Boston Properties LTD Partnership 10-Q 11 May 20 2020 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - $ / shares	3 Months Ended
	Mar. 31, 2020	May 05, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 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	Q1
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		155,369,141
Boston Properties Limited Partnership
Entity Information [Line Items]
Document Type	10-Q
Document Period End Date	Mar. 31, 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	Q1
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	Depository 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	Mar. 31, 2020	Dec. 31, 2019
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,564,762 and $6,497,031 at March 31, 2020 and December 31, 2019, respectively)	$ 22,342,209	$ 22,502,976
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at March 31, 2020 and December 31, 2019, respectively)	237,394	237,394
Right of use assets - operating leases	148,057	148,640
Less: accumulated depreciation (amounts related to VIEs of $(1,082,486) and$(1,058,495) at March 31, 2020 and December 31, 2019, respectively)	(5,209,487)	(5,266,798)
Total real estate	17,518,173	17,622,212
Cash and cash equivalents (amounts related to VIEs of $268,415 and $280,033 at March 31, 2020 and December 31, 2019, respectively)	660,733	644,950
Cash held in escrows	197,845	46,936
Investments in securities	28,101	36,747
Tenant and other receivables, net (amounts related to VIEs of $19,954 and $28,918 at March 31, 2020 and December 31, 2019, respectively)	89,431	112,807
Related party note receivable, net	78,800	80,000
Note receivable, net	15,794	15,920
Accrued rental income, net (amounts related to VIEs of $308,482 and $298,318 at March 31, 2020 and December 31, 2019, respectively)	1,059,677	1,038,788
Deferred charges, net (amounts related to VIEs of $205,688 and $214,769 at March 31, 2020 and December 31, 2019, respectively)	667,076	689,213
Prepaid expenses and other assets (amounts related to VIEs of $52,641 and $20,931 at March 31, 2020 and December 31, 2019, respectively)	136,730	41,685
Investments in unconsolidated joint ventures	1,377,338	955,647
Total assets	21,829,698	21,284,905
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,916,068 and $2,918,806 at March 31, 2020 and December 31, 2019, respectively)	2,919,157	2,922,408
Unsecured senior notes, net	8,393,009	8,390,459
Unsecured line of credit	250,000	0
Unsecured term loan, net	499,058	498,939
Lease liabilities - finance leases (amounts related to VIEs of $20,198 and $20,189 at March 31, 2020 and December 31, 2019, respectively)	227,067	224,042
Lease liabilities - operating leases	200,573	200,180
Accounts payable and accrued expenses (amounts related to VIEs of $28,437 and $45,777 at March 31, 2020 and December 31, 2019, respectively)	293,831	377,553
Dividends and distributions payable	171,026	170,713
Accrued interest payable	82,388	90,016
Other liabilities (amounts related to VIEs of $142,381 and $140,110 at March 31, 2020 and December 31, 2019, respectively)	366,852	387,994
Total liabilities	13,402,961	13,262,304
Commitments and contingencies	0	0
Redeemable deferred stock units— 63,475 and 60,676 units outstanding at redemption value at March 31, 2020 and December 31, 2019, respectively	5,854	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 March 31, 2020 and December 31, 2019, respectively	200,000	200,000
Common stock, $0.01 par value, 250,000,000 shares authorized, 155,393,455 and 154,869,198 issued and 155,314,555 and 154,790,298 outstanding at March 31, 2020 and December 31, 2019, respectively	1,553	1,548
Additional paid-in capital	6,321,475	6,294,719
Dividends in excess of earnings	(416,740)	(760,523)
Treasury common stock at cost, 78,900 shares at March 31, 2020 and December 31, 2019	(2,722)	(2,722)
Accumulated other comprehensive loss	(55,700)	(48,335)
Total stockholders' equity attributable to Boston Properties, Inc.	6,047,866	5,684,687
Noncontrolling interests:
Common units of the Operating Partnership	636,572	600,860
Property partnerships	1,736,445	1,728,689
Total equity / capital	8,420,883	8,014,236
Total liabilities and equity / capital	21,829,698	21,284,905
Boston Properties Limited Partnership
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,564,762 and $6,497,031 at March 31, 2020 and December 31, 2019, respectively)	21,959,932	22,107,755
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at March 31, 2020 and December 31, 2019, respectively)	237,394	237,394
Right of use assets - operating leases	148,057	148,640
Less: accumulated depreciation (amounts related to VIEs of $(1,082,486) and$(1,058,495) at March 31, 2020 and December 31, 2019, respectively)	(5,107,243)	(5,162,908)
Total real estate	17,238,140	17,330,881
Cash and cash equivalents (amounts related to VIEs of $268,415 and $280,033 at March 31, 2020 and December 31, 2019, respectively)	660,733	644,950
Cash held in escrows	197,845	46,936
Investments in securities	28,101	36,747
Tenant and other receivables, net (amounts related to VIEs of $19,954 and $28,918 at March 31, 2020 and December 31, 2019, respectively)	89,431	112,807
Related party note receivable, net	78,800	80,000
Note receivable, net	15,794	15,920
Accrued rental income, net (amounts related to VIEs of $308,482 and $298,318 at March 31, 2020 and December 31, 2019, respectively)	1,059,677	1,038,788
Deferred charges, net (amounts related to VIEs of $205,688 and $214,769 at March 31, 2020 and December 31, 2019, respectively)	667,076	689,213
Prepaid expenses and other assets (amounts related to VIEs of $52,641 and $20,931 at March 31, 2020 and December 31, 2019, respectively)	136,730	41,685
Investments in unconsolidated joint ventures	1,377,338	955,647
Total assets	21,549,665	20,993,574
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,916,068 and $2,918,806 at March 31, 2020 and December 31, 2019, respectively)	2,919,157	2,922,408
Unsecured senior notes, net	8,393,009	8,390,459
Unsecured line of credit	250,000	0
Unsecured term loan, net	499,058	498,939
Lease liabilities - finance leases (amounts related to VIEs of $20,198 and $20,189 at March 31, 2020 and December 31, 2019, respectively)	227,067	224,042
Lease liabilities - operating leases	200,573	200,180
Accounts payable and accrued expenses (amounts related to VIEs of $28,437 and $45,777 at March 31, 2020 and December 31, 2019, respectively)	293,831	377,553
Dividends and distributions payable	171,026	170,713
Accrued interest payable	82,388	90,016
Other liabilities (amounts related to VIEs of $142,381 and $140,110 at March 31, 2020 and December 31, 2019, respectively)	366,852	387,994
Total liabilities	13,402,961	13,262,304
Commitments and contingencies	0	0
Redeemable deferred stock units— 63,475 and 60,676 units outstanding at redemption value at March 31, 2020 and December 31, 2019, respectively	5,854	8,365
Redeemable partnership units— 16,421,888 and 16,764,466 common units and 1,343,299 and 1,143,215 long term incentive units outstanding at redemption value at March 31, 2020 and December 31, 2019, respectively	1,639,855	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 March 31, 2020 and December 31, 2019, respectively	193,623	193,623
Boston Properties Limited Partnership partners’ capital— 1,730,797 and 1,726,980 general partner units and 153,583,758 and 153,063,318 limited partner units outstanding at March 31, 2020 and December 31, 2019, respectively	4,626,627	3,380,175
Accumulated other comprehensive loss	(55,700)	(48,335)
Total partners’ capital	4,764,550	3,525,463
Noncontrolling interests in property partnerships	1,736,445	1,728,689
Noncontrolling interests:
Total equity / capital	6,500,995	5,254,152
Total liabilities and equity / capital	$ 21,549,665	$ 20,993,574

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
General Partners' Capital Account, Units Outstanding (in units)	1,730,797
Limited Partners' Capital Account, Units Outstanding (in units)	153,583,758
Excess stock, par value	$ 0.01	$ 0.01
Excess stock, shares authorized	150,000,000	150,000,000
Excess stock, shares issued	0	0
Excess stock, shares outstanding	0	0
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	155,393,455	154,869,198
Common stock, shares outstanding	155,314,555	154,790,298
Treasury common stock at cost, shares	78,900	78,900
Reddemable deferred stock units, units	63,475	60,676
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,564,762 and $6,497,031 at March 31, 2020 and December 31, 2019, respectively)	$ 22,342,209	$ 22,502,976
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at March 31, 2020 and December 31, 2019, respectively)	237,394	237,394
Less: accumulated depreciation (amounts related to VIEs of $(1,082,486) and$(1,058,495) at March 31, 2020 and December 31, 2019, respectively)	(5,209,487)	(5,266,798)
Cash and cash equivalents (amounts related to VIEs of $268,415 and $280,033 at March 31, 2020 and December 31, 2019, respectively)	660,733	644,950
Cash held in escrows	197,845	46,936
Tenant and other receivables, net (amounts related to VIEs of $19,954 and $28,918 at March 31, 2020 and December 31, 2019, respectively)	89,431	112,807
Accrued rental income, net (amounts related to VIEs of $308,482 and $298,318 at March 31, 2020 and December 31, 2019, respectively)	1,059,677	1,038,788
Deferred charges, net (amounts related to VIEs of $205,688 and $214,769 at March 31, 2020 and December 31, 2019, respectively)	667,076	689,213
Prepaid expenses and other assets (amounts related to VIEs of $52,641 and $20,931 at March 31, 2020 and December 31, 2019, respectively)	136,730	41,685
Mortgage notes payable, net (amounts related to VIEs of $2,916,068 and $2,918,806 at March 31, 2020 and December 31, 2019, respectively)	2,919,157	2,922,408
Lease liabilities - finance leases (amounts related to VIEs of $20,198 and $20,189 at March 31, 2020 and December 31, 2019, respectively)	227,067	224,042
Accounts payable and accrued expenses (amounts related to VIEs of $28,437 and $45,777 at March 31, 2020 and December 31, 2019, respectively)	293,831	377,553
Other liabilities (amounts related to VIEs of $142,381 and $140,110 at March 31, 2020 and December 31, 2019, respectively)	$ 366,852	$ 387,994
Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	92,000	92,000
Series B Dividend Rate Percentage	5.25%	5.25%
Preferred stock / units, shares / units issued (in shares / units)	80,000	80,000
Series B Liquidation Preference Per Share/ Unit	$ 2,500	$ 2,500
Preferred stock / units, shares / units outstanding (in shares / units)	80,000	80,000
Boston Properties Limited Partnership
Redeemable Partnership Units Common Units Shares Outstanding (in units)	16,421,888	16,764,466
Redeemable Partnership Units Common Units Long Term Incentive Units At Redemption Value Units Outstanding (in units)	1,343,299	1,143,215
General Partners' Capital Account, Units Outstanding (in units)	1,730,797	1,726,980
Limited Partners' Capital Account, Units Outstanding (in units)	153,583,758	153,063,318
Reddemable deferred stock units, units	63,475	60,676
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,564,762 and $6,497,031 at March 31, 2020 and December 31, 2019, respectively)	$ 21,959,932	$ 22,107,755
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at March 31, 2020 and December 31, 2019, respectively)	237,394	237,394
Less: accumulated depreciation (amounts related to VIEs of $(1,082,486) and$(1,058,495) at March 31, 2020 and December 31, 2019, respectively)	(5,107,243)	(5,162,908)
Cash and cash equivalents (amounts related to VIEs of $268,415 and $280,033 at March 31, 2020 and December 31, 2019, respectively)	660,733	644,950
Cash held in escrows	197,845	46,936
Tenant and other receivables, net (amounts related to VIEs of $19,954 and $28,918 at March 31, 2020 and December 31, 2019, respectively)	89,431	112,807
Accrued rental income, net (amounts related to VIEs of $308,482 and $298,318 at March 31, 2020 and December 31, 2019, respectively)	1,059,677	1,038,788
Deferred charges, net (amounts related to VIEs of $205,688 and $214,769 at March 31, 2020 and December 31, 2019, respectively)	667,076	689,213
Prepaid expenses and other assets (amounts related to VIEs of $52,641 and $20,931 at March 31, 2020 and December 31, 2019, respectively)	136,730	41,685
Mortgage notes payable, net (amounts related to VIEs of $2,916,068 and $2,918,806 at March 31, 2020 and December 31, 2019, respectively)	2,919,157	2,922,408
Lease liabilities - finance leases (amounts related to VIEs of $20,198 and $20,189 at March 31, 2020 and December 31, 2019, respectively)	227,067	224,042
Accounts payable and accrued expenses (amounts related to VIEs of $28,437 and $45,777 at March 31, 2020 and December 31, 2019, respectively)	293,831	377,553
Other liabilities (amounts related to VIEs of $142,381 and $140,110 at March 31, 2020 and December 31, 2019, respectively)	$ 366,852	$ 387,994
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock / Unit [Member]
Series B Dividend Rate Percentage	5.25%	5.25%
Preferred stock / units, shares / units issued (in shares / units)	80,000	80,000
Series B Liquidation Preference Per Share/ Unit	$ 2,500	$ 2,500
Preferred stock / units, shares / units outstanding (in shares / units)	80,000	80,000
Variable Interest Entity, Primary Beneficiary [Member]
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,564,762 and $6,497,031 at March 31, 2020 and December 31, 2019, respectively)	$ 6,564,762	$ 6,497,031
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at March 31, 2020 and December 31, 2019, respectively)	21,000	21,000
Less: accumulated depreciation (amounts related to VIEs of $(1,082,486) and$(1,058,495) at March 31, 2020 and December 31, 2019, respectively)	(1,082,486)	(1,058,495)
Cash and cash equivalents (amounts related to VIEs of $268,415 and $280,033 at March 31, 2020 and December 31, 2019, respectively)	268,415	280,033
Tenant and other receivables, net (amounts related to VIEs of $19,954 and $28,918 at March 31, 2020 and December 31, 2019, respectively)	19,954	28,918
Accrued rental income, net (amounts related to VIEs of $308,482 and $298,318 at March 31, 2020 and December 31, 2019, respectively)	308,482	298,318
Deferred charges, net (amounts related to VIEs of $205,688 and $214,769 at March 31, 2020 and December 31, 2019, respectively)	205,688	214,769
Prepaid expenses and other assets (amounts related to VIEs of $52,641 and $20,931 at March 31, 2020 and December 31, 2019, respectively)	52,641	20,931
Mortgage notes payable, net (amounts related to VIEs of $2,916,068 and $2,918,806 at March 31, 2020 and December 31, 2019, respectively)	2,916,068	2,918,806
Lease liabilities - finance leases (amounts related to VIEs of $20,198 and $20,189 at March 31, 2020 and December 31, 2019, respectively)	20,198	20,189
Accounts payable and accrued expenses (amounts related to VIEs of $28,437 and $45,777 at March 31, 2020 and December 31, 2019, respectively)	28,437	45,777
Other liabilities (amounts related to VIEs of $142,381 and $140,110 at March 31, 2020 and December 31, 2019, respectively)	142,381	140,110
Variable Interest Entity, Primary Beneficiary [Member] | Boston Properties Limited Partnership
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,564,762 and $6,497,031 at March 31, 2020 and December 31, 2019, respectively)	6,564,762	6,497,031
Right of use assets - finance leases (amounts related to VIEs of $21,000 and $21,000 at March 31, 2020 and December 31, 2019, respectively)	21,000	21,000
Less: accumulated depreciation (amounts related to VIEs of $(1,082,486) and$(1,058,495) at March 31, 2020 and December 31, 2019, respectively)	(1,082,486)	(1,058,495)
Cash and cash equivalents (amounts related to VIEs of $268,415 and $280,033 at March 31, 2020 and December 31, 2019, respectively)	268,415	280,033
Tenant and other receivables, net (amounts related to VIEs of $19,954 and $28,918 at March 31, 2020 and December 31, 2019, respectively)	19,954	28,918
Accrued rental income, net (amounts related to VIEs of $308,482 and $298,318 at March 31, 2020 and December 31, 2019, respectively)	308,482	298,318
Deferred charges, net (amounts related to VIEs of $205,688 and $214,769 at March 31, 2020 and December 31, 2019, respectively)	205,688	214,769
Prepaid expenses and other assets (amounts related to VIEs of $52,641 and $20,931 at March 31, 2020 and December 31, 2019, respectively)	52,641	20,931
Mortgage notes payable, net (amounts related to VIEs of $2,916,068 and $2,918,806 at March 31, 2020 and December 31, 2019, respectively)	2,916,068	2,918,806
Lease liabilities - finance leases (amounts related to VIEs of $20,198 and $20,189 at March 31, 2020 and December 31, 2019, respectively)	20,198	20,189
Accounts payable and accrued expenses (amounts related to VIEs of $28,437 and $45,777 at March 31, 2020 and December 31, 2019, respectively)	28,437	45,777
Other liabilities (amounts related to VIEs of $142,381 and $140,110 at March 31, 2020 and December 31, 2019, respectively)	$ 142,381	$ 140,110

