 1,552 — — 3,211 4,763 Hotel 23,942 — — — 23,942 Total 250,996 280,569 77,204 111,255 720,024 % of Grand Totals 34.86 % 38.97 % 10.72 % 15.45 % 100.00 % Net operating income $ 360,266 $ 454,916 $ 180,082 $ 206,911 $ 1,202,175 % of Grand Totals 29.97 % 37.84 % 14.98 % 17.21 % 100.00 % For the nine months ended September 30, 2016 : Boston New York San Francisco Washington, DC Total Rental Revenue: Office $ 540,850 $ 773,077 $ 235,076 $ 300,742 $ 1,849,745 Residential 3,578 — — 8,931 12,509 Hotel 33,919 — — — 33,919 Total 578,347 773,077 235,076 309,673 1,896,173 % of Grand Totals 30.50 % 40.77 % 12.40 % 16.33 % 100.00 % Rental Expenses: Office 210,695 272,620 75,412 101,514 660,241 Residential 2,174 — — 3,255 5,429 Hotel 23,730 — — — 23,730 Total 236,599 272,620 75,412 104,769 689,400 % of Grand Totals 34.32 % 39.54 % 10.94 % 15.20 % 100.00 % Net operating income $ 341,748 $ 500,457 $ 159,664 $ 204,904 $ 1,206,773 % of Grand Totals 28.32 % 41.47 % 13.23 % 16.98 % 100.00 %

Organization (Details)

Organization (Details) ft² in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017ft²seriesReal_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 | series	1
Commercial Real Estate Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	177
Net Rentable Area (in sf) | ft²	49.8
Total Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	10
Net Rentable Area (in sf) | ft²	5.7
Total Office Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	166
Office Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	7
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	5
Residential Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	3
Series B Cumulative Redeemable Preferred Stock [Member]
Real Estate Properties [Line Items]
Ratio of depository shares to shares of Series B Preferred Stock	0.01
Series B, Shares Outstanding (in shares) | shares	80,000	80,000
Series B, Dividend Rate, Percentage	5.25%
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Real Estate Properties [Line Items]
Series B, Shares Outstanding (in shares) | shares	8,000,000
Series B Preferred Units [Member]
Real Estate Properties [Line Items]
Series B, Shares Outstanding (in shares) | shares	80,000

Basis Of Presentation And Sum31

Basis Of Presentation And Summary Of Significant Accounting Policies (Narrative) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	$ 2,035
Boston Properties Limited Partnership
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	272
Dividends In Excess Of Earnings [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	272
Noncontrolling Interests [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	1,763
Noncontrolling Interests [Member] | Boston Properties Limited Partnership
Entity Information [Line Items]
Cumulative effect of a change in accounting principle	$ 1,763

Basis Of Presentation And Sum32

Basis Of Presentation And Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	$ 2,982,067	$ 2,063,087
Mezzanine notes payable	0	307,093
Unsecured line of credit	0	0
Unsecured senior notes, net	7,252,567	7,245,953
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	2,982,067	2,063,087
Mezzanine notes payable	0	307,093
Unsecured senior notes, net	7,252,567	7,245,953
Total	10,234,634	9,616,133
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Mortgage notes payable, net	3,049,617	2,092,237
Mezzanine notes payable	0	308,344
Unsecured senior notes, net	7,533,164	7,428,077
Total	$ 10,582,781	$ 9,828,658

Real Estate Real Estate Propert

Real Estate Real Estate Properties Table (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Land		$ 4,880,331	$ 4,879,020
Land held for future development	[1]	212,585	246,656
Buildings and improvements		12,155,126	11,890,626
Tenant improvements		2,186,953	2,060,315
Furniture, fixtures and equipment		37,612	32,687
Construction in Progress		1,386,638	1,037,959
Total		20,859,245	20,147,263
Accumulated depreciation		(4,484,798)	(4,222,235)
Total real estate		16,374,447	15,925,028
Boston Properties Limited Partnership
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Land		4,775,955	4,774,460
Land held for future development	[1]	212,585	246,656
Buildings and improvements		11,848,024	11,581,795
Tenant improvements		2,186,953	2,060,315
Furniture, fixtures and equipment		37,612	32,687
Construction in Progress		1,386,638	1,037,959
Total		20,447,767	19,733,872
Accumulated depreciation		(4,394,077)	(4,136,364)
Total real estate		$ 16,053,690	$ 15,597,508
[1]	Includes pre-development costs.

Real Estate Narrative (Details)

Real Estate Narrative (Details)	Aug. 30, 2017USD ($)a	Jun. 13, 2017USD ($)ft²	Apr. 19, 2017USD ($)a	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Jun. 13, 2017USD ($)ft²	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 16, 2017ft²	Aug. 24, 2017ft²yr	Jun. 29, 2017USD ($)yrapartments	May 27, 2017ft²	May 15, 2017USD ($)ft²	Apr. 06, 2017ft²
Real Estate [Line Items]
Revenues				$ 657,712,000	$ 625,228,000			$ 1,946,847,000	$ 1,914,759,000
Earnings				233,729,000	157,605,000			678,644,000	626,082,000
Proceeds from sales of real estate								29,810,000	122,750,000
Gains on sales of real estate				2,891,000	12,983,000			6,791,000	80,606,000
145 Broadway [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²															485,000
Reservoir Place North [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²													73,000
6595 Springfield Center Drive [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²											623,000
Term of Lease Signed (in years) | yr											15
888 Boylston Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²										417,000
MacArthur Transit Center [Member]
Real Estate [Line Items]
Term of Lease Signed (in years) | yr												99
Number of apartment units | apartments												402
Capital Lease Obligations												$ 28,962,000
103 Carnegie Center [Member] | 103 Carnegie Center [Member]
Real Estate [Line Items]
Revenues						$ 1,100,000
Earnings						$ (100,000)
Net Rentable Area (in sf) | ft²														96,000
Aggregate purchase price														$ 15,800,000
Boston Properties Limited Partnership
Real Estate [Line Items]
Revenues				657,712,000	625,228,000			1,946,847,000	1,914,759,000
Earnings				235,683,000	162,771,000			684,830,000	635,219,000
Proceeds from sales of real estate								29,810,000	122,750,000
Gains on sales of real estate				$ 2,891,000	12,983,000			$ 7,368,000	82,775,000
30 Shattuck Road [Member]
Real Estate [Line Items]
Area of Land | a			9.5
Contractual Sales Price			$ 5,000,000
Proceeds from sales of real estate			5,000,000
Gains on sales of real estate			$ 3,700,000
40 Shattuck Road [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²		122,000					122,000
Contractual Sales Price		$ 12,000,000					$ 12,000,000
Net income (loss)					$ (33,000)		$ (28,000)		$ (18,000)
Proceeds from sales of real estate		11,900,000
Gains on sales of real estate		28,000
40 Shattuck Road [Member] | Boston Properties Limited Partnership
Real Estate [Line Items]
Gains on sales of real estate		$ 600,000
Reston Eastgate [Member]
Real Estate [Line Items]
Area of Land | a	21.7
Contractual Sales Price	$ 14,000,000
Proceeds from sales of real estate	13,200,000
Gains on sales of real estate	$ 2,800,000

