Boston Properties LTD Partnership 10-Q 10 Aug 20 2020 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - $ / shares	6 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	1-13087
Entity Registrant Name	BOSTON PROPERTIES, INC.
Entity Central Index Key	0001037540
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-2473675
Entity Address, Address Line One	Prudential Center, 800 Boylston Street, Suite 1900
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02199-8103
City Area Code	617
Local Phone Number	236-3300
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		155,633,800
Boston Properties Limited Partnership
Entity Information [Line Items]
Document Type	10-Q
Document Period End Date	Jun. 30, 2020
Entity File Number	0-50209
Entity Registrant Name	BOSTON PROPERTIES LIMITED PARTNERSHIP
Entity Central Index Key	0001043121
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3372948
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Common Stock [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	BXP
Security Exchange Name	NYSE
Entity Listing, Par Value Per Share	$ 0.01
5.25% Series B Cumulative Redeemable Preferred Stock, par value $0.01 per share [Member]
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares Each Representing 1/100th of a share
Trading Symbol	BXP PRB
Security Exchange Name	NYSE
Entity Listing, Par Value Per Share	$ 0.01

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,581,689 and $6,497,031 at June 30, 2020 and December 31, 2019, respectively)	$ 22,575,903	$ 22,502,976
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at June 30, 2020 and December 31, 2019, respectively)	237,394	237,394
Right of use assets - operating leases	147,512	148,640
Less: accumulated depreciation (amounts related to VIEs of $(1,112,769) and $(1,058,495) at June 30, 2020 and December 31, 2019, respectively)	(5,292,389)	(5,266,798)
Total real estate	17,668,420	17,622,212
Cash and cash equivalents (amounts related to VIEs of $300,552 and $280,033 at June 30, 2020 and December 31, 2019, respectively)	1,691,047	644,950
Cash held in escrows	300,608	46,936
Investments in securities	32,848	36,747
Tenant and other receivables, net (amounts related to VIEs of $11,989 and $28,918 at June 30, 2020 and December 31, 2019, respectively)	82,545	112,807
Related party note receivable, net	78,520	80,000
Notes receivable, net	25,480	15,920
Accrued rental income, net (amounts related to VIEs of $304,929 and $298,318 at June 30, 2020 and December 31, 2019, respectively)	1,069,004	1,038,788
Deferred charges, net (amounts related to VIEs of $190,708 and $214,769 at June 30, 2020 and December 31, 2019, respectively)	655,813	689,213
Prepaid expenses and other assets (amounts related to VIEs of $18,741 and $20,931 at June 30, 2020 and December 31, 2019, respectively)	56,768	41,685
Investments in unconsolidated joint ventures	1,339,724	955,647
Total assets	23,000,777	21,284,905
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,913,287 and $2,918,806 at June 30, 2020 and December 31, 2019, respectively)	2,915,852	2,922,408
Unsecured senior notes, net	9,633,577	8,390,459
Unsecured line of credit	0	0
Unsecured term loan, net	499,150	498,939
Lease liabilities - finance leases (amounts related to VIEs of $20,227 and $20,189 at June 30, 2020 and December 31, 2019, respectively)	230,146	224,042
Lease liabilities - operating leases	200,979	200,180
Accounts payable and accrued expenses (amounts related to VIEs of $25,685 and $45,777 at June 30, 2020 and December 31, 2019, respectively)	328,292	377,553
Dividends and distributions payable	171,077	170,713
Accrued interest payable	95,274	90,016
Other liabilities (amounts related to VIEs of $132,460 and $140,110 at June 30, 2020 and December 31, 2019, respectively)	373,281	387,994
Total liabilities	14,447,628	13,262,304
Commitments and contingencies	0	0
Redeemable deferred stock units— 66,424 and 60,676 units outstanding at redemption value at June 30, 2020 and December 31, 2019, respectively	6,003	8,365
Equity / Capital:
Excess stock, $0.01 par value, 150,000,000 shares authorized, none issued or outstanding	0	0
Preferred stock, $0.01 par value, 50,000,000 shares authorized;
5.25% Series B cumulative redeemable preferred stock / units, liquidation preference $2,500 per share / unit, 80,000 shares / units issued and outstanding at June 30, 2020 and December 31, 2019, respectively	200,000	200,000
Common stock, $0.01 par value, 250,000,000 shares authorized, 155,701,186 and 154,869,198 issued and 155,622,286 and 154,790,298 outstanding at June 30, 2020 and December 31, 2019, respectively	1,556	1,548
Additional paid-in capital	6,340,665	6,294,719
Dividends in excess of earnings	(302,511)	(760,523)
Treasury common stock at cost, 78,900 shares at June 30, 2020 and December 31, 2019	(2,722)	(2,722)
Accumulated other comprehensive loss	(54,921)	(48,335)
Total stockholders' equity attributable to Boston Properties, Inc.	6,182,067	5,684,687
Noncontrolling interests:
Common units of the Operating Partnership	640,491	600,860
Property partnerships	1,724,588	1,728,689
Total equity / capital	8,547,146	8,014,236
Total liabilities and equity / capital	$ 23,000,777	$ 21,284,905
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 or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Treasury common stock at cost, shares	78,900	78,900
Common stock, shares issued	155,701,186	154,869,198
Common Stock, Shares, Outstanding	155,622,286	154,790,298
General Partners' Capital Account, Units Outstanding (in units)	1,730,919
Limited Partners' Capital Account, Units Outstanding (in units)	153,891,367
Reddemable deferred stock units, units	66,424	60,676
Variable Interest Entity, Primary Beneficiary [Member]
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,581,689 and $6,497,031 at June 30, 2020 and December 31, 2019, respectively)	$ 6,581,689	$ 6,497,031
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at June 30, 2020 and December 31, 2019, respectively)	21,000	21,000
Less: accumulated depreciation (amounts related to VIEs of $(1,112,769) and $(1,058,495) at June 30, 2020 and December 31, 2019, respectively)	(1,112,769)	(1,058,495)
Cash and cash equivalents (amounts related to VIEs of $300,552 and $280,033 at June 30, 2020 and December 31, 2019, respectively)	300,552	280,033
Tenant and other receivables, net (amounts related to VIEs of $11,989 and $28,918 at June 30, 2020 and December 31, 2019, respectively)	11,989	28,918
Accrued rental income, net (amounts related to VIEs of $304,929 and $298,318 at June 30, 2020 and December 31, 2019, respectively)	304,929	298,318
Deferred charges, net (amounts related to VIEs of $190,708 and $214,769 at June 30, 2020 and December 31, 2019, respectively)	190,708	214,769
Prepaid expenses and other assets (amounts related to VIEs of $18,741 and $20,931 at June 30, 2020 and December 31, 2019, respectively)	18,741	20,931
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,913,287 and $2,918,806 at June 30, 2020 and December 31, 2019, respectively)	2,913,287	2,918,806
Lease liabilities - finance leases (amounts related to VIEs of $20,227 and $20,189 at June 30, 2020 and December 31, 2019, respectively)	20,227	20,189
Accounts payable and accrued expenses (amounts related to VIEs of $25,685 and $45,777 at June 30, 2020 and December 31, 2019, respectively)	25,685	45,777
Other liabilities (amounts related to VIEs of $132,460 and $140,110 at June 30, 2020 and December 31, 2019, respectively)	$ 132,460	$ 140,110
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Noncontrolling interests:
Preferred stock / units, shares / units outstanding (in shares / units)	80,000	80,000
Preferred stock / units, shares / units issued (in shares / units)	80,000	80,000
Series B Dividend Rate Percentage	5.25%	5.25%
Series B Liquidation Preference Per Share/ Unit	$ 2,500	$ 2,500
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	92,000	92,000
Boston Properties Limited Partnership
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,581,689 and $6,497,031 at June 30, 2020 and December 31, 2019, respectively)	$ 22,199,094	$ 22,107,755
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at June 30, 2020 and December 31, 2019, respectively)	237,394	237,394
Right of use assets - operating leases	147,512	148,640
Less: accumulated depreciation (amounts related to VIEs of $(1,112,769) and $(1,058,495) at June 30, 2020 and December 31, 2019, respectively)	(5,190,360)	(5,162,908)
Total real estate	17,393,640	17,330,881
Cash and cash equivalents (amounts related to VIEs of $300,552 and $280,033 at June 30, 2020 and December 31, 2019, respectively)	1,691,047	644,950
Cash held in escrows	300,608	46,936
Investments in securities	32,848	36,747
Tenant and other receivables, net (amounts related to VIEs of $11,989 and $28,918 at June 30, 2020 and December 31, 2019, respectively)	82,545	112,807
Related party note receivable, net	78,520	80,000
Notes receivable, net	25,480	15,920
Accrued rental income, net (amounts related to VIEs of $304,929 and $298,318 at June 30, 2020 and December 31, 2019, respectively)	1,069,004	1,038,788
Deferred charges, net (amounts related to VIEs of $190,708 and $214,769 at June 30, 2020 and December 31, 2019, respectively)	655,813	689,213
Prepaid expenses and other assets (amounts related to VIEs of $18,741 and $20,931 at June 30, 2020 and December 31, 2019, respectively)	56,768	41,685
Investments in unconsolidated joint ventures	1,339,724	955,647
Total assets	22,725,997	20,993,574
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,913,287 and $2,918,806 at June 30, 2020 and December 31, 2019, respectively)	2,915,852	2,922,408
Unsecured senior notes, net	9,633,577	8,390,459
Unsecured line of credit	0	0
Unsecured term loan, net	499,150	498,939
Lease liabilities - finance leases (amounts related to VIEs of $20,227 and $20,189 at June 30, 2020 and December 31, 2019, respectively)	230,146	224,042
Lease liabilities - operating leases	200,979	200,180
Accounts payable and accrued expenses (amounts related to VIEs of $25,685 and $45,777 at June 30, 2020 and December 31, 2019, respectively)	328,292	377,553
Dividends and distributions payable	171,077	170,713
Accrued interest payable	95,274	90,016
Other liabilities (amounts related to VIEs of $132,460 and $140,110 at June 30, 2020 and December 31, 2019, respectively)	373,281	387,994
Total liabilities	14,447,628	13,262,304
Commitments and contingencies	0	0
Redeemable deferred stock units— 66,424 and 60,676 units outstanding at redemption value at June 30, 2020 and December 31, 2019, respectively	6,003	8,365
Redeemable partnership units— 16,123,912 and 16,764,466 common units and 1,345,723 and 1,143,215 long term incentive units outstanding at redemption value at June 30, 2020 and December 31, 2019, respectively	1,581,010	2,468,753
Preferred stock, $0.01 par value, 50,000,000 shares authorized;
5.25% Series B cumulative redeemable preferred stock / units, liquidation preference $2,500 per share / unit, 80,000 shares / units issued and outstanding at June 30, 2020 and December 31, 2019, respectively	193,623	193,623
Boston Properties Limited Partnership partners’ capital— 1,730,919 and 1,726,980 general partner units and 153,891,367 and 153,063,318 limited partner units outstanding at June 30, 2020 and December 31, 2019, respectively	4,828,066	3,380,175
Accumulated other comprehensive loss	(54,921)	(48,335)
Total partners’ capital	4,966,768	3,525,463
Noncontrolling interests in property partnerships	1,724,588	1,728,689
Noncontrolling interests:
Total equity / capital	6,691,356	5,254,152
Total liabilities and equity / capital	$ 22,725,997	$ 20,993,574
General Partners' Capital Account, Units Outstanding (in units)	1,730,919	1,726,980
Limited Partners' Capital Account, Units Outstanding (in units)	153,891,367	153,063,318
Reddemable deferred stock units, units	66,424	60,676
NonControlling Interest Redeemable Partnership Units Common Units Shares Outstanding	16,123,912	16,764,466
NonControlling Interest Redeemable Partnership Units Common Units Long Term Incentive Units At Redemption Value Shares Outstanding	1,345,723	1,143,215
Boston Properties Limited Partnership | Variable Interest Entity, Primary Beneficiary [Member]
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,581,689 and $6,497,031 at June 30, 2020 and December 31, 2019, respectively)	$ 6,581,689	$ 6,497,031
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at June 30, 2020 and December 31, 2019, respectively)	21,000	21,000
Less: accumulated depreciation (amounts related to VIEs of $(1,112,769) and $(1,058,495) at June 30, 2020 and December 31, 2019, respectively)	(1,112,769)	(1,058,495)
Cash and cash equivalents (amounts related to VIEs of $300,552 and $280,033 at June 30, 2020 and December 31, 2019, respectively)	300,552	280,033
Tenant and other receivables, net (amounts related to VIEs of $11,989 and $28,918 at June 30, 2020 and December 31, 2019, respectively)	11,989	28,918
Accrued rental income, net (amounts related to VIEs of $304,929 and $298,318 at June 30, 2020 and December 31, 2019, respectively)	304,929	298,318
Deferred charges, net (amounts related to VIEs of $190,708 and $214,769 at June 30, 2020 and December 31, 2019, respectively)	190,708	214,769
Prepaid expenses and other assets (amounts related to VIEs of $18,741 and $20,931 at June 30, 2020 and December 31, 2019, respectively)	18,741	20,931
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,913,287 and $2,918,806 at June 30, 2020 and December 31, 2019, respectively)	2,913,287	2,918,806
Lease liabilities - finance leases (amounts related to VIEs of $20,227 and $20,189 at June 30, 2020 and December 31, 2019, respectively)	20,227	20,189
Accounts payable and accrued expenses (amounts related to VIEs of $25,685 and $45,777 at June 30, 2020 and December 31, 2019, respectively)	25,685	45,777
Other liabilities (amounts related to VIEs of $132,460 and $140,110 at June 30, 2020 and December 31, 2019, respectively)	$ 132,460	$ 140,110
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Noncontrolling interests:
Preferred stock / units, shares / units outstanding (in shares / units)	80,000	80,000
Preferred stock / units, shares / units issued (in shares / units)	80,000	80,000
Series B Dividend Rate Percentage	5.25%	5.25%
Series B Liquidation Preference Per Share/ Unit	$ 2,500	$ 2,500

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue
Lease		$ 630,119	$ 680,189	$ 1,340,230	$ 1,359,440
Total revenue		654,773	733,741	1,407,329	1,459,508
Expenses
Rental		239,787	257,971	502,753	515,488
General and administrative		37,743	35,071	74,197	76,833
Transaction costs		332	417	947	877
Depreciation and amortization		178,188	177,411	349,282	342,005
Total expenses		460,507	482,353	941,694	957,944
Other income (expense)
Income from unconsolidated joint ventures		1,832	47,964	1,463	48,177
Gain on sales of real estate		203,767	1,686	613,932	781
Interest and other income		1,305	3,615	4,322	7,368
Gains (losses) from investments in securities		4,552	1,165	(893)	4,134
Impairment losses		0	0	0	(24,038)
Interest expense		(107,142)	(102,357)	(208,733)	(203,366)
Net income		298,580	203,461	875,726	334,620
Net (income) loss attributable to noncontrolling interests
Noncontrolling interests in property partnerships		767	(17,482)	(18,719)	(36,312)
Noncontrolling interest - common units of the Operating Partnership		(30,197)	(19,036)	(87,525)	(30,627)
Net income attributable to the Company		269,150	166,943	769,482	267,681
Preferred dividends / distributions		(2,625)	(2,625)	(5,250)	(5,250)
Net income attributable to the Company's common shareholders / unitholders		$ 266,525	$ 164,318	$ 764,232	$ 262,431
Earnings Per Share After Allccation of Undistributed Earnings to Particiapting Securities Basic (dollars per share)		$ 1.71	$ 1.06	$ 4.92	$ 1.70
Basic earnings per common share / unit attributable to the Company
Net income (in dollars per share / unit)		$ 1.72	$ 1.06	$ 4.92	$ 1.70
Weighted average number of common shares / units outstanding (in shares / units)		155,386	154,555	155,199	154,540
Diluted earnings per common share / unit attributable to the Company
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)		$ 1.71	$ 1.06	$ 4.91	$ 1.69
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)		155,407	154,874	155,333	154,859
Boston Properties Limited Partnership
Revenue
Lease		$ 630,119	$ 680,189	$ 1,340,230	$ 1,359,440
Total revenue		654,773	733,741	1,407,329	1,459,508
Expenses
Rental		239,787	257,971	502,753	515,488
General and administrative		37,743	35,071	74,197	76,833
Transaction costs		332	417	947	877
Depreciation and amortization		176,409	175,199	345,694	337,881
Total expenses		458,728	480,141	938,106	953,820
Other income (expense)
Income from unconsolidated joint ventures		1,832	47,964	1,463	48,177
Gain on sales of real estate		207,241	1,835	626,895	930
Interest and other income		1,305	3,615	4,322	7,368
Gains (losses) from investments in securities		4,552	1,165	(893)	4,134
Impairment losses		0	0	0	(22,272)
Interest expense		(107,142)	(102,357)	(208,733)	(203,366)
Net income		303,833	205,822	892,277	340,659
Net (income) loss attributable to noncontrolling interests
Noncontrolling interests in property partnerships		767	(17,482)	(18,719)	(36,312)
Net income attributable to the Company		304,600	188,340	873,558	304,347
Preferred dividends / distributions		(2,625)	(2,625)	(5,250)	(5,250)
Net income attributable to the Company's common shareholders / unitholders		$ 301,975	$ 185,715	$ 868,308	$ 299,097
Earnings Per Share After Allccation of Undistributed Earnings to Particiapting Securities Basic (dollars per share)		$ 1.75	$ 1.08	$ 5.02	$ 1.74
Basic earnings per common share / unit attributable to the Company
Net income (in dollars per share / unit)		$ 1.75	$ 1.08	$ 5.03	$ 1.74
Weighted average number of common shares / units outstanding (in shares / units)		172,659	172,202	172,604	172,167
Diluted earnings per common share / unit attributable to the Company
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)		$ 1.75	$ 1.08	$ 5.02	$ 1.73
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)		172,680	172,521	172,738	172,486
Parking and Other [Member]
Revenue
Other revenue		$ 13,946	$ 26,319	$ 38,450	$ 51,225
Parking and Other [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		13,946	26,319	38,450	51,225
Hotel [Member]
Revenue
Other revenue	[1]	99	14,844	6,924	23,782
Expenses
Operating expense		1,973	9,080	8,794	16,943
Hotel [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		99	14,844	6,924	23,782
Expenses
Operating expense		1,973	9,080	8,794	16,943
Real Estate, Other [Member]
Revenue
Other revenue		2,484	2,403	5,721	5,798
Expenses
Operating expense		2,484	2,403	5,721	5,798
Real Estate, Other [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		2,484	2,403	5,721	5,798
Management Service [Member]
Revenue
Other revenue		8,125	9,986	16,004	19,263
Management Service [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		8,125	9,986	16,004	19,263
Expenses
Operating expense		$ 2,484	$ 2,403	$ 5,721	$ 5,798
[1]	Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income		$ 298,580	$ 203,461	$ 875,726	$ 334,620
Other comprehensive income (loss):
Effective portion of interest rate contracts		(659)	(4,426)	(10,379)	(7,054)
Amortization of interest rate contracts	[1]	1,677	1,666	3,343	3,332
Other comprehensive income (loss)		1,018	(2,760)	(7,036)	(3,722)
Comprehensive Income		299,598	200,701	868,690	330,898
Comprehensive income attributable to noncontrolling interests		(29,430)	(36,518)	(106,244)	(66,939)
Other comprehensive income (loss) attributable to noncontrolling interests		(239)	154	450	123
Comprehensive income attributable to the Company		269,929	164,337	762,896	264,082
Boston Properties Limited Partnership
Net income		303,833	205,822	892,277	340,659
Other comprehensive income (loss):
Effective portion of interest rate contracts		(659)	(4,426)	(10,379)	(7,054)
Amortization of interest rate contracts	[2]	1,677	1,666	3,343	3,332
Other comprehensive income (loss)		1,018	(2,760)	(7,036)	(3,722)
Comprehensive Income		304,851	203,062	885,241	336,937
Comprehensive income attributable to noncontrolling interests		623	(17,626)	(19,007)	(36,600)
Comprehensive income attributable to the Company		$ 305,474	$ 185,436	$ 866,234	$ 300,337
[1]	Amounts reclassified from comprehensive income primarily to interest expense within Boston Properties, Inc.’s Consolidated Statements of Operations
[2]	Amounts reclassified from comprehensive income primarily to interest expense within Boston Properties Limited Partnership’s Consolidated Statements of Operations.