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Revenue
Lease		$ 710,111	$ 679,251
Total revenue		752,556	725,767
Expenses
Rental		262,966	257,517
General and administrative		36,454	41,762
Transaction costs		615	460
Depreciation and amortization		171,094	164,594
Total expenses		481,187	475,591
Other income (expense)
Income (loss) from unconsolidated joint ventures		(369)	213
Gains (losses) on sales of real estate		410,165	(905)
Interest and other income		3,017	3,753
Gains (losses) from investments in securities		(5,445)	2,969
Impairment losses		0	(24,038)
Interest expense		(101,591)	(101,009)
Net income		577,146	131,159
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships		(19,486)	(18,830)
Noncontrolling interest - common units of the Operating Partnership		(57,539)	(11,599)
Net income attributable to the Company		500,121	100,730
Preferred dividends / distributions		(2,625)	(2,625)
Net income attributable to the Company's common shareholders / unitholders		$ 497,496	$ 98,105
Earnings Per Share After Allccation of Undistributed Earnings to Particiapting Securities Basic (dollars per share)		$ 3.20	$ 0.63
Basic earnings per common share / unit attributable to the Company
Net income (in dollars per share / unit)		$ 3.21	$ 0.63
Weighted average number of common shares / units outstanding (in shares / units)		155,011	154,525
Diluted earnings per common share / unit attributable to the Company
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)		$ 3.20	$ 0.63
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)		155,258	154,844
Boston Properties Limited Partnership
Revenue
Lease		$ 710,111	$ 679,251
Total revenue		752,556	725,767
Expenses
Rental		262,966	257,517
General and administrative		36,454	41,762
Transaction costs		615	460
Depreciation and amortization		169,285	162,682
Total expenses		479,378	473,679
Other income (expense)
Income (loss) from unconsolidated joint ventures		(369)	213
Gains (losses) on sales of real estate		419,654	(905)
Interest and other income		3,017	3,753
Gains (losses) from investments in securities		(5,445)	2,969
Impairment losses		0	(22,272)
Interest expense		(101,591)	(101,009)
Net income		588,444	134,837
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships		(19,486)	(18,830)
Net income attributable to the Company		568,958	116,007
Preferred dividends / distributions		(2,625)	(2,625)
Net income attributable to the Company's common shareholders / unitholders		$ 566,333	$ 113,382
Earnings Per Share After Allccation of Undistributed Earnings to Particiapting Securities Basic (dollars per share)		$ 3.28	$ 0.66
Basic earnings per common share / unit attributable to the Company
Net income (in dollars per share / unit)		$ 3.28	$ 0.66
Weighted average number of common shares / units outstanding (in shares / units)		172,549	172,131
Diluted earnings per common share / unit attributable to the Company
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)		$ 3.27	$ 0.66
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)		172,796	172,450
Parking and Other [Member]
Revenue
Other revenue		$ 24,504	$ 24,906
Parking and Other [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		24,504	24,906
Hotel [Member]
Revenue
Other revenue	[1]	6,825	8,938
Expenses
Operating expense		6,821	7,863
Hotel [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		6,825	8,938
Expenses
Operating expense		6,821	7,863
Real Estate, Other [Member]
Revenue
Other revenue		3,237	3,395
Real Estate, Other [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		3,237	3,395
Management Service [Member]
Revenue
Other revenue		7,879	9,277
Expenses
Operating expense		3,237	3,395
Management Service [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		7,879	9,277
Expenses
Operating expense		$ 3,237	$ 3,395
[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
		Mar. 31, 2020	Mar. 31, 2019
Net income		$ 577,146	$ 131,159
Other comprehensive income (loss):
Effective portion of interest rate contracts		(9,720)	(2,628)
Amortization of interest rate contracts	[1]	1,666	1,666
Other comprehensive income (loss)		(8,054)	(962)
Comprehensive Income		569,092	130,197
Comprehensive income attributable to noncontrolling interests		(77,025)	(30,429)
Other comprehensive income (loss) attributable to noncontrolling interests		689	(31)
Comprehensive income attributable to the Company		492,756	99,737
Boston Properties Limited Partnership
Net income		588,444	134,837
Other comprehensive income (loss):
Effective portion of interest rate contracts		(9,720)	(2,628)
Amortization of interest rate contracts	[2]	1,666	1,666
Other comprehensive income (loss)		(8,054)	(962)
Comprehensive Income		580,390	133,875
Comprehensive income attributable to noncontrolling interests		(19,630)	(18,974)
Comprehensive income attributable to the Company		$ 560,760	$ 114,901
[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		14,000
Redemption of operating partnership units to common stock, value	0	$ 0		492				(492)
Allocated net income for the year	131,159				100,730			11,599	18,830
Dividends/distributions declared	166,600				(149,415)			(17,185)
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		39,000
Net activity from stock option and incentive plan, value	16,469			3,059				13,410
Contributions from noncontrolling interests in property partnerships	4,387								4,387
Distributions to noncontrolling interests in property partnerships	(24,128)								(24,128)
Effective portion of interest rate contracts	(2,628)						(2,359)	(269)	0
Amortization of interest rate contracts	1,666						1,366	156	144
Reallocation of noncontrolling interest				3,065				(3,065)
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
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		462,000
Redemption of operating partnership units to common stock, value	0	$ 5		15,490				(15,495)
Allocated net income for the year	577,146				500,121			57,539	19,486
Dividends/distributions declared	(172,277)				(154,833)			(17,444)
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		61,000
Net activity from stock option and incentive plan, value	23,060	$ 0		7,383				15,677
Contributions from noncontrolling interests in property partnerships	3,876								3,876
Distributions to noncontrolling interests in property partnerships	(15,750)								(15,750)
Effective portion of interest rate contracts	(9,720)						(8,732)	(988)	0
Amortization of interest rate contracts	1,666						1,367	155	144
Reallocation of noncontrolling interest	$ 0			3,558				(3,558)
Equity, shares at Mar. 31, 2020	155,314,555	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

Consolidated Statement of Capit

Consolidated Statement of Capital and Noncontrolling Interests Statement - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Common Stock, Shares, Outstanding	155,314,555		154,790,298
Cumulative effect of a change in accounting principle	$ (1,679)	$ (4,379)
Effective portion of interest rate contracts	(9,720)	(2,628)
Amortization of interest rate contracts	1,666	1,666
Contributions from noncontrolling interests in property partnerships	3,876	4,387
Distributions to noncontrolling interests in property partnerships	$ (15,750)	$ (24,128)
General Partner [Member]
Common Stock, Shares, Outstanding	1,731,000	1,725,000	1,727,000	1,722,000
Contributions, units	1,000	2,000
Conversion of redeemable partnership units	3,000	1,000
Limited Partner [Member]
Common Stock, Shares, Outstanding	153,584,000	152,790,000	153,063,000	152,736,000
Contributions, units	63,000	41,000
Conversion of redeemable partnership units	458,000	13,000
Boston Properties Limited Partnership
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 1,639,855		$ 2,468,753
Contributions from noncontrolling interests in property partnerships	3,876	$ 4,387
Partners' Capital (General and Limited Partners) [Member]
Beginning Balance	4,626,627	3,603,174	3,380,175	$ 4,054,996
Cumulative effect of a change in accounting principle	(1,505)	(3,864)
Contributions, value	6,712	4,820
Allocated net income for the period	508,794	101,783
Distributions	(152,208)	(146,790)
Unearned compensation	996	(1,388)
Conversion of redeemable partnership units, value	15,495	492
Adjustment to reflect redeemable partnership units at redemption value	868,168	(406,875)
Preferred Units [Member]
Beginning Balance	193,623	193,623	193,623	193,623
Allocated net income for the period	2,625	2,625
Distributions	(2,625)	(2,625)
Accumulated Other Comprehensive Loss [Member]
Beginning Balance	(55,700)	(48,734)	(48,335)	(47,741)
Effective portion of interest rate contracts	(8,732)	(2,359)
Amortization of interest rate contracts	1,367	1,366
Noncontrolling interest - property partnerships [Member]
Beginning Balance	1,736,445	1,710,608	1,728,689	1,711,445
Cumulative effect of a change in accounting principle	0	(70)
Allocated net income for the period	19,486	18,830
Effective portion of interest rate contracts	0	0
Amortization of interest rate contracts	144	144
Contributions from noncontrolling interests in property partnerships	3,876	4,387
Distributions to noncontrolling interests in property partnerships	(15,750)	(24,128)
Total Capital [Member]
Beginning Balance	6,500,995	5,458,671	5,254,152	5,912,323
Cumulative effect of a change in accounting principle	(1,505)	(3,934)
Contributions, value	6,712	4,820
Allocated net income for the period	530,905	123,238
Distributions	(154,833)	(149,415)
Unearned compensation	996	(1,388)
Conversion of redeemable partnership units, value	15,495	492
Adjustment to reflect redeemable partnership units at redemption value	868,168	(406,875)
Effective portion of interest rate contracts	(8,732)	(2,359)
Amortization of interest rate contracts	1,511	1,510
Contributions from noncontrolling interests in property partnerships	3,876	4,387
Distributions to noncontrolling interests in property partnerships	(15,750)	(24,128)
Noncontrolling interest - Redeemable partnership units [Member]
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	1,639,855	2,414,240	$ 2,468,753	$ 2,000,591
Cumulative effect of a change in accounting principle	(174)	(445)
Contributions, value	39,741	34,400
Allocated net income for the period	57,539	11,599
Distributions	(17,444)	(17,185)
Unearned compensation	(24,064)	(20,990)
Conversion of redeemable partnership units, value	(15,495)	(492)
Adjustment to reflect redeemable partnership units at redemption value	(868,168)	406,875
Effective portion of interest rate contracts	(988)	(269)
Amortization of interest rate contracts	$ 155	$ 156