Real Estate Future minimum paym

Real Estate Future minimum payments for MacArthur Transit capital lease (Details) - MacArthur Transit Center [Member] $ in Thousands	Jun. 29, 2017USD ($)
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 obligations	38,826
Interest portion	(9,864)
Present value of net expected minimum payments	$ 28,962

Real Estate Purchase price allo

Real Estate 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 Amortization of fin

Real Estate Amortization of finite lived intangible assets (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)
Acquired In-Place Lease Intangibles
Business Acquisition [Line Items]
Period from May 15, 2017 through December 31, 2017	660
2,018	590
2,019	367
2,020	243
2,021	96
Acquired Below- Market Lease Intangibles
Business Acquisition [Line Items]
Period from May 15, 2017 through December 31, 2017	(248)
2,018	(363)
2,019	(337)
2,020	(308)
2,021	$ (105)

Investments in Unconsolidated38

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) $ in Thousands		9 Months Ended
		Sep. 30, 2017USD ($)ft²Land_ParcelsBuildingspayments		Sep. 06, 2017	Aug. 07, 2017	Dec. 31, 2016USD ($)
Schedule of Equity Method Investments [Line Items]
Carrying Value of investment		$ (419,215)				$ (450,821)
Carrying value of the Company's investments in unconsolidated joint ventures		$ 611,800				775,198
Square 407 Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Market Square North
Ownership Percentage		50.00%
Carrying Value of investment	[1]	$ (8,474)				(8,134)
The Metropolitan Square Associates LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Metropolitan Square
Ownership Percentage		20.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 2,537				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%
Carrying Value of investment	[1]	$ (10,747)				(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%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 40,158				41,605
Entity Owning Land And Infrastructure Of Project [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		33.30%
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Annapolis Junction
Ownership Percentage	[4]	50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 18,771				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%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 67,046				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%
Carrying Value of investment	[1]	$ (3,642)				(3,389)
501 K Street LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		1001 6th Street
Ownership Percentage	[5]	50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 42,442				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%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 55,917				29,869
Residential Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		The Hub on Causeway - Residential
Ownership Percentage		50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 25,811				20,803
Hotel Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		The Hub on Causeway - Hotel
Ownership Percentage		50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 1,596				933
1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		1265 Main Street
Ownership Percentage		50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 4,686				4,779
BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Dock 72 at the Brooklyn Navy Yard
Ownership Percentage	[6]	50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 67,901				33,699
CA-Colorado Center Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Colorado Center
Ownership Percentage		50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 263,834				510,623
7750 Wisconsin Avenue [Member]
Schedule of Equity Method Investments [Line Items]
Properties		7750 Wisconsin Avenue
Ownership Percentage		50.00%	[6]		50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]	$ 21,101
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value of the Company's investments in unconsolidated joint ventures		(22,900)				(22,100)
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value of investment		(86,971)				(67,167)
Carrying value of the Company's investments in unconsolidated joint ventures	[1],[7]	$ 588,937				$ 753,111
[1]	Investments with deficit balances aggregating approximately $22.9 million and $22.1 million at September 30, 2017 and December 31, 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 entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land, parking garage and infrastructure of the project.
[4]	The joint venture owns 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]	The entity is a VIE (See Note 2).
[7]	Investments with deficit balances aggregating approximately $22.9 million and $22.1 million at September 30, 2017 and December 31, 2016, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

Investments in Unconsolidated39

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
ASSETS
Real estate and development in process, net		$ 16,374,447	$ 15,925,028
Liabilities and Members'/Partners' Equity [Abstract]
Mortgage notes payable, net		2,982,067	2,063,087
Other Liabilities		419,215	450,821
Total liabilities and equity / capital		19,308,518	18,851,643
Carrying value of the Company's investments in unconsolidated joint ventures		611,800	775,198
Unconsolidated Joint Ventures [Member]
ASSETS
Real estate and development in process, net		1,716,447	1,519,217
Other assets		374,484	297,263
Total assets		2,090,931	1,816,480
Liabilities and Members'/Partners' Equity [Abstract]
Mortgage notes payable, net		1,411,401	865,665
Other Liabilities		86,971	67,167
Members'/Partners' equity		592,559	883,648
Total liabilities and equity / capital		2,090,931	1,816,480
Company's share of equity		291,029	450,662
Basis differentials	[1]	297,908	302,449
Carrying value of the Company's investments in unconsolidated joint ventures	[2],[3]	588,937	753,111
Unconsolidated Joint Ventures [Member]
Liabilities and Members'/Partners' Equity [Abstract]
Basis differentials		324,400	328,800
Carrying value of the Company's investments in unconsolidated joint ventures		$ (22,900)	$ (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 September 30, 2017 and December 31, 2016, there was an aggregate basis differential of approximately $324.4 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 $22.9 million and $22.1 million at September 30, 2017 and December 31, 2016, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[3]	Investments with deficit balances aggregating approximately $22.9 million and $22.1 million at September 30, 2017 and December 31, 2016, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

