Boston Properties (BXP) 10-Q 7 Aug 19 2019 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - $ / shares	6 Months Ended
	Jun. 30, 2019	Aug. 02, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
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	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-2473675
Entity Address, Address Line One	Prudential Center, 800 Boylston Street, Suite 1900
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02199-8103
City Area Code	(617)
Local Phone Number	236-3300
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		154,567,750
Boston Properties Limited Partnership
Entity Information [Line Items]
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
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	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3372948
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		0
Common Stock [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Entity Listing, Par Value Per Share	$ 0.01
Trading Symbol	BXP
Security Exchange Name	NYSE
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
Entity Listing, Par Value Per Share	$ 0.01
Trading Symbol	BXP PRB
Security Exchange Name	NYSE

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,426,427 and $7,481,015 at June 30, 2019 and December 31, 2018, respectively)	$ 21,943,208	$ 21,649,896
Right of use assets - finance leases (amount related to VIEs of $21,000 at June 30, 2019)	187,269	0
Right of use assets - operating leases	149,839	0
Less: accumulated depreciation (amounts related to VIEs of $(1,011,743) and $(965,500) at June 30, 2019 and December 31, 2018, respectively)	(5,050,606)	(4,897,777)
Total real estate	17,229,710	16,752,119
Cash and cash equivalents (amounts related to VIEs of $245,444 and $296,806 at June 30, 2019 and December 31, 2018, respectively)	1,087,001	543,359
Cash held in escrows	75,923	95,832
Investments in securities	33,411	28,198
Tenant and other receivables (amounts related to VIEs of $10,309 and $15,519 at June 30, 2019 and December 31, 2018, respectively)	87,727	86,629
Note receivable	19,718	19,468
Related party note receivable	80,000	80,000
Accrued rental income (amounts related to VIEs of $283,891 and $272,466 at June 30, 2019 and December 31, 2018, respectively)	973,167	934,896
Deferred charges, net (amounts related to VIEs of $226,426 and $263,402 at June 30, 2019 and December 31, 2018, respectively)	676,082	678,724
Prepaid expenses and other assets (amounts related to VIEs of $25,635 and $26,513 at June 30, 2019 and December 31, 2018, respectively)	68,701	80,943
Investments in unconsolidated joint ventures	936,835	956,309
Total assets	21,268,275	20,256,477
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,924,151 and $2,929,326 at June 30, 2019 and December 31, 2018, respectively)	2,956,833	2,964,572
Unsecured senior notes, net	8,390,708	7,544,697
Unsecured line of credit	0	0
Unsecured term loan, net	498,700	498,488
Lease liabilities - finance leases (amount related to VIEs of $20,107 at June 30, 2019)	172,902	0
Lease liabilities - operating leases	199,344	0
Accounts payable and accrued expenses (amounts related to VIEs of $45,917 and $75,786 at June 30, 2019 and December 31, 2018, respectively)	418,429	276,645
Dividends and distributions payable	165,419	165,114
Accrued interest payable	89,289	89,267
Other liabilities (amounts related to VIEs of $128,504 and $200,344 at June 30, 2019 and December 31, 2018, respectively)	355,984	503,726
Total liabilities	13,247,608	12,042,509
Commitments and contingencies	0	0
Equity / Capital:
Excess stock, $0.01 par value, 150,000,000 shares authorized, none issued or outstanding	0	0
Preferred stock, $.01 par value, 50,000,000 shares authorized
5.25% Series B cumulative redeemable preferred stock/unit, liquidation preference $2,500 per share/unit, 92,000 shares authorized, 80,000 shares/units issued and outstanding at June 30, 2019 and December 31, 2018	200,000	200,000
Common stock, $0.01 par value, 250,000,000 shares authorized, 154,642,030 and 154,537,378 issued and 154,563,130 and 154,458,478 outstanding at June 30, 2019 and December 31, 2018, respectively	1,546	1,545
Additional paid-in capital	6,278,961	6,407,623
Dividends in excess of earnings	(710,592)	(675,534)
Treasury common stock at cost, 78,900 shares at June 30, 2019 and December 31, 2018	(2,722)	(2,722)
Accumulated other comprehensive loss	(51,340)	(47,741)
Total stockholders’ equity attributable to Boston Properties, Inc.	5,715,853	5,883,171
Noncontrolling interests:
Common units of Boston Properties Limited Partnership	608,593	619,352
Property partnerships	1,696,221	1,711,445
Total equity	8,020,667	8,213,968
Total liabilities and equity / capital	21,268,275	20,256,477
Boston Properties Limited Partnership
ASSETS
Real estate, at cost (amounts related to variable interest entities (“VIEs”) of $6,426,427 and $7,481,015 at June 30, 2019 and December 31, 2018, respectively)	21,547,409	21,251,540
Right of use assets - finance leases (amount related to VIEs of $21,000 at June 30, 2019)	187,269	0
Right of use assets - operating leases	149,839	0
Less: accumulated depreciation (amounts related to VIEs of $(1,011,743) and $(965,500) at June 30, 2019 and December 31, 2018, respectively)	(4,949,822)	(4,800,475)
Total real estate	16,934,695	16,451,065
Cash and cash equivalents (amounts related to VIEs of $245,444 and $296,806 at June 30, 2019 and December 31, 2018, respectively)	1,087,001	543,359
Cash held in escrows	75,923	95,832
Investments in securities	33,411	28,198
Tenant and other receivables (amounts related to VIEs of $10,309 and $15,519 at June 30, 2019 and December 31, 2018, respectively)	87,727	86,629
Note receivable	19,718	19,468
Related party note receivable	80,000	80,000
Accrued rental income (amounts related to VIEs of $283,891 and $272,466 at June 30, 2019 and December 31, 2018, respectively)	973,167	934,896
Deferred charges, net (amounts related to VIEs of $226,426 and $263,402 at June 30, 2019 and December 31, 2018, respectively)	676,082	678,724
Prepaid expenses and other assets (amounts related to VIEs of $25,635 and $26,513 at June 30, 2019 and December 31, 2018, respectively)	68,701	80,943
Investments in unconsolidated joint ventures	936,835	956,309
Total assets	20,973,260	19,955,423
Liabilities:
Mortgage notes payable, net (amounts related to VIEs of $2,924,151 and $2,929,326 at June 30, 2019 and December 31, 2018, respectively)	2,956,833	2,964,572
Unsecured senior notes, net	8,390,708	7,544,697
Unsecured line of credit	0	0
Unsecured term loan, net	498,700	498,488