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 577,146	$ 131,159
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	171,094	164,594
Amortization of right of use assets - operating leases	583	605
Impairment loss	0	24,038
Non-cash compensation expense	17,525	15,050
Loss (income) from unconsolidated joint ventures	369	(213)
Distributions of net cash flow from operations of unconsolidated joint ventures	5,917	2,650
Losses (gains) from investments in securities	5,445	(2,969)
Non-cash portion of interest expense	5,646	5,447
(Gains) losses on sales of real estate	(410,165)	905
Change in assets and liabilities:
Tenant and other receivables, net	17,784	(14,000)
Note receivable, net	(128)	(125)
Accrued rental income, net	(27,285)	(15,570)
Prepaid expenses and other assets	(93,819)	(68,554)
Lease liabilities - operating leases	393	370
Accounts payable and accrued expenses	(48,591)	258
Accrued interest payable	(7,644)	(160)
Other liabilities	(21,296)	(17,831)
Tenant leasing costs	(17,777)	(18,420)
Total adjustments	(401,949)	76,075
Net cash provided by operating activities	175,197	207,234
Cash flows from investing activities:
Acquisition of real estate	0	(43,061)
Construction in progress	(143,160)	(85,632)
Building and other capital improvements	(39,154)	(32,719)
Tenant improvements	(64,172)	(54,242)
Proceeds from sales of real estate	259,489	20,019
Capital contributions to unconsolidated joint ventures	(89,997)	(26,995)
Investments in securities, net	3,201	(885)
Net cash used in investing activities	(73,793)	(223,515)
Cash flows from financing activities:
Repayments of mortgage notes payable	(4,212)	(5,645)
Borrowings on unsecured line of credit	265,000	50,000
Repayments of unsecured line of credit	(15,000)	(50,000)
Payments on finance lease obligations	0	(470)
Deferred financing costs	(11)	(186)
Net proceeds from equity transactions	3,349	1,792
Dividends and distributions	(171,964)	(166,362)
Contributions from noncontrolling interests in property partnerships	3,876	4,387
Distributions to noncontrolling interests in property partnerships	(15,750)	(24,128)
Net cash provided by (used in) financing activities	65,288	(190,612)
Net increase (decrease) in cash and cash equivalents and cash held in escrows	166,692	(206,893)
Cash and cash equivalents and cash held in escrows, beginning of year	691,886	639,191
Cash and cash equivalents and cash held in escrows, end of year	858,578	432,298
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	660,733	360,091
Cash held in escrows,end of period	197,845	72,207
Supplemental disclosures:
Cash paid for interest	114,696	107,094
Interest capitalized	14,149	11,813
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(38,782)	(31,640)
Change in real estate included in accounts payable and accrued expenses	(27,415)	49,689
Real estate acquired through capital leases	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	171,026	165,352
Conversions of noncontrolling interests to stockholders’ equity	15,495	492
Issuance of restricted securities to employees and directors	43,104	37,428
Boston Properties Limited Partnership
Net income	588,444	134,837
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	169,285	162,682
Amortization of right of use assets - operating leases	583	605
Impairment loss	0	22,272
Non-cash compensation expense	17,525	15,050
Loss (income) from unconsolidated joint ventures	369	(213)
Distributions of net cash flow from operations of unconsolidated joint ventures	5,917	2,650
Losses (gains) from investments in securities	5,445	(2,969)
Non-cash portion of interest expense	5,646	5,447
(Gains) losses on sales of real estate	(419,654)	905
Change in assets and liabilities:
Tenant and other receivables, net	17,784	(14,000)
Note receivable, net	(128)	(125)
Accrued rental income, net	(27,285)	(15,570)
Prepaid expenses and other assets	(93,819)	(68,554)
Lease liabilities - operating leases	393	370
Accounts payable and accrued expenses	(48,591)	258
Accrued interest payable	(7,644)	(160)
Other liabilities	(21,296)	(17,831)
Tenant leasing costs	(17,777)	(18,420)
Total adjustments	(413,247)	72,397
Net cash provided by operating activities	175,197	207,234
Cash flows from investing activities:
Acquisition of real estate	0	(43,061)
Construction in progress	(143,160)	(85,632)
Building and other capital improvements	(39,154)	(32,719)
Tenant improvements	(64,172)	(54,242)
Proceeds from sales of real estate	259,489	20,019
Capital contributions to unconsolidated joint ventures	(89,997)	(26,995)
Investments in securities, net	3,201	(885)
Net cash used in investing activities	(73,793)	(223,515)
Cash flows from financing activities:
Repayments of mortgage notes payable	(4,212)	(5,645)
Borrowings on unsecured line of credit	265,000	50,000
Repayments of unsecured line of credit	(15,000)	(50,000)
Payments on finance lease obligations	0	(470)
Deferred financing costs	(11)	(186)
Net proceeds from equity transactions	3,349	1,792
Dividends and distributions	(171,964)	(166,362)
Contributions from noncontrolling interests in property partnerships	3,876	4,387
Distributions to noncontrolling interests in property partnerships	(15,750)	(24,128)
Net cash provided by (used in) financing activities	65,288	(190,612)
Net increase (decrease) in cash and cash equivalents and cash held in escrows	166,692	(206,893)
Cash and cash equivalents and cash held in escrows, beginning of year	691,886	639,191
Cash and cash equivalents and cash held in escrows, end of year	858,578	432,298
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	660,733	360,091
Cash held in escrows,end of period	197,845	72,207
Supplemental disclosures:
Cash paid for interest	114,696	107,094
Interest capitalized	14,149	11,813
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(38,782)	(31,640)
Change in real estate included in accounts payable and accrued expenses	(27,415)	49,689
Real estate acquired through capital leases	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	171,026	165,352
Conversions of noncontrolling interests to stockholders’ equity	15,495	492
Issuance Of Restricted Units To Employees And Directors	$ 43,104	$ 37,428

Organization

Organization	3 Months Ended
	Mar. 31, 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 March 31, 2020 owned an approximate 89.7% ( 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 7 and 10 ). At March 31, 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 8 ). Properties At March 31, 2020 , the Company owned or had interests in a portfolio of 196 commercial real estate properties (the “Properties”) aggregating approximately 51.8 million net rentable square feet of primarily Class A office properties, including 10 properties under construction/redevelopment totaling approximately 5.2 million net rentable square feet. At March 31, 2020 , the Properties consisted of: • 177 office properties (including eight properties under construction/redevelopment); • twelve retail properties; • six residential properties (including two properties under construction); and • one hotel.

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	3 Months Ended
	Mar. 31, 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 impact 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 March 31, 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 (i.e., excluding Boston Properties Limited Partnership’s interest) are reflected as noncontrolling interest in property partnerships in the accompanying consolidated financial statements (See Note 7 ). 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 they are categorized at (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 Note 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 4.49% 4.49% Note receivable Level 3 3.62% 3.62% Mortgage notes payable Level 3 2.82% - 3.25% 2.91% Unsecured term loan / line of credit Level 3 1.84% 1.84% 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, note 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 March 31, 2020 and December 31, 2019 (in thousands): March 31, 2020 December 31, 2019 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Related party note receivable, net $ 78,800 $ 83,707 $ 80,000 $ 81,931 Note receivable, net 15,794 15,593 15,920 14,978 Total $ 94,594 $ 99,300 $ 95,920 $ 96,909 Mortgage notes payable, net $ 2,919,157 $ 3,054,533 $ 2,922,408 $ 2,984,956 Unsecured senior notes, net 8,393,009 8,449,511 8,390,459 8,826,375 Unsecured line of credit 250,000 249,873 — — Unsecured term loan, net 499,058 500,506 498,939 500,561 Total $ 12,061,224 $ 12,254,423 $ 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 note 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 note 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 three months ended March 31, 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	3 Months Ended
	Mar. 31, 2020
Real Estate [Abstract]
Real Estate	3. Real Estate Boston Properties, Inc. Real estate consisted of the following at March 31, 2020 and December 31, 2019 (in thousands): March 31, 2020 December 31, 2019 Land $ 5,070,208 $ 5,111,606 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 148,057 148,640 Land held for future development (1) 264,893 254,828 Buildings and improvements 13,517,218 13,646,054 Tenant improvements 2,641,448 2,656,439 Furniture, fixtures and equipment 44,263 44,313 Construction in progress 804,179 789,736 Total 22,727,660 22,889,010 Less: Accumulated depreciation (5,209,487 ) (5,266,798 ) $ 17,518,173 $ 17,622,212 _______________ (1) Includes pre-development costs. Boston Properties Limited Partnership Real estate consisted of the following at March 31, 2020 and December 31, 2019 (in thousands): March 31, 2020 December 31, 2019 Land $ 4,972,992 $ 5,011,153 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 148,057 148,640 Land held for future development (1) 264,893 254,828 Buildings and improvements 13,232,157 13,351,286 Tenant improvements 2,641,448 2,656,439 Furniture, fixtures and equipment 44,263 44,313 Construction in progress 804,179 789,736 Total 22,345,383 22,493,789 Less: Accumulated depreciation (5,107,243 ) (5,162,908 ) $ 17,238,140 $ 17,330,881 _______________ (1) Includes pre-development costs. Developments On January 28, 2020, the Company exercised its option to acquire real property at 425 Fourth Street located in San Francisco, California for a purchase price totaling approximately $134.1 million . 425 Fourth Street is expected to support the development of approximately 804,000 square feet of primarily commercial office space. There can be no assurance that the acquisition will be consummated on the terms currently contemplated or at all. 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. 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 third party’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 three months ended March 31, 2020 within Gains (Losses) 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 $2.9 million of net income to the Company for the three months ended March 31, 2019. 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 of net income to the Company for the three months ended March 31, 2019.