Investments in Unconsolidated40

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 657,712	$ 625,228	$ 1,946,847	$ 1,914,759
Expenses
Depreciation and amortization		152,164	203,748	463,288	516,371
Total expenses		423,983	467,623	1,268,203	1,288,677
Operating income		233,729	157,605	678,644	626,082
Other expense
Interest expense		92,032	104,641	282,709	314,953
Losses on Extinguishment of Debt		0	371	(14,354)	371
Net income		147,704	71,504	430,278	405,083
Income from unconsolidated joint ventures		843	1,464	7,035	5,489
Mortgage notes payable, net		2,982,067		2,982,067		$ 2,063,087
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]	55,516	49,002	166,139	125,039
Expenses
Operating		23,128	21,753	67,310	54,779
Depreciation and amortization		16,440	12,038	44,973	30,306
Total expenses		39,568	33,791	112,283	85,085
Operating income		15,948	15,211	53,856	39,954
Other expense
Interest expense		13,088	8,400	31,815	25,172
Net income		2,860	6,811	22,041	14,782
Company's share of net income		2,909	3,179	11,576	6,830
Basis differential	[2]	(2,066)	(1,715)	(4,541)	(1,341)
Income from unconsolidated joint ventures		843	1,464	7,035	5,489
Straight-line rent adjustments		5,100	5,200	16,400	11,000
Mortgage notes payable, net		1,411,401		1,411,401		$ 865,665
Colorado Center [Member] | Unconsolidated Joint Ventures [Member]
Other expense
Straight-line rent adjustments		700	700	2,200	700
"Above" and "below" market rent adjustments, net		$ 400	$ 500	$ 1,300	$ 500
[1]	Includes straight-line rent adjustments of approximately $5.1 million and $5.2 million for the three months ended September 30, 2017 and 2016, respectively, and $16.4 million and $11.0 million for the nine months ended September 30, 2017 and 2016, respectively.
[2]	Includes straight-line rent adjustments of approximately $0.7 million and $0.7 million for the three months ended September 30, 2017 and 2016, respectively, and $2.2 million and $0.7 million for the nine months ended September 30, 2017 and 2016, respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.5 million for the three months ended September 30, 2017 and 2016, respectively, and $1.3 million and $0.5 million for the nine months ended September 30, 2017 and 2016, respectively.

Investments in Unconsolidated41

Investments in Unconsolidated Joint Ventures Narrative (Details) $ in Thousands	Sep. 06, 2017USD ($)ft²	Aug. 07, 2017USD ($)ft²yr	Jul. 28, 2017USD ($)ft²aVehiclesBuildings	Sep. 30, 2017USD ($)		Sep. 30, 2016USD ($)	Jul. 10, 2017	Dec. 31, 2016USD ($)
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments				$ 89,874		$ 546,982
Proceeds from mortgage notes payable				2,300,000		0
Cash held in escrow				83,779				$ 63,174
Capital distributions from unconsolidated joint ventures				$ 251,000		0
Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%			50.00%
Net Rentable Area (in sf) | ft²	385,000
Colorado Center [Member]
Schedule of Equity Method Investments [Line Items]
Vehicles In Structured Parking | Vehicles			3,100
Ownership Percentage							50.00%
number of buildings | Buildings			6
Area of Land | a			15
Net Rentable Area (in sf) | ft²			1,118,000
7750 Wisconsin Avenue [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%		50.00%	[1]
Net Rentable Area (in sf) | ft²		722,000
Term of Lease Signed (in years) | yr		20
Payments and improvementst to enter into an equity method investments		$ 20,800
Cash held in escrow		$ 25,000
Secured Debt [Member] | Colorado Center [Member]
Schedule of Equity Method Investments [Line Items]
Coupon/Stated Rate			3.56%
Proceeds from mortgage notes payable			$ 550,000
Capital distributions from unconsolidated joint ventures			502,000
Boston Properties Limited Partnership
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Equity Method Investments				$ 89,874		546,982
Proceeds from mortgage notes payable				2,300,000		0
Cash held in escrow				83,779				$ 63,174
Capital distributions from unconsolidated joint ventures				$ 251,000		$ 0
Boston Properties Limited Partnership | Secured Debt [Member] | Colorado Center [Member]
Schedule of Equity Method Investments [Line Items]
Capital distributions from unconsolidated joint ventures			$ 251,000
Joint venture partner [Member] | 7750 Wisconsin Avenue [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
Contribution of Property		$ 72,000
Payments and improvementst to enter into an equity method investments		4,900
Capital distributions from unconsolidated joint ventures		11,000
Secured Debt [Member] | Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Construction Loan	$ 204,600
Coupon/Stated 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
[1]	The entity is a VIE (See Note 2).

Debt (Details)