Lease liabilities - finance leases (amount related to VIEs of $20,107 at June 30, 2019)	172,902	0
Lease liabilities - operating leases	199,344	0
Accounts payable and accrued expenses (amounts related to VIEs of $45,917 and $75,786 at June 30, 2019 and December 31, 2018, respectively)	418,429	276,645
Dividends and distributions payable	165,419	165,114
Accrued interest payable	89,289	89,267
Other liabilities (amounts related to VIEs of $128,504 and $200,344 at June 30, 2019 and December 31, 2018, respectively)	355,984	503,726
Total liabilities	13,247,608	12,042,509
Commitments and contingencies	0	0
Noncontrolling interest:
Redeemable partnership units—16,828,230 and 16,783,558 common units and 1,189,117 and 991,577 long term incentive units outstanding at redemption value at June 30, 2019 and December 31, 2018, respectively	2,324,238	2,000,591
Preferred stock, $.01 par value, 50,000,000 shares authorized
5.25% Series B cumulative redeemable preferred stock/unit, liquidation preference $2,500 per share/unit, 92,000 shares authorized, 80,000 shares/units issued and outstanding at June 30, 2019 and December 31, 2018	193,623	193,623
Boston Properties Limited Partnership partners’ capital — 1,725,805 and 1,722,336 general partner units and 152,837,325 and 152,736,142 limited partner units outstanding at June 30, 2019 and December 31, 2018, respectively	3,562,910	4,054,996
Accumulated other comprehensive loss	(51,340)	(47,741)
Noncontrolling interests:
Total partners’ capital	3,705,193	4,200,878
Partners' Capital Attributable to Noncontrolling Interest	1,696,221	1,711,445
Total equity / capital	5,401,414	5,912,323
Total liabilities and equity / capital	$ 20,973,260	$ 19,955,423

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Excess stock, par value	$ 0.01	$ 0.01
Excess stock, shares authorized	150,000,000	150,000,000
Excess stock, shares issued	0	0
Excess stock, shares outstanding	0	0
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	154,642,030	154,537,378
Common stock, shares outstanding	154,563,130	154,458,478
Treasury common stock at cost, shares	78,900	78,900
General Partners' Capital Account, Units Outstanding	1,725,805
Limited Partners' Capital Account, Units Outstanding	152,837,325
Real Estate Investment Property, at Cost	$ 21,943,208	$ 21,649,896
Right of use assets - finance leases (amount related to VIEs of $21,000 at June 30, 2019)	187,269	0
Accumulated depreciation	(5,050,606)	(4,897,777)
Cash and Cash Equivalents	1,087,001	543,359
Tenant and other receivables	87,727	86,629
Accrued rental income	973,167	934,896
Deferred Charges, net	676,082	678,724
Prepaid expense and other assets	68,701	80,943
Mortgage notes payable, net	2,956,833	2,964,572
Lease liabilities - finance leases	172,902	0
Accounts payable and accrued expenses	418,429	276,645
Accrued interest payable	89,289	89,267
Other Liabilities	$ 355,984	$ 503,726
Series B Cumulative Redeemable Preferred Stock [Member]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	92,000	92,000
Series B Dividend Rate Percentage	5.25%	5.25%
Series B, Liquidation Preference Per Share (dollars per share)	$ 2,500	$ 2,500
Series B, shares issued	80,000	80,000
Series B, Shares Outstanding (in shares)	80,000	80,000
Boston Properties Limited Partnership
NonControlling Interest Redeemable Partnership Units Common Units Shares Outstanding	16,828,230	16,783,558
NonControlling Interest Redeemable Partnership Units Common Units Long Term Incentive Units At Redemption Value Shares Outstanding	1,189,117	991,577
General Partners' Capital Account, Units Outstanding	1,725,805	1,722,336
Limited Partners' Capital Account, Units Outstanding	152,837,325	152,736,142
Real Estate Investment Property, at Cost	$ 21,547,409	$ 21,251,540
Right of use assets - finance leases (amount related to VIEs of $21,000 at June 30, 2019)	187,269	0
Accumulated depreciation	(4,949,822)	(4,800,475)
Cash and Cash Equivalents	1,087,001	543,359
Tenant and other receivables	87,727	86,629
Accrued rental income	973,167	934,896
Deferred Charges, net	676,082	678,724
Prepaid expense and other assets	68,701	80,943
Mortgage notes payable, net	2,956,833	2,964,572
Lease liabilities - finance leases	172,902	0
Accounts payable and accrued expenses	418,429	276,645
Accrued interest payable	89,289	89,267
Other Liabilities	$ 355,984	$ 503,726
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock [Member]
Series B Dividend Rate Percentage	5.25%	5.25%
Series B, Liquidation Preference Per Share (dollars per share)	$ 2,500	$ 2,500
Series B, shares issued	80,000	80,000
Series B, Shares Outstanding (in shares)	80,000	80,000
VIE
Real Estate Investment Property, at Cost	$ 6,426,427	$ 7,481,015
Right of use assets - finance leases (amount related to VIEs of $21,000 at June 30, 2019)	21,000
Accumulated depreciation	(1,011,743)	(965,500)
Cash and Cash Equivalents	245,444	296,806
Tenant and other receivables	10,309	15,519
Accrued rental income	283,891	272,466
Deferred Charges, net	226,426	263,402
Prepaid expense and other assets	25,635	26,513
Mortgage notes payable, net	2,924,151	2,929,326
Lease liabilities - finance leases	20,107
Accounts payable and accrued expenses	45,917	75,786
Other Liabilities	128,504	200,344
VIE | Boston Properties Limited Partnership
Real Estate Investment Property, at Cost	6,426,427	7,481,015
Right of use assets - finance leases (amount related to VIEs of $21,000 at June 30, 2019)	21,000
Accumulated depreciation	(1,011,743)	(965,500)
Cash and Cash Equivalents	245,444	296,806
Tenant and other receivables	10,309	15,519
Accrued rental income	283,891	272,466
Deferred Charges, net	226,426	263,402
Prepaid expense and other assets	25,635	26,513
Mortgage notes payable, net	2,924,151	2,929,326
Lease liabilities - finance leases	20,107
Accounts payable and accrued expenses	45,917	75,786
Other Liabilities	$ 128,504	$ 200,344

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) shares in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue
Lease		$ 680,189,000	$ 0	$ 1,359,440,000	$ 0
Base rent		0	516,439,000	0	1,035,946,000
Recoveries from tenants		0	95,259,000	0	190,377,000
Total revenue		733,741,000	664,484,000	1,459,508,000	1,325,635,000
Expenses
Rental		257,971,000	237,790,000	515,488,000	478,119,000
General and administrative		35,071,000	28,468,000	76,833,000	64,362,000
Transaction costs		417,000	474,000	877,000	495,000
Depreciation and amortization		177,411,000	156,417,000	342,005,000	322,214,000
Total expenses		482,353,000	433,860,000	957,944,000	886,859,000
Other income (expense)
Income from unconsolidated joint ventures		47,964,000	769,000	48,177,000	1,230,000