Leases

Leases	3 Months Ended
	Mar. 31, 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. The following table summarizes the components of lease revenue recognized during the three months ended March 31, 2020 and 2019 included within the Company's Consolidated Statements of Operations (in thousands): Three months ended March 31, Lease Revenue 2020 2019 Fixed contractual payments $ 586,957 $ 553,986 Variable lease payments 123,154 125,265 $ 710,111 $ 679,251

Investments in Unconsolidated J

Investments in Unconsolidated Joint Ventures	3 Months Ended
	Mar. 31, 2020
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	5. Investments in Unconsolidated Joint Ventures The investments in unconsolidated joint ventures consist of the following at March 31, 2020 and December 31, 2019 : Carrying Value of Investment (1) Entity Properties Nominal % Ownership March 31, December 31, (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (4,469 ) $ (4,872 ) BP/CRF Metropolitan Square, LLC Metropolitan Square 20.0 % 13,130 9,134 901 New York, LLC 901 New York Avenue 25.0 % (2) (12,069 ) (12,113 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 36,446 36,789 Annapolis Junction NFM LLC Annapolis Junction 50.0 % (4) 25,461 25,391 540 Madison Venture LLC 540 Madison Avenue 60.0 % (5) 2,961 2,953 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (5,688 ) (5,439 ) 501 K Street LLC 1001 6th Street 50.0 % (6) 42,774 42,496 Podium Developer LLC The Hub on Causeway - Podium 50.0 % 49,605 49,466 Residential Tower Developer LLC Hub50House 50.0 % 54,414 55,092 Hotel Tower Developer LLC The Hub on Causeway - Hotel Air Rights 50.0 % 9,889 9,883 Office Tower Developer LLC 100 Causeway Street 50.0 % 57,079 56,606 1265 Main Office JV LLC 1265 Main Street 50.0 % 3,636 3,780 BNY Tower Holdings LLC Dock 72 50.0 % 95,362 94,804 BNYTA Amenity Operator LLC Dock 72 50.0 % — — CA-Colorado Center Limited Partnership Colorado Center 50.0 % 251,146 252,069 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % 57,003 56,247 BP-M 3HB Venture LLC 3 Hudson Boulevard 25.0 % 84,301 67,499 SMBP Venture LP Santa Monica Business Park 55.0 % 151,997 163,937 Platform 16 Holdings LP Platform 16 55.0 % (7) 93,991 29,501 Gateway Portfolio Holdings LLC Gateway Commons 50.0 % (8) 348,143 N/A $ 1,355,112 $ 933,223 _______________ (1) Investments with deficit balances aggregating approximately $22.2 million and $22.4 million at March 31, 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 March 31, 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 three in-service buildings and two undeveloped land parcels. (5) T he property was sold on June 27, 2019. As of March 31, 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 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. Certain of the Company’s unconsolidated joint venture agreements include provisions whereby, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exceptions under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. Under certain of the Company’s joint venture agreements, if certain return thresholds are achieved, the partners or the Company will be entitled to an additional promoted interest or payments. The combined summarized balance sheets of the Company’s unconsolidated joint ventures are as follows: March 31, December 31, (in thousands) ASSETS Real estate and development in process, net (1) $ 4,469,460 $ 3,904,400 Other assets 578,468 502,706 Total assets $ 5,047,928 $ 4,407,106 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 2,312,938 $ 2,218,853 Other liabilities (2) 638,892 749,675 Members’/Partners’ equity 2,096,098 1,438,578 Total liabilities and members’/partners’ equity $ 5,047,928 $ 4,407,106 Company’s share of equity $ 956,136 $ 591,905 Basis differentials (3) 398,976 341,318 Carrying value of the Company’s investments in unconsolidated joint ventures (4) $ 1,355,112 $ 933,223 _______________ (1) At March 31, 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 $11.9 million and $12.1 million , respectively. (2) At March 31, 2020 and December 31, 2019 , this amount includes lease liabilities - finance leases totaling approximately $391.0 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 March 31, 2020 and December 31, 2019 , there was an aggregate basis differential of approximately $310.1 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 March 31, 2020 , there was an aggregate basis differential of approximately $55.7 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) shall be amortized over the remaining lives of the related assets and liabilities. (4) Investments with deficit balances aggregating approximately $22.2 million and $22.4 million at March 31, 2020 and December 31, 2019 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets. The combined summarized statements of operations of the Company’s unconsolidated joint ventures are as follows: Three months ended March 31, 2020 2019 (in thousands) Total revenue (1) $ 93,203 $ 82,955 Expenses Operating 35,401 30,499 Depreciation and amortization 32,035 28,646 Total expenses 67,436 59,145 Other income (expense) Interest expense (22,583 ) (20,757 ) Net income $ 3,184 $ 3,053 Company’s share of net income $ 1,252 $ 1,584 Basis differential (2) (1,621 ) (1,371 ) Income (loss) from unconsolidated joint ventures $ (369 ) $ 213 _______________ (1) Includes straight-line rent adjustments of approximately $9.7 million and $5.8 million for the three months ended March 31, 2020 and 2019 , respectively. (2) Includes straight-line rent adjustments of approximately $0.5 million and $0.5 million for the three months ended March 31, 2020 and 2019 , respectively. Also includes net above-/below-market rent adjustments of approximately $0.3 million and $0.4 million for the three months ended March 31, 2020 and 2019 , respectively. 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 (See Note 3 ). 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. On January 28, 2020, a joint venture in which the Company has a 55% interest commenced development of the first phase of its Platform 16 project located in San Jose, California. The first phase of the Platform 16 development project consists of an approximately 390,000 net rentable square foot Class A office building and a below-grade parking garage. Though the joint venture has completed site preparation work, in consultation with the Company’s partner, the joint venture has paused construction activities and it will revisit its plans once the economic impact of COVID-19 becomes clearer. On February 20, 2020, the joint venture acquired the land underlying the ground lease for a purchase price totaling approximately $134.8 million . The joint venture had previously made a deposit totaling $15.0 million , which deposit was credited against the purchase price. Platform 16 consists of a parcel of land totaling approximately 5.6 acres that is expected to support the development of approximately 1.1 million square feet of commercial office space. On March 18, 2020, a joint venture in which the Company has a 50% interest extended the mortgage loan collateralized by Annapolis Junction Building Seven and Building Eight. At the time of the extension, the outstanding balance of the loan totaled approximately $34.6 million , bore interest at a variable rate equal to LIBOR plus 2.35% per annum and matured on March 6, 2020. The extended loan matures on June 30, 2020. Annapolis Junction Building Seven and Building Eight are Class A office properties with approximately 127,000 and 126,000 net rentable square feet, respectively, located in Annapolis, Maryland.

Commitments And Contingencies

Commitments And Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	6. Commitments and Contingencies General In the normal course of business, the Company guarantees its performance of services or indemnifies third parties against its negligence. In addition, in the normal course of business, the Company guarantees to certain tenants the obligations of its subsidiaries for the payment of tenant improvement allowances and brokerage commissions in connection with their leases and limited costs arising from delays in delivery of their premises. The Company has letter of credit and performance obligations related to lender and development requirements that total approximately $21.7 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 March 31, 2020 , the maximum funding obligation under the guarantee was approximately $57.1 million . The Company earns a fee from the joint venture for providing the guarantee and has an agreement with the outside partners to reimburse the joint venture for their share of any payments made under the guarantee. As of March 31, 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 has exercised an option to borrow up to $15.0 million from the Company under such agreements. As of March 31, 2020, no funding request has been received by the Company. 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 March 31, 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 March 31, 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. 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 March 31, 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	3 Months Ended
	Mar. 31, 2020
Noncontrolling Interest [Abstract]
Noncontrolling Interests	7. 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 March 31, 2020 , the noncontrolling interests in Boston Properties Limited Partnership consisted of 16,421,888 OP Units, 1,343,299 LTIP Units (including 105,080 2012 OPP Units, 64,468 2013 MYLTIP Units, 23,100 2014 MYLTIP Units, 28,724 2015 MYLTIP Units, 89,791 2016 MYLTIP Units and 116,167 2017 MYLTIP Units), 336,195 2018 MYLTIP Units, 220,734 2019 MYLTIP Units and 203,278 2020 MYLTIP Units held by parties other than Boston Properties, Inc. Noncontrolling Interest—Common Units During the three months ended March 31, 2020 , 461,856 OP Units were presented by the holders for redemption (including 71,303 OP Units issued upon conversion of LTIP Units, 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2016 MYLTIP Units and 2017 MYLTIP Units) and were redeemed by Boston Properties, Inc. in exchange for an equal number of shares of Common Stock. At March 31, 2020 , Boston Properties Limited Partnership had outstanding 336,195 2018 MYLTIP Units, 220,734 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 three months ended March 31, 2020 : Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit 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 three months ended March 31, 2019 : Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit 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 March 31, 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 $92.23 per share on March 31, 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 March 31, 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	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Stockholders' Equity / Partners' Capital	8. Stockholders’ Equity / Partners’ Capital Boston Properties, Inc. As of March 31, 2020 , Boston Properties, Inc. had 155,314,555 shares of Common Stock outstanding. As of March 31, 2020 , Boston Properties, Inc. owned 1,730,797 general partnership units and 153,583,758 limited partnership units in Boston Properties Limited Partnership. On June 2, 2017, Boston Properties, Inc. renewed its “at the market” (“ATM”) stock offering program through which it may sell from time to time up to an aggregate of $600.0 million of its common stock through sales agents over a three -year period. This program replaced the Company’s prior $600.0 million ATM stock offering program that was scheduled to expire on June 3, 2017. The Company intends to use the net proceeds from any offering for general business purposes, which may include investment opportunities and debt reduction. No shares of common stock have been issued under this ATM stock offering program. During the three months ended March 31, 2020 , Boston Properties, Inc. issued 43,792 shares of Common Stock upon the exercise of options to purchase Common Stock. During the three months ended March 31, 2020 , Boston Properties, Inc. issued 461,856 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 three months ended March 31, 2019 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) March 31, 2020 April 30, 2020 $0.98 $0.98 December 31, 2019 January 30, 2020 $0.98 $0.98 March 29, 2019 April 30, 2019 $0.95 $0.95 December 31, 2018 January 30, 2019 $0.95 $0.95 Preferred Stock As of March 31, 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 three months ended March 31, 2019 : Record Date Payment Date Dividend (Per Share) May 1, 2020 May 15, 2020 $32.8125 February 4, 2020 February 18, 2020 $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	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share / Common Unit	9. 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 March 31, 2020 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 497,496 155,011 $ 3.21 Allocation of undistributed earnings to participating securities (1,011 ) — (0.01 ) Net income attributable to Boston Properties, Inc. common shareholders $ 496,485 155,011 $ 3.20 Effect of Dilutive Securities: Stock Based Compensation — 247 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 496,485 155,258 $ 3.20 Three months ended March 31, 2019 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 98,105 154,525 $ 0.63 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 98,105 154,844 $ 0.63 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 17,538,000 and 17,606,000 redeemable common units for the three months ended March 31, 2020 and 2019 , respectively. Three months ended March 31, 2020 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 566,333 172,549 $ 3.28 Allocation of undistributed earnings to participating securities (1,126 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 565,207 172,549 $ 3.28 Effect of Dilutive Securities: Stock Based Compensation — 247 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 565,207 172,796 $ 3.27 Three months ended March 31, 2019 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 113,382 172,131 $ 0.66 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 113,382 172,450 $ 0.66