Consolidated Statements Of Stoc

Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Dividends In Excess Of Earnings [Member]	Treasury Stock, At Cost [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]	Noncontrolling interest - property partnerships [Member]
Equity, shares at Dec. 31, 2018		154,458,000
Equity, value at Dec. 31, 2018	$ 8,213,968	$ 1,545	$ 200,000	$ 6,407,623	$ (675,534)	$ (2,722)	$ (47,741)	$ 619,352	$ 1,711,445
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	(4,379)				(3,864)			(445)	(70)
Redemption of operating partnership units to common stock, shares		35,000
Redemption of operating partnership units to common stock, value	0	$ 1		1,211				(1,212)
Allocated net income for the year	334,620				267,681			30,627	36,312
Dividends/distributions declared	(333,266)				(298,875)			(34,391)
Shares issued pursuant to stock purchase plan, shares		4,000
Shares issued pursuant to stock purchase plan, value	373			373
Net activity from stock option and incentive plan, shares		66,000
Net activity from stock option and incentive plan, value	27,332			4,554				22,778
Acquisition of noncontrolling interest in property partnership	(187,006)			(162,505)					(24,501)
Contributions from noncontrolling interests in property partnerships	12,148								12,148
Distributions to noncontrolling interests in property partnerships	(39,401)								(39,401)
Effective portion of interest rate contracts	(7,054)						(6,332)	(722)	0
Amortization of interest rate contracts	3,332						2,733	311	288
Reallocation of noncontrolling interest				27,705				(27,705)
Equity, shares at Jun. 30, 2019		154,563,000
Equity, value at Jun. 30, 2019	8,020,667	$ 1,546	200,000	6,278,961	(710,592)	(2,722)	(51,340)	608,593	1,696,221
Equity, shares at Mar. 31, 2019		154,515,000
Equity, value at Mar. 31, 2019	8,170,287	$ 1,545	200,000	6,414,612	(728,083)	(2,722)	(48,734)	623,061	1,710,608
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of operating partnership units to common stock, shares		21,000
Redemption of operating partnership units to common stock, value	0	$ 1		719				(720)
Allocated net income for the year	203,461				166,951			19,028	17,482
Dividends/distributions declared	(166,666)				(149,460)			(17,206)
Net activity from stock option and incentive plan, shares		27,000
Net activity from stock option and incentive plan, value	10,863			1,495				9,368
Acquisition of noncontrolling interest in property partnership	(187,006)			(162,505)					(24,501)
Contributions from noncontrolling interests in property partnerships	7,761								7,761
Distributions to noncontrolling interests in property partnerships	(15,273)								(15,273)
Effective portion of interest rate contracts	(4,426)						(3,973)	(453)
Amortization of interest rate contracts	1,666						1,367	155	144
Reallocation of noncontrolling interest	0			24,640				(24,640)
Equity, shares at Jun. 30, 2019		154,563,000
Equity, value at Jun. 30, 2019	$ 8,020,667	$ 1,546	200,000	6,278,961	(710,592)	(2,722)	(51,340)	608,593	1,696,221
Equity, shares at Dec. 31, 2019	154,790,298	154,790,000
Equity, value at Dec. 31, 2019	$ 8,014,236	$ 1,548	200,000	6,294,719	(760,523)	(2,722)	(48,335)	600,860	1,728,689
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	(1,679)				(1,505)			(174)	0
Redemption of operating partnership units to common stock, shares		765,000
Redemption of operating partnership units to common stock, value	0	$ 8		26,336				(26,344)
Allocated net income for the year	875,726				769,482			87,525	18,719
Dividends/distributions declared	(344,603)				(309,965)			(34,638)
Shares issued pursuant to stock purchase plan, shares		2,000
Shares issued pursuant to stock purchase plan, value	325			325
Net activity from stock option and incentive plan, shares		65,000
Net activity from stock option and incentive plan, value	33,285	$ 0		8,256				25,029
Contributions from noncontrolling interests in property partnerships	5,957								5,957
Distributions to noncontrolling interests in property partnerships	(29,065)								(29,065)
Effective portion of interest rate contracts	(10,379)						(9,333)	(1,046)	0
Amortization of interest rate contracts	3,343						2,747	308	288
Reallocation of noncontrolling interest	$ 0			11,029				(11,029)
Equity, shares at Jun. 30, 2020	155,622,286	155,622,000
Equity, value at Jun. 30, 2020	$ 8,547,146	$ 1,556	200,000	6,340,665	(302,511)	(2,722)	(54,921)	640,491	1,724,588
Equity, shares at Mar. 31, 2020		155,315,000
Equity, value at Mar. 31, 2020	8,420,883	$ 1,553	200,000	6,321,475	(416,740)	(2,722)	(55,700)	636,572	1,736,445
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of operating partnership units to common stock, shares		303,000
Redemption of operating partnership units to common stock, value	0	$ 3		10,846				(10,849)
Allocated net income for the year	298,580				269,361			29,986	(767)
Dividends/distributions declared	(172,326)				(155,132)			(17,194)
Net activity from stock option and incentive plan, shares		4,000
Net activity from stock option and incentive plan, value	10,225			873				9,352
Contributions from noncontrolling interests in property partnerships	2,081								2,081
Distributions to noncontrolling interests in property partnerships	(13,315)								(13,315)
Effective portion of interest rate contracts	(659)						(601)	(58)
Amortization of interest rate contracts	1,677						1,380	153	144
Reallocation of noncontrolling interest	$ 0			7,471				(7,471)
Equity, shares at Jun. 30, 2020	155,622,286	155,622,000
Equity, value at Jun. 30, 2020	$ 8,547,146	$ 1,556	$ 200,000	$ 6,340,665	$ (302,511)	$ (2,722)	$ (54,921)	$ 640,491	$ 1,724,588

Consolidated Statement of Capit

Consolidated Statement of Capital and Noncontrolling Interests Statement - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Common Stock, Shares, Outstanding	155,622,286		155,622,286			154,790,298
Cumulative effect of a change in accounting principle			$ (1,679)	$ (4,379)
Effective portion of interest rate contracts	$ (659)	$ (4,426)	(10,379)	(7,054)
Amortization of interest rate contracts	1,677	1,666	3,343	3,332
Acquisition of noncontrolling interest in property partnership		(187,006)		(187,006)
Contributions from noncontrolling interests in property partnerships	2,081	7,761	5,957	12,148
Distributions to noncontrolling interests in property partnerships	$ (13,315)	$ (15,273)	$ (29,065)	$ (39,401)
General Partner [Member]
Common Stock, Shares, Outstanding	1,731,000	1,726,000	1,731,000	1,726,000	1,731,000	1,727,000	1,725,000	1,722,000
Contributions, units	0	1,000	1,000	3,000
Conversion of redeemable partnership units	0		3,000	1,000
Limited Partner [Member]
Common Stock, Shares, Outstanding	153,891,000	152,837,000	153,891,000	152,837,000	153,584,000	153,063,000	152,790,000	152,736,000
Contributions, units	5,000	26,000	68,000	67,000
Conversion of redeemable partnership units	302,000	21,000	760,000	34,000
Preferred Units [Member]
Beginning Balance	$ 193,623	$ 193,623	$ 193,623	$ 193,623	$ 193,623	$ 193,623	$ 193,623	$ 193,623
Allocated net income for the period	2,625	2,625	5,250	5,250
Distributions	(2,625)	(2,625)	(5,250)	(5,250)
Accumulated Other Comprehensive Loss [Member]
Beginning Balance	(54,921)	(51,340)	(54,921)	(51,340)	(55,700)	(48,335)	(48,734)	(47,741)
Effective portion of interest rate contracts	(601)	(3,973)	(9,333)	(6,332)
Amortization of interest rate contracts	1,380	1,367	2,747	2,733
Noncontrolling interest - property partnerships [Member]
Beginning Balance	1,724,588	1,696,221	1,724,588	1,696,221	1,736,445	1,728,689	1,710,608	1,711,445
Cumulative effect of a change in accounting principle			0	(70)
Allocated net income for the period	(767)	17,482	18,719	36,312
Effective portion of interest rate contracts			0	0
Amortization of interest rate contracts	144	144	288	288
Acquisition of noncontrolling interest in property partnership		(24,501)		(24,501)
Contributions from noncontrolling interests in property partnerships	2,081	7,761	5,957	12,148
Distributions to noncontrolling interests in property partnerships	(13,315)	(15,273)	(29,065)	(39,401)
Total Capital [Member]
Beginning Balance	6,691,356	5,401,414	6,691,356	5,401,414	6,500,995	5,254,152	5,458,671	5,912,323
Cumulative effect of a change in accounting principle			(1,505)	(3,934)
Contributions, value	450	882	7,162	5,702
Allocated net income for the period	273,847	186,794	804,752	310,032
Distributions	(155,132)	(149,460)	(309,965)	(298,875)
Unearned compensation	423	613	1,419	(775)
Conversion of redeemable partnership units, value	10,849	720	26,344	1,212
Adjustment to reflect redeemable partnership units at redemption value	70,235	100,174	938,403	(306,701)
Effective portion of interest rate contracts	(601)	(3,973)	(9,333)	(6,332)
Amortization of interest rate contracts	1,524	1,511	3,035	3,021
Acquisition of noncontrolling interest in property partnership		(187,006)		(187,006)
Contributions from noncontrolling interests in property partnerships	2,081	7,761	5,957	12,148
Distributions to noncontrolling interests in property partnerships	(13,315)	(15,273)	(29,065)	(39,401)
Noncontrolling interest - Redeemable partnership units [Member]
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	1,581,010	2,324,238	1,581,010	2,324,238	1,639,855	2,468,753	2,414,240	2,000,591
Cumulative effect of a change in accounting principle			(174)	(445)
Contributions, value	(98)	1,082	39,643	35,482
Allocated net income for the period	29,986	19,028	87,525	30,627
Distributions	(17,194)	(17,206)	(34,638)	(34,391)
Unearned compensation	9,450	8,286	(14,614)	(12,704)
Conversion of redeemable partnership units, value	(10,849)	(720)	(26,344)	(1,212)
Adjustment to reflect redeemable partnership units at redemption value	(70,235)	(100,174)	(938,403)	306,701
Effective portion of interest rate contracts	(58)	(453)	(1,046)	(722)
Amortization of interest rate contracts	153	155	308	311
Partners' Capital (General and Limited Partners)[Member]
Beginning Balance	4,828,066	3,562,910	4,828,066	3,562,910	$ 4,626,627	$ 3,380,175	$ 3,603,174	$ 4,054,996
Cumulative effect of a change in accounting principle			(1,505)	(3,864)
Contributions, value	450	882	7,162	5,702
Allocated net income for the period	271,989	166,687	780,783	268,470
Distributions	(152,507)	(146,835)	(304,715)	(293,625)
Unearned compensation	423	613	1,419	(775)
Conversion of redeemable partnership units, value	10,849	720	26,344	1,212
Adjustment to reflect redeemable partnership units at redemption value	$ 70,235	100,174	$ 938,403	(306,701)
Acquisition of noncontrolling interest in property partnership		$ (162,505)		$ (162,505)

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Net income	$ 875,726	$ 334,620
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	349,282	342,005
Amortization of right of use assets - operating leases	1,128	1,213
Impairment loss	0	24,038
Non-cash compensation expense	27,899	25,444
Income from unconsolidated joint ventures	(1,463)	(48,177)
Distributions of net cash flow from operations of unconsolidated joint ventures	13,382	3,890
Losses (gains) from investments in securities	893	(4,134)
Allowance for current expected credit losses	484	0
Non-cash portion of interest expense	11,483	10,900
Gains on sales of real estate	(613,932)	(781)
Change in assets and liabilities:
Tenant and other receivables, net	18,516	(11,514)
Notes receivable, net	(258)	(250)
Accrued rental income, net	(43,399)	(37,473)
Prepaid expenses and other assets	(12,057)	(9,319)
Lease liabilities - operating leases	799	780
Accounts payable and accrued expenses	(20,493)	17,458
Accrued interest payable	5,262	(78)
Other liabilities	(21,912)	(30,503)
Tenant leasing costs	(37,068)	(52,515)
Total adjustments	(321,454)	230,984
Net cash provided by operating activities	554,272	565,604
Cash flows from investing activities:
Acquisitions of real estate	(133,406)	(43,061)
Construction in progress	(247,615)	(203,259)
Building and other capital improvements	(68,386)	(79,943)
Tenant improvements	(118,903)	(115,940)
Proceeds from sales of real estate	506,337	60,398
Capital contributions to unconsolidated joint ventures	(106,168)	(50,068)
Capital distributions from unconsolidated joint ventures	54,413	105,000
Issuance of notes receivable, net	(9,800)	0
Investments in securities, net	3,006	(1,079)
Net cash used in investing activities	(120,522)	(327,952)
Cash flows from financing activities:
Repayments of mortgage notes payable	(8,477)	(9,702)
Proceeds from unsecured senior notes	1,248,125	848,428
Borrowings on unsecured line of credit	265,000	380,000
Repayments of unsecured line of credit	(265,000)	(380,000)
Payments on finance lease obligations	0	(628)
Deferred financing costs	(9,465)	(7,112)
Net proceeds from equity transactions	3,183	2,261
Dividends and distributions	(344,239)	(332,961)
Contributions from noncontrolling interests in property partnerships	5,957	12,148
Distributions to noncontrolling interests in property partnerships	(29,065)	(39,401)
Acquisition of noncontrolling interest in property partnership	0	(186,952)
Net cash provided by financing activities	866,019	286,081
Net increase (decrease) in cash and cash equivalents and cash held in escrows	1,299,769	523,733
Cash and cash equivalents and cash held in escrows, beginning of period	691,886	639,191
Cash and cash equivalents and cash held in escrows, end of period	1,991,655	1,162,924
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of period	644,950	543,359
Cash held in escrows, beginning of period	46,936	95,832
Cash and cash equivalents, end of period	1,691,047	1,087,001
Cash held in escrows,end of period	300,608	75,923
Supplemental disclosures:
Cash paid for interest	213,754	216,754
Interest capitalized	27,866	25,069
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(50,141)	(61,283)
Change in real estate included in accounts payable and accrued expenses	(25,461)	115,150
Real estate acquired through finance lease	0	122,563
Accrued rental income, net deconsolidated	(4,558)	0
Tenant leasing costs, net deconsolidated	(3,462)	0
Building and other capital improvements, net deconsolidated	(111,889)	0
Tenant improvements, net deconsolidated	(12,331)	0
Investment in unconsolidated joint venture recorded upon deconsolidation	347,898	0
Dividends and distributions declared but not paid	171,077	165,419
Conversions of noncontrolling interests to stockholders’ equity	26,344	1,212
Issuance of restricted securities to employees and non-employee directors	43,462	38,923
Boston Properties Limited Partnership
Net income	892,277	340,659
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	345,694	337,881
Amortization of right of use assets - operating leases	1,128	1,213
Impairment loss	0	22,272
Non-cash compensation expense	27,899	25,444
Income from unconsolidated joint ventures	(1,463)	(48,177)
Distributions of net cash flow from operations of unconsolidated joint ventures	13,382	3,890
Losses (gains) from investments in securities	893	(4,134)
Allowance for current expected credit losses	484	0
Non-cash portion of interest expense	11,483	10,900
Gains on sales of real estate	(626,895)	(930)
Change in assets and liabilities:
Tenant and other receivables, net	18,516	(11,514)
Notes receivable, net	(258)	(250)
Accrued rental income, net	(43,399)	(37,473)
Prepaid expenses and other assets	(12,057)	(9,319)
Lease liabilities - operating leases	799	780
Accounts payable and accrued expenses	(20,493)	17,458
Accrued interest payable	5,262	(78)
Other liabilities	(21,912)	(30,503)
Tenant leasing costs	(37,068)	(52,515)
Total adjustments	(338,005)	224,945
Net cash provided by operating activities	554,272	565,604
Cash flows from investing activities:
Acquisitions of real estate	(133,406)	(43,061)
Construction in progress	(247,615)	(203,259)
Building and other capital improvements	(68,386)	(79,943)
Tenant improvements	(118,903)	(115,940)
Proceeds from sales of real estate	506,337	60,398
Capital contributions to unconsolidated joint ventures	(106,168)	(50,068)
Capital distributions from unconsolidated joint ventures	54,413	105,000
Issuance of notes receivable, net	(9,800)	0
Investments in securities, net	3,006	(1,079)
Net cash used in investing activities	(120,522)	(327,952)
Cash flows from financing activities:
Repayments of mortgage notes payable	(8,477)	(9,702)
Proceeds from unsecured senior notes	1,248,125	848,428
Borrowings on unsecured line of credit	265,000	380,000
Repayments of unsecured line of credit	(265,000)	(380,000)
Payments on finance lease obligations	0	(628)
Deferred financing costs	(9,465)	(7,112)
Net proceeds from equity transactions	3,183	2,261
Dividends and distributions	(344,239)	(332,961)
Contributions from noncontrolling interests in property partnerships	5,957	12,148
Distributions to noncontrolling interests in property partnerships	(29,065)	(39,401)
Acquisition of noncontrolling interest in property partnership	0	(186,952)
Net cash provided by financing activities	866,019	286,081
Net increase (decrease) in cash and cash equivalents and cash held in escrows	1,299,769	523,733
Cash and cash equivalents and cash held in escrows, beginning of period	691,886	639,191
Cash and cash equivalents and cash held in escrows, end of period	1,991,655	1,162,924
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of period	644,950	543,359
Cash held in escrows, beginning of period	46,936	95,832
Cash and cash equivalents, end of period	1,691,047	1,087,001
Cash held in escrows,end of period	300,608	75,923
Supplemental disclosures:
Cash paid for interest	213,754	216,754
Interest capitalized	27,866	25,069
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(50,141)	(61,283)
Change in real estate included in accounts payable and accrued expenses	(25,461)	115,150
Real estate acquired through finance lease	0	122,563
Accrued rental income, net deconsolidated	(4,558)	0
Tenant leasing costs, net deconsolidated	(3,462)	0
Building and other capital improvements, net deconsolidated	(111,889)	0
Tenant improvements, net deconsolidated	(12,331)	0
Investment in unconsolidated joint venture recorded upon deconsolidation	347,898	0
Dividends and distributions declared but not paid	171,077	165,419
Conversions of noncontrolling interests to stockholders’ equity	26,344	1,212
Issuance Of Restricted Units To Employees And Directors	$ 43,462	$ 38,923

Organization

Organization	6 Months Ended
	Jun. 30, 2020
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 June 30, 2020 owned an approximate 89.9% (89.6% at December 31, 2019) 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 the OP Unit for cash equal to the value of a share of common stock of Boston Properties, Inc. (“Common Stock”). In lieu of a cash redemption, Boston Properties, Inc. may elect to acquire the OP Unit for one share of Common Stock. Because the number of shares of Common Stock outstanding at all times equals the number of OP Units that Boston Properties, Inc. owns, one share of Common Stock is generally the economic equivalent of one OP Unit, and the quarterly distribution that may be paid to the holder of an OP Unit equals the quarterly dividend that may be paid to the holder of a share of Common Stock. The Company uses LTIP Units as a form of equity-based award for annual long term incentive equity compensation. The Company has also issued LTIP Units to employees in the form of (1) 2012 outperformance plan awards (“2012 OPP Units”) and (2) 2013 - 2020 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 and the 2013 - 2017 MYLTIP Units have ended 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 2018 - 2020 MYLTIP Units differ from other LTIP Units granted to employees (including the 2012 OPP Units and the 2013 - 2017 MYLTIP Units, which have been earned). Therefore, unless specifically noted otherwise, all references to LTIP Units exclude the 2018 - 2020 MYLTIP Units. LTIP Units (including the earned 2012 OPP Units and the earned 2013 - 2017 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 and 11). At June 30, 2020, 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 June 30, 2020, the Company owned or had interests in a portfolio of 195 commercial real estate properties (the “Properties”) aggregating approximately 51.2 million net rentable square feet of primarily Class A office properties, including nine properties under construction/redevelopment totaling approximately 5.0 million net rentable square feet. At June 30, 2020, the Properties consisted of: • 176 office properties (including seven properties under construction/redevelopment); • 12 retail properties; • six residential properties (including two properties under construction); and • one hotel.