Gains on sales of real estate		1,686,000	18,292,000	781,000	114,689,000
Interest and other income		3,615,000	2,579,000	7,368,000	4,227,000
Gains (losses) from investments in securities		1,165,000	505,000	4,134,000	379,000
Impairment loss		0	0	(24,038,000)	0
Interest expense		(102,357,000)	(92,204,000)	(203,366,000)	(182,424,000)
Net income		203,461,000	160,565,000	334,620,000	376,877,000
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships		(17,482,000)	(14,400,000)	(36,312,000)	(31,634,000)
Noncontrolling interest—common units of Boston Properties Limited Partnership		(19,036,000)	(14,859,000)	(30,627,000)	(35,311,000)
Net income attributable to the Company		166,943,000	131,306,000	267,681,000	309,932,000
Preferred dividends / distributions		(2,625,000)	(2,625,000)	(5,250,000)	(5,250,000)
Net income attributable to the Company's common shareholders / unitholders		$ 164,318,000	$ 128,681,000	$ 262,431,000	$ 304,682,000
Basic earnings per common share / unit attributable to the Company's common shareholders / unitholders
Earnings Per Share, Basic		$ 1.06	$ 0.83	$ 1.70	$ 1.97
Weighted average number of common shares / units outstanding		154,555	154,415	154,540	154,400
Diluted earnings per common share / unit attributable to the Company's common shareholders / unitholders
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)		$ 1.06	$ 0.83	$ 1.69	$ 1.97
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)		154,874	154,571	154,859	154,638
Boston Properties Limited Partnership
Revenue
Lease		$ 680,189,000	$ 0	$ 1,359,440,000	$ 0
Base rent		0	516,439,000	0	1,035,946,000
Recoveries from tenants		0	95,259,000	0	190,377,000
Total revenue		733,741,000	664,484,000	1,459,508,000	1,325,635,000
Expenses
Rental		257,971,000	237,790,000	515,488,000	478,119,000
Operating expense				5,798,000	4,855,000
General and administrative		35,071,000	28,468,000	76,833,000	64,362,000
Transaction costs		417,000	474,000	877,000	495,000
Depreciation and amortization		175,199,000	154,474,000	337,881,000	318,327,000
Total expenses		480,141,000	431,917,000	953,820,000	882,972,000
Other income (expense)
Income from unconsolidated joint ventures		47,964,000	769,000	48,177,000	1,230,000
Gains on sales of real estate		1,835,000	18,770,000	930,000	117,677,000
Interest and other income		3,615,000	2,579,000	7,368,000	4,227,000
Gains (losses) from investments in securities		1,165,000	505,000	4,134,000	379,000
Impairment loss		0	0	(22,272,000)	0
Interest expense		(102,357,000)	(92,204,000)	(203,366,000)	(182,424,000)
Net income		205,822,000	162,986,000	340,659,000	383,752,000
Net income attributable to noncontrolling interests
Noncontrolling interests in property partnerships		(17,482,000)	(14,400,000)	(36,312,000)	(31,634,000)
Net income attributable to the Company		188,340,000	148,586,000	304,347,000	352,118,000
Preferred dividends / distributions		(2,625,000)	(2,625,000)	(5,250,000)	(5,250,000)
Net income attributable to the Company's common shareholders / unitholders		$ 185,715,000	$ 145,961,000	$ 299,097,000	$ 346,868,000
Basic earnings per common share / unit attributable to the Company's common shareholders / unitholders
Earnings Per Share, Basic		$ 1.08	$ 0.85	$ 1.74	$ 2.02
Weighted average number of common shares / units outstanding		172,202	171,916	172,167	171,892
Diluted earnings per common share / unit attributable to the Company's common shareholders / unitholders
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)		$ 1.08	$ 0.85	$ 1.73	$ 2.01
Weighted average number of common and common equivalent shares / units outstanding (in shares / units)		172,521	172,072	172,486	172,130
Parking and Other [Member]
Revenue
Other revenue		$ 26,319,000	$ 26,904,000	$ 51,225,000	$ 53,038,000
Parking and Other [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		26,319,000	26,904,000	51,225,000	53,038,000
Hotel [Member]
Revenue
Other revenue	[1]	14,844,000	14,607,000	23,782,000	23,709,000
Expenses
Operating expense		9,080,000	8,741,000	16,943,000	16,814,000
Hotel [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		14,844,000	14,607,000	23,782,000	23,709,000
Expenses
Operating expense		9,080,000	8,741,000	16,943,000	16,814,000
Development and Management Services [Member]
Revenue
Other revenue		9,986,000	9,305,000	19,263,000	17,710,000
Expenses
Operating expense		2,403,000	1,970,000	5,798,000	4,855,000
Development and Management Services [Member] | Boston Properties Limited Partnership
Revenue
Other revenue		9,986,000	9,305,000	19,263,000	17,710,000
Expenses
Operating expense		2,403,000	1,970,000
Direct reimbursements of payroll and related costs from management services contracts
Revenue
Other revenue		2,403,000	1,970,000	5,798,000	4,855,000
Expenses
Rental		253,849,000	234,877,000	507,592,000	472,934,000
Direct reimbursements of payroll and related costs from management services contracts | Boston Properties Limited Partnership
Revenue
Other revenue		$ 2,403,000	$ 1,970,000	$ 5,798,000	$ 4,855,000
[1]	Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net income		$ 203,461	$ 160,565	$ 334,620	$ 376,877
Other comprehensive income (loss):
Effective portion of interest rate contracts		(4,426)	0	(7,054)	0
Amortization of interest rate contracts	[1]	1,666	1,666	3,332	3,332
Other comprehensive income (loss)		(2,760)	1,666	(3,722)	3,332
Comprehensive income		200,701	162,231	330,898	380,209
Comprehensive income attributable to noncontrolling interests		(36,518)	(29,259)	(66,939)	(66,945)
Other comprehensive (income) loss attributable to noncontrolling interests		154	(299)	123	(598)
Comprehensive income attributable to the Company		164,337	132,673	264,082	312,666
Boston Properties Limited Partnership
Net income		205,822	162,986	340,659	383,752
Other comprehensive income (loss):
Effective portion of interest rate contracts		(4,426)	0	(7,054)	0
Amortization of interest rate contracts	[2]	1,666	1,666	3,332	3,332
Other comprehensive income (loss)		(2,760)	1,666	(3,722)	3,332
Comprehensive income		203,062	164,652	336,937	387,084
Comprehensive income attributable to noncontrolling interests		(17,626)	(14,544)	(36,600)	(31,922)
Comprehensive income attributable to the Company		$ 185,436	$ 150,108	$ 300,337	$ 355,162
[1]	Amounts reclassified from comprehensive income primarily to interest expense within the Boston Properties, Inc.’s Consolidated Statements of Operations.
[2]	Amounts reclassified from comprehensive income primarily to interest expense within the Boston Properties Limited Partnership’s Consolidated Statements of Operations.