Debt (Details) $ in Thousands	Jun. 07, 2017USD ($)	Apr. 24, 2017USD ($)mo	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)yr	Sep. 30, 2016USD ($)	Dec. 31, 2008USD ($)	Jun. 06, 2017	Apr. 23, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Proceeds from mortgage notes payable					$ 2,300,000	$ 0
Interest Payable			$ 99,100		99,100					$ 243,933
Outside members’ notes payable			0		0					$ 180,000
Repayments of mortgage notes payable					1,313,890	1,323,284
Repayments of Mezzannine notes payable					306,000	0
Gains from early extinguishments of debt			$ 0	$ (371)	$ 14,354	$ (371)
767 Fifth Avenue (the General Motors Building)
Debt Instrument [Line Items]
Gains from early extinguishments of debt	$ 14,600
767 Fifth Avenue (the General Motors Building) | Secured Debt [Member]
Debt Instrument [Line Items]
Coupon/Stated Rate		3.43%
767 Fifth Avenue (the General Motors Building) | Members' notes Payables [Member]
Debt Instrument [Line Items]
Repayment of a portion of members loans accrued interest and principal balance	176,100
Consolidation, Eliminations [Member] | 767 Fifth Avenue (the General Motors Building) | Other Mezzanine Debt [Member]
Debt Instrument [Line Items]
Repayments of Other Mezzanine Debt							$ 263,100
Consolidated Entities [Member] | 767 Fifth Avenue (the General Motors Building)
Debt Instrument [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) | Secured Debt [Member]
Debt Instrument [Line Items]
Ownership Percentage by the Company	60.00%
Proceeds from mortgage notes payable	$ 2,300,000
Coupon/Stated Rate	3.43%							5.95%
Repayments of mortgage notes payable	$ 1,300,000
Consolidated Entities [Member] | 767 Fifth Avenue (the General Motors Building) | Mezzanine Debt [Member]
Debt Instrument [Line Items]
Coupon/Stated Rate	6.02%
Repayments of Mezzannine notes payable	$ 306,000
Consolidated Entities [Member] | 767 Fifth Avenue (the General Motors Building) | Other Mezzanine Debt [Member]
Debt Instrument [Line Items]
Other Long-term Debt	$ 294,000
Coupon/Stated Rate	6.02%
Consolidated Entities [Member] | 767 Fifth Avenue (the General Motors Building) | Members' notes Payables [Member]
Debt Instrument [Line Items]
Coupon/Stated Rate	11.00%
Interest Payable	$ 425,000
Outside members’ notes payable	450,000
Consolidated Entities [Member] | Consolidation, Eliminations [Member] | 767 Fifth Avenue (the General Motors Building)
Debt Instrument [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity	164,400
Consolidated Entities [Member] | Consolidation, Eliminations [Member] | 767 Fifth Avenue (the General Motors Building) | Members' notes Payables [Member]
Debt Instrument [Line Items]
Interest Payable	255,000
Outside members’ notes payable	270,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Competitive bid quote		65.00%
Maximum Leverage Ratio					60.00%
Line of Credit Facility, Current Borrowing Capacity		$ 1,500,000							$ 1,000,000
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 | yr					1
Unsecured Debt Interest Coverage Ratio Minimum.					1.75
Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.10%
Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.30%
Delayed Draw Facility [Member]
Debt Instrument [Line Items]
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
Line of Credit Facility, Current Borrowing Capacity		$ 500,000
Alternative Base Interest Rate Calculation [Member] | Revolving Credit Facility [Member]
Debt Instrument [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] | Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		0.00%
Alternative Base Interest Rate Calculation [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		0.55%
Alternative Base Interest Rate Calculation [Member] | Delayed Draw Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		0.00%
Alternative Base Interest Rate Calculation [Member] | Delayed Draw Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		0.75%
Interest Rate Based on LIBOR or CDOR [Member] | Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		0.775%
Interest Rate Based on LIBOR or CDOR [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		1.55%
Interest Rate Based on LIBOR or CDOR [Member] | Delayed Draw Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		0.85%
Interest Rate Based on LIBOR or CDOR [Member] | Delayed Draw Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate		1.75%
Current credit rating [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage					0.15%
Current credit rating [Member] | Alternative Base Interest Rate Calculation [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate			0.00%		0.00%
Current credit rating [Member] | Alternative Base Interest Rate Calculation [Member] | Delayed Draw Facility [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate			0.00%		0.00%
Current credit rating [Member] | Interest Rate Based on LIBOR or CDOR [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate			0.875%		0.875%
Current credit rating [Member] | Interest Rate Based on LIBOR or CDOR [Member] | Delayed Draw Facility [Member]
Debt Instrument [Line Items]
Margin added to Calculated Interest Rate			0.95%		0.95%
Parent Company [Member] | Consolidated Entities [Member] | 767 Fifth Avenue (the General Motors Building) | Members' notes Payables [Member]
Debt Instrument [Line Items]
Interest Payable	170,000
Outside members’ notes payable	$ 180,000

Derivative Instruments and He43

Derivative Instruments and Hedging Activities (Details) $ in Thousands	Apr. 24, 2017USD ($)	Aug. 17, 2016USD ($)yr	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)swapsyr	Dec. 31, 2015USD ($)swaps	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Mortgage notes payable, net			$ 2,982,067		$ 2,982,067			$ 2,063,087
Cash payment to settle interest rate swap contracts					(65,031)	$ (114,321)
Losses from interest rate contracts			$ 0	$ 140	$ 0	$ 140
Boston Properties Limited Partnership | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Number of interest rate swap agreements entered into (swap contracts) | swaps							17
Term of anticipated mortgage loan (in years) | yr		10
Average Fixed Interest Rate							2.423%
Notional Amount							$ 550,000
Cash payment to settle interest rate swap contracts		$ 49,300
Losses from interest rate contracts		100
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion		49,200
Derivative Instruments Loss Reclassified From Accumulated OCI Into Income Effective yearly amount		$ 4,900
767 Fifth Partners LLC [Member]
Debt Instrument [Line Items]
Ownership Percentage by the Company			60.00%		60.00%
767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Number of interest rate swap agreements entered into (swap contracts) | swaps						16
Maximum period of hedging exposure to the variability in future cash flows for forecasted transactions (in years) | yr						10
Average Fixed Interest Rate				2.619%		2.619%
Notional Amount				$ 450,000		$ 450,000		450,000
Cash payment to settle interest rate swap contracts	$ 14,400
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	14,400
Derivative Instruments Loss Reclassified From Accumulated OCI Into Income Effective yearly amount	1,400
Unsecured Debt [Member] | Boston Properties Limited Partnership
Debt Instrument [Line Items]
Coupon/Stated Rate		2.75%
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Mortgage notes payable, net			$ 2,982,067		$ 2,982,067			$ 2,063,087
Cash payment to settle interest rate swap contracts					(65,031)	(114,321)
Losses from interest rate contracts			$ 0	$ 140	$ 0	$ 140
767 Fifth Avenue (the General Motors Building) | Secured Debt [Member]
Debt Instrument [Line Items]
Mortgage notes payable, net	$ 2,300,000
Coupon/Stated Rate	3.43%

Derivative Instruments and He44

Derivative Instruments and Hedging Activities Derivative Instrument and Hedging Activities Notional Table (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Fair Value	$ 0	$ 5,712	$ (6,133)	$ (85,285)
Boston Properties Limited Partnership | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount						$ 550,000
767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount					$ 350,000
Derivative Asset, Notional Amount					100,000
Notional Amount		$ 450,000		$ 450,000	450,000
Fair Value					(8,264)
Liability [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Fair Value					$ (8,773)
Liability [Member] | Minimum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate					2.418%
Liability [Member] | Maximum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate					2.95%
Assets [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Fair Value					$ 509
Assets [Member] | Minimum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate					2.336%
Assets [Member] | Maximum [Member] | 767 Fifth Partners LLC [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate					2.388%

Derivative Instruments and He45

Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Gain or Loss Recognized Related to Cash Flow hedges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Amount of gain (loss) related to the effective portion recognized in other comprehensive loss	$ 0	$ 5,712	$ (6,133)	$ (85,285)
Amount of loss related to the effective portion subsequently reclassified to earnings	(1,665)	(1,190)	(4,368)	(2,445)
Amount of loss related to the ineffective portion and amount excluded from effectiveness testing	$ 0	$ (140)	$ 0	$ (140)