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
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, 2019. The Company bases its estimates on historical experience and on various other assumptions that it considers to be reasonable under the circumstances, including the impact of extraordinary events such as the novel coronavirus (“COVID-19”) pandemic, the results of which form the basis for making significant judgments about the carrying values of assets and liabilities, assessments of future collectability, and other areas of the financial statements that are impacted by the use of estimates. Actual results may differ from these estimates under different assumptions or conditions. Variable Interest Entities (VIEs) Consolidated VIEs are those for which 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 six of the seven entities that are VIEs. Consolidated Variable Interest Entities As of June 30, 2020, Boston Properties, Inc. has identified six consolidated VIEs, including Boston Properties Limited Partnership. Excluding Boston Properties Limited Partnership, the VIEs consisted of 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. The Company consolidates these VIEs because it is the primary beneficiary. The third parties’ interests in these consolidated entities (excluding Boston Properties Limited Partnership’s interest) are reflected as noncontrolling interests in property partnerships in the accompanying consolidated financial statements (See Note 8). In addition, Boston Properties, Inc.’s only significant asset is its investment in Boston Properties Limited Partnership and, consequently, substantially all of Boston Properties, Inc.’s assets and liabilities are the assets and liabilities of Boston Properties Limited Partnership. Variable Interest Entities Not Consolidated The Company has determined that the Platform 16 Holdings LP joint venture is a VIE. The Company does not consolidate this entity as the Company does not have the power to direct the activities that, when taken together, most significantly impact the VIE’s performance and, therefore, the Company is not considered to be the primary beneficiary. Fair Value of Financial Instruments The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. The table below presents the financial instruments that are being valued for disclosure purposes as well as the Level at which they are categorized (as defined in Accounting Standards Codification (“ASC”) 820 “Fair Value Measurements and Disclosures” (“ASC 820”)). Financial Instrument Level Unsecured senior notes (1) Level 1 Related party note receivable Level 3 Notes receivable Level 3 Mortgage notes payable Level 3 Unsecured term loan / line of credit Level 3 _______________ (1) If trading value for the period is low, the valuation could be categorized as Level 2. Because the Company’s valuations of its financial instruments are based on the above Levels and involve the use of estimates, the actual fair values of its financial instruments may differ materially from those estimates. The following table identifies the range and weighted average of significant unobservable inputs for the Company’s Level 3 fair value measured instruments. Financial Instrument Level Range Weighted Average Related party note receivable Level 3 3.66% 3.66% Notes receivable Level 3 3.66% - 8.00% 5.35% Mortgage notes payable Level 3 2.09% - 3.25% 2.33% Unsecured term loan / line of credit Level 3 1.01% 1.01% In addition, the Company’s estimated fair values for these instruments as of the end of the applicable reporting period are not projections of, nor necessarily indicative of, estimated or actual fair values in future reporting periods. The following table presents the aggregate carrying value of the Company’s related party note receivable, net, notes receivable, net, mortgage notes payable, net, unsecured senior notes, net, unsecured line of credit and unsecured term loan, net and the Company’s corresponding estimate of fair value as of June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 December 31, 2019 Carrying Estimated Carrying Estimated Related party note receivable, net $ 78,520 $ 85,394 $ 80,000 $ 81,931 Notes receivable, net 25,480 25,648 15,920 14,978 Total $ 104,000 $ 111,042 $ 95,920 $ 96,909 Mortgage notes payable, net $ 2,915,852 $ 3,155,771 $ 2,922,408 $ 2,984,956 Unsecured senior notes, net 9,633,577 10,517,869 8,390,459 8,826,375 Unsecured line of credit — — — — Unsecured term loan, net 499,150 500,450 498,939 500,561 Total $ 13,048,579 $ 14,174,090 $ 11,811,806 $ 12,311,892 New Accounting Pronouncements Adopted Financial Instruments - Credit Losses In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). ASU 2016-13 is intended to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date by replacing the current incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. In November 2018, the FASB issued ASU 2018-19, “Codification Improvements to Topic 326, Financial Instruments - Credit Losses” (“ASU 2018-19”). ASU 2018-19 clarifies that receivables arising from operating leases are not within the scope of ASC 326-20, “Financial Instruments - Credit Losses - Measured at Amortized Cost,” which addresses financial assets measured at amortized cost basis, including net investments in leases arising from sales-type and direct financing leases. Instead, impairment of receivables arising from operating leases should be accounted for in accordance with ASC 842 - “Leases” (“ASC 842”). ASU 2016-13 and ASU 2018-19 were effective for the Company for reporting periods beginning after December 15, 2019, with early adoption permitted. ASU 2016-13 and ASU 2018-19 are applicable to the Company with respect to (1) certain of its accounts receivable, except for amounts arising from operating leases accounted for under ASC 842, (2) its related party note receivable, (3) its notes receivable and (4) certain of its off-balance sheet credit exposures. The Company adopted ASU 2016-13 and ASU 2018-19 effective January 1, 2020 using the modified retrospective approach. The adoption of ASU 2016-13 and ASU 2018-19 resulted in the Company recognizing an allowance for current expected credit losses associated with (1) its related party note receivable, (2) its notes receivable and (3) an off-balance sheet loan commitment arrangement. As a result, the modified retrospective approach resulted in the Company recognizing on January 1, 2020, the cumulative effect of adopting ASU 2016-13 and ASU 2018-19 aggregating approximately $1.5 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners’ Capital of Boston Properties Limited Partnership and approximately $0.2 million to Noncontrolling Interests - Common Units of Boston Properties, Inc. and Noncontrolling Interests - Redeemable Partnership Units of Boston Properties Limited Partnership on the corresponding Consolidated Balance Sheets. Fair Value Measurement In August 2018, the FASB issued ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement” (“ASU 2018-13”). ASU 2018-13 is intended to improve the effectiveness of disclosures required by entities regarding recurring and nonrecurring fair value measurements. ASU 2018-13 was effective for the Company for reporting periods beginning after December 15, 2019, with early adoption permitted. The Company adopted ASU 2018-13 on January 1, 2020 and the adoption did not have a material impact on the Company’s consolidated financial statements. Derivatives and Hedging In October 2018, the FASB issued ASU 2018-16, “Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes” (“ASU 2018-16”). ASU 2018-16 permits the use of the overnight index swap rate based on the Secured Overnight Financing Rate (“SOFR”) to be used as a U.S. benchmark interest rate for purposes of applying hedge accounting under ASC 815, “Derivatives and Hedging (Topic 815).” ASU 2018-16 was effective for the Company, which has already adopted ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities” for reporting periods beginning after December 15, 2018 and was required to be adopted on a prospective basis for qualifying new or re-designated hedging relationships entered into on or after the date of adoption. The Company adopted ASU 2018-16 on January 1, 2019 and the adoption did not have a material impact on the Company’s consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (“ASU 2020-04”). ASU 2020-04 contains practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance in ASU 2020-04 is optional and may be elected over time as reference rate reform activities occur. During the six months ended June 30, 2020, the Company elected to apply the hedge accounting expedients related to probability and the assessments of effectiveness for future LIBOR-indexed cash flows to assume that the index upon which future hedged transactions will be based matches the index on the corresponding derivatives. Application of these expedients preserves the presentation of derivatives consistent with past presentation. The Company continues to evaluate the impact of the guidance and may apply other elections as applicable as additional changes in the market occur. Consolidation

Real Estate

Real Estate	6 Months Ended
	Jun. 30, 2020
Real Estate [Abstract]
Real Estate	3. Real Estate Boston Properties, Inc. Real estate consisted of the following at June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 December 31, 2019 Land $ 5,070,126 $ 5,111,606 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 147,512 148,640 Land held for future development (1) 414,053 254,828 Buildings and improvements 13,488,860 13,646,054 Tenant improvements 2,664,294 2,656,439 Furniture, fixtures and equipment 44,635 44,313 Construction in progress 893,935 789,736 Total 22,960,809 22,889,010 Less: Accumulated depreciation (5,292,389) (5,266,798) $ 17,668,420 $ 17,622,212 _______________ (1) Includes pre-development costs. Boston Properties Limited Partnership Real estate consisted of the following at June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 December 31, 2019 Land $ 4,972,910 $ 5,011,153 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 147,512 148,640 Land held for future development (1) 414,053 254,828 Buildings and improvements 13,209,267 13,351,286 Tenant improvements 2,664,294 2,656,439 Furniture, fixtures and equipment 44,635 44,313 Construction in progress 893,935 789,736 Total 22,584,000 22,493,789 Less: Accumulated depreciation (5,190,360) (5,162,908) $ 17,393,640 $ 17,330,881 _______________ (1) Includes pre-development costs. Developments On March 26, 2020, the Company completed and fully placed in-service 17Fifty Presidents Street located in Reston, Virginia. 17Fifty Presidents Street is a build-to-suit project with approximately 276,000 net rentable square feet of Class A office space that is 100% leased. On June 1, 2020, the Company completed and fully placed in-service 20 CityPoint, a Class A office project with approximately 211,000 net rentable square feet located in Waltham, Massachusetts that is 62% leased. On June 26, 2020, the Company completed the acquisition of real property at 777 Harrison Street (known as Fourth + Harrison and formerly known as 425 Fourth Street) located in San Francisco, California for a gross purchase price, including entitlements, totaling approximately $140.1 million. Fourth + Harrison is expected to support the development of approximately 804,000 square feet of primarily commercial office space. Dispositions On January 28, 2020, the Company entered into a joint venture with a third party to own, operate and develop properties at its Gateway Commons complex located in South San Francisco, California. The Company contributed its 601, 611 and 651 Gateway properties and development rights with an agreed upon value aggregating approximately $350.0 million for its 50% interest in the joint venture. 601, 611 and 651 Gateway consist of three Class A office properties aggregating approximately 768,000 net rentable square feet. The partner contributed three properties and development rights with an agreed upon value aggregating approximately $280.8 million at closing and will contribute cash totaling approximately $69.2 million in the future for its 50% ownership interest in the joint venture. As a result of the partner’s deferred contribution, the Company has an initial approximately 55% interest in the joint venture. Future development projects will be owned 49% by the Company and 51% by its partner. Upon the partner’s contribution, the Company ceased accounting for the joint venture entity on a consolidated basis and is accounting for the joint venture entity on an unconsolidated basis using the equity method of accounting, as it has reduced its ownership interest in the joint venture entity and no longer has a controlling financial or operating interest in the joint venture entity (See Note 5). The Company recognized a gain on the retained and sold interest in the real estate contributed to the joint venture totaling approximately $217.7 million for Boston Properties, Inc. and $222.4 million for Boston Properties Limited Partnership during the six months ended June 30, 2020 within Gains on Sales of Real Estate on the respective Consolidated Statements of Operations, as the fair value of the real estate exceeded its carrying value. 601, 611 and 651 Gateway contributed approximately $0.2 million of net income to the Company for the period from January 1, 2020 through January 27, 2020 and contributed approximately $3.1 million and $6.0 million of net income to the Company for the three and six months ended June 30, 2019, respectively. On February 20, 2020, the Company completed the sale of New Dominion Technology Park located in Herndon, Virginia for a gross sale price of $256.0 million. Net cash proceeds totaled approximately $254.0 million, resulting in a gain on sale of real estate totaling approximately $192.3 million for Boston Properties, Inc. and approximately $197.1 million for Boston Properties Limited Partnership. New Dominion Technology Park is comprised of two Class A office properties aggregating approximately 493,000 net rentable square feet. New Dominion Technology Park contributed approximately $1.6 million of net income to the Company for the period from January 1, 2020 through February 19, 2020 and contributed approximately $2.1 million and $4.2 million of net income to the Company for the three and six months ended June 30, 2019, respectively. On June 25, 2020, the Company completed the sale of a portion of its Capital Gallery property located in Washington, DC for a gross sale price of approximately $253.7 million. Net cash proceeds totaled approximately $246.9 million, resulting in a gain on sale of real estate totaling approximately $203.8 million for Boston Properties, Inc. and approximately $207.2 million for Boston Properties Limited Partnership. Capital Gallery is an approximately 631,000 net rentable square foot Class A office property. The portion sold was comprised of approximately 455,000 net rentable square feet of commercial office space. The Company continues to own the land, underground parking garage and remaining commercial office and retail space containing approximately 176,000 net rentable square feet at the property. The sold portion of Capital Gallery contributed approximately $2.9 million and $6.3 million of net income to the Company for the period from April 1, 2020 through June 24, 2020 and the period from January 1, 2020 through June 24, 2020, respectively, and contributed approximately $3.5 million and $7.0 million of net income to the Company for the three and six months ended June 30, 2019, respectively.

Leases

Leases	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Leases of Lessor Disclosure [Text Block]	4. Leases The Company must make estimates as to the collectability of its accrued rent and accounts receivable related to lease revenue. Management analyzes accrued rent and accounts receivable by considering tenant creditworthiness, current economic trends, including the impact of COVID-19 on tenants’ businesses, and changes in tenants’ payment patterns when evaluating the collectability of the tenant’s receivable balance, including the accrued rent receivable, on a lease-by-lease basis. As a result of this analysis, during the three and six months ended June 30, 2020, the Company wrote off approximately $35.9 million and $37.4 million, respectively, related to accrued rent balances and approximately $18.0 million and $18.9 million, respectively, related to accounts receivable balances. The write-offs were for tenants, primarily in the retail sector, that either terminated their leases or that the Company considered their accrued rent and/or accounts receivable balances no longer probable of collection. In April 2020, the FASB staff issued a question and answer document (“Lease Modification Q & A”) related to the application of lease accounting guidance for lease concessions, in accordance with ASC 842, as a result of COVID-19. Under existing lease guidance, the Company would have to determine, on a lease-by-lease basis, if a lease concession was the result of a new arrangement reached with the tenant (treated within the lease modification accounting framework) or if a lease concession was under the enforceable rights and obligations within the existing lease agreement (precluded from applying the lease modification accounting framework). The Lease Modification Q & A allows the Company, if certain criteria have been met, to assume that a lease concession was included within the enforceable rights and obligations of the existing lease agreement and instead elect to either apply the lease modification accounting framework or not, with such election applied consistently to leases with similar characteristics and similar circumstances. The Company did not utilize the guidance provided in the Lease Modification Q & A and instead elected to continue to account for the COVID-19 lease concessions on a lease-by-lease basis in accordance with the existing lease modification accounting framework. The following table summarizes the components of lease revenue recognized during the three and six months ended June 30, 2020 and 2019 included within the Company's Consolidated Statements of Operations (in thousands): Three months ended June 30, Six months ended June 30, Lease Revenue 2020 2019 2020 2019 Fixed contractual payments $ 529,514 $ 557,820 $ 1,116,471 $ 1,111,806 Variable lease payments 100,605 122,369 223,759 247,634 $ 630,119 $ 680,189 $ 1,340,230 $ 1,359,440

Unsecured Senior Notes

Unsecured Senior Notes	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Debt Disclosure	6. Unsecured Senior Notes The following summarizes the unsecured senior notes outstanding as of June 30, 2020 (dollars in thousands): Coupon/ Effective Principal Maturity Date(2) 10 Year Unsecured Senior Notes 4.125 % 4.289 % $ 850,000 May 15, 2021 11 Year Unsecured Senior Notes 3.850 % 3.954 % 1,000,000 February 1, 2023 10.5 Year Unsecured Senior Notes 3.125 % 3.279 % 500,000 September 1, 2023 10.5 Year Unsecured Senior Notes 3.800 % 3.916 % 700,000 February 1, 2024 7 Year Unsecured Senior Notes 3.200 % 3.350 % 850,000 January 15, 2025 10 Year Unsecured Senior Notes 3.650 % 3.766 % 1,000,000 February 1, 2026 10 Year Unsecured Senior Notes 2.750 % 3.495 % 1,000,000 October 1, 2026 10 Year Unsecured Senior Notes 4.500 % 4.628 % 1,000,000 December 1, 2028 10 Year Unsecured Senior Notes 3.400 % 3.505 % 850,000 June 21, 2029 10.5 Year Unsecured Senior Notes 2.900 % 2.984 % 700,000 March 15, 2030 10.75 Year Unsecured Senior Notes 3.250 % 3.343 % 1,250,000 January 30, 2031 Total principal 9,700,000 Net unamortized discount (17,719) Deferred financing costs, net (48,704) Total $ 9,633,577 _______________ (1) Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs. (2) No principal amounts are due prior to maturity.