Consolidated Statements Of Stoc

Consolidated Statements Of Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Dividends In Excess Of Earnings [Member]	Treasury Stock, At Cost [Member]	Accumulated Other Comprehensive (Income) Loss [Member]	Noncontrolling Interests - Common units [Member]	Noncontrolling interest - property partnerships [Member]
Equity, value at Dec. 31, 2017	$ 8,102,456,000	$ 1,543,000	$ 200,000,000	$ 6,377,908,000	$ (712,343,000)	$ (2,722,000)	$ (50,429,000)	$ 604,739,000	$ 1,683,760,000
Equity, shares at Dec. 31, 2017		154,325,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	5,496,000				4,933,000			563,000
Redemption of operating partnership units to Common Stock, shares		35,000
Redemption of operating partnership units to Common Stock, value	0	$ 1,000		1,195,000				(1,196,000)
Allocated net income for the year	376,877,000				309,932,000			35,311,000	31,634,000
Dividends/distributions declared	(280,977,000)				(252,269,000)			(28,708,000)
Shares issued pursuant to stock purchase plan, shares		3,000
Shares issued pursuant to stock purchase plan, value	429,000			429,000
Net activity from stock option and incentive plan, shares		49,000
Net activity from stock option and incentive plan, value	22,130,000			600,000				21,530,000
Contributions from noncontrolling interests in property partnerships	(27,532,000)								(27,532,000)
Distributions to noncontrolling interests in property partnerships	(44,033,000)								(44,033,000)
Amortization of interest rate contracts	3,332,000						2,734,000	310,000	288,000
Reallocation of noncontrolling interest	0			11,328,000				(11,328,000)
Equity, value at Jun. 30, 2018	8,213,242,000	$ 1,544,000	200,000,000	6,391,460,000	(649,747,000)	(2,722,000)	(47,695,000)	621,221,000	1,699,181,000
Equity, shares at Jun. 30, 2018		154,412,000
Equity, value at Mar. 31, 2018	8,184,090,000	$ 1,544,000	200,000,000	6,384,147,000	(654,879,000)	(2,722,000)	(49,062,000)	619,347,000	1,685,715,000
Equity, shares at Mar. 31, 2018		154,362,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of operating partnership units to Common Stock, shares		11,000
Redemption of operating partnership units to Common Stock, value	0	$ 0		364,000				(364,000)
Allocated net income for the year	160,565,000				131,286,000			14,879,000	14,400,000
Dividends/distributions declared	(140,511,000)				(126,154,000)			(14,357,000)
Shares issued pursuant to stock purchase plan, shares		0
Shares issued pursuant to stock purchase plan, value	0			0
Net activity from stock option and incentive plan, shares		39,000
Net activity from stock option and incentive plan, value	8,510,000			785,000				7,725,000
Contributions from noncontrolling interests in property partnerships	12,265,000								12,265,000
Distributions to noncontrolling interests in property partnerships	(13,343,000)								(13,343,000)
Amortization of interest rate contracts	1,666,000						1,367,000	155,000	144,000
Reallocation of noncontrolling interest	0			6,164,000				(6,164,000)
Equity, value at Jun. 30, 2018	8,213,242,000	$ 1,544,000	200,000,000	6,391,460,000	(649,747,000)	(2,722,000)	(47,695,000)	621,221,000	1,699,181,000
Equity, shares at Jun. 30, 2018		154,412,000
Equity, value at Dec. 31, 2018	$ 8,213,968,000	$ 1,545,000	200,000,000	6,407,623,000	(675,534,000)	(2,722,000)	(47,741,000)	619,352,000	1,711,445,000
Equity, shares at Dec. 31, 2018	154,458,478	154,458,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	$ (4,379,000)				(3,864,000)			(445,000)	(70,000)
Redemption of operating partnership units to Common Stock, shares		35,000
Redemption of operating partnership units to Common Stock, value	0	$ 1,000		1,211,000				(1,212,000)
Allocated net income for the year	334,620,000				267,681,000			30,627,000	36,312,000
Dividends/distributions declared	(333,266,000)				(298,875,000)			(34,391,000)
Shares issued pursuant to stock purchase plan, shares		4,000
Shares issued pursuant to stock purchase plan, value	373,000			373,000
Net activity from stock option and incentive plan, shares		66,000
Net activity from stock option and incentive plan, value	27,332,000			4,554,000				22,778,000
Acquisition of noncontrolling interest in property partnerships	(187,006,000)			(162,505,000)					(24,501,000)
Contributions from noncontrolling interests in property partnerships	(12,148,000)								(12,148,000)
Distributions to noncontrolling interests in property partnerships	(39,401,000)								39,401,000
Effective portion of interest rate contracts	(7,054,000)						(6,332,000)	(722,000)
Amortization of interest rate contracts	3,332,000						2,733,000	311,000	288,000
Reallocation of noncontrolling interest	0			27,705,000				(27,705,000)
Equity, value at Jun. 30, 2019	$ 8,020,667,000	$ 1,546,000	200,000,000	6,278,961,000	(710,592,000)	(2,722,000)	(51,340,000)	608,593,000	1,696,221,000
Equity, shares at Jun. 30, 2019	154,563,130	154,563,000
Equity, value at Mar. 31, 2019	$ 8,170,287,000	$ 1,545,000	200,000,000	6,414,612,000	(728,083,000)	(2,722,000)	(48,734,000)	623,061,000	1,710,608,000
Equity, shares at Mar. 31, 2019		154,515,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle									0
Redemption of operating partnership units to Common Stock, shares		21,000
Redemption of operating partnership units to Common Stock, value	0	$ 1,000		719,000				(720,000)
Allocated net income for the year	203,461,000				166,951,000			19,028,000	17,482,000
Dividends/distributions declared	(166,666,000)				(149,460,000)			(17,206,000)
Shares issued pursuant to stock purchase plan, shares		0
Shares issued pursuant to stock purchase plan, value				0
Net activity from stock option and incentive plan, shares		27,000
Net activity from stock option and incentive plan, value	10,863,000			1,495,000				9,368,000
Acquisition of noncontrolling interest in property partnerships	(187,006,000)			(162,505,000)					(24,501,000)
Contributions from noncontrolling interests in property partnerships	7,761,000								7,761,000
Distributions to noncontrolling interests in property partnerships	(15,273,000)								(15,273,000)
Effective portion of interest rate contracts	(4,426,000)						(3,973,000)	(453,000)
Amortization of interest rate contracts	1,666,000						1,367,000	155,000	144,000
Reallocation of noncontrolling interest	0			24,640,000				(24,640,000)
Equity, value at Jun. 30, 2019	$ 8,020,667,000	$ 1,546,000	$ 200,000,000	$ 6,278,961,000	$ (710,592,000)	$ (2,722,000)	$ (51,340,000)	$ 608,593,000	$ 1,696,221,000
Equity, shares at Jun. 30, 2019	154,563,130	154,563,000

Consolidated Statements of Capi

Consolidated Statements of Capital and Noncontrolling Interests - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Common Stock, Shares, Outstanding	154,563,130		154,563,130			154,458,478
Cumulative effect of a change in accounting principle			$ (4,379,000)	$ 5,496,000
Effective portion of interest rate contracts	$ (4,426,000)		(7,054,000)
Amortization of interest rate contracts	1,666,000	$ 1,666,000	3,332,000	3,332,000
Acquisition of noncontrolling interest in property partnerships	(187,006,000)		(187,006,000)
Contributions from noncontrolling interests in property partnerships	(7,761,000)	(12,265,000)	12,148,000	27,532,000
Distributions to noncontrolling interests in property partnerships	(15,273,000)	$ (13,343,000)	(39,401,000)	(44,033,000)
Boston Properties Limited Partnership
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	2,324,238,000		2,324,238,000			$ 2,000,591,000
Beginning Balance			5,912,323,000
Contributions from noncontrolling interests in property partnerships			12,148,000	$ 27,532,000