Stock Option and Incentive Plan

Stock Option and Incentive Plan	3 Months Ended
	Mar. 31, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	10. Stock Option and Incentive Plan On February 4, 2020, Boston Properties, Inc.’s Compensation Committee approved 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 be based on Boston Properties, Inc.’s TSR relative to the FTSE Russell Nareit Office Index, adjusted to include Vornado Realty Trust. 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. During the three months ended March 31, 2020 , Boston Properties, Inc. issued 24,503 shares of restricted common stock and Boston Properties Limited Partnership issued 196,927 LTIP Units and 203,278 2020 MYLTIP Units to employees under the 2012 Plan. Employees paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit and 2020 MYLTIP Unit. When issued, LTIP Units are not economically equivalent in value to a share of Common Stock, but over time can increase in value to one-for-one parity with Common Stock if there is sufficient appreciation in the value of the Company’s assets. The aggregate value of the LTIP Units is included in noncontrolling interests in the Consolidated Balance Sheets of Boston Properties, Inc. and Boston Properties Limited Partnership. A substantial majority of the grants of restricted common stock and LTIP Units to employees vest in four equal annual installments. Restricted common stock is measured at fair value on the date of grant based on the number of shares granted and the closing price of Boston Properties, Inc.’s Common Stock on the date of grant as quoted on the New York Stock Exchange. Such value is recognized as an expense ratably over the corresponding employee service period. The shares of restricted common stock granted during the three months ended March 31, 2020 were valued at approximately $3.5 million ( $143.45 per share weighted-average). The LTIP Units granted were valued at approximately $25.5 million (approximately $129.65 per unit weighted-average fair value) using a Monte Carlo simulation method model. The per unit fair values of the LTIP Units granted were estimated on the dates of grant and for a substantial majority of such units were valued using the following assumptions: an expected life of 5.7 years, a risk-free interest rate of 1.47% and an expected price volatility of 18.0% . Because the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units, 2017 MYLTIP Units, 2018 MYLTIP Units, 2019 MYLTIP Units and 2020 MYLTIP Units are subject to both a service condition and a market condition, the Company recognizes the related compensation expense under the graded vesting attribution method. Under the graded vesting attribution method, each portion of the award that vests at a different date is accounted for as a separate award and recognized over the period appropriate to that portion so that the compensation cost for each portion should be recognized in full by the time that portion vests. The Company recognizes forfeitures as they occur on its awards of stock-based compensation. Dividends paid on both vested and unvested shares of restricted stock are charged directly to Dividends in Excess of Earnings in Boston Properties, Inc.’s Consolidated Balance Sheets and Partners’ Capital in Boston Properties Limited Partnership’s Consolidated Balance Sheets. Aggregate stock-based compensation expense associated with restricted stock, LTIP Units, 2016 MYLTIP Units, 2017 MYLTIP Units, 2018 MYLTIP Units, 2019 MYLTIP Units and 2020 MYLTIP Units was approximately $17.2 million and $14.8 million for the three months ended March 31, 2020 and 2019 , respectively. At March 31, 2020 , there was (1) an aggregate of approximately $42.2 million of unrecognized compensation expense related to unvested restricted stock, LTIP Units and 2017 MYLTIP Units and (2) an aggregate of approximately $19.8 million of unrecognized compensation expense related to unvested 2018 MYLTIP Units, 2019 MYLTIP Units and 2020 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 2.6 years.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Segment Reporting Disclosure [Text Block]	11. 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 months ended March 31, 2020 and 2019 . Boston Properties, Inc. Three months ended March 31, 2020 2019 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 497,496 $ 98,105 Add: Preferred dividends 2,625 2,625 Noncontrolling interest—common units of the Operating Partnership 57,539 11,599 Noncontrolling interests in property partnerships 19,486 18,830 Interest expense 101,591 101,009 Impairment loss — 24,038 Net operating income from unconsolidated joint ventures 28,758 25,349 Depreciation and amortization expense 171,094 164,594 Transaction costs 615 460 Payroll and related costs from management services contracts 3,237 3,395 General and administrative expense 36,454 41,762 Less: Net operating income attributable to noncontrolling interests in property partnerships 47,661 47,085 Gains (losses) from investments in securities (5,445 ) 2,969 Interest and other income 3,017 3,753 Gains (losses) on sales of real estate 410,165 (905 ) Income (loss) from unconsolidated joint ventures (369 ) 213 Direct reimbursements of payroll and related costs from management services contracts 3,237 3,395 Development and management services revenue 7,879 9,277 Company’s share of Net Operating Income $ 452,750 $ 425,979 Boston Properties Limited Partnership Three months ended March 31, 2020 2019 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 566,333 $ 113,382 Add: Preferred distributions 2,625 2,625 Noncontrolling interests in property partnerships 19,486 18,830 Interest expense 101,591 101,009 Impairment loss — 22,272 Net operating income from unconsolidated joint ventures 28,758 25,349 Depreciation and amortization expense 169,285 162,682 Transaction costs 615 460 Payroll and related costs from management services contracts 3,237 3,395 General and administrative expense 36,454 41,762 Less: Net operating income attributable to noncontrolling interests in property partnerships 47,661 47,085 Gains (losses) from investments in securities (5,445 ) 2,969 Interest and other income 3,017 3,753 Gains (losses) on sales of real estate 419,654 (905 ) Income (loss) from unconsolidated joint ventures (369 ) 213 Direct reimbursements of payroll and related costs from management services contracts 3,237 3,395 Development and management services revenue 7,879 9,277 Company’s share of Net Operating Income $ 452,750 $ 425,979 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, gains (losses) on sales of real estate, income (loss) 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 (Loss) 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, gains (losses) 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 shown as a reduction to lease revenue. The degree to which our commercial and retail tenants’ and parking operators’ businesses are or will continue to be negatively impacted by the ongoing COVID-19 pandemic 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 a tenant’s accrued rent balance, and this could have a material adverse effect on lease revenue and thus the results of the Company’s Office property type. In addition, as a result of COVID-19, the Boston Marriott Cambridge was closed in March 2020. The Company is uncertain as to when the hotel will re-open, and the continued closure is expected to have a material impact on the hotel’s operations and thus the results of the Company’s Hotel property type. See Item 1A: “Risk Factors” for additional details. Information by geographic area and property type (dollars in thousands): For the three months ended March 31, 2020 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 239,498 $ — $ 255,286 $ 136,739 $ 93,136 $ 724,659 Residential 4,068 — — — 5,888 9,956 Hotel 6,825 — — — — 6,825 Total 250,391 — 255,286 136,739 99,024 741,440 % of Grand Totals 33.77 % — % 34.43 % 18.44 % 13.36 % 100.00 % Rental Expenses: Office 82,545 — 99,140 42,569 34,648 258,902 Residential 1,340 — — — 2,724 4,064 Hotel 6,821 — — — — 6,821 Total 90,706 — 99,140 42,569 37,372 269,787 % of Grand Totals 33.62 % — % 36.75 % 15.78 % 13.85 % 100.00 % Net operating income $ 159,685 $ — $ 156,146 $ 94,170 $ 61,652 $ 471,653 % of Grand Totals 33.85 % — % 33.11 % 19.97 % 13.07 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,663 ) — (36,998 ) — — (47,661 ) Add: Company’s share of net operating income from unconsolidated joint ventures 3,099 15,930 756 3,159 5,814 28,758 Company’s share of net operating income $ 152,121 $ 15,930 $ 119,904 $ 97,329 $ 67,466 $ 452,750 % of Grand Totals 33.60 % 3.52 % 26.48 % 21.50 % 14.90 % 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 March 31, 2019 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 217,411 $ — $ 258,631 $ 124,055 $ 96,345 $ 696,442 Residential 2,701 — — — 5,014 7,715 Hotel 8,938 — — — — 8,938 Total 229,050 — 258,631 124,055 101,359 713,095 % of Grand Totals 32.12 % — % 36.27 % 17.40 % 14.21 % 100.00 % Rental Expenses: Office 79,500 — 96,971 41,125 36,147 253,743 Residential 1,206 — — — 2,568 3,774 Hotel 7,863 — — — — 7,863 Total 88,569 — 96,971 41,125 38,715 265,380 % of Grand Totals 33.37 % — % 36.54 % 15.50 % 14.59 % 100.00 % Net operating income $ 140,481 $ — $ 161,660 $ 82,930 $ 62,644 $ 447,715 % of Grand Totals 31.38 % — % 36.11 % 18.52 % 13.99 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (9,373 ) — (37,264 ) (448 ) — (47,085 ) Add: Company’s share of net operating income from unconsolidated joint ventures 772 15,708 1,786 — 7,083 25,349 Company’s share of net operating income $ 131,880 $ 15,708 $ 126,182 $ 82,482 $ 69,727 $ 425,979 % of Grand Totals 30.96 % 3.69 % 29.62 % 19.36 % 16.37 % 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	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events There are many uncertainties regarding COVID-19, and the Company is closely monitoring the impact of the pandemic on all aspects of its business, including how it will impact its tenants, employees, contractors, lenders, suppliers, vendors and joint venture partners. The Company is unable to predict the impact that COVID-19 will have on its future financial position and operating results due to numerous uncertainties. The Company has received requests from many of its retail and some of its office tenants seeking either rent concessions, deferrals, rent abatements related to lease provision interpretations, or other relief, in each case, as a result of COVID-19. The Company is evaluating these requests on a case-by-case basis and is considering a number of factors to determine the appropriate response. The Company expects to continue to assess the evolving impact of COVID-19 and intends to make adjustments to its responses accordingly. On April 22, 2020, a joint venture in which the Company has a 20% interest extended the mortgage loan collateralized by Metropolitan Square located in Washington, DC. At the time of the extension, the outstanding balance of the loan totaled approximately $156.4 million and was scheduled to mature on May 5, 2020. The extended loan continues to bear interest at a fixed rate of 5.75% per annum and matures on August 5, 2020. Metropolitan Square is a Class A office property with approximately 654,000 net rentable square feet. On May 5, 2020, Boston Properties Limited Partnership completed a public offering of $1.25 billion in aggregate principal amount of its 3.250% unsecured senior notes due 2031. The notes were priced at 99.850% of the principal amount to yield an effective rate (including financing fees) of approximately 3.343% per annum to maturity. The notes will mature on January 30, 2031, unless earlier redeemed. The aggregate net proceeds from the offering were approximately $1.24 billion after deducting underwriting discounts and estimated transaction expenses.

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 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)	3 Months Ended
	Mar. 31, 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 they are categorized at (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 Note 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 4.49% 4.49% Note receivable Level 3 3.62% 3.62% Mortgage notes payable Level 3 2.82% - 3.25% 2.91% Unsecured term loan / line of credit Level 3 1.84% 1.84%
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, note 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 March 31, 2020 and December 31, 2019 (in thousands): March 31, 2020 December 31, 2019 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Related party note receivable, net $ 78,800 $ 83,707 $ 80,000 $ 81,931 Note receivable, net 15,794 15,593 15,920 14,978 Total $ 94,594 $ 99,300 $ 95,920 $ 96,909 Mortgage notes payable, net $ 2,919,157 $ 3,054,533 $ 2,922,408 $ 2,984,956 Unsecured senior notes, net 8,393,009 8,449,511 8,390,459 8,826,375 Unsecured line of credit 250,000 249,873 — — Unsecured term loan, net 499,058 500,506 498,939 500,561 Total $ 12,061,224 $ 12,254,423 $ 11,811,806 $ 12,311,892

Real Estate (Tables)

Real Estate (Tables)	3 Months Ended
	Mar. 31, 2020
Real Estate Properties [Line Items]
Schedule of Real Estate Properties	Boston Properties, Inc. Real estate consisted of the following at March 31, 2020 and December 31, 2019 (in thousands): March 31, 2020 December 31, 2019 Land $ 5,070,208 $ 5,111,606 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 148,057 148,640 Land held for future development (1) 264,893 254,828 Buildings and improvements 13,517,218 13,646,054 Tenant improvements 2,641,448 2,656,439 Furniture, fixtures and equipment 44,263 44,313 Construction in progress 804,179 789,736 Total 22,727,660 22,889,010 Less: Accumulated depreciation (5,209,487 ) (5,266,798 ) $ 17,518,173 $ 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 March 31, 2020 and December 31, 2019 (in thousands): March 31, 2020 December 31, 2019 Land $ 4,972,992 $ 5,011,153 Right of use assets - finance leases 237,394 237,394 Right of use assets - operating leases 148,057 148,640 Land held for future development (1) 264,893 254,828 Buildings and improvements 13,232,157 13,351,286 Tenant improvements 2,641,448 2,656,439 Furniture, fixtures and equipment 44,263 44,313 Construction in progress 804,179 789,736 Total 22,345,383 22,493,789 Less: Accumulated depreciation (5,107,243 ) (5,162,908 ) $ 17,238,140 $ 17,330,881 _______________ (1) Includes pre-development costs.

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Operating Lease, Lease Income [Table Text Block]	The following table summarizes the components of lease revenue recognized during the three months ended March 31, 2020 and 2019 included within the Company's Consolidated Statements of Operations (in thousands): Three months ended March 31, Lease Revenue 2020 2019 Fixed contractual payments $ 586,957 $ 553,986 Variable lease payments 123,154 125,265 $ 710,111 $ 679,251