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 30, 2020
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 $20.4 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, either the Company or its partners may be entitled to an additional promoted interest or payments. 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, tenants 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 June 30, 2020, the maximum funding obligation under the guarantee was approximately $48.9 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 June 30, 2020, 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 provided a financing guaranty as required with respect to the third-party construction financing. The Company earns fees 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 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 (the Company’s partner in the 7750 Wisconsin Avenue joint venture) 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. An affiliate of The Bernstein Companies exercised its option to borrow $10.0 million from the Company under such agreements, which financing was provided by the Company on June 1, 2020. The financing bears interest at a fixed rate of 8.00% per annum, compounded monthly, and matures on the fifth anniversary of the date on which the base building of the affiliate of The Bernstein Companies’ hotel property is substantially completed. The financing is collateralized by a pledge of the partner’s equity interest in the joint venture that owns and is developing 7750 Wisconsin Avenue . 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 June 30, 2020, no amounts related to the contingent aspect of any of the guarantees are recorded as liabilities in the Company’s consolidated financial statements. In connection with the sale and development of the Company’s 6595 Springfield Center Drive development project, the Company has guaranteed the completion of the project and the payment of certain cost overruns in accordance with the development management agreement with the buyer. Although the project has been sold and the lease with the Federal Government tenant has been assigned to the buyer, pursuant to the terms of the Federal Government lease, the Federal Government tenant is not obligated to release the prior owner/landlord from such landlord’s obligations under the lease until completion of the construction. As a result, the entity which previously owned the land remains liable to the Federal Government tenant for the completion of the construction obligations under the lease. The buyer is obligated to fund the balance of the costs to meet such construction obligations, subject to the Company’s obligation to fund cost overruns (if any), as noted above. An affiliate of the buyer has provided a guaranty of the obligations of the buyer to fund such construction costs and the buyer has agreed to use commercially reasonable efforts to require the construction lender to provide certain remedies to the Company in the event the buyer does not fund such construction obligations. As of June 30, 2020, no amounts related to the contingent aspect of the guarantee are recorded as a liability in the Company’s consolidated financial statements. In connection with the redevelopment of the Company’s 325 Main Street property located in Cambridge, Massachusetts, the Company is required, pursuant to the local zoning ordinance, to commence construction of a residential building of at least 200,000 square feet with 25% of the project designated as income-restricted (with a minimum of 20% of the square footage devoted to home ownership units) prior to the occupancy of the 325 Main Street property, which is expected to occur during the third quarter of 2022. 325 Main Street consisted of an approximately 115,000 net rentable square foot Class A office property that was demolished and is being developed into an approximately 420,000 net rentable square foot Class A office property, including approximately 41,000 net rentable square feet of retail space. 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 the years 2014 through 2018, the Company received distributions aggregating approximately $18.0 million, leaving a remaining claim of approximately $27.2 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 June 30, 2020. Insurance 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 the Federal Terrorism Risk Insurance Act (as amended, “TRIA”) (“NBCR Coverage”), which is provided by IXP as a direct insurer, for the properties in the Company’s portfolio, including 767 Fifth Avenue, but excluding certain other properties owned in joint ventures with third parties or which the Company manages. The per occurrence limit for NBCR Coverage is $1.0 billion. Under TRIA, after the payment of the required deductible and coinsurance, the NBCR Coverage provided by IXP is backstopped by the Federal Government if the aggregate industry insured losses resulting from a certified act of terrorism exceed a “program trigger.” The program trigger is $200 million, the coinsurance is 20% and the deductible is 20% of the premiums earned by the insurer for the year prior to a claim. 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 TRIA. The Company may elect to terminate the NBCR Coverage if the Federal Government seeks recoupment for losses paid under TRIA, if TRIA is not extended after its expiration on December 31, 2027, 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. The Company also currently carries earthquake insurance on its properties located in areas known to be subject to earthquakes. 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 and Los Angeles regions with a $240 million per occurrence limit, and a $240 million annual aggregate limit, $20 million of which is provided by IXP, as a direct insurer. 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. Due to the current COVID-19 pandemic, the Company anticipates the possibility of business interruption, loss of lease revenue and/or other associated expenses related to the Company’s operations across its portfolio. Because this is an ongoing situation it is not yet possible to quantify the Company’s losses and expenses, which continue to develop. Because of the complexity of the Company’s insurance policies and limited precedent for claims being made related to pandemics, it is not yet possible to determine if such losses and expenses will be covered by the Company’s insurance policies. Therefore, at this time, the Company is providing notice to the applicable insurers of the potential for claims in order to protect the Company’s rights under its policies. The Company continues to monitor the state of the insurance market in general, and the scope and costs of coverage for acts of terrorism, California earthquake risk and pandemics, 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	6 Months Ended
	Jun. 30, 2020
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 June 30, 2020, the noncontrolling interests in Boston Properties Limited Partnership consisted of 16,123,912 OP Units, 1,345,723 LTIP Units (including 105,080 2012 OPP Units, 64,468 2013 MYLTIP Units, 23,100 2014 MYLTIP Units, 24,966 2015 MYLTIP Units, 89,791 2016 MYLTIP Units and 116,078 2017 MYLTIP Units), 336,195 2018 MYLTIP Units, 220,325 2019 MYLTIP Units and 203,278 2020 MYLTIP Units held by parties other than Boston Properties, Inc. Noncontrolling Interest—Common Units During the six months ended June 30, 2020, 764,640 OP Units were presented by the holders for redemption (including 82,551 O P Units issued upon conversion of LTIP Units, 2012 OPP Units and 2013 - 2017 MYLTIP Units) and were redeemed by Boston Properties, Inc. in exchange for an equal number of shares of Common Stock. At June 30, 2020, Boston Properties Limited Partnership had outstanding 336,195 2018 MYLTIP Units, 220,325 2019 MYLTIP Units and 203,278 2020 MYLTIP Units. Prior to the applicable measurement date (February 5, 2021 for 2018 MYLTIP Units, February 4, 2022 for 2019 MYLTIP Units and February 3, 2023 for 2020 MYLTIP Units), holders of MYLTIP Units will be entitled to receive per unit distributions equal to one-tenth (10%) of the regular quarterly distributions payable on an OP Unit, but will not be entitled to receive any special distributions. After the measurement date, the number of MYLTIP Units, both vested and unvested, that MYLTIP award recipients have earned, if any, based on the establishment of a performance pool, will be entitled to receive distributions in an amount per unit equal to distributions, both regular and special, payable on an OP Unit. On February 6, 2020, the measurement period for the Company’s 2017 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 83.8% of target or an aggregate of approximately $17.6 million (after giving effect to employee separations). As a result, an aggregate of 270,942 2017 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, 2013 - 2016 MYLTIP Units and, after the February 6, 2020 measurement date, the 2017 MYLTIP Units) and its distributions on the 2017 MYLTIP Units (prior to the February 6, 2020 measurement date), 2018 MYLTIP Units, 2019 MYLTIP Units and 2020 MYLTIP Units (after the February 4, 2020 issuance date) that occurred during the six months ended June 30, 2020: Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 30, 2020 July 31, 2020 $0.98 $0.098 March 31, 2020 April 30, 2020 $0.98 $0.098 December 31, 2019 January 30, 2020 $0.98 $0.098 The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units, 2013 - 2015 MYLTIP Units and, after the February 9, 2019 measurement date, the 2016 MYLTIP Units) and its distributions on the 2016 MYLTIP Units (prior to the February 9, 2019 measurement date), 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units (after the February 5, 2019 issuance date) that occurred during the six months ended June 30, 2019: Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 28, 2019 July 31, 2019 $0.95 $0.095 March 29, 2019 April 30, 2019 $0.95 $0.095 December 31, 2018 January 30, 2019 $0.95 $0.095 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 - 2017 MYLTIP Units) assuming that all conditions had been met for the conversion thereof) had all of such units been redeemed at June 30, 2020 was approximately $1.6 billion based on the last reported price of a share of Common Stock on the New York Stock Exchange of $90.38 per share on June 30, 2020. 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 June 30, 2020 and December 31, 2019, are included in Noncontrolling Interests—Property Partnerships on the accompanying Consolidated Balance Sheets.

Stockholders' Equity _ Partners

Stockholders' Equity / Partners' Capital	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Stockholders' Equity / Partners' Capital	9. Stockholders’ Equity / Partners’ Capital Boston Properties, Inc. As of June 30, 2020, Boston Properties, Inc. had 155,622,286 shares of Common Stock outstanding. As of June 30, 2020, Boston Properties, Inc. owned 1,730,919 general partnership units and 153,891,367 limited partnership units in Boston Properties Limited Partnership. On May 22, 2020, 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. Under the ATM stock offering program, Boston Properties, Inc. may also engage in forward sale transactions with affiliates of certain sales agents for the sale of its Common Stock on a forward basis. This program replaced Boston Properties, Inc.’s prior $600.0 million ATM stock offering program that was scheduled to expire on June 2, 2020. Boston Properties, Inc. 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 six months ended June 30, 2020, Boston Properties, Inc. issued 43,792 shares of Common Stock upon the exercise of options to purchase Common Stock. During the six months ended June 30, 2020, Boston Properties, Inc. issued 764,640 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 or declared in 2020 and during the six months ended June 30, 2019: Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) June 30, 2020 July 31, 2020 $0.98 $0.98 March 31, 2020 April 30, 2020 $0.98 $0.98 December 31, 2019 January 30, 2020 $0.98 $0.98 June 28, 2019 July 31, 2019 $0.95 $0.95 March 29, 2019 April 30, 2019 $0.95 $0.95 December 31, 2018 January 30, 2019 $0.95 $0.95 Preferred Stock As of June 30, 2020, 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. did not have the right to 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 and after March 27, 2018, Boston Properties, Inc., at its option, may redeem the Series B Preferred Stock for a cash redemption price of $2,500.00 per share ($25.00 per depositary share), plus all accrued and unpaid dividends. The Series B Preferred Stock is not redeemable by the holders, has no maturity date and is not convertible into any other security of Boston Properties, Inc. or its affiliates. The following table presents Boston Properties Inc.’s dividends per share on its outstanding Series B Preferred Stock paid or declared during 2020 and during the six months ended June 30, 2019: Record Date Payment Date Dividend (Per Share) August 3, 2020 August 17, 2020 $32.8125 May 1, 2020 May 15, 2020 $32.8125 February 4, 2020 February 18, 2020 $32.8125 August 2, 2019 August 15, 2019 $32.8125 May 3, 2019 May 15, 2019 $32.8125 February 4, 2019 February 15, 2019 $32.8125

Earnings Per Share _ Common Uni

Earnings Per Share / Common Unit	6 Months Ended
	Jun. 30, 2020
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 Boston Properties, Inc. and Boston Properties Limited Partnership’s LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic EPS of Boston Properties, Inc. using the two-class method. Participating securities are included in the computation of diluted EPS of Boston Properties, Inc. using the if-converted method if the impact is dilutive. Because the 2012 OPP Units and 2013 - 2017 MYLTIP Units required, and the 2018 - 2020 MYLTIP Units require, Boston Properties, Inc. to outperform absolute and relative return thresholds, unless such thresholds have been met by the end of the applicable reporting period, Boston Properties, Inc. excludes such units from the diluted EPS calculation. Other potentially dilutive common shares, including stock options, restricted stock and other securities of Boston Properties Limited Partnership that are exchangeable for Boston Properties, Inc.’s Common Stock, and the related impact on earnings, are considered when calculating diluted EPS. Three months ended June 30, 2020 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 266,525 155,386 $ 1.72 Allocation of undistributed earnings to participating securities (336) — (0.01) Net income attributable to Boston Properties, Inc. common shareholders $ 266,189 155,386 $ 1.71 Effect of Dilutive Securities: Stock Based Compensation — 21 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 266,189 155,407 $ 1.71 Three months ended June 30, 2019 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 164,318 154,555 $ 1.06 Allocation of undistributed earnings to participating securities (48) — — Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,555 $ 1.06 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,874 $ 1.06 Six months ended June 30, 2020 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 764,232 155,199 $ 4.92 Allocation of undistributed earnings to participating securities (1,344) — — Net income attributable to Boston Properties, Inc. common shareholders $ 762,888 155,199 $ 4.92 Effect of Dilutive Securities: Stock Based Compensation — 134 (0.01) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 762,888 155,333 $ 4.91 Six months ended June 30, 2019 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 262,431 154,540 $ 1.70 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 262,431 154,859 $ 1.69 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 and 2013 - 2017 MYLTIP Units required, and the 2018 - 2020 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 17,273,000 and 17,647,000 redeemable common units for the three months ended June 30, 2020 and 2019, respectively, and 17,405,000 and 17,627,000 redeemable common units for the six months ended June 30, 2020 and 2019, respectively. Three months ended June 30, 2020 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,975 172,659 $ 1.75 Allocation of undistributed earnings to participating securities (374) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,601 172,659 $ 1.75 Effect of Dilutive Securities: Stock Based Compensation — 21 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,601 172,680 $ 1.75 Three months ended June 30, 2019 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,715 172,202 $ 1.08 Allocation of undistributed earnings to participating securities (54) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,202 $ 1.08 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,521 $ 1.08 Six months ended June 30, 2020 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 868,308 172,604 $ 5.03 Allocation of undistributed earnings to participating securities (1,495) — (0.01) Net income attributable to Boston Properties Limited Partnership common unitholders $ 866,813 172,604 $ 5.02 Effect of Dilutive Securities: Stock Based Compensation — 134 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 866,813 172,738 $ 5.02 Six months ended June 30, 2019 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 299,097 172,167 $ 1.74 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 299,097 172,486 $ 1.73

Stock Option and Incentive Plan

Stock Option and Incentive Plan	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock Option and Incentive Plan	11. Stock Option and Incentive Plan On February 4, 2020, Boston Properties, Inc.’s Compensation Committee granted the 2020 MYLTIP awards under the Boston Properties, Inc.’s 2012 Stock Option and Incentive Plan (the “2012 Plan”) to certain officers and employees of Boston Properties, Inc. The 2020 MYLTIP awards utilize Boston Properties, Inc.’s TSR over a three-year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will range from zero to a maximum of 203,278 LTIP Units depending on Boston Properties, Inc.’s TSR relative to the FTSE Russell Nareit Office Index, adjusted to include Vornado Realty Trust, with a target of approximately 101,638 LTIP Units and linear interpolation between zero and maximum. Earned awards (if any) will vest 50% on February 3, 2023 and 50% on February 3, 2024, 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 3, 2023, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2020 MYLTIP awards are in the form of LTIP Units issued on the grant date which (i) are subject to forfeiture to the extent awards are not earned and (ii) prior to the performance measurement date are only entitled to one-tenth (10%) of the regular quarterly distributions payable on common partnership units. Under ASC 718 “Compensation - Stock Compensation,” the 2020 MYLTIP awards have an aggregate value of approximately $13.7 million, which amount will generally be amortized into earnings under the graded vesting method. On February 6, 2020, the measurement period for the Company’s 2017 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 83.8% of target or an aggregate of approximately $17.6 million (after giving effect to employee separations). As a result, an aggregate of 270,942 2017 MYLTIP Units that had been previously granted were automatically forfeited.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Segment Reporting Disclosure [Text Block]	12. Segment Information The following tables present reconciliations of Net Income Attributable to Boston Properties, Inc. Common Shareholders to the Company’s share of Net Operating Income and Net Income Attributable to Boston Properties Limited Partnership Common Unitholders to the Company’s share of Net Operating Income for the three and six months ended June 30, 2020 and 2019. Boston Properties, Inc. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 266,525 $ 164,318 $ 764,232 $ 262,431 Add: Preferred dividends 2,625 2,625 5,250 5,250 Noncontrolling interest—common units of the Operating Partnership 30,197 19,036 87,525 30,627 Noncontrolling interests in property partnerships (767) 17,482 18,719 36,312 Interest expense 107,142 102,357 208,733 203,366 Impairment loss — — — 24,038 Net operating income from unconsolidated joint ventures 27,911 24,715 56,669 50,064 Depreciation and amortization expense 178,188 177,411 349,282 342,005 Transaction costs 332 417 947 877 Payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 General and administrative expense 37,743 35,071 74,197 76,833 Less: Net operating income attributable to noncontrolling interests in property partnerships 32,427 45,562 80,088 92,647 Gains (losses) from investments in securities 4,552 1,165 (893) 4,134 Interest and other income (loss) 1,305 3,615 4,322 7,368 Gains on sales of real estate 203,767 1,686 613,932 781 Income from unconsolidated joint ventures 1,832 47,964 1,463 48,177 Direct reimbursements of payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 Development and management services revenue 8,125 9,986 16,004 19,263 Company’s share of Net Operating Income $ 397,888 $ 433,454 $ 850,638 $ 859,433 Boston Properties Limited Partnership Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,975 $ 185,715 $ 868,308 $ 299,097 Add: Preferred distributions 2,625 2,625 5,250 5,250 Noncontrolling interests in property partnerships (767) 17,482 18,719 36,312 Interest expense 107,142 102,357 208,733 203,366 Impairment loss — — — 22,272 Net operating income from unconsolidated joint ventures 27,911 24,715 56,669 50,064 Depreciation and amortization expense 176,409 175,199 345,694 337,881 Transaction costs 332 417 947 877 Payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 General and administrative expense 37,743 35,071 74,197 76,833 Less: Net operating income attributable to noncontrolling interests in property partnerships 32,427 45,562 80,088 92,647 Gains (losses) from investments in securities 4,552 1,165 (893) 4,134 Interest and other income (loss) 1,305 3,615 4,322 7,368 Gains on sales of real estate 207,241 1,835 626,895 930 Income from unconsolidated joint ventures 1,832 47,964 1,463 48,177 Direct reimbursements of payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 Development and management services revenue 8,125 9,986 16,004 19,263 Company’s share of Net Operating Income $ 397,888 $ 433,454 $ 850,638 $ 859,433 Net operating income (“NOI”) is a non-GAAP financial measure equal to net income attributable to Boston Properties, Inc. common shareholders and net income attributable to Boston Properties Limited Partnership common unitholders, as applicable, the most directly comparable GAAP financial measures, plus (1) preferred dividends/distributions, net income attributable to noncontrolling interests, interest expense, impairment loss, depreciation and amortization expense, transaction costs, payroll and related costs from management services contracts and corporate general and administrative expense less (2) gains (losses) from investments in securities, interest and other income (loss), gains on sales of real estate, income from unconsolidated joint ventures, direct reimbursements of payroll and related costs from management services contracts and development and management services revenue. The Company believes NOI is useful to investors as a performance measure and believes it provides useful information to investors regarding its results of operations and financial condition because, when compared across periods, it reflects the impact on operations from trends in occupancy rates, rental rates, operating costs and acquisition and development activity on an unleveraged basis, providing perspective not immediately apparent from net income attributable to Boston Properties, Inc. common shareholders and net income attributable to Boston Properties Limited Partnership common unitholders. For example, interest expense is not necessarily linked to the operating performance of a real estate asset and is often incurred at the corporate level as opposed to the property level. Similarly, interest expense may be incurred at the property level even though the financing proceeds may be used at the corporate level (e.g., used for other investment activity). In addition, depreciation and amortization expense, because of historical cost accounting and useful life estimates, may distort operating performance measures at the property level. NOI presented by the Company may not be comparable to NOI reported by other REITs or real estate companies that define NOI differently. The Company’s internal reporting utilizes its share of NOI, which includes its share of NOI from consolidated and unconsolidated joint ventures, which is a non-GAAP financial measure that is calculated as the consolidated amount, plus the Company’s share of the amount from the Company’s unconsolidated joint ventures (calculated based upon the Company’s economic percentage ownership interest and, in some cases, after priority allocations), minus the Company’s partners’ share of the amount from the Company’s consolidated joint ventures (calculated based upon the partners’ economic percentage ownership interests and, in some cases, after priority allocations, income allocation to private REIT shareholders and their share of fees due to the Company). The Company’s share of NOI from unconsolidated joint ventures does not include its share of gains on sale of real estate from unconsolidated joint ventures, which is included within Income From Unconsolidated Joint Ventures in the Company’s Consolidated Statements of Operations. Management utilizes its share of NOI in assessing its performance as the Company has several significant joint ventures and, in some cases, the Company exercises significant influence over, but does not control, the joint venture, in which case GAAP requires that the Company account for the joint venture entity using the equity method of accounting and the Company does not consolidate it for financial reporting purposes. In other cases, GAAP requires that the Company consolidate the venture even though the Company’s partner(s) owns a significant percentage interest. As a result, the presentations of the Company’s share of NOI should not be considered a substitute for, and should only be considered together with and as a supplement to, the Company’s financial information presented in accordance with GAAP. 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, interest expense, impairment loss, depreciation and amortization expense, transaction costs, payroll and related costs from management services contracts, corporate general and administrative expense, gains (losses) from investments in securities, interest and other income (loss), gains on sales of real estate, direct reimbursements of payroll and related costs from management services contracts and development and management services revenue are not included in NOI and are provided as reconciling items to the Company’s reconciliations of its share of NOI to net income attributable to common shareholders/unitholders. The Company’s segments are based on the Company’s method of internal reporting which classifies its operations by geographic area. The Company’s segments by geographic area are Boston, Los Angeles, New York, San Francisco and Washington, DC. The Company also presents information for each segment by property type, including Office, Residential and Hotel. Included within the Office property type are commercial office and retail leases, as well as parking revenue. Upon the adoption of ASC 842, any write-off for bad debt, including accrued rent, will be recorded as a reduction to lease revenue. As a result of COVID-19, during the three and six months ended June 30, 2020, the Company wrote off approximately $35.9 million and $37.4 million, respectively, related to accrued rent balances and approximately $18.0 million and $18.9 million, respectively, related to accounts receivable balances. The write-offs were for tenants, primarily in the retail sector, that either terminated their leases or that the Company considered their accrued rent and/or accounts receivable balances no longer probable of collection. In addition, parking and other revenue for the three and six months ended June 30, 2020 decreased by approximately $12.4 million and $12.8 million, respectively, compared to 2019. These decreases were primarily in transient and monthly parking revenue. The degree to which the Company’s commercial and retail tenants’ and parking operators’ businesses are, or will continue to be, negatively impacted by COVID-19, including by measures intended to reduce its spread, such as mandatory business closures and “stay-at-home” orders, could result in a reduction in the Company’s cash flows or require that the Company write off additional accrued rent and/or accounts receivable balances, and this could have a material adverse effect on lease revenue and thus the results of the Company’s Office property type. The Boston Marriott Cambridge closed in March 2020 and did not re-open during the second quarter. The Company is uncertain as to when the hotel will re-open. The hotel is operating at a monthly deficit and its continued closure has had, and will continue to have, a material adverse impact on the hotel’s operations and thus the results of the Company’s Hotel property type. Information by geographic area and property type (dollars in thousands): For the three months ended June 30, 2020: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 218,351 $ — $ 204,242 $ 128,233 $ 83,837 $ 634,663 Residential 3,401 — — — 6,001 9,402 Hotel 99 — — — — 99 Total 221,851 — 204,242 128,233 89,838 644,164 % of Grand Totals 34.43 % — % 31.71 % 19.91 % 13.95 % 100.00 % Rental Expenses: Office 75,694 — 88,367 39,081 32,680 235,822 Residential 1,235 — — — 2,730 3,965 Hotel 1,973 — — — — 1,973 Total 78,902 — 88,367 39,081 35,410 241,760 % of Grand Totals 32.64 % — % 36.54 % 16.17 % 14.65 % 100.00 % Net operating income $ 142,949 $ — $ 115,875 $ 89,152 $ 54,428 $ 402,404 % of Grand Totals 35.52 % — % 28.80 % 22.15 % 13.53 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,576) — (21,851) — — (32,427) Add: Company’s share of net operating income from unconsolidated joint ventures 2,627 15,026 815 4,127 5,316 27,911 Company’s share of net operating income $ 135,000 $ 15,026 $ 94,839 $ 93,279 $ 59,744 $ 397,888 % of Grand Totals 33.92 % 3.78 % 23.84 % 23.44 % 15.02 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the three months ended June 30, 2019: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 217,961 $ — $ 251,556 $ 131,506 $ 96,486 $ 697,509 Residential 3,222 — — — 5,777 8,999 Hotel 14,844 — — — — 14,844 Total 236,027 — 251,556 131,506 102,263 721,352 % of Grand Totals 32.72 % — % 34.87 % 18.23 % 14.18 % 100.00 % Rental Expenses: Office 77,660 — 96,809 43,708 35,672 253,849 Residential 1,279 — — — 2,843 4,122 Hotel 9,080 — — — — 9,080 Total 88,019 — 96,809 43,708 38,515 267,051 % of Grand Totals 32.96 % — % 36.25 % 16.37 % 14.42 % 100.00 % Net operating income $ 148,008 $ — $ 154,747 $ 87,798 $ 63,748 $ 454,301 % of Grand Totals 32.58 % — % 34.06 % 19.33 % 14.03 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,031) — (35,531) — — (45,562) Add: Company’s share of net operating income from unconsolidated joint ventures 818 15,454 1,696 — 6,747 24,715 Company’s share of net operating income $ 138,795 $ 15,454 $ 120,912 $ 87,798 $ 70,495 $ 433,454 % of Grand Totals 32.01 % 3.57 % 27.90 % 20.26 % 16.26 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2020: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 457,849 $ — $ 459,528 $ 264,972 $ 176,973 $ 1,359,322 Residential 7,469 — — — 11,889 19,358 Hotel 6,924 — — — — 6,924 Total 472,242 — 459,528 264,972 188,862 1,385,604 % of Grand Totals 34.09 % — % 33.16 % 19.12 % 13.63 % 100.00 % Rental Expenses: Office 158,239 — 187,507 81,650 67,328 494,724 Residential 2,575 — — — 5,454 8,029 Hotel 8,794 — — — — 8,794 Total 169,608 — 187,507 81,650 72,782 511,547 % of Grand Totals 33.16 % — % 36.65 % 15.96 % 14.23 % 100.00 % Net operating income $ 302,634 $ — $ 272,021 $ 183,322 $ 116,080 $ 874,057 % of Grand Totals 34.63 % — % 31.12 % 20.97 % 13.28 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (21,239) — (58,849) — — (80,088) Add: Company’s share of net operating income from unconsolidated joint ventures 5,726 30,956 1,571 7,286 11,130 56,669 Company’s share of net operating income $ 287,121 $ 30,956 $ 214,743 $ 190,608 $ 127,210 $ 850,638 % of Grand Totals 33.76 % 3.64 % 25.24 % 22.41 % 14.95 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2019: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 435,372 $ — $ 510,187 $ 255,561 $ 192,831 $ 1,393,951 Residential 5,923 — — — 10,791 16,714 Hotel 23,782 — — — — 23,782 Total 465,077 — 510,187 255,561 203,622 1,434,447 % of Grand Totals 32.42 % — % 35.56 % 17.82 % 14.20 % 100.00 % Rental Expenses: Office 157,160 — 193,780 84,833 71,819 507,592 Residential 2,485 — — — 5,411 7,896 Hotel 16,943 — — — — 16,943 Total 176,588 — 193,780 84,833 77,230 532,431 % of Grand Totals 33.17 % — % 36.39 % 15.93 % 14.51 % 100.00 % Net operating income $ 288,489 $ — $ 316,407 $ 170,728 $ 126,392 $ 902,016 % of Grand Totals 31.98 % — % 35.08 % 18.93 % 14.01 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (19,404) — (72,795) (448) — (92,647) Add: Company’s share of net operating income from unconsolidated joint ventures 1,590 31,162 3,482 — 13,830 50,064 Company’s share of net operating income $ 270,675 $ 31,162 $ 247,094 $ 170,280 $ 140,222 $ 859,433 % of Grand Totals 31.49 % 3.63 % 28.75 % 19.81 % 16.32 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events On July 23, 2020, the Company acquired a 50% interest in a joint venture entity that owns Beach Cities Media Center, a 6.4-acre parcel of land located in El Segundo, California, for a purchase price of approximately $21.2 million. Beach Cities Media Center is expected to support the development of approximately 275,000 square feet of Class A office space.