Ending Balance	$ 5,401,414,000		$ 5,401,414,000
General Partner [Member]
Common Stock, Shares, Outstanding	1,726,000	1,722,000	1,726,000	1,722,000	1,725,000	1,722,000	1,722,000	1,720,000
Contributions, units	1,000	0	3,000	1,000
Conversion of redeemable partnership units	0	0	1,000	1,000
Limited Partner [Member]
Common Stock, Shares, Outstanding	152,837,000	152,689,000	152,837,000	152,689,000	152,790,000	152,736,000	152,640,000	152,606,000
Contributions, units	26,000	39,000	67,000	50,000
Conversion of redeemable partnership units	21,000	10,000	34,000	33,000
Partners' Capital (General and Limited Partners) [Member]
Beginning Balance	$ 3,603,174,000	$ 3,842,862,000	$ 4,054,996,000	$ 3,664,436,000
Cumulative effect of a change in accounting principle	0	0	(3,864,000)	4,933,000
Contributions, value	882,000	233,000	5,702,000	1,685,000
Allocated net income for the year	166,687,000	131,082,000	268,470,000	314,182,000
Distributions	(146,835,000)	(123,529,000)	(293,625,000)	(249,644,000)
Unearned compensation	613,000	552,000	(775,000)	(656,000)
Conversion of redeemable partnership units	720,000	364,000	1,212,000	1,196,000
Adjustment to reflect redeemable partnership units at redemption value	100,174,000	(30,791,000)	(306,701,000)	84,641,000
Acquisition of noncontrolling interest in property partnerships	(162,505,000)		(162,505,000)
Ending Balance	3,562,910,000	3,820,773,000	3,562,910,000	3,820,773,000
Preferred Units [Member]
Beginning Balance	193,623,000	193,623,000	193,623,000	193,623,000
Allocated net income for the year	2,625,000	2,625,000	5,250,000	2,625,000
Distributions	(2,625,000)	(2,625,000)	(5,250,000)	(2,625,000)
Ending Balance	193,623,000	193,623,000	193,623,000	193,623,000
Accumulated Other Comprehensive (Income) Loss [Member]
Beginning Balance	(48,734,000)	(49,062,000)	(47,741,000)	(50,429,000)
Effective portion of interest rate contracts	(3,973,000)		(6,332,000)
Amortization of interest rate contracts	1,367,000	1,367,000	2,733,000	2,734,000
Ending Balance	(51,340,000)	(47,695,000)	(51,340,000)	(47,695,000)
Noncontrolling interest - property partnerships [Member]
Beginning Balance	1,710,608,000	1,685,715,000	1,711,445,000	1,683,760,000
Cumulative effect of a change in accounting principle	0		(70,000)
Allocated net income for the year	17,482,000	14,400,000	36,312,000	31,634,000
Amortization of interest rate contracts	144,000	144,000	288,000	288,000
Acquisition of noncontrolling interest in property partnerships	(24,501,000)		(24,501,000)
Contributions from noncontrolling interests in property partnerships	(7,761,000)	(12,265,000)	12,148,000	27,532,000
Distributions to noncontrolling interests in property partnerships	(15,273,000)	(13,343,000)	39,401,000	(44,033,000)
Ending Balance	1,696,221,000	1,699,181,000	1,696,221,000	1,699,181,000
Noncontrolling interest - property partnerships [Member] | Boston Properties Limited Partnership
Cumulative effect of a change in accounting principle			(70,000)
Total Capital [Member]
Beginning Balance	5,458,671,000	5,673,138,000	5,912,323,000	5,491,390,000
Cumulative effect of a change in accounting principle	0	0	(3,934,000)	4,933,000
Contributions, value	882,000	233,000	5,702,000	1,685,000
Allocated net income for the year	186,794,000	148,107,000	310,032,000	348,441,000
Distributions	(149,460,000)	(126,154,000)	(298,875,000)	(252,269,000)
Unearned compensation	613,000	552,000	(775,000)	(656,000)
Conversion of redeemable partnership units	720,000	364,000	1,212,000	1,196,000
Adjustment to reflect redeemable partnership units at redemption value	100,174,000	(30,791,000)	(306,701,000)	84,641,000
Effective portion of interest rate contracts	(3,973,000)		(6,332,000)
Amortization of interest rate contracts	1,511,000	1,511,000	3,021,000	3,022,000
Acquisition of noncontrolling interest in property partnerships	(187,006,000)
Contributions from noncontrolling interests in property partnerships	(7,761,000)	(12,265,000)	12,148,000	(27,532,000)
Distributions to noncontrolling interests in property partnerships	(15,273,000)	(13,343,000)	(39,401,000)	(44,033,000)
Ending Balance	5,401,414,000	5,665,882,000	5,401,414,000	5,665,882,000
Noncontrolling interest - Redeemable partnership units [Member]
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	2,324,238,000	2,235,432,000	2,324,238,000	2,235,432,000	$ 2,414,240,000	$ 2,000,591,000	$ 2,196,603,000	$ 2,292,263,000
Cumulative effect of a change in accounting principle	0	0	(445,000)	563,000
Contributions, value	1,082,000	715,000	35,482,000	34,973,000
Allocated net income for the year	19,028,000	14,879,000	30,627,000	35,311,000
Distributions	(17,206,000)	(14,357,000)	(34,391,000)	(28,708,000)
Unearned compensation	8,286,000	7,010,000	(12,704,000)	(13,443,000)
Conversion of redeemable partnership units	(720,000)	(364,000)	(1,212,000)	(1,196,000)
Adjustment to reflect redeemable partnership units at redemption value	(100,174,000)	30,791,000	306,701,000	(84,641,000)
Effective portion of interest rate contracts	453,000		722,000
Amortization of interest rate contracts	$ 155,000	$ 155,000	$ 311,000	$ 310,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 334,620	$ 376,877
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	342,005	322,214
Amortization of right of use assets - operating leases	1,213	0
Impairment loss	24,038	0
Non-cash compensation expense	25,444	23,243
Income from unconsolidated joint ventures	(48,177)	(1,230)
Distributions of net cash flow from operations of unconsolidated joint ventures	3,890	1,663
Gains from investments in securities	(4,134)	(379)
Non-cash portion of interest expense	10,900	10,607
(Losses) gains on sales of real estate	(781)	(114,689)
Change in assets and liabilities:
Tenant and other receivables, net	(11,514)	33,012
Note receivable	(250)	0
Accrued rental income, net	(37,473)	(45,759)
Prepaid expenses and other assets	(9,319)	(4,641)
Lease liabilities - operating leases	780	0
Accounts payable and accrued expenses	17,458	(9,899)
Accrued interest payable	(78)	12,999
Other liabilities	(30,503)	11,571
Tenant leasing costs	(52,515)	(54,743)
Total adjustments	230,984	183,969
Net cash provided by operating activities	565,604	560,846
Cash flows from investing activities:
Acquisition of real estate	(43,061)	0
Construction in progress	(203,259)	(380,565)
Building and other capital improvements	(79,943)	(96,730)
Tenant improvements	(115,940)	(83,982)
Proceeds from sales of real estate	60,398	141,249
Capital contributions to unconsolidated joint ventures	(50,068)	(65,250)
Capital distributions from unconsolidated joint ventures	105,000	0
Investments in securities, net	(1,079)	(523)
Net cash used in investing activities	(327,952)	(485,801)
Cash flows from financing activities:
Repayments of mortgage notes payable	(9,702)	(9,192)
Proceeds from unsecured senior notes	848,428	0
Borrowings on unsecured line of credit	380,000	345,000
Repayments of unsecured line of credit	(380,000)	(390,000)
Proceeds from unsecured term loan	0	500,000
Payments on finance lease obligations	(628)	0
Payments on real estate financing transaction	0	(960)
Deferred financing costs	(7,112)	(263)
Net proceeds from equity transactions	2,261	(684)
Distributions	(332,961)	(280,754)
Contributions from noncontrolling interests in property partnerships	12,148	27,532
Distributions to noncontrolling interests in property partnerships	(39,401)	(44,033)
Acquisition of noncontrolling interest in property partnership	(186,952)	0
Net cash provided by financing activities	286,081	146,646
Net increase in cash and cash equivalents and cash held in escrows	523,733	221,691