Investments in Unconsolidated_2

Investments in Unconsolidated Joint Ventures (Tables)	3 Months Ended
	Mar. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investments In Unconsolidated Joint Ventures	The investments in unconsolidated joint ventures consist of the following at March 31, 2020 and December 31, 2019 : Carrying Value of Investment (1) Entity Properties Nominal % Ownership March 31, December 31, (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (4,469 ) $ (4,872 ) BP/CRF Metropolitan Square, LLC Metropolitan Square 20.0 % 13,130 9,134 901 New York, LLC 901 New York Avenue 25.0 % (2) (12,069 ) (12,113 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 36,446 36,789 Annapolis Junction NFM LLC Annapolis Junction 50.0 % (4) 25,461 25,391 540 Madison Venture LLC 540 Madison Avenue 60.0 % (5) 2,961 2,953 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (5,688 ) (5,439 ) 501 K Street LLC 1001 6th Street 50.0 % (6) 42,774 42,496 Podium Developer LLC The Hub on Causeway - Podium 50.0 % 49,605 49,466 Residential Tower Developer LLC Hub50House 50.0 % 54,414 55,092 Hotel Tower Developer LLC The Hub on Causeway - Hotel Air Rights 50.0 % 9,889 9,883 Office Tower Developer LLC 100 Causeway Street 50.0 % 57,079 56,606 1265 Main Office JV LLC 1265 Main Street 50.0 % 3,636 3,780 BNY Tower Holdings LLC Dock 72 50.0 % 95,362 94,804 BNYTA Amenity Operator LLC Dock 72 50.0 % — — CA-Colorado Center Limited Partnership Colorado Center 50.0 % 251,146 252,069 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % 57,003 56,247 BP-M 3HB Venture LLC 3 Hudson Boulevard 25.0 % 84,301 67,499 SMBP Venture LP Santa Monica Business Park 55.0 % 151,997 163,937 Platform 16 Holdings LP Platform 16 55.0 % (7) 93,991 29,501 Gateway Portfolio Holdings LLC Gateway Commons 50.0 % (8) 348,143 N/A $ 1,355,112 $ 933,223 _______________ (1) Investments with deficit balances aggregating approximately $22.2 million and $22.4 million at March 31, 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 March 31, 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 three in-service buildings and two undeveloped land parcels. (5) T he property was sold on June 27, 2019. As of March 31, 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 ).
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: March 31, December 31, (in thousands) ASSETS Real estate and development in process, net (1) $ 4,469,460 $ 3,904,400 Other assets 578,468 502,706 Total assets $ 5,047,928 $ 4,407,106 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 2,312,938 $ 2,218,853 Other liabilities (2) 638,892 749,675 Members’/Partners’ equity 2,096,098 1,438,578 Total liabilities and members’/partners’ equity $ 5,047,928 $ 4,407,106 Company’s share of equity $ 956,136 $ 591,905 Basis differentials (3) 398,976 341,318 Carrying value of the Company’s investments in unconsolidated joint ventures (4) $ 1,355,112 $ 933,223 _______________ (1) At March 31, 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 $11.9 million and $12.1 million , respectively. (2) At March 31, 2020 and December 31, 2019 , this amount includes lease liabilities - finance leases totaling approximately $391.0 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 March 31, 2020 and December 31, 2019 , there was an aggregate basis differential of approximately $310.1 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 March 31, 2020 , there was an aggregate basis differential of approximately $55.7 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) shall be amortized over the remaining lives of the related assets and liabilities. (4) Investments with deficit balances aggregating approximately $22.2 million and $22.4 million at March 31, 2020 and December 31, 2019 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
Statements Of Operations Of The Joint Ventures	The combined summarized statements of operations of the Company’s unconsolidated joint ventures are as follows: Three months ended March 31, 2020 2019 (in thousands) Total revenue (1) $ 93,203 $ 82,955 Expenses Operating 35,401 30,499 Depreciation and amortization 32,035 28,646 Total expenses 67,436 59,145 Other income (expense) Interest expense (22,583 ) (20,757 ) Net income $ 3,184 $ 3,053 Company’s share of net income $ 1,252 $ 1,584 Basis differential (2) (1,621 ) (1,371 ) Income (loss) from unconsolidated joint ventures $ (369 ) $ 213 _______________ (1) Includes straight-line rent adjustments of approximately $9.7 million and $5.8 million for the three months ended March 31, 2020 and 2019 , respectively. (2) Includes straight-line rent adjustments of approximately $0.5 million and $0.5 million for the three months ended March 31, 2020 and 2019 , respectively. Also includes net above-/below-market rent adjustments of approximately $0.3 million and $0.4 million for the three months ended March 31, 2020 and 2019 , respectively.

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 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 three months ended March 31, 2019 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) March 31, 2020 April 30, 2020 $0.98 $0.98 December 31, 2019 January 30, 2020 $0.98 $0.98 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 three months ended March 31, 2020 : Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit 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 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)	3 Months Ended
	Mar. 31, 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 three months ended March 31, 2019 : Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) March 31, 2020 April 30, 2020 $0.98 $0.98 December 31, 2019 January 30, 2020 $0.98 $0.98 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 three months ended March 31, 2019 : Record Date Payment Date Dividend (Per Share) May 1, 2020 May 15, 2020 $32.8125 February 4, 2020 February 18, 2020 $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)	3 Months Ended
	Mar. 31, 2020
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share / Unit	Three months ended March 31, 2020 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 497,496 155,011 $ 3.21 Allocation of undistributed earnings to participating securities (1,011 ) — (0.01 ) Net income attributable to Boston Properties, Inc. common shareholders $ 496,485 155,011 $ 3.20 Effect of Dilutive Securities: Stock Based Compensation — 247 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 496,485 155,258 $ 3.20 Three months ended March 31, 2019 Income (Numerator) Shares (Denominator) Per Share Amount (in thousands, except for per share amounts) Basic Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 98,105 154,525 $ 0.63 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 98,105 154,844 $ 0.63
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 17,538,000 and 17,606,000 redeemable common units for the three months ended March 31, 2020 and 2019 , respectively. Three months ended March 31, 2020 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 566,333 172,549 $ 3.28 Allocation of undistributed earnings to participating securities (1,126 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 565,207 172,549 $ 3.28 Effect of Dilutive Securities: Stock Based Compensation — 247 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 565,207 172,796 $ 3.27 Three months ended March 31, 2019 Income (Numerator) Units (Denominator) Per Unit Amount (in thousands, except for per unit amounts) Basic Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 113,382 172,131 $ 0.66 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 113,382 172,450 $ 0.66

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Schedule Of Reconciliation Of Net Operating Income To Net Income	Boston Properties, Inc. Three months ended March 31, 2020 2019 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 497,496 $ 98,105 Add: Preferred dividends 2,625 2,625 Noncontrolling interest—common units of the Operating Partnership 57,539 11,599 Noncontrolling interests in property partnerships 19,486 18,830 Interest expense 101,591 101,009 Impairment loss — 24,038 Net operating income from unconsolidated joint ventures 28,758 25,349 Depreciation and amortization expense 171,094 164,594 Transaction costs 615 460 Payroll and related costs from management services contracts 3,237 3,395 General and administrative expense 36,454 41,762 Less: Net operating income attributable to noncontrolling interests in property partnerships 47,661 47,085 Gains (losses) from investments in securities (5,445 ) 2,969 Interest and other income 3,017 3,753 Gains (losses) on sales of real estate 410,165 (905 ) Income (loss) from unconsolidated joint ventures (369 ) 213 Direct reimbursements of payroll and related costs from management services contracts 3,237 3,395 Development and management services revenue 7,879 9,277 Company’s share of Net Operating Income $ 452,750 $ 425,979 Boston Properties Limited Partnership Three months ended March 31, 2020 2019 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 566,333 $ 113,382 Add: Preferred distributions 2,625 2,625 Noncontrolling interests in property partnerships 19,486 18,830 Interest expense 101,591 101,009 Impairment loss — 22,272 Net operating income from unconsolidated joint ventures 28,758 25,349 Depreciation and amortization expense 169,285 162,682 Transaction costs 615 460 Payroll and related costs from management services contracts 3,237 3,395 General and administrative expense 36,454 41,762 Less: Net operating income attributable to noncontrolling interests in property partnerships 47,661 47,085 Gains (losses) from investments in securities (5,445 ) 2,969 Interest and other income 3,017 3,753 Gains (losses) on sales of real estate 419,654 (905 ) Income (loss) from unconsolidated joint ventures (369 ) 213 Direct reimbursements of payroll and related costs from management services contracts 3,237 3,395 Development and management services revenue 7,879 9,277 Company’s share of Net Operating Income $ 452,750 $ 425,979
Schedule Of Segment Information By Geographic Area And Property Type	Information by geographic area and property type (dollars in thousands): For the three months ended March 31, 2020 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 239,498 $ — $ 255,286 $ 136,739 $ 93,136 $ 724,659 Residential 4,068 — — — 5,888 9,956 Hotel 6,825 — — — — 6,825 Total 250,391 — 255,286 136,739 99,024 741,440 % of Grand Totals 33.77 % — % 34.43 % 18.44 % 13.36 % 100.00 % Rental Expenses: Office 82,545 — 99,140 42,569 34,648 258,902 Residential 1,340 — — — 2,724 4,064 Hotel 6,821 — — — — 6,821 Total 90,706 — 99,140 42,569 37,372 269,787 % of Grand Totals 33.62 % — % 36.75 % 15.78 % 13.85 % 100.00 % Net operating income $ 159,685 $ — $ 156,146 $ 94,170 $ 61,652 $ 471,653 % of Grand Totals 33.85 % — % 33.11 % 19.97 % 13.07 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,663 ) — (36,998 ) — — (47,661 ) Add: Company’s share of net operating income from unconsolidated joint ventures 3,099 15,930 756 3,159 5,814 28,758 Company’s share of net operating income $ 152,121 $ 15,930 $ 119,904 $ 97,329 $ 67,466 $ 452,750 % of Grand Totals 33.60 % 3.52 % 26.48 % 21.50 % 14.90 % 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 March 31, 2019 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 217,411 $ — $ 258,631 $ 124,055 $ 96,345 $ 696,442 Residential 2,701 — — — 5,014 7,715 Hotel 8,938 — — — — 8,938 Total 229,050 — 258,631 124,055 101,359 713,095 % of Grand Totals 32.12 % — % 36.27 % 17.40 % 14.21 % 100.00 % Rental Expenses: Office 79,500 — 96,971 41,125 36,147 253,743 Residential 1,206 — — — 2,568 3,774 Hotel 7,863 — — — — 7,863 Total 88,569 — 96,971 41,125 38,715 265,380 % of Grand Totals 33.37 % — % 36.54 % 15.50 % 14.59 % 100.00 % Net operating income $ 140,481 $ — $ 161,660 $ 82,930 $ 62,644 $ 447,715 % of Grand Totals 31.38 % — % 36.11 % 18.52 % 13.99 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (9,373 ) — (37,264 ) (448 ) — (47,085 ) Add: Company’s share of net operating income from unconsolidated joint ventures 772 15,708 1,786 — 7,083 25,349 Company’s share of net operating income $ 131,880 $ 15,708 $ 126,182 $ 82,482 $ 69,727 $ 425,979 % of Grand Totals 30.96 % 3.69 % 29.62 % 19.36 % 16.37 % 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	3 Months Ended	12 Months Ended
	Mar. 31, 2020ft²Real_Estate_Propertiesyrshares	Dec. 31, 2019shares
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.70%	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	196
Net Rentable Area (in sf) | ft²	51.8
Total Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	10
Net Rentable Area (in sf) | ft²	5.2
Total Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	177
Office Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	8
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)	Mar. 31, 2020
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	6
Number of VIEs - Total	7
Total Office Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of VIEs	5

Summary Of Significant Accoun_5

Summary Of Significant Accounting Policies Fair Value of Debt (Level 3) (Details) - Measurement Input, Discount Rate [Member]	Mar. 31, 2020
Mortgage Notes [Member] | Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0282
Mortgage Notes [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0291
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	0.0184
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	0.0184
Related Party Note Receivable [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0449
Related Party Note Receivable [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0449
Notes Receivables [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0362
Notes Receivables [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt Instrument, Measurement Input	0.0362

Summary Of Significant Accoun_6

Summary Of Significant Accounting Policies (Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable, net	$ 78,800	$ 80,000
Note receivable, net	15,794	15,920
Mortgage notes payable, net	2,919,157	2,922,408
Unsecured senior notes, net	8,393,009	8,390,459
Unsecured line of credit	250,000	0
Unsecured term loan, net	499,058	498,939
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable, net	78,800	80,000
Note receivable, net	15,794	15,920
Assets, Fair Value Disclosure	94,594	95,920
Mortgage notes payable, net	2,919,157	2,922,408
Unsecured senior notes, net	8,393,009	8,390,459
Unsecured line of credit	250,000	0
Unsecured term loan, net	499,058	498,939
Total	12,061,224	11,811,806
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable, net	83,707	81,931
Note receivable, net	15,593	14,978
Assets, Fair Value Disclosure	99,300	96,909
Mortgage notes payable, net	3,054,533	2,984,956
Unsecured senior notes, net	8,449,511	8,826,375
Unsecured line of credit	249,873	0
Unsecured term loan, net	500,506	500,561
Total	$ 12,254,423	$ 12,311,892

Real Estate Schedule of Real Es

Real Estate Schedule of Real Estate Properties (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Real Estate Properties [Line Items]
Land		$ 5,070,208	$ 5,111,606
Right-of-use assets - finance leases		237,394	237,394
Right of use assets - operating leases		148,057	148,640
Land held for future development	[1]	264,893	254,828
Buildings and improvements		13,517,218	13,646,054
Tenant improvements		2,641,448	2,656,439
Furniture, Fixtures and Equipment		44,263	44,313
Construction in progress		804,179	789,736
Total		22,727,660	22,889,010
Less: accumulated depreciation		(5,209,487)	(5,266,798)
Total real estate		17,518,173	17,622,212
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Land		4,972,992	5,011,153
Right-of-use assets - finance leases		237,394	237,394
Right of use assets - operating leases		148,057	148,640
Land held for future development	[1]	264,893	254,828
Buildings and improvements		13,232,157	13,351,286
Tenant improvements		2,641,448	2,656,439
Furniture, Fixtures and Equipment		44,263	44,313
Construction in progress		804,179	789,736
Total		22,345,383	22,493,789
Less: accumulated depreciation		(5,107,243)	(5,162,908)
Total real estate		$ 17,238,140	$ 17,330,881
[1]	Includes pre-development costs.