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	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, 2019.

Summary Of Significant Accoun_3

Summary Of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2020
Summary Of Significant Accounting Policies [Line Items]
Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]	The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. The table below presents the financial instruments that are being valued for disclosure purposes as well as the Level at which they are categorized (as defined in Accounting Standards Codification (“ASC”) 820 “Fair Value Measurements and Disclosures” (“ASC 820”)). Financial Instrument Level Unsecured senior notes (1) Level 1 Related party note receivable Level 3 Notes receivable Level 3 Mortgage notes payable Level 3 Unsecured term loan / line of credit Level 3 _______________ (1) If trading value for the period is low, the valuation could be categorized as Level 2. Because the Company’s valuations of its financial instruments are based on the above Levels and involve the use of estimates, the actual fair values of its financial instruments may differ materially from those estimates. The following table identifies the range and weighted average of significant unobservable inputs for the Company’s Level 3 fair value measured instruments. Financial Instrument Level Range Weighted Average Related party note receivable Level 3 3.66% 3.66% Notes receivable Level 3 3.66% - 8.00% 5.35% Mortgage notes payable Level 3 2.09% - 3.25% 2.33% Unsecured term loan / line of credit Level 3 1.01% 1.01%
Fair Value, by Balance Sheet Grouping [Table Text Block]	The following table presents the aggregate carrying value of the Company’s related party note receivable, net, notes receivable, net, mortgage notes payable, net, unsecured senior notes, net, unsecured line of credit and unsecured term loan, net and the Company’s corresponding estimate of fair value as of June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 December 31, 2019 Carrying Estimated Carrying Estimated Related party note receivable, net $ 78,520 $ 85,394 $ 80,000 $ 81,931 Notes receivable, net 25,480 25,648 15,920 14,978 Total $ 104,000 $ 111,042 $ 95,920 $ 96,909 Mortgage notes payable, net $ 2,915,852 $ 3,155,771 $ 2,922,408 $ 2,984,956 Unsecured senior notes, net 9,633,577 10,517,869 8,390,459 8,826,375 Unsecured line of credit — — — — Unsecured term loan, net 499,150 500,450 498,939 500,561 Total $ 13,048,579 $ 14,174,090 $ 11,811,806 $ 12,311,892

Real Estate (Tables)

Real Estate (Tables)	6 Months Ended
	Jun. 30, 2020
Real Estate Properties [Line Items]
Schedule of Real Estate Properties	Boston Properties, Inc. Real estate consisted of the following at June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 December 31, 2019 Land $ 5,070,126 $ 5,111,606 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 147,512 148,640 Land held for future development (1) 414,053 254,828 Buildings and improvements 13,488,860 13,646,054 Tenant improvements 2,664,294 2,656,439 Furniture, fixtures and equipment 44,635 44,313 Construction in progress 893,935 789,736 Total 22,960,809 22,889,010 Less: Accumulated depreciation (5,292,389) (5,266,798) $ 17,668,420 $ 17,622,212 _______________ (1) Includes pre-development costs.
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Schedule of Real Estate Properties	Boston Properties Limited Partnership Real estate consisted of the following at June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 December 31, 2019 Land $ 4,972,910 $ 5,011,153 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 147,512 148,640 Land held for future development (1) 414,053 254,828 Buildings and improvements 13,209,267 13,351,286 Tenant improvements 2,664,294 2,656,439 Furniture, fixtures and equipment 44,635 44,313 Construction in progress 893,935 789,736 Total 22,584,000 22,493,789 Less: Accumulated depreciation (5,190,360) (5,162,908) $ 17,393,640 $ 17,330,881 _______________ (1) Includes pre-development costs.

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Operating Lease, Lease Income [Table Text Block]	The following table summarizes the components of lease revenue recognized during the three and six months ended June 30, 2020 and 2019 included within the Company's Consolidated Statements of Operations (in thousands): Three months ended June 30, Six months ended June 30, Lease Revenue 2020 2019 2020 2019 Fixed contractual payments $ 529,514 $ 557,820 $ 1,116,471 $ 1,111,806 Variable lease payments 100,605 122,369 223,759 247,634 $ 630,119 $ 680,189 $ 1,340,230 $ 1,359,440

Investments in Unconsolidated J

Investments in Unconsolidated Joint Ventures (Tables)	6 Months Ended
	Jun. 30, 2020
Schedule of Equity Method Investments [Line Items]
Investments In Unconsolidated Joint Ventures	The investments in unconsolidated joint ventures consist of the following at June 30, 2020 and December 31, 2019: Carrying Value of Investment (1) Entity Properties Nominal % June 30, December 31, (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (4,123) $ (4,872) BP/CRF Metropolitan Square, LLC Metropolitan Square 20.0 % (7,319) 9,134 901 New York, LLC 901 New York Avenue 25.0 % (2) (12,174) (12,113) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 36,102 36,789 Annapolis Junction NFM LLC Annapolis Junction 50.0 % (4) 12,967 25,391 540 Madison Venture LLC 540 Madison Avenue 60.0 % (5) 201 2,953 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (5,530) (5,439) 501 K Street LLC 1001 6th Street 50.0 % (6) 42,673 42,496 Podium Developer LLC The Hub on Causeway - Podium 50.0 % 49,160 49,466 Residential Tower Developer LLC Hub50House 50.0 % 53,340 55,092 Hotel Tower Developer LLC The Hub on Causeway - Hotel Air Rights 50.0 % 10,228 9,883 Office Tower Developer LLC 100 Causeway Street 50.0 % 56,544 56,606 1265 Main Office JV LLC 1265 Main Street 50.0 % 4,116 3,780 BNY Tower Holdings LLC Dock 72 50.0 % 96,013 94,804 BNYTA Amenity Operator LLC Dock 72 50.0 % — — CA-Colorado Center Limited Partnership Colorado Center 50.0 % 236,287 252,069 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % 57,130 56,247 BP-M 3HB Venture LLC 3 Hudson Boulevard 25.0 % 91,422 67,499 SMBP Venture LP Santa Monica Business Park 55.0 % 148,665 163,937 Platform 16 Holdings LP Platform 16 55.0 % (7) 99,734 29,501 Gateway Portfolio Holdings LLC Gateway Commons 50.0 % (8) 345,142 N/A $ 1,310,578 $ 933,223 _______________ (1) Investments with deficit balances aggregating approximately $29.1 million and $22.4 million at June 30, 2020 and December 31, 2019, respectively, are included 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. At June 30, 2020 and December 31, 2019, the Company’s economic ownership was approximately 50%. (3) The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project. (4) The joint venture owns two in-service buildings. (5) T he property was sold on June 27, 2019. As of June 30, 2020 and December 31, 2019, the investment is comprised of undistributed cash. (6) 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. (7) This entity is a VIE (See Note 2). (8) As a result of the partner’s deferred contribution, the Company owns an approximately 55% interest in the joint venture at June 30, 2020. Future development projects will be owned 49% by the Company and 51% by its partner.
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: June 30, December 31, (in thousands) ASSETS Real estate and development in process, net (1) $ 4,527,828 $ 3,904,400 Other assets 535,870 502,706 Total assets $ 5,063,698 $ 4,407,106 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 2,465,039 $ 2,218,853 Other liabilities (2) 655,709 749,675 Members’/Partners’ equity 1,942,950 1,438,578 Total liabilities and members’/partners’ equity $ 5,063,698 $ 4,407,106 Company’s share of equity $ 911,682 $ 591,905 Basis differentials (3) 398,896 341,318 Carrying value of the Company’s investments in unconsolidated joint ventures (4) $ 1,310,578 $ 933,223 _______________ (1) At June 30, 2020 and December 31, 2019, this amount includes right of use assets - finance leases totaling approximately $248.9 million and $383.9 million, respectively, and right of use assets - operating leases totaling approximately $11.7 million and $12.1 million, respectively. (2) At June 30, 2020 and December 31, 2019, this amount includes lease liabilities - finance leases totaling approximately $390.2 million and $510.8 million, respectively, and lease liabilities - operating leases totaling approximately $17.4 million and $17.3 million, respectively. (3) 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 June 30, 2020 and December 31, 2019, there was an aggregate basis differential of approximately $309.0 million and $311.3 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. At June 30, 2020, there was an aggregate basis differential of approximately $54.4 million between the carrying value of the Company’s investment in the joint venture that owns Gateway Commons and the joint venture’s basis in the assets and liabilities. These basis differentials (excluding land) will be amortized over the remaining lives of the related assets and liabilities. (4) Investments with deficit balances aggregating approximately $29.1 million and $22.4 million at June 30, 2020 and December 31, 2019, respectively, are 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 June 30, Six months ended June 30, 2020 2019 2020 2019 (in thousands) Total revenue (1) $ 89,563 $ 80,204 $ 182,766 $ 163,159 Expenses Operating 33,704 30,134 69,105 60,633 Depreciation and amortization 37,390 24,818 69,425 53,464 Total expenses 71,094 54,952 138,530 114,097 Other income (expense) Interest expense (23,306) (20,803) (45,889) (41,560) Gains on sales of real estate 11,720 34,572 11,720 34,572 Net income $ 6,883 $ 39,021 $ 10,067 $ 42,074 Company’s share of net income $ 4,024 $ 22,376 $ 5,276 $ 23,960 Basis differential (2) (2,192) 25,588 (3,813) 24,217 Income from unconsolidated joint ventures $ 1,832 $ 47,964 $ 1,463 $ 48,177 _______________ (1) Includes straight-line rent adjustments of approximately $8.5 million and $7.6 million for the three months ended June 30, 2020 and 2019, respectively, and $18.2 million and $13.4 million for the six months ended June 30, 2020 and 2019, respectively.

Unsecured Senior Notes (Tables)

Unsecured Senior Notes (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following summarizes the unsecured senior notes outstanding as of June 30, 2020 (dollars in thousands): Coupon/ Effective Principal Maturity Date(2) 10 Year Unsecured Senior Notes 4.125 % 4.289 % $ 850,000 May 15, 2021 11 Year Unsecured Senior Notes 3.850 % 3.954 % 1,000,000 February 1, 2023 10.5 Year Unsecured Senior Notes 3.125 % 3.279 % 500,000 September 1, 2023 10.5 Year Unsecured Senior Notes 3.800 % 3.916 % 700,000 February 1, 2024 7 Year Unsecured Senior Notes 3.200 % 3.350 % 850,000 January 15, 2025 10 Year Unsecured Senior Notes 3.650 % 3.766 % 1,000,000 February 1, 2026 10 Year Unsecured Senior Notes 2.750 % 3.495 % 1,000,000 October 1, 2026 10 Year Unsecured Senior Notes 4.500 % 4.628 % 1,000,000 December 1, 2028 10 Year Unsecured Senior Notes 3.400 % 3.505 % 850,000 June 21, 2029 10.5 Year Unsecured Senior Notes 2.900 % 2.984 % 700,000 March 15, 2030 10.75 Year Unsecured Senior Notes 3.250 % 3.343 % 1,250,000 January 30, 2031 Total principal 9,700,000 Net unamortized discount (17,719) Deferred financing costs, net (48,704) Total $ 9,633,577 _______________ (1) Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs. (2) No principal amounts are due prior to maturity.

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	6 Months Ended
	Jun. 30, 2020
Noncontrolling Interest [Line Items]
Distribution 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 or declared in 2020 and during the six months ended June 30, 2019: Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) June 30, 2020 July 31, 2020 $0.98 $0.98 March 31, 2020 April 30, 2020 $0.98 $0.98 December 31, 2019 January 30, 2020 $0.98 $0.98 June 28, 2019 July 31, 2019 $0.95 $0.95 March 29, 2019 April 30, 2019 $0.95 $0.95 December 31, 2018 January 30, 2019 $0.95 $0.95
Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Distribution 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, 2013 - 2016 MYLTIP Units and, after the February 6, 2020 measurement date, the 2017 MYLTIP Units) and its distributions on the 2017 MYLTIP Units (prior to the February 6, 2020 measurement date), 2018 MYLTIP Units, 2019 MYLTIP Units and 2020 MYLTIP Units (after the February 4, 2020 issuance date) that occurred during the six months ended June 30, 2020: Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 30, 2020 July 31, 2020 $0.98 $0.098 March 31, 2020 April 30, 2020 $0.98 $0.098 December 31, 2019 January 30, 2020 $0.98 $0.098 Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 28, 2019 July 31, 2019 $0.95 $0.095 March 29, 2019 April 30, 2019 $0.95 $0.095 December 31, 2018 January 30, 2019 $0.95 $0.095

Stockholders' Equity _ Partne_2

Stockholders' Equity / Partners' Capital (Tables)	6 Months Ended
	Jun. 30, 2020
Class of Stock [Line Items]
Dividends Declared [Table Text Block]	The following table presents Boston Properties, Inc.’s dividends per share and Boston Properties Limited Partnership’s distributions per OP Unit and LTIP Unit paid or declared in 2020 and during the six months ended June 30, 2019: Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) June 30, 2020 July 31, 2020 $0.98 $0.98 March 31, 2020 April 30, 2020 $0.98 $0.98 December 31, 2019 January 30, 2020 $0.98 $0.98 June 28, 2019 July 31, 2019 $0.95 $0.95 March 29, 2019 April 30, 2019 $0.95 $0.95 December 31, 2018 January 30, 2019 $0.95 $0.95
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Dividends Declared [Table Text Block]	The following table presents Boston Properties Inc.’s dividends per share on its outstanding Series B Preferred Stock paid or declared during 2020 and during the six months ended June 30, 2019: Record Date Payment Date Dividend (Per Share) August 3, 2020 August 17, 2020 $32.8125 May 1, 2020 May 15, 2020 $32.8125 February 4, 2020 February 18, 2020 $32.8125 August 2, 2019 August 15, 2019 $32.8125 May 3, 2019 May 15, 2019 $32.8125 February 4, 2019 February 15, 2019 $32.8125

Earnings Per Share _ Common U_2

Earnings Per Share / Common Unit (Tables)	6 Months Ended
	Jun. 30, 2020
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share / Unit	Three months ended June 30, 2020 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 266,525 155,386 $ 1.72 Allocation of undistributed earnings to participating securities (336) — (0.01) Net income attributable to Boston Properties, Inc. common shareholders $ 266,189 155,386 $ 1.71 Effect of Dilutive Securities: Stock Based Compensation — 21 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 266,189 155,407 $ 1.71 Three months ended June 30, 2019 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 164,318 154,555 $ 1.06 Allocation of undistributed earnings to participating securities (48) — — Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,555 $ 1.06 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,874 $ 1.06 Six months ended June 30, 2020 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 764,232 155,199 $ 4.92 Allocation of undistributed earnings to participating securities (1,344) — — Net income attributable to Boston Properties, Inc. common shareholders $ 762,888 155,199 $ 4.92 Effect of Dilutive Securities: Stock Based Compensation — 134 (0.01) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 762,888 155,333 $ 4.91 Six months ended June 30, 2019 Income Shares Per Share (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 262,431 154,540 $ 1.70 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 262,431 154,859 $ 1.69
Boston Properties Limited Partnership
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share / Unit	Included in the number of units (the denominator) below are approximately 17,273,000 and 17,647,000 redeemable common units for the three months ended June 30, 2020 and 2019, respectively, and 17,405,000 and 17,627,000 redeemable common units for the six months ended June 30, 2020 and 2019, respectively. Three months ended June 30, 2020 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,975 172,659 $ 1.75 Allocation of undistributed earnings to participating securities (374) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,601 172,659 $ 1.75 Effect of Dilutive Securities: Stock Based Compensation — 21 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,601 172,680 $ 1.75 Three months ended June 30, 2019 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,715 172,202 $ 1.08 Allocation of undistributed earnings to participating securities (54) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,202 $ 1.08 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,521 $ 1.08 Six months ended June 30, 2020 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 868,308 172,604 $ 5.03 Allocation of undistributed earnings to participating securities (1,495) — (0.01) Net income attributable to Boston Properties Limited Partnership common unitholders $ 866,813 172,604 $ 5.02 Effect of Dilutive Securities: Stock Based Compensation — 134 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 866,813 172,738 $ 5.02 Six months ended June 30, 2019 Income Units Per Unit (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 299,097 172,167 $ 1.74 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 299,097 172,486 $ 1.73