Cash and cash equivalents and cash held in escrows, beginning of period	639,191	505,369
Cash and cash equivalents and cash held in escrows, end of period	1,162,924	727,060
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	543,359	434,767
Cash held in escrows, beginning of period	95,832	70,602
Cash and cash equivalents, end of period	1,087,001	472,555
Cash held in escrows, end of period	75,923	254,505
Supplemental disclosures:
Cash paid for interest	216,754	192,898
Interest capitalized	25,069	34,999
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(61,283)	(78,900)
Additions to real estate included in accounts payable and accrued expenses	115,150	326
Real estate acquired through finance lease	122,563	0
Dividends and distributions payable	165,419	139,263
Conversions of redeemable partnership units to partners’ capital	1,212	1,196
Issuance of restricted securities to employees and directors	38,923	37,342
Boston Properties Limited Partnership
Cash flows from operating activities:
Net income	340,659	383,752
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	337,881	318,327
Amortization of right of use assets - operating leases	1,213	0
Impairment loss	22,272	0
Non-cash compensation expense	25,444	23,243
Income from unconsolidated joint ventures	(48,177)	(1,230)
Distributions of net cash flow from operations of unconsolidated joint ventures	3,890	1,663
Gains from investments in securities	(4,134)	(379)
Non-cash portion of interest expense	10,900	10,607
(Losses) gains on sales of real estate	(930)	(117,677)
Change in assets and liabilities:
Tenant and other receivables, net	(11,514)	33,012
Note receivable	(250)	0
Accrued rental income, net	(37,473)	(45,759)
Prepaid expenses and other assets	(9,319)	(4,641)
Lease liabilities - operating leases	780	0
Accounts payable and accrued expenses	17,458	(9,899)
Accrued interest payable	(78)	12,999
Other liabilities	(30,503)	11,571
Tenant leasing costs	(52,515)	(54,743)
Total adjustments	224,945	177,094
Net cash provided by operating activities	565,604	560,846
Cash flows from investing activities:
Acquisition of real estate	(43,061)	0
Construction in progress	(203,259)	(380,565)
Building and other capital improvements	(79,943)	(96,730)
Tenant improvements	(115,940)	(83,982)
Proceeds from sales of real estate	60,398	141,249
Capital contributions to unconsolidated joint ventures	(50,068)	(65,250)
Capital distributions from unconsolidated joint ventures	105,000	0
Investments in securities, net	(1,079)	(523)
Net cash used in investing activities	(327,952)	(485,801)
Cash flows from financing activities:
Repayments of mortgage notes payable	(9,702)	(9,192)
Proceeds from unsecured senior notes	848,428	0
Borrowings on unsecured line of credit	380,000	345,000
Repayments of unsecured line of credit	(380,000)	(390,000)
Proceeds from unsecured term loan	0	500,000
Payments on finance lease obligations	(628)	0
Payments on real estate financing transaction	0	(960)
Deferred financing costs	(7,112)	(263)
Net proceeds from equity transactions	2,261	(684)
Distributions	(332,961)	(280,754)
Contributions from noncontrolling interests in property partnerships	12,148	27,532
Distributions to noncontrolling interests in property partnerships	(39,401)	(44,033)
Acquisition of noncontrolling interest in property partnership	(186,952)	0
Net cash provided by financing activities	286,081	146,646
Net increase in cash and cash equivalents and cash held in escrows	523,733	221,691
Cash and cash equivalents and cash held in escrows, beginning of period	639,191	505,369
Cash and cash equivalents and cash held in escrows, end of period	1,162,924	727,060
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	543,359	434,767
Cash held in escrows, beginning of period	95,832	70,602
Cash and cash equivalents, end of period	1,087,001	472,555
Cash held in escrows, end of period	75,923	254,505
Supplemental disclosures:
Cash paid for interest	216,754	192,898
Interest capitalized	25,069	34,999
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(61,283)	(78,900)
Additions to real estate included in accounts payable and accrued expenses	115,150	326
Real estate acquired through finance lease	122,563	0
Dividends and distributions payable	165,419	139,263
Conversions of redeemable partnership units to partners’ capital	1,212	1,196
Issuance of restricted securities to employees	$ 38,923	$ 37,342

Organization

Organization	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Boston Properties, Inc., a Delaware corporation, is a fully integrated, self-administered and self-managed real estate investment trust (“REIT”). Boston Properties, Inc. is the sole general partner of Boston Properties Limited Partnership, its operating partnership, and at June 30, 2019 owned an approximate 89.6% ( 89.7% at December 31, 2018 ) 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, 2014, 2015, 2016, 2017, 2018 and 2019 multi-year, long-term incentive program awards (also referred to as “MYLTIP Units”), each of which, upon the satisfaction of certain performance and vesting conditions, is convertible into one OP Unit. The three-year measurement periods for the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units expired on February 6, 2015, February 4, 2016, February 3, 2017, February 4, 2018 and February 9, 2019, respectively, and Boston Properties, Inc.’s total stockholder return (“TSR”) was sufficient for employees to earn and therefore become eligible to vest in a portion of the awards. Unless and until they are earned, the rights, preferences and privileges of the 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units differ from other LTIP Units granted to employees (including the 2012 OPP Units, the 2013 MYLTIP Units, the 2014 MYLTIP Units, the 2015 MYLTIP Units and the 2016 MYLTIP Units, which have been earned). Therefore, unless specifically noted otherwise, all references to LTIP Units exclude the 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units. LTIP Units (including the earned 2012 OPP Units, the 2013 MYLTIP Units, the 2014 MYLTIP Units, the 2015 MYLTIP Units and 2016 MYLTIP Units), whether vested or not, will receive the same quarterly per unit distributions as OP Units, which equal per share dividends on Common Stock (See Notes 8 , 9 and 11 ). At June 30, 2019 , there was one series of Preferred Units outstanding (i.e., Series B Preferred Units). The Series B Preferred Units were issued to Boston Properties, Inc. on March 27, 2013 in connection with the issuance of 80,000 shares ( 8,000,000 depositary shares each representing 1/100th of a share) of 5.25% Series B Cumulative Redeemable Preferred Stock (the “Series B Preferred Stock”). Boston Properties, Inc. contributed the net proceeds from the offering to Boston Properties Limited Partnership in exchange for 80,000 Series B Preferred Units having terms and preferences generally mirroring those of the Series B Preferred Stock (See Note 9 ). Properties At June 30, 2019 , the Company owned or had interests in a portfolio of 193 commercial real estate properties (the “Properties”) aggregating approximately 50.9 million net rentable square feet of primarily Class A office properties, including twelve properties under construction/redevelopment totaling approximately 5.7 million net rentable square feet. At June 30, 2019 , the Properties consisted of: • 174 office properties (including ten properties under construction/redevelopment); • twelve retail properties; • six residential properties (including two properties under construction); and • one hotel.