Derivative Instruments and He46

Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accumulated Other Comprehensive Income or Loss [Roll Forward]
Beginning Balance				$ (52,251)	$ (14,114)	$ (14,114)
Effective portion of interest rate contracts		$ 0	$ 5,712	(6,133)	(85,285)
Amortization of interest rate contracts	[1]	1,665	1,190	4,368	2,445
Other comprehensive loss attributable to noncontrolling interests		(300)	(1,097)	2,220	23,011
Ending Balance		(51,796)	(73,943)	(51,796)	(73,943)	(52,251)
Boston Properties Limited Partnership
Accumulated Other Comprehensive Income or Loss [Roll Forward]
Beginning Balance				(60,853)	(18,337)	(18,337)
Effective portion of interest rate contracts		0	5,712	(6,133)	(85,285)
Amortization of interest rate contracts	[2]	1,665	1,190	4,368	2,445
Other comprehensive income (loss) attributable to noncontrolling interests				2,272	16,134
Ending Balance		$ (60,346)	$ (85,043)	$ (60,346)	$ (85,043)	$ (60,853)
[1]	Amounts reclassified from comprehensive income primarily to interest expense within the Boston Properties, Inc.’s Consolidated Statements of Operations.
[2]	Amounts reclassified from comprehensive income primarily to interest expense within the Boston Properties Limited Partnership's Consolidated Statements of Operations.

Commitments And Contingencies (

Commitments And Contingencies (Details) - USD ($) $ in Millions	2 Months Ended	7 Months Ended	9 Months Ended	12 Months Ended
	Feb. 28, 2017	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2009	May 19, 2017	Jul. 05, 2016	Dec. 31, 2015	Dec. 31, 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 Salesforce Tower	$ 60
767 Venture, LLC [Member]
Commitments And Contingencies [Line Items]
Maximum funding obligation		222.7	222.7
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	$ 1.4	$ 8.1	$ 7.7
Bankruptcy remaining claim amount allowed by court to creditor		27.6	27.6
601 Lexington Avenue [Member]
Commitments And Contingencies [Line Items]
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP			250
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) - Boston Properties Limited Partnership	Sep. 30, 2017shares
Noncontrolling Interests [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operating Partnership (OP) Units (in shares)	16,812,329
Long-Term Incentive Plan (LTIP) Units (in shares)	816,982
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
2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP (in units)	85,405
MYLTIP 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP (in units)	25,107
2015 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIPS (in units)	366,618
2016 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIPs (in units)	473,360
2017 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP (in units)	400,000

(Common Units) (Narrative) (Det

(Common Units) (Narrative) (Details) $ / shares in Units, $ in Millions	Feb. 03, 2017USD ($)shares	Sep. 30, 2017USD ($)yr$ / sharesshares
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)		492,617
Redemption of OP units issued on conversion of LTIP Units (in shares)		33,466
Restriction on redemption of OP Unit to Common Stock (in years) | yr		1
Redemption of OP Unit equivalent to Common Stock (in shares)		1
Common units of operating partnership if converted value | $		$ 2,200
Closing price of common stock (in dollars per share) | $ / shares		$ 122.88
MYLTIP 2014 [Member]
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
2014 MYLTIP Units Forfeited	447,386
Boston Properties Limited Partnership | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
MYLTIP distribution prior to measurement date		10.00%
Boston Properties Limited Partnership | MYLTIP 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP (in units)		25,107
Boston Properties Limited Partnership | 2015 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIPS (in units)		366,618
Boston Properties Limited Partnership | 2016 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIPs (in units)		473,360
Boston Properties Limited Partnership | 2017 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP (in units)		400,000

Noncontrolling Interests Common

Noncontrolling Interests Common units distributions (Details) - $ / shares	Jul. 31, 2017	Apr. 28, 2017	Jan. 30, 2017	Sep. 15, 2017
Dividends Payable [Line Items]
Distributions Declared To OP And LTIP Units Per Unit				$ 0.75
Distributions Declared To MYLTIP Units Per Unit (in dollars per unit)				$ 0.075
Boston Properties Limited Partnership
Dividends Payable [Line Items]
Distributions made to OP and LTIP units per unit (in dollars per unit)	$ 0.75	$ 0.75	$ 0.75
Distribution paid to MYLTIP Units (in dollars per unit)	$ 0.075	$ 0.075	$ 0.075

Noncontrolling Interests Comm51

Noncontrolling Interests Common units for Boston Properties Limited Partnership (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Conversion of redeemable partnership units		$ 0
Cumulative effect of a change in accounting principle	$ (2,035)
Accumulated other comprehensive income (loss)	(51,796)	(73,943)	$ (52,251)	$ (14,114)
Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Conversion of redeemable partnership units	16,986	10,094
Cumulative effect of a change in accounting principle	(1,763)
Boston Properties Limited Partnership
Noncontrolling Interest [Line Items]
Cumulative effect of a change in accounting principle	(272)
Accumulated other comprehensive income (loss)	(60,346)	(85,043)	$ (60,853)	$ (18,337)
Boston Properties Limited Partnership | Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Beginning balance	2,262,040	2,286,689
Contributions	31,465	31,492
Net income	40,350	42,120
Distributions	(40,292)	(35,500)
Conversion of redeemable partnership units	(16,812)	(5,881)
Unearned compensation	(5,194)	(10,072)
Cumulative effect of a change in accounting principle	(1,763)
Accumulated other comprehensive income (loss)	52	(6,877)
Adjustments to reflect redeemable preferred units at redemption value	(103,556)	151,545
Ending balance	$ 2,166,290	$ 2,453,516

Noncontrolling Interests (Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) - USD ($) $ in Thousands	May 12, 2016	Sep. 30, 2017	Jun. 06, 2017	Dec. 31, 2016
Noncontrolling Interest [Line Items]
Noncontrolling Interest in Limited Partnerships		$ 1,668,675		$ 1,530,647
Salesforce Tower[Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Portion of project costs covered by a construction loan	50.00%
Portion of costs funded (in percentage)	50.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	5.00%
Debt Instrument, Basis Spread on Variable Rate	3.00%
Salesforce Tower[Member] | Parent Company [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Costs funded (in percentage)	2.50%
Preferred equity funded		$ 15,200
767 Fifth Avenue (the General Motors Building) | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest in Limited Partnerships			$ 109,600
Ownership Percentage by the Company			60.00%
Unpaid principal balance of the members' notes payable contributed to equity			$ 273,900
767 Fifth Avenue (the General Motors Building) | Consolidation, Eliminations [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Unpaid principal balance of the members' notes payable contributed to equity			$ 164,400