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Schedule Of Reconciliation Of Net Operating Income To Net Income	Boston Properties, Inc. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 266,525 $ 164,318 $ 764,232 $ 262,431 Add: Preferred dividends 2,625 2,625 5,250 5,250 Noncontrolling interest—common units of the Operating Partnership 30,197 19,036 87,525 30,627 Noncontrolling interests in property partnerships (767) 17,482 18,719 36,312 Interest expense 107,142 102,357 208,733 203,366 Impairment loss — — — 24,038 Net operating income from unconsolidated joint ventures 27,911 24,715 56,669 50,064 Depreciation and amortization expense 178,188 177,411 349,282 342,005 Transaction costs 332 417 947 877 Payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 General and administrative expense 37,743 35,071 74,197 76,833 Less: Net operating income attributable to noncontrolling interests in property partnerships 32,427 45,562 80,088 92,647 Gains (losses) from investments in securities 4,552 1,165 (893) 4,134 Interest and other income (loss) 1,305 3,615 4,322 7,368 Gains on sales of real estate 203,767 1,686 613,932 781 Income from unconsolidated joint ventures 1,832 47,964 1,463 48,177 Direct reimbursements of payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 Development and management services revenue 8,125 9,986 16,004 19,263 Company’s share of Net Operating Income $ 397,888 $ 433,454 $ 850,638 $ 859,433 Boston Properties Limited Partnership Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 301,975 $ 185,715 $ 868,308 $ 299,097 Add: Preferred distributions 2,625 2,625 5,250 5,250 Noncontrolling interests in property partnerships (767) 17,482 18,719 36,312 Interest expense 107,142 102,357 208,733 203,366 Impairment loss — — — 22,272 Net operating income from unconsolidated joint ventures 27,911 24,715 56,669 50,064 Depreciation and amortization expense 176,409 175,199 345,694 337,881 Transaction costs 332 417 947 877 Payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 General and administrative expense 37,743 35,071 74,197 76,833 Less: Net operating income attributable to noncontrolling interests in property partnerships 32,427 45,562 80,088 92,647 Gains (losses) from investments in securities 4,552 1,165 (893) 4,134 Interest and other income (loss) 1,305 3,615 4,322 7,368 Gains on sales of real estate 207,241 1,835 626,895 930 Income from unconsolidated joint ventures 1,832 47,964 1,463 48,177 Direct reimbursements of payroll and related costs from management services contracts 2,484 2,403 5,721 5,798 Development and management services revenue 8,125 9,986 16,004 19,263 Company’s share of Net Operating Income $ 397,888 $ 433,454 $ 850,638 $ 859,433
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 June 30, 2020: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 218,351 $ — $ 204,242 $ 128,233 $ 83,837 $ 634,663 Residential 3,401 — — — 6,001 9,402 Hotel 99 — — — — 99 Total 221,851 — 204,242 128,233 89,838 644,164 % of Grand Totals 34.43 % — % 31.71 % 19.91 % 13.95 % 100.00 % Rental Expenses: Office 75,694 — 88,367 39,081 32,680 235,822 Residential 1,235 — — — 2,730 3,965 Hotel 1,973 — — — — 1,973 Total 78,902 — 88,367 39,081 35,410 241,760 % of Grand Totals 32.64 % — % 36.54 % 16.17 % 14.65 % 100.00 % Net operating income $ 142,949 $ — $ 115,875 $ 89,152 $ 54,428 $ 402,404 % of Grand Totals 35.52 % — % 28.80 % 22.15 % 13.53 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,576) — (21,851) — — (32,427) Add: Company’s share of net operating income from unconsolidated joint ventures 2,627 15,026 815 4,127 5,316 27,911 Company’s share of net operating income $ 135,000 $ 15,026 $ 94,839 $ 93,279 $ 59,744 $ 397,888 % of Grand Totals 33.92 % 3.78 % 23.84 % 23.44 % 15.02 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the three months ended June 30, 2019: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 217,961 $ — $ 251,556 $ 131,506 $ 96,486 $ 697,509 Residential 3,222 — — — 5,777 8,999 Hotel 14,844 — — — — 14,844 Total 236,027 — 251,556 131,506 102,263 721,352 % of Grand Totals 32.72 % — % 34.87 % 18.23 % 14.18 % 100.00 % Rental Expenses: Office 77,660 — 96,809 43,708 35,672 253,849 Residential 1,279 — — — 2,843 4,122 Hotel 9,080 — — — — 9,080 Total 88,019 — 96,809 43,708 38,515 267,051 % of Grand Totals 32.96 % — % 36.25 % 16.37 % 14.42 % 100.00 % Net operating income $ 148,008 $ — $ 154,747 $ 87,798 $ 63,748 $ 454,301 % of Grand Totals 32.58 % — % 34.06 % 19.33 % 14.03 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,031) — (35,531) — — (45,562) Add: Company’s share of net operating income from unconsolidated joint ventures 818 15,454 1,696 — 6,747 24,715 Company’s share of net operating income $ 138,795 $ 15,454 $ 120,912 $ 87,798 $ 70,495 $ 433,454 % of Grand Totals 32.01 % 3.57 % 27.90 % 20.26 % 16.26 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2020: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 457,849 $ — $ 459,528 $ 264,972 $ 176,973 $ 1,359,322 Residential 7,469 — — — 11,889 19,358 Hotel 6,924 — — — — 6,924 Total 472,242 — 459,528 264,972 188,862 1,385,604 % of Grand Totals 34.09 % — % 33.16 % 19.12 % 13.63 % 100.00 % Rental Expenses: Office 158,239 — 187,507 81,650 67,328 494,724 Residential 2,575 — — — 5,454 8,029 Hotel 8,794 — — — — 8,794 Total 169,608 — 187,507 81,650 72,782 511,547 % of Grand Totals 33.16 % — % 36.65 % 15.96 % 14.23 % 100.00 % Net operating income $ 302,634 $ — $ 272,021 $ 183,322 $ 116,080 $ 874,057 % of Grand Totals 34.63 % — % 31.12 % 20.97 % 13.28 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (21,239) — (58,849) — — (80,088) Add: Company’s share of net operating income from unconsolidated joint ventures 5,726 30,956 1,571 7,286 11,130 56,669 Company’s share of net operating income $ 287,121 $ 30,956 $ 214,743 $ 190,608 $ 127,210 $ 850,638 % of Grand Totals 33.76 % 3.64 % 25.24 % 22.41 % 14.95 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2019: Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 435,372 $ — $ 510,187 $ 255,561 $ 192,831 $ 1,393,951 Residential 5,923 — — — 10,791 16,714 Hotel 23,782 — — — — 23,782 Total 465,077 — 510,187 255,561 203,622 1,434,447 % of Grand Totals 32.42 % — % 35.56 % 17.82 % 14.20 % 100.00 % Rental Expenses: Office 157,160 — 193,780 84,833 71,819 507,592 Residential 2,485 — — — 5,411 7,896 Hotel 16,943 — — — — 16,943 Total 176,588 — 193,780 84,833 77,230 532,431 % of Grand Totals 33.17 % — % 36.39 % 15.93 % 14.51 % 100.00 % Net operating income $ 288,489 $ — $ 316,407 $ 170,728 $ 126,392 $ 902,016 % of Grand Totals 31.98 % — % 35.08 % 18.93 % 14.01 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (19,404) — (72,795) (448) — (92,647) Add: Company’s share of net operating income from unconsolidated joint ventures 1,590 31,162 3,482 — 13,830 50,064 Company’s share of net operating income $ 270,675 $ 31,162 $ 247,094 $ 170,280 $ 140,222 $ 859,433 % of Grand Totals 31.49 % 3.63 % 28.75 % 19.81 % 16.32 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Organization (Details)

Organization (Details) ft² in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020ft²Real_Estate_Propertiesyrshares	Dec. 31, 2019shares
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.90%	89.60%
Restriction on redemption of OP units from date of issuance (years) | yr	1
One OP unit is equivalent to one share of Common Stock (in shares) | shares	1
OP unit conversion rate (in shares) | shares	1
Number Of series Of preferred units outstanding	1
Commercial Real Estate Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	195
Net Rentable Area (in sf) | ft²	51.2
Total Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	9
Net Rentable Area (in sf) | ft²	5
Total Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	176
Office Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	7
Retail Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	12
Residential Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	6
Residential Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	2
Hotel Property [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	1
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Real Estate Properties [Line Items]
Preferred Stock, Dividend Rate, Percentage	5.25%
Preferred stock / units, shares / units outstanding (in shares / units) | shares	80,000	80,000
Depositary shares of Series B Cumulative Redeemable Preferred [Member]
Real Estate Properties [Line Items]
Preferred stock / units, shares / units outstanding (in shares / units) | shares	8,000,000
Series B Preferred Units [Member]
Real Estate Properties [Line Items]
Preferred stock / units, shares / units outstanding (in shares / units) | shares	80,000

Summary Of Significant Accoun_4

Summary Of Significant Accounting Policies (Narrative) (Details) $ in Thousands	Jan. 01, 2020USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs		6
Number of VIEs - Total		7
Cumulative effect of a change in accounting principle		$ (1,679)	$ (4,379)
Dividends In Excess Of Earnings [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of a change in accounting principle	$ 1,500	(1,505)	(3,864)
Dividends In Excess Of Earnings [Member] | Boston Properties Limited Partnership
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of a change in accounting principle	1,500
Noncontrolling Interests [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of a change in accounting principle	200	(174)	(445)
Noncontrolling Interests [Member] | Boston Properties Limited Partnership
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of a change in accounting principle	$ 200
Noncontrolling interest - property partnerships [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of a change in accounting principle		$ 0	$ (70)

Summary Of Significant Accoun_5

Summary Of Significant Accounting Policies Fair Value of Debt (Level 3) (Details) - Measurement Input, Discount Rate [Member]	Jun. 30, 2020
Mortgage Notes [Member] | Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0209
Mortgage Notes [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0233
Mortgage Notes [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0325
Unsecured Term Loan / Line of Credit[Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0101
Unsecured Term Loan / Line of Credit[Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0101
Related Party Note Receivable [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0366
Related Party Note Receivable [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0366
Notes Receivables [Member] | Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0366
Notes Receivables [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0535
Notes Receivables [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0800

Summary Of Significant Accoun_6

Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable, net	$ 78,520	$ 80,000
Notes receivable, net	25,480	15,920
Mortgage notes payable, net	2,915,852	2,922,408
Unsecured senior notes, net	9,633,577	8,390,459
Unsecured line of credit	0	0
Unsecured term loan, net	499,150	498,939
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable, net	78,520	80,000
Notes receivable, net	25,480	15,920
Total	104,000	95,920
Mortgage notes payable, net	2,915,852	2,922,408
Unsecured senior notes, net	9,633,577	8,390,459
Unsecured line of credit	0	0
Unsecured term loan, net	499,150	498,939
Total	13,048,579	11,811,806
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable, net	85,394	81,931
Notes receivable, net	25,648	14,978
Total	111,042	96,909
Mortgage notes payable, net	3,155,771	2,984,956
Unsecured senior notes, net	10,517,869	8,826,375
Unsecured line of credit	0	0
Unsecured term loan, net	500,450	500,561
Total	$ 14,174,090	$ 12,311,892

Real Estate Schedule of Real Es

Real Estate Schedule of Real Estate Properties (Details) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
Real Estate Properties [Line Items]
Land		$ 5,070,126	$ 5,111,606
Right-of-use assets - finance leases		237,394	237,394
Right of use assets - operating leases		147,512	148,640
Land held for future development	[1]	414,053	254,828
Buildings and improvements		13,488,860	13,646,054
Tenant improvements		2,664,294	2,656,439
Furniture, Fixtures and Equipment		44,635	44,313
Construction in progress		893,935	789,736
Total		22,960,809	22,889,010
Less: accumulated depreciation		(5,292,389)	(5,266,798)
Total real estate		17,668,420	17,622,212
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Land		4,972,910	5,011,153
Right-of-use assets - finance leases		237,394	237,394
Right of use assets - operating leases		147,512	148,640
Land held for future development	[1]	414,053	254,828
Buildings and improvements		13,209,267	13,351,286
Tenant improvements		2,664,294	2,656,439
Furniture, Fixtures and Equipment		44,635	44,313
Construction in progress		893,935	789,736
Total		22,584,000	22,493,789
Less: accumulated depreciation		(5,190,360)	(5,162,908)
Total real estate		$ 17,393,640	$ 17,330,881
[1]	Includes pre-development costs.

Real Estate (Narrative) (Detail

Real Estate (Narrative) (Details) $ in Thousands	Jun. 25, 2020USD ($)ft²	Feb. 20, 2020USD ($)ft²Buildings	Jan. 28, 2020USD ($)ft²Buildings	Jan. 27, 2020USD ($)	Feb. 19, 2020USD ($)	Jun. 30, 2020USD ($)		Jun. 24, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)		Jun. 24, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 26, 2020USD ($)ft²	Jun. 01, 2020ft²	Mar. 26, 2020ft²
Real Estate Properties [Line Items]
Proceeds from sales of real estate										$ 506,337			$ 60,398
Gains on sales of real estate						$ 203,767			$ 1,686	613,932			781
Payments to Acquire Equity Method Investments										106,168			50,068
Revenues						$ 654,773			733,741	$ 1,407,329			1,459,508
Capital Gallery [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²	455,000
Contractual Sales Price	$ 253,700
Proceeds from sales of real estate	246,900
Gains on sales of real estate	$ 203,800
Operating Income (Loss)								$ 2,900	3,500			$ 6,300	7,000
New Dominion Technology Park [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²		493,000
Contractual Sales Price		$ 256,000
Proceeds from sales of real estate		254,000
Gains on sales of real estate		$ 192,300
Operating Income (Loss)					$ 1,600				2,100				4,200
number of buildings | Buildings		2
Gateway Center [Member]
Real Estate Properties [Line Items]
Gains on sales of real estate			$ 217,700
Operating Income (Loss)				$ 200					3,100				6,000
425 Fourth Street [Member]
Real Estate Properties [Line Items]
Aggregate purchase price														$ 140,100
Net Rentable Area (in sf) | ft²														804,000
17Fifty Presidents Street [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²																276,000
Leased percentage																100.00%
20 Citypoint [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²															211,000
Leased percentage															62.00%
Capital Gallery [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²	631,000													176,000
Gateway Commons Complex [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²			768,000
Payments to Acquire Equity Method Investments			$ 350,000
Ownership Percentage			50.00%			50.00%	[1]			50.00%	[1]
number of buildings | Buildings			3
Gateway Commons Complex prior to deferred contribution [Member] [Member]
Real Estate Properties [Line Items]
Ownership Percentage			55.00%
Gateway Commons Complex Future Development[Member] [Member]
Real Estate Properties [Line Items]
Ownership Percentage			49.00%
Joint Venture Partner [Member] | Gateway Commons Complex [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²			768,000
Payments to Acquire Equity Method Investments			$ 280,800
Future payment to acquire interest in equity method investment			$ 69,200
Ownership Percentage			50.00%
number of buildings | Buildings			3
Joint Venture Partner [Member] | Gateway Commons Complex Future Development[Member] [Member]
Real Estate Properties [Line Items]
Ownership Percentage			51.00%
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Proceeds from sales of real estate										$ 506,337			60,398
Gains on sales of real estate						$ 207,241			1,835	626,895			930
Payments to Acquire Equity Method Investments										106,168			50,068
Revenues						$ 654,773			$ 733,741	$ 1,407,329			$ 1,459,508
Boston Properties Limited Partnership | Capital Gallery [Member]
Real Estate Properties [Line Items]
Gains on sales of real estate	$ 207,200
Boston Properties Limited Partnership | New Dominion Technology Park [Member]
Real Estate Properties [Line Items]
Gains on sales of real estate		$ 197,100
Boston Properties Limited Partnership | Gateway Center [Member]
Real Estate Properties [Line Items]
Gains on sales of real estate			$ 222,400
[1]	As a result of the partner’s deferred contribution, the Company owns an approximately 55% interest in the joint venture at June 30, 2020. Future development projects will be owned 49% by the Company and 51% by its partner.

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Leases [Abstract]
Fixed contractual payments	$ 529,514	$ 557,820	$ 1,116,471	$ 1,111,806
Variable lease payments	100,605	122,369	223,759	247,634
Lease	$ 630,119	$ 680,189	$ 1,340,230	$ 1,359,440

Leases Narrative (Details)

Leases Narrative (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Leases [Abstract]
Write-off for accrued rent	$ 35,900,000	$ 37,400,000
Write-off for accounts receivable	$ 18,000,000	$ 18,900,000

Investments in Unconsolidated_2

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) $ in Thousands		6 Months Ended
		Jun. 30, 2020USD ($)ft²paymentsBuildings		Jun. 25, 2020Land_Parcels	Jan. 28, 2020	Dec. 31, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Other Liabilities		$ 373,281				$ 387,994
Investments in unconsolidated joint ventures		1,339,724				955,647
Investments In Affiliates Subsidiaries Associates And Joint Ventures net	[1]	1,310,578				933,223
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Other Liabilities		$ 29,100				22,400
Square 407 Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Market Square North
Ownership Percentage		50.00%
Other Liabilities	[1]	$ 4,123				4,872
BP/CRF Metropolitan Square LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Metropolitan Square
Ownership Percentage		20.00%
Investments in unconsolidated joint ventures	[1]	$ (7,319)				9,134
901 New York Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		901 New York Avenue
Ownership Percentage	[2]	25.00%
Other Liabilities	[1]	$ 12,174				12,113
901 New York Avenue LLC (economic ownership) [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
WP Project Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Wisconsin Place Land and Infrastructure
Ownership Percentage	[3]	33.30%
Investments in unconsolidated joint ventures	[1]	$ 36,102				36,789
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Annapolis Junction
Ownership Percentage		50.00%	[4]	50.00%
Investments in unconsolidated joint ventures	[1]	$ 12,967				25,391
Number of real estate properties | Buildings		2
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	[5]	60.00%
Investments in unconsolidated joint ventures	[1]	$ 201				2,953
500 North Capitol Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		500 North Capitol Street, NW
Ownership Percentage		30.00%
Other Liabilities	[1]	$ 5,530				5,439
501 K Street LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		1001 6th Street
Ownership Percentage	[6]	50.00%
Investments in unconsolidated joint ventures	[1]	$ 42,673				42,496
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 - Podium
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 49,160				49,466
Residential Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Hub50House
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 53,340				55,092
Hotel Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		The Hub on Causeway - Hotel Air Rights
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 10,228				9,883
Office Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		100 Causeway Street
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 56,544				56,606
1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		1265 Main Street
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 4,116				3,780
BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Dock 72
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 96,013				94,804
BNYA Amenity Operator LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Dock 72
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 0				0
CA-Colorado Center Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Colorado Center
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 236,287				252,069
7750 Wisconsin Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		7750 Wisconsin Avenue
Ownership Percentage		50.00%
Investments in unconsolidated joint ventures	[1]	$ 57,130				56,247
BP-M 3HB Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		3 Hudson Boulevard
Ownership Percentage		25.00%
Investments in unconsolidated joint ventures	[1]	$ 91,422				67,499
SMBP Venture LP [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Santa Monica Business Park
Ownership Percentage		55.00%
Investments in unconsolidated joint ventures	[1]	$ 148,665				163,937
Platform 16 Holdings LP [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Platform 16
Ownership Percentage		55.00%	[7]		55.00%
Investments in unconsolidated joint ventures	[1]	$ 99,734				$ 29,501
Gateway Portfolio Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Gateway Commons
Ownership Percentage		50.00%	[8]		50.00%
Investments in unconsolidated joint ventures	[1]	$ 345,142
Entity Owning Land And Infrastructure Of Project [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		33.30%
Gateway Commons Complex prior to deferred contribution [Member] [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage					55.00%
Gateway Commons Complex Future Development[Member] [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage					49.00%
Joint Venture Partner [Member] | Gateway Portfolio Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage					50.00%
Joint Venture Partner [Member] | Gateway Commons Complex Future Development[Member] [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage					51.00%
[1]	Investments with deficit balances aggregating approximately $29.1 million and $22.4 million at June 30, 2020 and December 31, 2019, respectively, are included 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. At June 30, 2020 and December 31, 2019, the Company’s economic ownership was approximately 50%.
[3]	The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.
[4]	The joint venture owns two in-service buildings.
[5]	T he property was sold on June 27, 2019. As of June 30, 2020 and December 31, 2019, the investment is comprised of undistributed cash.
[6]	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.
[7]	This entity is a VIE (See Note 2).
[8]	As a result of the partner’s deferred contribution, the Company owns an approximately 55% interest in the joint venture at June 30, 2020. Future development projects will be owned 49% by the Company and 51% by its partner.