Basis Of Presentation And Summa

Basis Of Presentation And Summary Of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
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, 2018 . Fair Value of Financial Instruments The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. Boston Properties Limited Partnership determines the fair value of its unsecured senior notes using market prices. The inputs used in determining the fair value of Boston Properties Limited Partnership’s unsecured senior notes is categorized at a Level 1 basis (as defined in Accounting Standards Codification (“ASC”) 820 “Fair Value Measurements and Disclosures” (“ASC 820”)) due to the fact that it uses quoted market rates to value these instruments. However, the inputs used in determining the fair value could be categorized at a Level 2 basis (as defined in ASC 820) if trading volumes are low. The Company determines the fair value of its related party note receivable, note receivable and mortgage notes payable using discounted cash flow analysis by discounting the spread between the future contractual interest payments and hypothetical future interest payments on note receivables / mortgage debt based on current market rates for similar securities. In determining the current market rates, the Company adds its estimates of market spreads to the quoted yields on federal government treasury securities with similar maturity dates to its debt. The inputs used in determining the fair value of the Company’s related party note receivable, note receivable, and mortgage notes payable are categorized at a Level 3 basis (as defined in ASC 820) due to the fact that the Company considers the rates used in the valuation techniques to be unobservable inputs. To the extent that there are outstanding borrowings under the unsecured line of credit or unsecured term loan, the Company utilizes a discounted cash flow methodology in order to estimate the fair value. To the extent that credit spreads have changed since the origination, the net present value of the difference between future contractual interest payments and future interest payments based on the Company’s estimate of a current market rate would represent the difference between the book value and the fair value. The Company’s estimate of a current market rate is based upon the rate, considering current market conditions and Boston Properties Limited Partnership’s specific credit profile, at which it estimates it could obtain similar borrowings. To the extent there are outstanding borrowings, this current market rate is estimated and therefore would be primarily based upon a Level 3 input. Because the Company’s valuations of its financial instruments are based on these types of estimates, the actual fair values of its financial instruments may differ materially from those estimates, and 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, note receivable, mortgage notes payable, net, unsecured senior notes, net, unsecured line of credit and unsecured term loan, net and the Company’s corresponding estimate of fair value as of June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 December 31, 2018 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Related party note receivable $ 80,000 $ 80,321 $ 80,000 $ 80,000 Note receivable 19,718 18,205 19,468 19,468 $ 99,718 $ 98,526 $ 99,468 $ 99,468 Mortgage notes payable, net $ 2,956,833 $ 3,013,338 $ 2,964,572 $ 2,903,925 Unsecured senior notes, net 8,390,708 8,745,888 7,544,697 7,469,338 Unsecured line of credit — — — — Unsecured term loan, net 498,700 500,673 498,488 500,783 Total $ 11,846,241 $ 12,259,899 $ 11,007,757 $ 10,874,046 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 nine entities that are VIEs. Consolidated Variable Interest Entities As of June 30, 2019 , 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 8 ). In addition, Boston Properties, Inc.’s only significant asset is its investment in Boston Properties Limited Partnership and, consequently, substantially all of Boston Properties, Inc.’s assets and liabilities are the assets and liabilities of Boston Properties Limited Partnership. Variable Interest Entities Not Consolidated The Company has determined that its 7750 Wisconsin Avenue LLC and Office Tower Developer LLC joint ventures, which own 7750 Wisconsin Avenue and 100 Causeway Street (which is the office component of The Hub on Causeway mixed-use development project), respectively, are VIEs. The Company also determined that the landlord entity for its Platform 16 ground lease is a VIE. The Company does not consolidate these entities as the Company does not have the power to direct the activities that, when taken together, most significantly impact the VIE’s performance and, therefore, the Company is not considered to be the primary beneficiary. New Accounting Pronouncements New Accounting Pronouncements Adopted Leases On January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” (“ASU 2016-02” or “Topic 842”). For information pertaining to the Company’s adoption and disclosures with respect to leases, see Note 4 .