Noncontrolling Interests Proper

Noncontrolling Interests Property Partnerships (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Activity of Noncontrolling Interests [Roll Forward]
Beginning Balance			$ 1,530,647,000
Capital contributions			(147,772,000)		$ (6,737,000)
Net income	$ 14,340,000	$ (17,225,000)	33,967,000		53,000
Accumulated other comprehensive income (loss)	(300,000)	(1,097,000)	2,220,000		23,011,000
Ending Balance	1,668,675,000		1,668,675,000
Property Partnerships Member
Activity of Noncontrolling Interests [Roll Forward]
Beginning Balance			1,530,647,000		1,574,400,000
Capital contributions			147,772,000	[1]	5,417,000
Net income			33,967,000		53,000
Accumulated other comprehensive income (loss)			(2,272,000)		(16,134,000)
Distributions			(41,439,000)		(38,694,000)
Ending Balance	1,668,675,000	$ 1,525,042,000	1,668,675,000		$ 1,525,042,000
767 Fifth Avenue (the General Motors Building) | Property Partnerships Member
Activity of Noncontrolling Interests [Roll Forward]
Ending Balance	$ 109,576		$ 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 _ Partne54

Stockholders' Equity / Partners' Capital Narrative (Details)	Jun. 02, 2017USD ($)yr	Sep. 30, 2017USD ($)$ / sharesshares	Mar. 27, 2018$ / shares	Dec. 31, 2016USD ($)$ / sharesshares	Jun. 03, 2014USD ($)
Class of Stock [Line Items]
Common stock, shares outstanding		154,322,266		153,790,175
General Partners' Capital Account, Units Outstanding		1,719,516
Limited Partners' Capital Account, Units Outstanding		152,602,750
Shares of Common Stock in connection with the redemption of an equal number of OP Units (in shares)		492,617
Common Stock, Value, Issued | $		$ 1,543,000		$ 1,538,000
Atm Program [Member]
Class of Stock [Line Items]
At the market stock offering program, aggregate value of common stock | $	$ 600,000,000				$ 600,000,000
At Market Stock Offering Program Maximum Length Of Sale In Years | yr	3
Common Stock, Value, Issued | $		$ 0
Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		80,000		80,000
Series B, Dividend Rate, Percentage		5.25%
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares		$ 2,500		$ 2,500
Ratio of depository shares to shares of Series B Preferred Stock		0.01
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		8,000,000
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares		$ 25
Subsequent Event [Member] | Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares			$ 2,500
Subsequent Event [Member] | Depository shares of Series B Cumulative Redeemable Preferred [Member]
Class of Stock [Line Items]
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares			$ 25
Boston Properties Limited Partnership
Class of Stock [Line Items]
General Partners' Capital Account, Units Outstanding		1,719,516		1,717,743
Limited Partners' Capital Account, Units Outstanding		152,602,750		152,072,432
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		80,000		80,000
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares		$ 2,500		$ 2,500

Stockholders' Equity _ Partne55

Stockholders' Equity / Partners' Capital Stockholders' Equity / Partners' Capital Dividends / Distributions (Details) - $ / shares	Aug. 15, 2017	Jul. 31, 2017	May 15, 2017	Apr. 28, 2017	Feb. 15, 2017	Jan. 30, 2017	Sep. 15, 2017
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit							$ 0.75
Dividends, Per Share / Unit		$ 0.75		$ 0.75		$ 0.75
Boston Properties Limited Partnership
Entity Information [Line Items]
Dividends, Per Share / Unit		$ 0.75		$ 0.75		$ 0.75
Boston Properties Limited Partnership
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit							0.75
Series B Cumulative Redeemable Preferred Stock [Member]
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit							$ 32.8125
Dividends, Per Share / Unit	$ 32.8125		$ 32.8125		$ 32.8125

Earnings Per Share _ Common U56

Earnings Per Share / Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic Earnings:
Net income attributable to the Company's common shareholders / unitholders	$ 117,337	$ 76,753	$ 348,086	$ 355,114
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	154,355,000	153,754,000	154,132,000	153,681,000
Net income (in dollars per share / unit)	$ 0.76	$ 0.50	$ 2.26	$ 2.31
Allocation of undistributed earnings to participating securities (numerator)	$ (7)		$ (15)	$ (189)
Allocation of undistributed earnings to participating securities (in shares)	0		0	0
Allocation of undistributed earnings to participating securities (in dollars per shares / units)	$ 0		$ 0	$ 0
Net income attributable to the Company's common shareholders / unitholders	$ 117,330		$ 348,071	$ 354,925
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	154,355,000		154,132,000	153,681,000
Net income attributable to the Company's common shareholders / unitholders (in dollars per share / unit)	$ 0.76		$ 2.26	$ 2.31
Effect of Dilutive Securities:
Stock Based Compensation, Income (Numerator)	$ 0	$ 0	$ 0	$ 0
Stock Based Compensation, Shares / Units (Denominator)	128,000	382,000	212,000	290,000
Stock Based Compensation, Per Share / Unit Amount (in dollars per share / unit)	$ 0	$ 0	$ 0	$ 0
Diluted Earnings:
Net income attributable to the Company's common shareholders / unitholders (Numerator)	$ 117,330	$ 76,753	$ 348,071	$ 354,925
Net income attributable to to the Company's shareholders / unitholder (number of shares)	154,483,000	154,136,000	154,344,000	153,971,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 0.76	$ 0.50	$ 2.26	$ 2.31
Boston Properties Limited Partnership
Entity Information [Line Items]
Redeemable Common Units	17,336,000	17,625,000	17,517,000	17,672,000
Basic Earnings:
Net income attributable to the Company's common shareholders / unitholders	$ 132,693	$ 91,306	$ 395,199	$ 408,540
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	171,691,000	171,379,000	171,649,000	171,353,000
Net income (in dollars per share / unit)	$ 0.77	$ 0.53	$ 2.30	$ 2.38
Allocation of undistributed earnings to participating securities (numerator)	$ (8)		$ (17)	$ (210)
Allocation of undistributed earnings to participating securities (in shares)	0		0	0
Allocation of undistributed earnings to participating securities (in dollars per shares / units)	$ 0		$ 0	$ 0
Net income attributable to the Company's common shareholders / unitholders	$ 132,685		$ 395,182	$ 408,330
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	171,691,000		171,649,000	171,353,000
Net income attributable to the Company's common shareholders / unitholders (in dollars per share / unit)	$ 0.77		$ 2.30	$ 2.38
Effect of Dilutive Securities:
Stock Based Compensation, Income (Numerator)	$ 0	$ 0	$ 0	$ 0
Stock Based Compensation, Shares / Units (Denominator)	128,000	382,000	212,000	290,000
Stock Based Compensation, Per Share / Unit Amount (in dollars per share / unit)	$ 0	$ 0	$ 0	$ 0
Diluted Earnings:
Net income attributable to the Company's common shareholders / unitholders (Numerator)	$ 132,685	$ 91,306	$ 395,182	$ 408,330
Net income attributable to to the Company's shareholders / unitholder (number of shares)	171,819,000	171,761,000	171,861,000	171,643,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 0.77	$ 0.53	$ 2.30	$ 2.38