Investments in Unconsolidated_3

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
ASSETS
Real estate and development in process, net		$ 17,668,420	$ 17,622,212
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable, net		2,915,852	2,922,408
Other Liabilities		373,281	387,994
Total liabilities and equity / capital		23,000,777	21,284,905
Carying value of the Company's investment in unconsolidated joint ventures		1,339,724	955,647
Right-of-use assets - finance leases		237,394	237,394
Right of use assets - operating leases		147,512	148,640
Lease liabilities - finance leases		230,146	224,042
Lease liabilities - operating leases		200,979	200,180
Unconsolidated Joint Ventures [Member]
ASSETS
Real estate and development in process, net	[1]	4,527,828	3,904,400
Other assets		535,870	502,706
Total assets		5,063,698	4,407,106
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable, net		2,465,039	2,218,853
Other Liabilities	[2]	655,709	749,675
Members'/Partners' equity		1,942,950	1,438,578
Total liabilities and equity / capital		5,063,698	4,407,106
Company's share of equity		911,682	591,905
Basis differentials	[3]	398,896	341,318
Carying value of the Company's investment in unconsolidated joint ventures	[4]	1,310,578	933,223
Right-of-use assets - finance leases		248,900	383,900
Right of use assets - operating leases		11,700	12,100
Lease liabilities - finance leases		390,200	510,800
Lease liabilities - operating leases		17,400	17,300
Colorado Center [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Basis differentials		309,000	311,300
Unconsolidated Joint Ventures [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Other Liabilities		29,100	$ 22,400
Gateway Commons Complex [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Basis differentials		54,400
Carying value of the Company's investment in unconsolidated joint ventures	[5]	$ 345,142
[1]	At June 30, 2020 and December 31, 2019, this amount includes right of use assets - finance leases totaling approximately $248.9 million and $383.9 million, respectively, and right of use assets - operating leases totaling approximately $11.7 million and $12.1 million, respectively.
[2]	At June 30, 2020 and December 31, 2019, this amount includes lease liabilities - finance leases totaling approximately $390.2 million and $510.8 million, respectively, and lease liabilities - operating leases totaling approximately $17.4 million and $17.3 million, respectively.
[3]	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 June 30, 2020 and December 31, 2019, there was an aggregate basis differential of approximately $309.0 million and $311.3 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. At June 30, 2020, there was an aggregate basis differential of approximately $54.4 million between the carrying value of the Company’s investment in the joint venture that owns Gateway Commons and the joint venture’s basis in the assets and liabilities. These basis differentials (excluding land) will be amortized over the remaining lives of the related assets and liabilities.
[4]	Investments with deficit balances aggregating approximately $29.1 million and $22.4 million at June 30, 2020 and December 31, 2019, respectively, are reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[5]	Investments with deficit balances aggregating approximately $29.1 million and $22.4 million at June 30, 2020 and December 31, 2019, respectively, are included within Other Liabilities in the Company’s Consolidated Balance Sheets.

Investments in Unconsolidated_4

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 654,773	$ 733,741	$ 1,407,329	$ 1,459,508
Expenses
Transaction costs		332	417	947	877
Depreciation and amortization		178,188	177,411	349,282	342,005
Total expenses		460,507	482,353	941,694	957,944
Other income (expense)
Interest expense		(107,142)	(102,357)	(208,733)	(203,366)
Gain on sales of real estate		203,767	1,686	613,932	781
Net income		298,580	203,461	875,726	334,620
Income from unconsolidated joint ventures		1,832	47,964	1,463	48,177
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]	89,563	80,204	182,766	163,159
Expenses
Operating		33,704	30,134	69,105	60,633
Depreciation and amortization		37,390	24,818	69,425	53,464
Total expenses		71,094	54,952	138,530	114,097
Other income (expense)
Interest expense		(23,306)	(20,803)	(45,889)	(41,560)
Gain on sales of real estate		11,720	34,572	11,720	34,572
Net income		6,883	39,021	10,067	42,074
Company's share of net income		4,024	22,376	5,276	23,960
Basis differential	[2]	(2,192)	25,588	(3,813)	24,217
Income from unconsolidated joint ventures		1,832	47,964	1,463	48,177
Straight-line rent adjustments		8,500	7,600	18,200	13,400
Colorado Center [Member]
Other income (expense)
Straight-line rent adjustments		400	500	900	1,100
Above and below market rent adjustments, net		$ 200	$ 400	$ 500	$ 800
[1]	Includes straight-line rent adjustments of approximately $8.5 million and $7.6 million for the three months ended June 30, 2020 and 2019, respectively, and $18.2 million and $13.4 million for the six months ended June 30, 2020 and 2019, respectively.
[2]	Includes straight-line rent adjustments of approximately $0.4 million and $0.5 million for the three months ended June 30, 2020 and 2019, respectively, and $0.9 million and $1.1 million for the six months ended June 30, 2020 and 2019, respectively. Also includes net above-/below-market rent adjustments of approximately $0.2 million and $0.4 million for the three months ended June 30, 2020 and 2019, respectively, and $0.5 million and $0.8 million for the six months ended June 30, 2020 and 2019, respectively.

Investment in unconsolidated Jo

Investment in unconsolidated Joint Ventures (Narrative) (Details) $ in Thousands	Jun. 25, 2020USD ($)ft²Land_Parcels	Jun. 09, 2020USD ($)ft²Vehiclesyr	Jan. 28, 2020USD ($)ft²Buildings	Jun. 30, 2020USD ($)		Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)		Jun. 30, 2019USD ($)	Jun. 08, 2020USD ($)	Feb. 20, 2020USD ($)ft²a	Dec. 31, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Mortgage notes payable, net				$ 2,915,852			$ 2,915,852					$ 2,922,408
Payments to Acquire Equity Method Investments							106,168		$ 50,068
Number of Vehicles | Vehicles		511
Income (Loss) from Equity Method Investments				$ 1,832		$ 47,964	1,463		48,177
Capital distributions from unconsolidated joint ventures							54,413		105,000
Proceeds from sales of real estate							$ 506,337		$ 60,398
Gateway Commons Complex [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			50.00%	50.00%	[1]		50.00%	[1]
number of buildings | Buildings			3
Net Rentable Area (in sf) | ft²			768,000
Payments to Acquire Equity Method Investments			$ 350,000
Platform 16
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			55.00%	55.00%	[2]		55.00%	[2]
Net Rentable Area (in sf) | ft²			390,000								1,100,000
Finance Lease fixed purchase price											$ 134,800
Prepaid purchase price											$ 15,000
Area of Land | a											5.6
Annapolis Junction Building Seven [Member]
Schedule of Equity Method Investments [Line Items]
Mortgage notes payable, net	$ 18,400
Debt Instrument, Basis Spread on Variable Rate	2.35%
Net Rentable Area (in sf) | ft²	127,000
Annapolis Junction Building Eight [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%
Mortgage notes payable, net	$ 34,500
Debt Instrument, Basis Spread on Variable Rate	2.35%
Net Rentable Area (in sf) | ft²	126,000
Repayments of Debt	$ 16,100
Gateway Commons Complex prior to deferred contribution [Member] [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			55.00%
Gateway Commons Complex Future Development[Member] [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			49.00%
Metropolitan Square Associates Llc [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		20.00%
Extension Option (in years) | yr		1
Number of extensions		2
Debt instrument, borrowing capacity		$ 325,000
Debt Instrument, Basis Spread on Variable Rate		4.75%
Net Rentable Area (in sf) | ft²		654,000
Debt		$ 288,000								$ 155,900
Debt Instrument, Interest Rate, Stated Percentage										5.75%
Capital distributions from unconsolidated joint ventures		$ 112,700
Derivative, Cap Interest Rate		3.00%
Derivative, Notional Amount		$ 325,000
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%			50.00%	[3]		50.00%	[3]
Net Rentable Area (in sf) | ft²	300,000
Contractual Sales Price	$ 47,000
Parcels of undeveloped land | Land_Parcels	2
land parcel | Land_Parcels	1
Income (Loss) from Equity Method Investments	$ 5,800
Capital distributions from unconsolidated joint ventures	36,800
Proceeds from sales of real estate	$ 45,800
Joint Venture Partner [Member] | Gateway Commons Complex [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			50.00%
number of buildings | Buildings			3
Net Rentable Area (in sf) | ft²			768,000
Payments to Acquire Equity Method Investments			$ 280,800
Future payment to acquire interest in equity method investment			$ 69,200
Joint Venture Partner [Member] | Gateway Commons Complex Future Development[Member] [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			51.00%
Company's Share [Member] | Metropolitan Square Associates Llc [Member]
Schedule of Equity Method Investments [Line Items]
Capital distributions from unconsolidated joint ventures		$ 22,500
Company's Share [Member] | Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Parcels of undeveloped land | Land_Parcels	2
Capital distributions from unconsolidated joint ventures	$ 18,400
[1]	As a result of the partner’s deferred contribution, the Company owns an approximately 55% interest in the joint venture at June 30, 2020. Future development projects will be owned 49% by the Company and 51% by its partner.
[2]	This entity is a VIE (See Note 2).
[3]	The joint venture owns two in-service buildings.

Schedule of Unsecured Senior No

Schedule of Unsecured Senior Notes (Details) - USD ($) $ in Thousands		Jun. 30, 2020		May 05, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Senior Notes		$ 9,633,577			$ 8,390,459
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Senior Notes		9,633,577			$ 8,390,459
Boston Properties Limited Partnership | Senior Notes
Debt Instrument [Line Items]
Debt		9,700,000
Debt Instrument, Unamortized Discount		(17,719)
Debt Issuance Costs, Net		(48,704)
Senior Notes		$ 9,633,577
Boston Properties Limited Partnership | Senior Notes | 4.289% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.125%
Debt Instrument, Interest Rate, Effective Percentage	[1]	4.289%
Debt		$ 850,000
Long-term Debt, Maturity Date	[2]	May 15, 2021
Boston Properties Limited Partnership | Senior Notes | 3.954% unsecured senior notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.85%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.954%
Debt		$ 1,000,000
Long-term Debt, Maturity Date	[2]	Feb. 1, 2023
Boston Properties Limited Partnership | Senior Notes | 3.279% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.125%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.279%
Debt		$ 500,000
Long-term Debt, Maturity Date	[2]	Sep. 1, 2023
Boston Properties Limited Partnership | Senior Notes | 3.916% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.80%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.916%
Debt		$ 700,000
Long-term Debt, Maturity Date	[2]	Feb. 1, 2024
Boston Properties Limited Partnership | Senior Notes | 3.350% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.20%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.35%
Debt		$ 850,000
Long-term Debt, Maturity Date	[2]	Jan. 15, 2025
Boston Properties Limited Partnership | Senior Notes | 3.766% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.65%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.766%
Debt		$ 1,000,000
Long-term Debt, Maturity Date	[2]	Feb. 1, 2026
Boston Properties Limited Partnership | Senior Notes | 3.495% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.75%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.495%
Debt		$ 1,000,000
Long-term Debt, Maturity Date	[2]	Oct. 1, 2026
Boston Properties Limited Partnership | Senior Notes | 4.628% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.50%
Debt Instrument, Interest Rate, Effective Percentage	[1]	4.628%
Debt		$ 1,000,000
Long-term Debt, Maturity Date	[2]	Dec. 1, 2028
Boston Properties Limited Partnership | Senior Notes | 3.505% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.40%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.505%
Debt		$ 850,000
Long-term Debt, Maturity Date	[2]	Jun. 21, 2029
Boston Properties Limited Partnership | Senior Notes | 2.984% unsecured senior notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.90%
Debt Instrument, Interest Rate, Effective Percentage	[1]	2.984%
Debt		$ 700,000
Long-term Debt, Maturity Date	[2]	Mar. 15, 2030
Boston Properties Limited Partnership | Senior Notes | 3.343 % unsecured senior notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.25%		3.25%
Debt Instrument, Interest Rate, Effective Percentage		3.343%	[1]	3.343%
Debt		$ 1,250,000		$ 1,250,000
Long-term Debt, Maturity Date	[2]	Jan. 30, 2031
[1]	Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs.
[2]	No principal amounts are due prior to maturity.

Unsecured Senior Notes (Narrati

Unsecured Senior Notes (Narrative) (Details) - USD ($) $ in Thousands	May 05, 2020	Jun. 30, 2020		Jun. 30, 2019
Debt Instrument [Line Items]
Proceeds from unsecured senior notes		$ 1,248,125		$ 848,428
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Proceeds from unsecured senior notes		$ 1,248,125		$ 848,428
Debt Instrument, Covenant Description		The indenture relating to the unsecured senior notes contains certain financial restrictions and requirements, including (1) a leverage ratio not to exceed 60%, (2) a secured debt leverage ratio not to exceed 50%, (3) an interest coverage ratio of greater than 1.50, and (4) an unencumbered asset value of not less than 150% of unsecured debt.
Debt Instrument, Covenant Compliance		At June 30, 2020, Boston Properties Limited Partnership was in compliance with each of these financial restrictions and requirements.
Senior Notes | Boston Properties Limited Partnership
Debt Instrument [Line Items]
Debt		$ 9,700,000
3.343 % unsecured senior notes [Member] | Senior Notes | Boston Properties Limited Partnership
Debt Instrument [Line Items]
Debt	$ 1,250,000	$ 1,250,000
Debt Instrument, Interest Rate, Stated Percentage	3.25%	3.25%
Senior Notes Pricing	99.85%
Debt Instrument, Interest Rate, Effective Percentage	3.343%	3.343%	[1]
Proceeds from unsecured senior notes	$ 1,240,000
[1]	Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs.

Commitments And Contingencies (

Commitments And Contingencies (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2020USD ($)ft²	Dec. 31, 2009USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jan. 10, 2014USD ($)
Commitments And Contingencies [Line Items]
Letter of credit and performance obligations	$ 20,400,000
Notes Receivable, Related Parties	78,520,000		$ 80,000,000
Property insurance program per occurrence limits	1,000,000,000
Per occurrence limit for NBCR Coverage	1,000,000,000
Value of program trigger	$ 200,000,000
Coinsurance of program trigger	20.00%
Program trigger deductible	20.00%
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	$ 240,000,000
Annual aggregate limit of the earthquake insurance which covers San Francisco and Los Angeles regions	240,000,000
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco and Los Angeles	20,000,000
Notes receivable, net	25,480,000		15,920,000
Affiliate of Bernstein Companies [Member]
Commitments And Contingencies [Line Items]
Notes receivable, net	$ 10,000,000
Note receivable fixed interest rate	8.00%
Boston Properties Limited Partnership
Commitments And Contingencies [Line Items]
Notes Receivable, Related Parties	$ 78,520,000		80,000,000
Operating partnership guarantee to cover liabilities of IXP	20,000,000
Notes receivable, net	25,480,000		$ 15,920,000
767 Venture, LLC [Member]
Commitments And Contingencies [Line Items]
Maximum funding obligation	48,900,000
Property insurance program per occurrence limits	1,625,000,000
7750 Wisconsin Avenue [Member]
Commitments And Contingencies [Line Items]
Liabilities for Contingent Guarantees	0
Lehman [Member]
Commitments And Contingencies [Line Items]
Bankruptcy claim, amount filed by general creditor		$ 45,300,000
Bankruptcy claim amount allowed by court to creditor					$ 45,200,000
Bankruptcy Claims, Amount of Claims Settled				$ 18,000,000
Bankruptcy remaining claim amount allowed by court to creditor	27,200,000
6595 Springfield Center Drive [Member]
Commitments And Contingencies [Line Items]
Liabilities for Contingent Guarantees	$ 0
325 Main Street
Commitments And Contingencies [Line Items]
Net Rentable Area (in sf) | ft²	115,000
601 Lexington Avenue
Commitments And Contingencies [Line Items]
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP	$ 250,000,000
Future Residential Building [Member] | 325 Main Street
Commitments And Contingencies [Line Items]
Net Rentable Area (in sf) | ft²	200,000
Affordable Housing requirement	25.00%
Future Office Building [Member] | 325 Main Street
Commitments And Contingencies [Line Items]
Net Rentable Area (in sf) | ft²	420,000
Future Retail Building [Member] | 325 Main Street
Commitments And Contingencies [Line Items]
Net Rentable Area (in sf) | ft²	41,000
Home Ownership Units [Member] | Future Residential Building [Member] | 325 Main Street
Commitments And Contingencies [Line Items]
Affordable Housing requirement	20.00%

Noncontrolling Interests (Narra

Noncontrolling Interests (Narrative) (Details) - Boston Properties Limited Partnership	Jun. 30, 2020shares
Noncontrolling Interest [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operating Partnership (OP) Units (in shares)	16,123,912
Long-Term Incentive Plan (LTIP) Units (in shares)	1,345,723
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)	105,080
MYLTIP 2013
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP	64,468
MYLTIP 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP	23,100
MYLTIP 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIP	24,966
MYLTIP 2016 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIP	89,791
MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP	116,078
MYLTIP 2018
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP	336,195
MYLTIP 2019 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS	220,325
MYLTIP 2020 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2020 MYLTIP	203,278

(Common Units) (Narrative) (Det

(Common Units) (Narrative) (Details) $ / shares in Units, $ in Millions	Feb. 06, 2020USD ($)shares	Jun. 30, 2020USD ($)yr$ / sharesshares
MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target	83.80%
Value of MYLTIP Awards | $	$ 17.6
MYLTIP Units forfeited	270,942
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)		764,640
Redemption of OP units issued on conversion of LTIP, OPP and MYLTIP units (in shares)		82,551
MYLTIP Units distribution as percentage of OP Unit distribution prior to measurement date		10.00%
Restriction on redemption of OP Unit to Common Stock (in years) | yr		1
Redemption of OP Unit equivalent to Common Stock (in shares)		1
Common units of operating partnership if converted value | $		$ 1,600
Closing price of common stock (in dollars per share) | $ / shares		$ 90.38

Noncontrolling Interests Common

Noncontrolling Interests Common Units Distributions (Details) - Boston Properties Limited Partnership - $ / shares	Apr. 30, 2020	Jan. 30, 2020	Jul. 31, 2019	Apr. 30, 2019	Jan. 30, 2019	Jun. 19, 2020
Dividends Payable [Line Items]
Distributions Declared To OP And LTIP Units Per Unit						$ 0.98
Distributions Declared To MYLTIP Units Per Unit						$ 0.098
Distributions made to OP and LTIP units per unit (in dollars per share)	$ 0.98	$ 0.98	$ 0.95	$ 0.95	$ 0.95
Distributions Made To MYLTIP Units Per Unit	$ 0.098	$ 0.098	$ 0.095	$ 0.095	$ 0.095

Noncontrolling Interests (Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Noncontrolling Interest [Line Items]
Noncontrolling Interest in Limited Partnerships	$ 1,724,588	$ 1,728,689

Stockholders' Equity _ Partne_3

Stockholders' Equity / Partners' Capital Narrative (Details) $ / shares in Units, $ in Millions	May 22, 2020USD ($)yr	Jun. 30, 2020$ / sharesshares	Dec. 31, 2019$ / sharesshares	Mar. 27, 2018$ / shares	Jun. 02, 2017USD ($)
Class of Stock [Line Items]
Common Stock, Shares, Outstanding		155,622,286	154,790,298
General Partners' Capital Account, Units Outstanding (in units)		1,730,919
Limited Partners' Capital Account, Units Outstanding (in units)		153,891,367
Options exercised		43,792
Shares of Common Stock issued in connection with redemption of an equal number of OP Units (in shares)		764,640
ATM Program [Member]
Class of Stock [Line Items]
At The Market Stock Offering Program Aggregate Value Of Common Stock | $	$ 600				$ 600
At Market Stock Offering Program Maximum Length Of Sale (in years) | yr	3
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Class of Stock [Line Items]
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	$ 2,500
Depositary 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		$ 25