Real Estate (Narrative) (Detail

Real Estate (Narrative) (Details) $ in Thousands	Feb. 20, 2020USD ($)ft²Buildings	Jan. 28, 2020USD ($)ft²Buildings	Jan. 27, 2020USD ($)	Feb. 19, 2020USD ($)	Mar. 31, 2020USD ($)		Mar. 31, 2019USD ($)	Mar. 26, 2020ft²
Real Estate Properties [Line Items]
Proceeds from sales of real estate					$ 259,489		$ 20,019
Gains (loss) on sales of real estate					410,165		(905)
Payments to Acquire Equity Method Investments					89,997		26,995
Revenues					752,556		725,767
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 (loss) on sales of real estate	$ 192,300
Operating Income (Loss)				$ 1,600			2,100
number of buildings | Buildings	2
Gateway Center [Member]
Real Estate Properties [Line Items]
Gains (loss) on sales of real estate		$ 217,700
Operating Income (Loss)			$ 200				2,900
425 Fourth Street [Member]
Real Estate Properties [Line Items]
Aggregate purchase price		$ 134,100
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%
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Proceeds from sales of real estate					259,489		20,019
Gains (loss) on sales of real estate					419,654		(905)
Payments to Acquire Equity Method Investments					89,997		26,995
Revenues					$ 752,556		$ 725,767
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]
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 | New Dominion Technology Park [Member]
Real Estate Properties [Line Items]
Gains (loss) on sales of real estate	$ 197,100
Boston Properties Limited Partnership | Gateway Center [Member]
Real Estate Properties [Line Items]
Gains (loss) on sales of real estate		$ 222,400
[1]	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.

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Fixed contractual payments	$ 586,957	$ 553,986
Variable lease payments	123,154	125,265
Lease	$ 710,111	$ 679,251

Investments in Unconsolidated_3

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2020USD ($)ft²Land_ParcelsBuildingspayments		Jan. 28, 2020	Dec. 31, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Other Liabilities		$ 366,852			$ 387,994
Investments in unconsolidated joint ventures		1,377,338			955,647
Investments In Affiliates Subsidiaries Associates And Joint Ventures net	[1]	1,355,112			933,223
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Other Liabilities		$ 22,200			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]	$ 4,469			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]	$ 13,130			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]	$ 12,069			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]	$ 36,446			36,789
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties		Annapolis Junction
Ownership Percentage	[4]	50.00%
Investments in unconsolidated joint ventures	[1]	$ 25,461			25,391
Number of real estate properties | Buildings		3
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]	$ 2,961			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]	$ 5,688			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]	$ 42,774			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]	$ 49,605			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]	$ 54,414			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]	$ 9,889			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]	$ 57,079			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]	$ 3,636			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]	$ 95,362			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]	$ 251,146			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]	$ 57,003			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]	$ 84,301			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]	$ 151,997			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]	$ 93,991			$ 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]	$ 348,143
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 $22.2 million and $22.4 million at March 31, 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 March 31, 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 three in-service buildings and two undeveloped land parcels.
[5]	T he property was sold on June 27, 2019. As of March 31, 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 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.

Investments in Unconsolidated_4

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
ASSETS
Real estate and development in process, net		$ 17,518,173	$ 17,622,212
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable, net		2,919,157	2,922,408
Other Liabilities		366,852	387,994
Total liabilities and equity / capital		21,829,698	21,284,905
Carying value of the Company's investment in unconsolidated joint ventures		1,377,338	955,647
Right-of-use assets - finance leases		237,394	237,394
Right of use assets - operating leases		148,057	148,640
Lease liabilities - finance leases		227,067	224,042
Lease liabilities - operating leases		200,573	200,180
Unconsolidated Joint Ventures [Member]
ASSETS
Real estate and development in process, net	[1]	4,469,460	3,904,400
Other assets		578,468	502,706
Total assets		5,047,928	4,407,106
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Mortgage and notes payable, net		2,312,938	2,218,853
Other Liabilities	[2]	638,892	749,675
Members'/Partners' equity		2,096,098	1,438,578
Total liabilities and equity / capital		5,047,928	4,407,106
Company's share of equity		956,136	591,905
Basis differentials	[3]	398,976	341,318
Carying value of the Company's investment in unconsolidated joint ventures	[4]	1,355,112	933,223
Right-of-use assets - finance leases		248,900	383,900
Right of use assets - operating leases		11,900	12,100
Lease liabilities - finance leases		391,000	510,800
Lease liabilities - operating leases		17,400	17,300
Colorado Center [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Basis differentials		310,100	311,300
Unconsolidated Joint Ventures [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Other Liabilities		22,200	$ 22,400
Gateway Commons Complex [Member]
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY
Basis differentials		55,700
Carying value of the Company's investment in unconsolidated joint ventures	[5]	$ 348,143
[1]	At March 31, 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 $11.9 million and $12.1 million , respectively.
[2]	At March 31, 2020 and December 31, 2019 , this amount includes lease liabilities - finance leases totaling approximately $391.0 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 March 31, 2020 and December 31, 2019 , there was an aggregate basis differential of approximately $310.1 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 March 31, 2020 , there was an aggregate basis differential of approximately $55.7 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) shall be amortized over the remaining lives of the related assets and liabilities.
[4]	Investments with deficit balances aggregating approximately $22.2 million and $22.4 million at March 31, 2020 and December 31, 2019 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[5]	Investments with deficit balances aggregating approximately $22.2 million and $22.4 million at March 31, 2020 and December 31, 2019 , respectively, are included within Other Liabilities in the Company’s Consolidated Balance Sheets.

Investments in Unconsolidated_5

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 752,556		$ 725,767
Expenses
Transaction costs		615		460
Depreciation and amortization		171,094		164,594
Total expenses		481,187		475,591
Other income (expense)
Interest expense		(101,591)		(101,009)
Net income		577,146		131,159
Income (loss) from unconsolidated joint ventures		(369)		213
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]	93,203		82,955
Expenses
Operating		35,401		30,499
Depreciation and amortization		32,035		28,646
Total expenses		67,436		59,145
Other income (expense)
Interest expense		(22,583)		(20,757)
Net income		3,184		3,053
Company's share of net income		1,252		1,584
Basis differential	[3]	(1,621)	[2]	(1,371)
Income (loss) from unconsolidated joint ventures		(369)		213
Straight-line rent adjustments		9,700		5,800
Colorado Center [Member]
Other income (expense)
Straight-line rent adjustments		500		500
Above and below market rent adjustments, net		$ 300		$ 400
[1]	Includes straight-line rent adjustments of approximately $9.7 million and $5.8 million for the three months ended March 31, 2020 and 2019 , respectively.
[2]	Includes straight-line rent adjustments of approximately $0.5 million and $0.5 million for the three months ended March 31, 2020 and 2019 , respectively. Also includes net above-/below-market rent adjustments of approximately $0.3 million and $0.4 million for the three months ended March 31, 2020 and 2019 , respectively.
[3]	Includes straight-line rent adjustments of approximately $0.5 million and $0.5 million for the three months ended March 31, 2020 and 2019 , respectively. Also includes net above-/below-market rent adjustments of approximately $0.3 million and $0.4 million for the three months ended March 31, 2020 and 2019

Investment in unconsolidated Jo

Investment in unconsolidated Joint Ventures (Narrative) (Details) $ in Thousands	Mar. 18, 2020USD ($)ft²	Jan. 28, 2020USD ($)ft²Buildings	Mar. 31, 2020USD ($)		Mar. 31, 2019USD ($)	Feb. 20, 2020USD ($)ft²a	Dec. 31, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Mortgage notes payable, net			$ 2,919,157				$ 2,922,408
Payments to Acquire Equity Method Investments			$ 89,997		$ 26,995
Gateway Commons Complex [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%	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]
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 and Eight [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%
Mortgage notes payable, net	$ 34,600
Debt Instrument, Basis Spread on Variable Rate	2.35%
Annapolis Junction Building Seven [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²	127,000
Annapolis Junction Building Eight [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²	126,000
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 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%
[1]	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.
[2]	This entity is a VIE (See Note 2 ).

Commitments And Contingencies (

Commitments And Contingencies (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 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	$ 21,700,000
Notes Receivable, Related Parties	78,800,000		$ 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
767 Venture, LLC [Member]
Commitments And Contingencies [Line Items]
Maximum funding obligation	57,100,000
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
Boston Properties Limited Partnership
Commitments And Contingencies [Line Items]
Notes Receivable, Related Parties	78,800,000		$ 80,000,000
Operating partnership guarantee to cover liabilities of IXP	$ 20,000,000
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%
Maximum [Member] | 7750 Wisconsin Avenue [Member]
Commitments And Contingencies [Line Items]
Notes Receivable, Related Parties	$ 15,000,000
Minimum [Member] | 7750 Wisconsin Avenue [Member]
Commitments And Contingencies [Line Items]
Notes Receivable, Related Parties	$ 0

Noncontrolling Interests (Narra

Noncontrolling Interests (Narrative) (Details) - Boston Properties Limited Partnership	Mar. 31, 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)	16,421,888
Long-Term Incentive Plan (LTIP) Units (in shares)	1,343,299
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	28,724
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	116,167
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	220,734
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 Thousands	Feb. 06, 2020USD ($)shares	Mar. 31, 2020USD ($)sharesyr$ / shares	Dec. 31, 2019USD ($)
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 | $	$ 17,600
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)		461,856
Redemption of OP units issued on conversion of LTIP, OPP and MYLTIP units (in shares)		71,303
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 | $		$ 1,600,000
Closing price of common stock (in dollars per share) | $ / shares		$ 92.23
Boston Properties Limited Partnership
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Common units of operating partnership if converted value | $		$ 1,639,855	$ 2,468,753
Boston Properties Limited Partnership | MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP		116,167
Boston Properties Limited Partnership | MYLTIP 2018
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP		336,195
Boston Properties Limited Partnership | MYLTIP 2019 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS		220,734
Boston Properties Limited Partnership | MYLTIP 2020 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2020 MYLTIP		203,278

Noncontrolling Interests Common

Noncontrolling Interests Common Units Distributions (Details) - Boston Properties Limited Partnership - $ / shares	Jan. 30, 2020	Apr. 30, 2019	Jan. 30, 2019	Mar. 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	$ 0.95	$ 0.95
Distributions Made To MYLTIP Units Per Unit	$ 0.098	$ 0.095	$ 0.095

Noncontrolling Interests (Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Noncontrolling Interest [Line Items]
Noncontrolling Interest in Limited Partnerships	$ 1,736,445	$ 1,728,689

Stockholders' Equity _ Partne_3

Stockholders' Equity / Partners' Capital Narrative (Details) $ / shares in Units, $ in Millions	Jun. 02, 2017USD ($)yr	Mar. 31, 2020$ / sharesshares	Dec. 31, 2019$ / sharesshares	Mar. 27, 2018$ / shares	Jun. 03, 2014USD ($)
Class of Stock [Line Items]
Common Stock, Shares, Outstanding		155,314,555	154,790,298
General Partners' Capital Account, Units Outstanding (in units)		1,730,797
Limited Partners' Capital Account, Units Outstanding (in units)		153,583,758
Options exercised		43,792
Shares of Common Stock issued in connection with redemption of an equal number of OP Units (in shares)		461,856
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
Boston Properties Limited Partnership
Class of Stock [Line Items]
General Partners' Capital Account, Units Outstanding (in units)		1,730,797	1,726,980
Limited Partners' Capital Account, Units Outstanding (in units)		153,583,758	153,063,318
Boston Properties Limited Partnership | 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, Liquidation Preference Per Share (dollars per share) | $ / shares		$ 2,500	$ 2,500

Stockholders' Equity _ Partne_4

Stockholders' Equity / Partners' Capital Dividends / Distributions (Details) - $ / shares	Feb. 18, 2020	Jan. 30, 2020	May 15, 2019	Apr. 30, 2019	Feb. 15, 2019	Jan. 30, 2019	Mar. 18, 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		$ 0.95		$ 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		$ 0.95		$ 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