Stock Option and Incentive Pl57

Stock Option and Incentive Plan Stock Option and Incentive Plan (Narrative) (Details)	Feb. 03, 2017USD ($)shares	Jan. 25, 2017USD ($)yrtiersindices
2017 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Measurement, Years | yr		3
Indices Used to Compare TSR | indices		2
Number of Tiers | tiers		4
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%
Distributions Percent Before Measurement Date		10.00%
Value of MYLTIP Awards		$ 17,700,000
MYLTIP Value Amortized Into Earnings, Years | yr		4
MYLTIP 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards	$ 3,500,000
Final awards percentage of target	27.70%
2014 MYLTIP Units Forfeited | shares	447,386
Cohen & Steers Realty Majors Portfolio Index [Member] | 2017 MYLTIP [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] | 2017 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
Minimum [Member] | 2017 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		$ 0
Maximum [Member] | 2017 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		$ 42,700,000
MYLTIP vesting 2020 [Member] | 2017 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%
MYLTIP vesting 2021 [Member] | 2017 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%

Stock Option and Incentive Pl58

Stock Option and Incentive Plan (Restricted Stock) (Narrative) (Details) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)VestingInstallments$ / sharesshares	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued | shares	154,401,166		154,401,166		153,869,075
Common Stock, Value, Issued	$ 1,543		$ 1,543		$ 1,538
Stock based Compensation Expense	$ 7,500	$ 7,100	$ 25,600	$ 23,600
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued | shares	37,414		37,414
Employee and director payment per share (in dollars per share) | $ / shares			$ 0.01
Common Stock, Value, Issued	$ 4,900		$ 4,900
Employee's weighted average cost per share (in dollars per share) | $ / shares	$ 130.32		$ 130.32
LTIPs (including 2012 OPP and 2013 and 2014 MYLTIPS) And Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting annual installments | VestingInstallments			4
Unrecognized compensation expenses	$ 22,800		$ 22,800
Unvested MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses	$ 24,700		$ 24,700
Weighted-average period (years)	2 years 6 months
Boston Properties Limited Partnership | LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP units issued (in shares) | shares	111,488		111,488
Value of LTIP units issued			$ 13,300
Per unit fair value weighted-average (in dollars per share) | $ / shares	$ 119.52		$ 119.52
Expected life assumed to calculate per unit fair value per LTIP unit (years)			5 years 8 months 12 days
Risk-free rate			2.14%
Expected price volatility			28.00%
Boston Properties Limited Partnership | 2017 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued (in shares) | shares	400,000		400,000
Boston Properties Limited Partnership | LTIPs and 2017 MYLTIP Units [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

Segment Information (Schedule O

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income attributable to the Company's common shareholders / unitholders	$ 117,337	$ 76,753	$ 348,086	$ 355,114
Preferred Stock Dividends / Distributions	(2,625)	(2,589)	(7,875)	(7,796)
Noncontrolling interest-common units of the Operating Partnership	(13,402)	(9,387)	(40,350)	(42,120)
Noncontrolling interest in property partnerships	(14,340)	17,225	(33,967)	(53)
Interest expense	(92,032)	(104,641)	(282,709)	(314,953)
Losses from interest rate contracts	0	(140)	0	(140)
Depreciation and amortization expense	(152,164)	(203,748)	(463,288)	(516,371)
Impairment of Real Estate	0	(1,783)	0	(1,783)
Transaction costs	(239)	(249)	(572)	(1,187)
General and administrative expense	(25,792)	(25,165)	(84,319)	(79,936)
Gains (losses) from early extinguishments of debt	0	371	(14,354)	371
Gains from investments in securities	(944)	(976)	(2,716)	(1,713)
Interest and other income	(1,329)	(3,628)	(3,447)	(6,657)
Income from unconsolidated joint ventures	(843)	(1,464)	(7,035)	(5,489)
Development and management services income	(10,811)	(6,364)	(24,648)	(18,586)
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	117,337	76,753	348,086	355,114
Preferred Stock Dividends / Distributions	2,625	2,589	7,875	7,796
Noncontrolling interest-common units of the Operating Partnership	13,402	9,387	40,350	42,120
Noncontrolling interest in property partnerships	14,340	(17,225)	33,967	53
Interest expense	92,032	104,641	282,709	314,953
Losses from interest rate contracts	0	140	0	140
Depreciation and amortization expense	152,164	203,748	463,288	516,371
Impairment of Real Estate	0	1,783	0	1,783
Transaction costs	239	249	572	1,187
General and administrative expense	25,792	25,165	84,319	79,936
Gains on sales of real estate	2,891	12,983	6,791	80,606
Gains (losses) from early extinguishments of debt	0	(371)	14,354	(371)
Gains from investments in securities	944	976	2,716	1,713
Interest and other income	1,329	3,628	3,447	6,657
Income from unconsolidated joint ventures	843	1,464	7,035	5,489
Development and management services income	10,811	6,364	24,648	18,586
Net Operating Income	401,113	382,186	1,202,175	1,206,773
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	132,693	91,306	395,199	408,540
Preferred Stock Dividends / Distributions	(2,625)	(2,589)	(7,875)	(7,796)
Noncontrolling interest in property partnerships	(14,340)	17,225	(33,967)	(53)
Interest expense	(92,032)	(104,641)	(282,709)	(314,953)
Losses from interest rate contracts	0	(140)	0	(140)
Depreciation and amortization expense	(150,210)	(198,582)	(457,102)	(507,234)
Impairment of Real Estate	0	(1,783)	0	(1,783)
Transaction costs	(239)	(249)	(572)	(1,187)
General and administrative expense	(25,792)	(25,165)	(84,319)	(79,936)
Gains (losses) from early extinguishments of debt	0	371	(14,354)	371
Gains from investments in securities	(944)	(976)	(2,716)	(1,713)
Interest and other income	(1,329)	(3,628)	(3,447)	(6,657)
Income from unconsolidated joint ventures	(843)	(1,464)	(7,035)	(5,489)
Development and management services income	(10,811)	(6,364)	(24,648)	(18,586)
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	132,693	91,306	395,199	408,540
Preferred Stock Dividends / Distributions	2,625	2,589	7,875	7,796
Noncontrolling interest in property partnerships	14,340	(17,225)	33,967	53
Interest expense	92,032	104,641	282,709	314,953
Losses from interest rate contracts	0	140	0	140
Depreciation and amortization expense	150,210	198,582	457,102	507,234
Impairment of Real Estate	0	1,783	0	1,783
Transaction costs	239	249	572	1,187
General and administrative expense	25,792	25,165	84,319	79,936
Gains on sales of real estate	2,891	12,983	7,368	82,775
Gains (losses) from early extinguishments of debt	0	(371)	14,354	(371)
Gains from investments in securities	944	976	2,716	1,713
Interest and other income	1,329	3,628	3,447	6,657
Income from unconsolidated joint ventures	843	1,464	7,035	5,489
Development and management services income	10,811	6,364	24,648	18,586
Net Operating Income	$ 401,113	$ 382,186	$ 1,202,175	$ 1,206,773