Stockholders' Equity _ Partne_4

Stockholders' Equity / Partners' Capital Dividends / Distributions (Details) - $ / shares	May 15, 2020	Apr. 30, 2020	Feb. 18, 2020	Jan. 30, 2020	Aug. 15, 2019	Jul. 31, 2019	May 15, 2019	Apr. 30, 2019	Feb. 15, 2019	Jan. 30, 2019	Jun. 19, 2020
Dividends / Distributions [Line Items]
Dividends Payable, Amount Per Share / Unit											$ 0.98
Common Stock / Unit, Dividends / Distributions, Per Share / Unit, Cash Paid		$ 0.98		$ 0.98		$ 0.95		$ 0.95		$ 0.95
Boston Properties Limited Partnership
Dividends / Distributions [Line Items]
Dividends Payable, Amount Per Share / Unit											0.98
Common Stock / Unit, Dividends / Distributions, Per Share / Unit, Cash Paid		$ 0.98		$ 0.98		$ 0.95		$ 0.95		$ 0.95
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Dividends / Distributions [Line Items]
Dividends Payable, Amount Per Share / Unit											$ 32.8125
Common Stock / Unit, Dividends / Distributions, Per Share / Unit, Cash Paid	$ 32.8125		$ 32.8125		$ 32.8125		$ 32.8125		$ 32.8125

Earnings Per Share _ Common U_3

Earnings Per Share / Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic Earnings:
Net income attributable to the company's common shareholders / unitholders	$ 266,525	$ 164,318	$ 764,232	$ 262,431
Net income attributable to the company's common shareholders / unitholders (in shares / units)	155,386,000	154,555,000	155,199,000	154,540,000
Net income attributable to the company's common shareholders / unitholders (in dollars per share / unit)	$ 1.72	$ 1.06	$ 4.92	$ 1.70
Allocation of undistributed earnings to participating securities	$ (336)	$ (48)	$ (1,344)
Allocation of undistributed earnings to participating securities (in shares / units)	0	0	0
Allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ (0.01)	$ 0	$ 0
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities	$ 266,189	$ 164,270	$ 762,888	$ 262,431
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in shares / units)	155,386,000	154,555,000	155,199,000	154,540,000
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ 1.71	$ 1.06	$ 4.92	$ 1.70
Effect of Dilutive Securities:
Stock Based Compensation	$ 0	$ 0	$ 0	$ 0
Stock Based Compensation (in shares / units)	21,000	319,000	134,000	319,000
Weighted Average Number Diluted Shares Outstanding Adjustment (per share)	$ 0	$ 0	$ (0.01)	$ (0.01)
Diluted Earnings:
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders	$ 266,189	$ 164,270	$ 762,888	$ 262,431
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders (in shares / units)	155,407,000	154,874,000	155,333,000	154,859,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 1.71	$ 1.06	$ 4.91	$ 1.69
Boston Properties Limited Partnership
Redeemable Common Units	17,273,000	17,647,000	17,405,000	17,627,000
Basic Earnings:
Net income attributable to the company's common shareholders / unitholders	$ 301,975	$ 185,715	$ 868,308	$ 299,097
Net income attributable to the company's common shareholders / unitholders (in shares / units)	172,659,000	172,202,000	172,604,000	172,167,000
Net income attributable to the company's common shareholders / unitholders (in dollars per share / unit)	$ 1.75	$ 1.08	$ 5.03	$ 1.74
Allocation of undistributed earnings to participating securities	$ (374)	$ (54)	$ (1,495)
Allocation of undistributed earnings to participating securities (in shares / units)	0	0	0
Allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ 0	$ 0	$ (0.01)
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities	$ 301,601	$ 185,661	$ 866,813	$ 299,097
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in shares / units)	172,659,000	172,202,000	172,604,000	172,167,000
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ 1.75	$ 1.08	$ 5.02	$ 1.74
Effect of Dilutive Securities:
Stock Based Compensation	$ 0	$ 0	$ 0	$ 0
Stock Based Compensation (in shares / units)	21,000	319,000	134,000	319,000
Weighted Average Number Diluted Shares Outstanding Adjustment (per share)	$ 0	$ 0	$ 0	$ (0.01)
Diluted Earnings:
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders	$ 301,601	$ 185,661	$ 866,813	$ 299,097
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders (in shares / units)	172,680,000	172,521,000	172,738,000	172,486,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 1.75	$ 1.08	$ 5.02	$ 1.73

Stock Option and Incentive Pl_2

Stock Option and Incentive Plan (Narrative) (Details) - USD ($) $ in Millions	Feb. 06, 2020	Feb. 04, 2020
MYLTIP 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
TSR measurement (in years)		three-year
Minimum earned awards		0
Maximum Earned Awards		203,278
Earned wards - Target		101,638
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights		Earned awards (if any) will vest 50% on February 3, 2023 and 50% on February 3, 2024, 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 3, 2023, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2020 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.
Value of MYLTIP Awards		$ 13.7
MYLTIP 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards	$ 17.6
Final awards percentage of target	83.80%
MYLTIP Units forfeited	270,942

Stock Option and Incentive Pl_3

Stock Option and Incentive Plan (Restricted Stock) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 04, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued		155,701,186		155,701,186		154,869,198
Stock based compensation expense		$ 10,100	$ 10,100	$ 27,300	$ 24,900
Common Stock, Value, Issued		$ 1,556		$ 1,556		$ 1,548
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued		29,630		29,630
Employee and director payment per share (in dollars per share)				$ 0.01
Common Stock, Value, Issued		$ 4,000		$ 4,000
Common Stock Weighted Average Price (in dollars per share)		$ 133.81		$ 133.81
LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value Of LTIP Units Issued				$ 26,300
Weighted Average Per Unit Fair Value (in dollars per share)		$ 127.14		$ 127.14
Expected life assumed to calculate per unit fair value per LTIP unit (in years)				5 years 8 months 12 days
Risk-free rate				1.47%
Expected price volatility				18.00%
LTIP Units [Member] | Boston Properties Limited Partnership
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP units issued (in shares)		207,181		207,181
MYLTIP 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
MYLTIP 2020 [Member] | Boston Properties Limited Partnership
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued (in shares)		203,278		203,278
LTIP and MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee and director payment per share (in dollars per share)				$ 0.25
Ltips (including vested MYLTIPS) And Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses		$ 37,100		$ 37,100
Unvested MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses		$ 15,300		$ 15,300
Weighted-average period (years)				2 years 4 months 24 days

Segment Information (Schedule O

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income attributable to the Company's common shareholders / unitholders	$ 266,525	$ 164,318	$ 764,232	$ 262,431
Preferred dividends / distributions	(2,625)	(2,625)	(5,250)	(5,250)
Noncontrolling interest-common units of the Operating Partnership	(30,197)	(19,036)	(87,525)	(30,627)
Noncontrolling interest in property partnerships	767	(17,482)	(18,719)	(36,312)
Interest expense	(107,142)	(102,357)	(208,733)	(203,366)
Company's share of net operating income from joint ventures	(402,404)	(454,301)	(874,057)	(902,016)
Depreciation and amortization expense	(178,188)	(177,411)	(349,282)	(342,005)
Transaction costs	(332)	(417)	(947)	(877)
General and administrative expense	(37,743)	(35,071)	(74,197)	(76,833)
Gains (losses) from investments in securities	(4,552)	(1,165)	893	(4,134)
Interest and other income (loss)	(1,305)	(3,615)	(4,322)	(7,368)
Gains on sales of real estate	(203,767)	(1,686)	(613,932)	(781)
Income from unconsolidated joint ventures	(1,832)	(47,964)	(1,463)	(48,177)
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	266,525	164,318	764,232	262,431
Preferred dividends / distributions	2,625	2,625	5,250	5,250
Noncontrolling interest-common units of the Operating Partnership	30,197	19,036	87,525	30,627
Noncontrolling interest in property partnerships	(767)	17,482	18,719	36,312
Interest expense	107,142	102,357	208,733	203,366
Impairment losses	0	0	0	24,038
Depreciation and amortization expense	178,188	177,411	349,282	342,005
Transaction costs	332	417	947	877
Operating expense	2,484	2,403	5,721	5,798
General and administrative expense	37,743	35,071	74,197	76,833
Gains (losses) from investments in securities	4,552	1,165	(893)	4,134
Interest and other income (loss)	1,305	3,615	4,322	7,368
Gains on sales of real estate	203,767	1,686	613,932	781
Income from unconsolidated joint ventures	1,832	47,964	1,463	48,177
Other revenue	2,484	2,403	5,721	5,798
Net Operating Income	397,888	433,454	850,638	859,433
Unconsolidated Joint Ventures [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense	(23,306)	(20,803)	(45,889)	(41,560)
Company's share of net operating income from joint ventures	(27,911)	(24,715)	(56,669)	(50,064)
Depreciation and amortization expense	(37,390)	(24,818)	(69,425)	(53,464)
Gains on sales of real estate	(11,720)	(34,572)	(11,720)	(34,572)
Income from unconsolidated joint ventures	(1,832)	(47,964)	(1,463)	(48,177)
Unconsolidated Joint Ventures [Member] | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Company's share of net operating income from joint ventures	27,911	24,715	56,669	50,064
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	301,975	185,715	868,308	299,097
Preferred dividends / distributions	(2,625)	(2,625)	(5,250)	(5,250)
Noncontrolling interest in property partnerships	767	(17,482)	(18,719)	(36,312)
Interest expense	(107,142)	(102,357)	(208,733)	(203,366)
Depreciation and amortization expense	(176,409)	(175,199)	(345,694)	(337,881)
Transaction costs	(332)	(417)	(947)	(877)
General and administrative expense	(37,743)	(35,071)	(74,197)	(76,833)
Gains (losses) from investments in securities	(4,552)	(1,165)	893	(4,134)
Interest and other income (loss)	(1,305)	(3,615)	(4,322)	(7,368)
Gains on sales of real estate	(207,241)	(1,835)	(626,895)	(930)
Income from unconsolidated joint ventures	(1,832)	(47,964)	(1,463)	(48,177)
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	301,975	185,715	868,308	299,097
Preferred dividends / distributions	2,625	2,625	5,250	5,250
Noncontrolling interest in property partnerships	(767)	17,482	18,719	36,312
Interest expense	107,142	102,357	208,733	203,366
Impairment losses	0	0	0	22,272
Depreciation and amortization expense	176,409	175,199	345,694	337,881
Transaction costs	332	417	947	877
Operating expense	2,484	2,403	5,721	5,798
General and administrative expense	37,743	35,071	74,197	76,833
Gains (losses) from investments in securities	4,552	1,165	(893)	4,134
Interest and other income (loss)	1,305	3,615	4,322	7,368
Gains on sales of real estate	207,241	1,835	626,895	930
Income from unconsolidated joint ventures	1,832	47,964	1,463	48,177
Other revenue	2,484	2,403	5,721	5,798
Net Operating Income	397,888	433,454	850,638	859,433
Management Service [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other revenue	(8,125)	(9,986)	(16,004)	(19,263)
Management Service [Member] | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other revenue	8,125	9,986	16,004	19,263
Management Service [Member] | Boston Properties Limited Partnership
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating expense	(2,484)	(2,403)	(5,721)	(5,798)
Other revenue	(8,125)	(9,986)	(16,004)	(19,263)
Management Service [Member] | Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other revenue	8,125	9,986	16,004	19,263
Noncontrolling interest - property partnerships [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Company's share of net operating income from joint ventures	32,427	45,562	80,088	92,647
Noncontrolling interest - property partnerships [Member] | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Company's share of net operating income from joint ventures	32,427	45,562	80,088	92,647
Noncontrolling interest - property partnerships [Member] | Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Company's share of net operating income from joint ventures	$ 32,427	$ 45,562	$ 80,088	$ 92,647

Segment Information (Schedule_2

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 634,663	$ 697,509	$ 1,359,322	$ 1,393,951
Rental Revenue: Residential	[1]	9,402	8,999	19,358	16,714
Rental Revenue Total	[1]	$ 644,164	$ 721,352	$ 1,385,604	$ 1,434,447
Rental Revenue: % of Grand Totals	[1]	100.00%	100.00%	100.00%	100.00%
Rental Expenses: Class A Office		$ 235,822	$ 253,849	$ 494,724	$ 507,592
Rental Expenses: Residential		3,965	4,122	8,029	7,896
Rental Expenses: Total		$ 241,760	$ 267,051	$ 511,547	$ 532,431
Rental Expenses: % Of Grand Totals		100.00%	100.00%	100.00%	100.00%
Net Operating Income		$ 402,404	$ 454,301	$ 874,057	$ 902,016
Net Operating Income: % of Grand Totals		100.00%	100.00%	100.00%	100.00%
Company's Share of Net Operating Income: % of Grand Totals		100.00%	100.00%	100.00%	100.00%
Total revenue		$ 654,773	$ 733,741	$ 1,407,329	$ 1,459,508
Boston [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	218,351	217,961	457,849	435,372
Rental Revenue: Residential	[1]	3,401	3,222	7,469	5,923
Rental Revenue Total	[1]	$ 221,851	$ 236,027	$ 472,242	$ 465,077
Rental Revenue: % of Grand Totals	[1]	34.43%	32.72%	34.09%	32.42%
Rental Expenses: Class A Office		$ 75,694	$ 77,660	$ 158,239	$ 157,160
Rental Expenses: Residential		1,235	1,279	2,575	2,485
Rental Expenses: Total		$ 78,902	$ 88,019	$ 169,608	$ 176,588
Rental Expenses: % Of Grand Totals		32.64%	32.96%	33.16%	33.17%
Net Operating Income		$ 142,949	$ 148,008	$ 302,634	$ 288,489
Net Operating Income: % of Grand Totals		35.52%	32.58%	34.63%	31.98%
Company's Share of Net Operating Income: % of Grand Totals		33.92%	32.01%	33.76%	31.49%
Los Angeles [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 0	$ 0	$ 0	$ 0
Rental Revenue: Residential	[1]	0	0	0	0
Rental Revenue Total	[1]	$ 0	$ 0	$ 0	$ 0
Rental Revenue: % of Grand Totals	[1]	0.00%	0.00%	0.00%	0.00%
Rental Expenses: Class A Office		$ 0	$ 0	$ 0	$ 0
Rental Expenses: Residential		0	0	0	0
Rental Expenses: Total		$ 0	$ 0	$ 0	$ 0
Rental Expenses: % Of Grand Totals		0.00%	0.00%	0.00%	0.00%
Net Operating Income		$ 0	$ 0	$ 0	$ 0
Net Operating Income: % of Grand Totals		0.00%	0.00%	0.00%	0.00%
Company's Share of Net Operating Income: % of Grand Totals		3.78%	3.57%	3.64%	3.63%
New York [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 204,242	$ 251,556	$ 459,528	$ 510,187
Rental Revenue: Residential	[1]	0	0	0	0
Rental Revenue Total	[1]	$ 204,242	$ 251,556	$ 459,528	$ 510,187
Rental Revenue: % of Grand Totals	[1]	31.71%	34.87%	33.16%	35.56%
Rental Expenses: Class A Office		$ 88,367	$ 96,809	$ 187,507	$ 193,780
Rental Expenses: Residential		0	0	0	0
Rental Expenses: Total		$ 88,367	$ 96,809	$ 187,507	$ 193,780
Rental Expenses: % Of Grand Totals		36.54%	36.25%	36.65%	36.39%
Net Operating Income		$ 115,875	$ 154,747	$ 272,021	$ 316,407
Net Operating Income: % of Grand Totals		28.80%	34.06%	31.12%	35.08%
Company's Share of Net Operating Income: % of Grand Totals		23.84%	27.90%	25.24%	28.75%
San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 128,233	$ 131,506	$ 264,972	$ 255,561
Rental Revenue: Residential	[1]	0	0	0	0
Rental Revenue Total	[1]	$ 128,233	$ 131,506	$ 264,972	$ 255,561
Rental Revenue: % of Grand Totals	[1]	19.91%	18.23%	19.12%	17.82%
Rental Expenses: Class A Office		$ 39,081	$ 43,708	$ 81,650	$ 84,833
Rental Expenses: Residential		0	0	0	0
Rental Expenses: Total		$ 39,081	$ 43,708	$ 81,650	$ 84,833
Rental Expenses: % Of Grand Totals		16.17%	16.37%	15.96%	15.93%
Net Operating Income		$ 89,152	$ 87,798	$ 183,322	$ 170,728
Net Operating Income: % of Grand Totals		22.15%	19.33%	20.97%	18.93%
Company's Share of Net Operating Income: % of Grand Totals		23.44%	20.26%	22.41%	19.81%
Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 83,837	$ 96,486	$ 176,973	$ 192,831
Rental Revenue: Residential	[1]	6,001	5,777	11,889	10,791
Rental Revenue Total	[1]	$ 89,838	$ 102,263	$ 188,862	$ 203,622
Rental Revenue: % of Grand Totals	[1]	13.95%	14.18%	13.63%	14.20%
Rental Expenses: Class A Office		$ 32,680	$ 35,672	$ 67,328	$ 71,819
Rental Expenses: Residential		2,730	2,843	5,454	5,411
Rental Expenses: Total		$ 35,410	$ 38,515	$ 72,782	$ 77,230
Rental Expenses: % Of Grand Totals		14.65%	14.42%	14.23%	14.51%
Net Operating Income		$ 54,428	$ 63,748	$ 116,080	$ 126,392
Net Operating Income: % of Grand Totals		13.53%	14.03%	13.28%	14.01%
Company's Share of Net Operating Income: % of Grand Totals		15.02%	16.26%	14.95%	16.32%
Hotel [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	$ 99	$ 14,844	$ 6,924	$ 23,782
Operating expense		1,973	9,080	8,794	16,943
Hotel [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	99	14,844	6,924	23,782
Operating expense		1,973	9,080	8,794	16,943
Hotel [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0	0	0
Operating expense		0	0	0	0
Hotel [Member] | New York [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0	0	0
Operating expense		0	0	0	0
Hotel [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0	0	0
Operating expense		0	0	0	0
Hotel [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0	0	0
Operating expense		0	0	0	0
Noncontrolling interest - property partnerships [Member]
Segment Reporting Information [Line Items]
Net Operating Income		(32,427)	(45,562)	(80,088)	(92,647)
Noncontrolling interest - property partnerships [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net Operating Income		(10,576)	(10,031)	(21,239)	(19,404)
Noncontrolling interest - property partnerships [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net Operating Income		0	0	0	0
Noncontrolling interest - property partnerships [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net Operating Income		(21,851)	(35,531)	(58,849)	(72,795)
Noncontrolling interest - property partnerships [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net Operating Income		0	0	0	(448)
Noncontrolling interest - property partnerships [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net Operating Income		0	0	0	0
Unconsolidated Joint Ventures [Member]
Segment Reporting Information [Line Items]
Net Operating Income		27,911	24,715	56,669	50,064
Total revenue	[2]	89,563	80,204	182,766	163,159
Unconsolidated Joint Ventures [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net Operating Income		2,627	818	5,726	1,590
Unconsolidated Joint Ventures [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net Operating Income		15,026	15,454	30,956	31,162
Unconsolidated Joint Ventures [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net Operating Income		815	1,696	1,571	3,482
Unconsolidated Joint Ventures [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net Operating Income		4,127	0	7,286	0
Unconsolidated Joint Ventures [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net Operating Income		5,316	6,747	11,130	13,830
Company's Share [Member]
Segment Reporting Information [Line Items]
Net Operating Income		397,888	433,454	850,638	859,433
Company's Share [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net Operating Income		135,000	138,795	287,121	270,675
Company's Share [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net Operating Income		15,026	15,454	30,956	31,162
Company's Share [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net Operating Income		94,839	120,912	214,743	247,094
Company's Share [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net Operating Income		93,279	87,798	190,608	170,280
Company's Share [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net Operating Income		$ 59,744	$ 70,495	$ 127,210	$ 140,222
[1]	Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.
[2]	Includes straight-line rent adjustments of approximately $8.5 million and $7.6 million for the three months ended June 30, 2020 and 2019, respectively, and $18.2 million and $13.4 million for the six months ended June 30, 2020 and 2019, respectively.

Segment Information Narrative (

Segment Information Narrative (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Segment Reporting Information [Line Items]
Write-off for accounts receivable	$ 18,000,000	$ 18,900,000
Write-off for accrued rent	35,900,000	37,400,000
Decrease in parking and other revenue primarily related to COVID-19	$ 12,400,000	$ 12,800,000

Subsequent Events (Details)

Subsequent Events (Details) $ in Thousands	Jul. 23, 2020USD ($)aft²	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)
Subsequent Event [Line Items]
Payments to Acquire Equity Method Investments		$ 106,168	$ 50,068
Beach City Media Center [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Ownership Percentage	50.00%
Net Rentable Area (in sf) | ft²	275,000
Payments to Acquire Equity Method Investments	$ 21,200
Area of Land | a	6.4