Earnings Per Share _ Common U_3

Earnings Per Share / Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Basic Earnings:
Net income attributable to the company's common shareholders / unitholders	$ 497,496	$ 98,105
Net income attributable to the company's common shareholders / unitholders (in shares / units)	155,011,000	154,525,000
Net income attributable to the company's common shareholders / unitholders (in dollars per share / unit)	$ 3.21	$ 0.63
Allocation of undistributed earnings to participating securities	$ (1,011)
Allocation of undistributed earnings to participating securities (in shares / units)	0
Allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ (0.01)
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities	$ 496,485	$ 98,105
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in shares / units)	155,011,000	154,525,000
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ 3.20	$ 0.63
Effect of Dilutive Securities:
Stock Based Compensation	$ 0	$ 0
Stock Based Compensation (in shares / units)	247,000	319,000
Weighted Average Number Diluted Shares Outstanding Adjustment (per share)	$ 0	$ 0
Diluted Earnings:
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders	$ 496,485	$ 98,105
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders (in shares / units)	155,258,000	154,844,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 3.20	$ 0.63
Boston Properties Limited Partnership
Redeemable Common Units	17,538,000	17,606,000
Basic Earnings:
Net income attributable to the company's common shareholders / unitholders	$ 566,333	$ 113,382
Net income attributable to the company's common shareholders / unitholders (in shares / units)	172,549,000	172,131,000
Net income attributable to the company's common shareholders / unitholders (in dollars per share / unit)	$ 3.28	$ 0.66
Allocation of undistributed earnings to participating securities	$ (1,126)
Allocation of undistributed earnings to participating securities (in shares / units)	0
Allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ 0
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities	$ 565,207	$ 113,382
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in shares / units)	172,549,000	172,131,000
Net income attributable to the company's common shareholders / unitholders, after allocation of undistributed earnings to participating securities (in dollars per share / unit)	$ 3.28	$ 0.66
Effect of Dilutive Securities:
Stock Based Compensation	$ 0	$ 0
Stock Based Compensation (in shares / units)	247,000	319,000
Weighted Average Number Diluted Shares Outstanding Adjustment (per share)	$ (0.01)	$ 0
Diluted Earnings:
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders	$ 565,207	$ 113,382
Diluted Earnings: Net income attributable to the Company's common shareholders / unitholders (in shares / units)	172,796,000	172,450,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 3.27	$ 0.66

Stock Option and Incentive Pl_2

Stock Option and Incentive Plan (Narrative) (Details) - USD ($) $ in Millions	Feb. 06, 2020	Feb. 04, 2020	Feb. 05, 2019
MYLTIP 2019 [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]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued	155,393,455		154,869,198
Stock based compensation expense	$ 17,200	$ 14,800
Common Stock, Value, Issued	$ 1,553		$ 1,548
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued	24,503
Employee and director payment per share (in dollars per share)	$ 0.01
Common Stock, Value, Issued	$ 3,500
Common Stock Weighted Average Price (in dollars per share)	$ 143.45
LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value Of LTIP Units Issued	$ 25,500
Weighted Average Per Unit Fair Value (in dollars per share)	$ 129.65
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 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	$ 42,200
Unvested MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses	$ 19,800
Weighted-average period (years)	2 years 7 months 6 days
Boston Properties Limited Partnership | LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP units issued (in shares)	196,927
Boston Properties Limited Partnership | MYLTIP 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued (in shares)	203,278

Segment Information (Schedule O

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 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	$ 497,496	$ 98,105
Preferred dividends / distributions	(2,625)	(2,625)
Noncontrolling interest-common units of the Operating Partnership	(57,539)	(11,599)
Noncontrolling interest in property partnerships	(19,486)	(18,830)
Interest expense	(101,591)	(101,009)
Company's share of net operating income from joint ventures	(471,653)	(447,715)
Depreciation and amortization expense	(171,094)	(164,594)
Transaction costs	(615)	(460)
General and administrative expense	(36,454)	(41,762)
Gains (losses) from investments in securities	5,445	(2,969)
Interest and other income	(3,017)	(3,753)
Income from unconsolidated joint ventures	369	(213)
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	497,496	98,105
Preferred dividends / distributions	2,625	2,625
Noncontrolling interest-common units of the Operating Partnership	57,539	11,599
Noncontrolling interest in property partnerships	19,486	18,830
Interest expense	101,591	101,009
Impairment losses	0	24,038
Depreciation and amortization expense	171,094	164,594
Transaction costs	615	460
Payroll and related costs from management services contracts	3,237	3,395
General and administrative expense	36,454	41,762
Gains (losses) from investments in securities	(5,445)	2,969
Interest and other income	3,017	3,753
Gains on sales of real estate	410,165	(905)
Income from unconsolidated joint ventures	(369)	213
Other revenue	3,237	3,395
Net Operating Income	452,750	425,979
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	566,333	113,382
Preferred dividends / distributions	(2,625)	(2,625)
Noncontrolling interest in property partnerships	(19,486)	(18,830)
Interest expense	(101,591)	(101,009)
Depreciation and amortization expense	(169,285)	(162,682)
Transaction costs	(615)	(460)
General and administrative expense	(36,454)	(41,762)
Gains (losses) from investments in securities	5,445	(2,969)
Interest and other income	(3,017)	(3,753)
Income from unconsolidated joint ventures	369	(213)
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	566,333	113,382
Preferred dividends / distributions	2,625	2,625
Noncontrolling interest in property partnerships	19,486	18,830
Interest expense	101,591	101,009
Impairment losses	0	22,272
Depreciation and amortization expense	169,285	162,682
Transaction costs	615	460
Payroll and related costs from management services contracts	3,237	3,395
General and administrative expense	36,454	41,762
Gains (losses) from investments in securities	(5,445)	2,969
Interest and other income	3,017	3,753
Gains on sales of real estate	419,654	(905)
Income from unconsolidated joint ventures	(369)	213
Other revenue	3,237	3,395
Net Operating Income	452,750	425,979
Unconsolidated Joint Ventures [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense	(22,583)	(20,757)
Company's share of net operating income from joint ventures	(28,758)	(25,349)
Depreciation and amortization expense	(32,035)	(28,646)
Income from unconsolidated joint ventures	369	(213)
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	(28,758)	(25,349)
Unconsolidated Joint Ventures [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	(28,758)	(25,349)
Management Service [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payroll and related costs from management services contracts	(3,237)	(3,395)
Other revenue	(7,879)	(9,277)
Management Service [Member] | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other revenue	7,879	9,277
Management Service [Member] | Boston Properties Limited Partnership
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payroll and related costs from management services contracts	(3,237)	(3,395)
Other revenue	(7,879)	(9,277)
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	7,879	9,277
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	47,661	47,085
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	47,661	47,085
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	$ 47,661	$ 47,085

Segment Information (Schedule_2

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 724,659	$ 696,442
Rental Revenue: Residential	[1]	9,956	7,715
Rental Revenue Total	[1]	$ 741,440	$ 713,095
Rental Revenue: % of Grand Totals	[1]	100.00%	100.00%
Rental Expenses: Class A Office		$ 258,902	$ 253,743
Rental Expenses: Residential		4,064	3,774
Rental Expenses: Total		$ 269,787	$ 265,380
Rental Expenses: % Of Grand Totals		100.00%	100.00%
Net Operating Income		$ 471,653	$ 447,715
Net Operating Income: % of Grand Totals		100.00%	100.00%
Company's Share of Net Operating Income: % of Grand Totals		100.00%	100.00%
Boston [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 239,498	$ 217,411
Rental Revenue: Residential	[1]	4,068	2,701
Rental Revenue Total	[1]	$ 250,391	$ 229,050
Rental Revenue: % of Grand Totals	[1]	33.77%	32.12%
Rental Expenses: Class A Office		$ 82,545	$ 79,500
Rental Expenses: Residential		1,340	1,206
Rental Expenses: Total		$ 90,706	$ 88,569
Rental Expenses: % Of Grand Totals		33.62%	33.37%
Net Operating Income		$ 159,685	$ 140,481
Net Operating Income: % of Grand Totals		33.85%	31.38%
Company's Share of Net Operating Income: % of Grand Totals		33.60%	30.96%
Los Angeles [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 0	$ 0
Rental Revenue: Residential	[1]	0	0
Rental Revenue Total	[1]	$ 0	$ 0
Rental Revenue: % of Grand Totals	[1]	0.00%	0.00%
Rental Expenses: Class A Office		$ 0	$ 0
Rental Expenses: Residential		0	0
Rental Expenses: Total		$ 0	$ 0
Rental Expenses: % Of Grand Totals		0.00%	0.00%
Net Operating Income		$ 0	$ 0
Net Operating Income: % of Grand Totals		0.00%	0.00%
Company's Share of Net Operating Income: % of Grand Totals		3.52%	3.69%
New York [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 255,286	$ 258,631
Rental Revenue: Residential	[1]	0	0
Rental Revenue Total	[1]	$ 255,286	$ 258,631
Rental Revenue: % of Grand Totals	[1]	34.43%	36.27%
Rental Expenses: Class A Office		$ 99,140	$ 96,971
Rental Expenses: Residential		0	0
Rental Expenses: Total		$ 99,140	$ 96,971
Rental Expenses: % Of Grand Totals		36.75%	36.54%
Net Operating Income		$ 156,146	$ 161,660
Net Operating Income: % of Grand Totals		33.11%	36.11%
Company's Share of Net Operating Income: % of Grand Totals		26.48%	29.62%
San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 136,739	$ 124,055
Rental Revenue: Residential	[1]	0	0
Rental Revenue Total	[1]	$ 136,739	$ 124,055
Rental Revenue: % of Grand Totals	[1]	18.44%	17.40%
Rental Expenses: Class A Office		$ 42,569	$ 41,125
Rental Expenses: Residential		0	0
Rental Expenses: Total		$ 42,569	$ 41,125
Rental Expenses: % Of Grand Totals		15.78%	15.50%
Net Operating Income		$ 94,170	$ 82,930
Net Operating Income: % of Grand Totals		19.97%	18.52%
Company's Share of Net Operating Income: % of Grand Totals		21.50%	19.36%
Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Class A Office	[1]	$ 93,136	$ 96,345
Rental Revenue: Residential	[1]	5,888	5,014
Rental Revenue Total	[1]	$ 99,024	$ 101,359
Rental Revenue: % of Grand Totals	[1]	13.36%	14.21%
Rental Expenses: Class A Office		$ 34,648	$ 36,147
Rental Expenses: Residential		2,724	2,568
Rental Expenses: Total		$ 37,372	$ 38,715
Rental Expenses: % Of Grand Totals		13.85%	14.59%
Net Operating Income		$ 61,652	$ 62,644
Net Operating Income: % of Grand Totals		13.07%	13.99%
Company's Share of Net Operating Income: % of Grand Totals		14.90%	16.37%
Hotel [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	$ 6,825	$ 8,938
Payroll and related costs from management services contracts		6,821	7,863
Hotel [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	6,825	8,938
Payroll and related costs from management services contracts		6,821	7,863
Hotel [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0
Payroll and related costs from management services contracts		0	0
Hotel [Member] | New York [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0
Payroll and related costs from management services contracts		0	0
Hotel [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0
Payroll and related costs from management services contracts		0	0
Hotel [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Other revenue	[1]	0	0
Payroll and related costs from management services contracts		0	0
Noncontrolling interest - property partnerships [Member]
Segment Reporting Information [Line Items]
Net Operating Income		(47,661)	(47,085)
Noncontrolling interest - property partnerships [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net Operating Income		(10,663)	(9,373)
Noncontrolling interest - property partnerships [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net Operating Income		0	0
Noncontrolling interest - property partnerships [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net Operating Income		(36,998)	(37,264)
Noncontrolling interest - property partnerships [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net Operating Income		0	(448)
Noncontrolling interest - property partnerships [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net Operating Income		0	0
Unconsolidated Joint Ventures [Member]
Segment Reporting Information [Line Items]
Net Operating Income		28,758	25,349
Unconsolidated Joint Ventures [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net Operating Income		3,099	772
Unconsolidated Joint Ventures [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net Operating Income		15,930	15,708
Unconsolidated Joint Ventures [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net Operating Income		756	1,786
Unconsolidated Joint Ventures [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net Operating Income		3,159	0
Unconsolidated Joint Ventures [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net Operating Income		5,814	7,083
Company's Share [Member]
Segment Reporting Information [Line Items]
Net Operating Income		452,750	425,979
Company's Share [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net Operating Income		152,121	131,880
Company's Share [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net Operating Income		15,930	15,708
Company's Share [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net Operating Income		119,904	126,182
Company's Share [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net Operating Income		97,329	82,482
Company's Share [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net Operating Income		$ 67,466	$ 69,727
[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 (Details)

Subsequent Events (Details) - Subsequent Event [Member] $ in Millions	May 05, 2020USD ($)	Apr. 22, 2020USD ($)ft²
Metropolitan Square Associates Llc [Member]
Subsequent Event [Line Items]
Debt		$ 156.4
Debt Instrument, Interest Rate, Stated Percentage		5.75%
Ownership Percentage		20.00%
Net Rentable Area (in sf) | ft²		654,000
3.343 % unsecured senior notes [Member]
Subsequent Event [Line Items]
Debt	$ 1,250
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Senior Notes Pricing	99.85%
Debt Instrument, Interest Rate, Effective Percentage	3.343%
Proceeds from Issuance of Unsecured Debt	$ 1,240