Segment Information (Schedule60

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Rental Revenue: Office	$ 629,542	$ 602,138	$ 1,875,879	$ 1,849,745
Rental Revenue: Residential	4,295	4,372	12,461	12,509
Rental Revenue: Hotel	13,064	12,354	33,859	33,919
Total revenue	$ 646,901	$ 618,864	$ 1,922,199	$ 1,896,173
Rental Revenue: % of Grand Totals	100.00%	100.00%	100.00%	100.00%
Rental Expenses: Office	$ 235,764	$ 226,337	$ 691,319	$ 660,241
Rental Expenses: Residential	1,577	2,223	4,763	5,429
Rental Expenses: Hotel	8,447	8,118	23,942	23,730
Rental Expenses: Total	$ 245,788	$ 236,678	$ 720,024	$ 689,400
Rental Expenses: % Of Grand Totals	100.00%	100.00%	100.00%	100.00%
Net operating Income	$ 401,113	$ 382,186	$ 1,202,175	$ 1,206,773
Net operating Income: % of Grand Totals	100.00%	100.00%	100.00%	100.00%
Boston [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	$ 196,687	$ 183,975	$ 573,883	$ 540,850
Rental Revenue: Residential	1,228	1,227	3,520	3,578
Rental Revenue: Hotel	13,064	12,354	33,859	33,919
Total revenue	$ 210,979	$ 197,556	$ 611,262	$ 578,347
Rental Revenue: % of Grand Totals	32.61%	31.92%	31.80%	30.50%
Rental Expenses: Office	$ 76,086	$ 71,254	$ 225,502	$ 210,695
Rental Expenses: Residential	512	1,141	1,552	2,174
Rental Expenses: Hotel	8,447	8,118	23,942	23,730
Rental Expenses: Total	$ 85,045	$ 80,513	$ 250,996	$ 236,599
Rental Expenses: % Of Grand Totals	34.60%	34.02%	34.86%	34.32%
Net operating Income	$ 125,934	$ 117,043	$ 360,266	$ 341,748
Net operating Income: % of Grand Totals	31.40%	30.62%	29.97%	28.32%
New York [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	$ 242,071	$ 237,262	$ 735,485	$ 773,077
Rental Revenue: Residential	0	0	0	0
Rental Revenue: Hotel	0	0	0	0
Total revenue	$ 242,071	$ 237,262	$ 735,485	$ 773,077
Rental Revenue: % of Grand Totals	37.43%	38.34%	38.27%	40.77%
Rental Expenses: Office	$ 95,775	$ 95,073	$ 280,569	$ 272,620
Rental Expenses: Residential	0	0	0	0
Rental Expenses: Hotel	0	0	0	0
Rental Expenses: Total	$ 95,775	$ 95,073	$ 280,569	$ 272,620
Rental Expenses: % Of Grand Totals	38.97%	40.17%	38.97%	39.54%
Net operating Income	$ 146,296	$ 142,189	$ 454,916	$ 500,457
Net operating Income: % of Grand Totals	36.47%	37.21%	37.84%	41.47%
San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	$ 87,162	$ 80,235	$ 257,286	$ 235,076
Rental Revenue: Residential	0	0	0	0
Rental Revenue: Hotel	0	0	0	0
Total revenue	$ 87,162	$ 80,235	$ 257,286	$ 235,076
Rental Revenue: % of Grand Totals	13.47%	12.96%	13.38%	12.40%
Rental Expenses: Office	$ 26,792	$ 26,037	$ 77,204	$ 75,412
Rental Expenses: Residential	0	0	0	0
Rental Expenses: Hotel	0	0	0	0
Rental Expenses: Total	$ 26,792	$ 26,037	$ 77,204	$ 75,412
Rental Expenses: % Of Grand Totals	10.90%	11.00%	10.72%	10.94%
Net operating Income	$ 60,370	$ 54,198	$ 180,082	$ 159,664
Net operating Income: % of Grand Totals	15.05%	14.18%	14.98%	13.23%
Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	$ 103,622	$ 100,666	$ 309,225	$ 300,742
Rental Revenue: Residential	3,067	3,145	8,941	8,931
Rental Revenue: Hotel	0	0	0	0
Total revenue	$ 106,689	$ 103,811	$ 318,166	$ 309,673
Rental Revenue: % of Grand Totals	16.49%	16.78%	16.55%	16.33%
Rental Expenses: Office	$ 37,111	$ 33,973	$ 108,044	$ 101,514
Rental Expenses: Residential	1,065	1,082	3,211	3,255
Rental Expenses: Hotel	0	0	0	0
Rental Expenses: Total	$ 38,176	$ 35,055	$ 111,255	$ 104,769
Rental Expenses: % Of Grand Totals	15.53%	14.81%	15.45%	15.20%
Net operating Income	$ 68,513	$ 68,756	$ 206,911	$ 204,904
Net operating Income: % of Grand Totals	17.08%	17.99%	17.21%	16.98%