Real Estate

Real Estate	6 Months Ended
	Jun. 30, 2019
Real Estate [Abstract]
Real Estate	3. Real Estate Boston Properties, Inc. Real estate consisted of the following at June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 December 31, 2018 Land $ 5,056,046 $ 5,072,568 Right of use assets - finance leases 187,269 — Right of use assets - operating leases 149,839 — Land held for future development (1) 272,332 200,498 Buildings and improvements 13,271,691 13,356,751 Tenant improvements 2,486,269 2,396,932 Furniture, fixtures and equipment 44,462 44,351 Construction in progress 812,408 578,796 Total 22,280,316 21,649,896 Less: Accumulated depreciation (5,050,606 ) (4,897,777 ) $ 17,229,710 $ 16,752,119 _______________ (1) Includes pre-development costs. Boston Properties Limited Partnership Real estate consisted of the following at June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 December 31, 2018 Land $ 4,955,593 $ 4,971,475 Right of use assets - finance leases 187,269 — Right of use assets - operating leases 149,839 — Land held for future development (1) 272,332 200,498 Buildings and improvements 12,976,345 13,059,488 Tenant improvements 2,486,269 2,396,932 Furniture, fixtures and equipment 44,462 44,351 Construction in progress 812,408 578,796 Total 21,884,517 21,251,540 Less: Accumulated depreciation (4,949,822 ) (4,800,475 ) $ 16,934,695 $ 16,451,065 _______________ (1) Includes pre-development costs. Development On May 9, 2019, the Company entered into a 15-year lease with Google, LLC for approximately 379,000 net rentable square feet of Class A office space in a build-to-suit development project to be located at the Company’s 325 Main Street property at Kendall Center in Cambridge, Massachusetts. 325 Main Street currently consists of an approximately 115,000 net rentable square foot Class A office property that will be demolished and 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. On May 9, 2019, the Company commenced development of the project. Boston Properties, Inc. and Boston Properties Limited Partnership recognized approximately $9.9 million and $9.5 million , respectively, of depreciation expense associated with the acceleration of depreciation on the assets being removed from service and demolished as part of the redevelopment of the property. Ground Lease On January 24, 2019, the ground lessor under the Company’s 65 -year ground lease for land totaling approximately 5.6 acres at Platform 16 located in San Jose, California made available for lease to the Company the remaining land parcels. As a result, the Company recognized the remaining portion of the right of use finance lease asset and finance lease liability. During 2018, the Company executed the ground lease. However, at the inception of the ground lease only a portion of the land was available for lease from the lessor, resulting in the Company recognizing only a portion of the ground lease. In the aggregate, the land will support the development of approximately 1.1 million square feet of commercial office space. The ground lease provides the Company with the right to purchase all of the land during a 12-month period commencing February 1, 2020 at a purchase price of approximately $134.8 million . The Company is reasonably certain that it will exercise the option to purchase the land and as a result, the Company has concluded that the lease should be accounted for as a finance lease. As a result, the Company recorded an approximately $122.6 million right of use asset - finance lease and a lease liability - finance lease on the Company’s Consolidated Balance Sheets reflecting the remaining land parcels made available for lease to the Company. Finance lease assets and liabilities are accounted for at the lower of fair market value or the present value of future lease payments. The finance lease is for land only. Therefore, the Company will not depreciate the right of use asset - finance lease because land is assumed to have an indefinite life. As of January 24, 2019, the lease payments from the finance lease related to the remaining parcels made available for lease to the Company are as follows (in thousands): Period from January 24, 2019 through December 31, 2019 $ 17,918 2020 109,460 Total expected minimum lease payments 127,378 Interest portion (4,815 ) Present value of expected net lease payments $ 122,563 Acquisitions On January 10, 2019, the Company acquired land parcels at its Carnegie Center property located in Princeton, New Jersey for a gross purchase price of approximately $51.5 million , which includes an aggregate of approximately $8.6 million of additional amounts that are payable in the future to the seller upon the development or sale of each of the parcels. The land parcels could support approximately 1.7 million square feet of development. Dispositions On January 24, 2019, the Company completed the sale of its 2600 Tower Oaks Boulevard property located in Rockville, Maryland for a gross sale price of approximately $22.7 million . Net cash proceeds totaled approximately $21.4 million , resulting in a loss on sale of real estate totaling approximately $0.6 million . The Company recognized an impairment loss totaling approximately $3.1 million for Boston Properties, Inc. and approximately $1.5 million for Boston Properties Limited Partnership during the year ended December 31, 2018. 2600 Tower Oaks Boulevard is an approximately 179,000 net rentable square foot Class A office property. 2600 Tower Oaks contributed approximately $(0.2) million of net loss to the Company for the period from January 1, 2019 through January 23, 2019 and contributed approximately $(0.1) million and $(0.3) million of net loss to the Company for the three and six months ended June 30, 2018 , respectively. At March 31, 2019, the Company evaluated the expected hold period of its One Tower Center property and, based on a shorter-than-expected hold period, the Company reduced the carrying value of the property to its estimated fair value at March 31, 2019 and recognized an impairment loss totaling approximately $24.0 million for Boston Properties, Inc. and approximately $22.3 million for Boston Properties Limited Partnership. The Company’s estimated fair value was based on a pending offer from a third party to acquire the property and the subsequent execution of a purchase and sale agreement on April 18, 2019 for a gross sale price of $38.0 million . On June 3, 2019, the Company completed the sale of the property. Net cash proceeds totaled approximately $36.6 million , resulting in a loss on sale of real estate totaling approximately $0.8 million . One Tower Center is an approximately 410,000 net rentable square foot Class A office property located in East Brunswick, New Jersey. One Tower Center contributed approximately $(0.1) million and $(0.9) million of net loss to the Company for the period from April 1, 2019 through June 2, 2019 and the period from January 1, 2019 through June 2, 2019, respectively, and contributed approximately $(0.7) million and $(1.3) million of net loss to the Company for the three and six months ended June 30, 2018 , respectively. On June 28, 2019, the Company completed the sale of its 164 Lexington Road property located in Billerica, Massachusetts for a gross sale price of $4.0 million . Net cash proceeds totaled approximately $3.8 million , resulting in a gain on sale of real estate totaling approximately $2.5 million for Boston Properties, Inc. and approximately $2.6 million for Boston Properties Limited Partnership. 164 Lexington Road is an approximately 64,000 net rentable square foot Class A office property. 164 Lexington Road contributed approximately $(0.1) million and $(0.1) million of net loss to the Company for the period from April 1, 2019 through June 27, 2019 and the period from January 1, 2019 through June 27, 2019, respectively, and contributed approximately $(0.1) million and $(0.1) million

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases of Lessee Disclosure	4. Leases General Adoption In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-02, which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease for accounting purposes is effectively a financed purchase of the leased asset by the lessee. This classification will determine whether the lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to the prior guidance in ASC 840 -“Leases” (“Topic 840”). ASU 2016-02 requires lessors to account for leases using an approach that is substantially equivalent to Topic 840 for sales-type leases, direct financing leases and operating leases. ASU 2016-02 supersedes previous leasing standards. On July 30, 2018, the FASB issued ASU 2018-11, “Leases (Topic 842): Targeted Improvements” (“ASU 2018-11”), that (1) simplifies transition requirements for both lessees and lessors by adding an option that permits an organization to apply the transition provisions of the new standard at its adoption date instead of at the earliest comparative period presented in its financial statements and (2) allows lessors to elect, as a practical expedient, by class of underlying asset, to not separate nonlease components from the associated lease component and, instead, to account for those components as a single component if the nonlease components otherwise would be accounted for under the revenue guidance (ASU 2014-09, “Revenue from Contracts with Customers (Topic 606) (“ASC 606”)) that was adopted on January 1, 2018, and both of the following are met: (1) the timing and pattern of transfer of the nonlease component(s) and associated lease components are the same; and (2) the lease component, if accounted for separately, would be classified as an operating lease. If the nonlease component or components associated with the lease component are the predominant component of the combined component, an entity is required to account for the combined component in accordance with ASC 606. The Company adopted ASU 2016-02 and ASU 2018-11 effective January 1, 2019. For purposes of transition, the Company elected the practical expedient package, which has been applied consistently to all of its leases, but did not elect the hindsight practical expedient. The practical expedient package did not require the Company to reassess the following: (i) whether an expired or existing contract meets the definition of a lease; (ii) the lease classification at the adoption date for existing leases; and (iii) whether costs previously capitalized as initial direct costs would continue to be amortized. This allows the Company to continue to account for its ground leases as operating leases. However, as of January 1, 2019, any new or modified ground leases may be classified as financing leases unless they meet certain conditions. The Company also elected to apply the transition provisions as of the adoption date, January 1, 2019, and not change its comparative statements. The Company recorded an adjustment to the opening balance of retained earnings related to initial direct costs that, as of January 1, 2019, had not started to amortize and are no longer allowed to be capitalized in accordance with ASU 2016-02, totaling approximately $3.9 million to Dividends in Excess of Earnings of Boston Properties, Inc. and Partners’ Capital of Boston Properties Limited Partnership, approximately $0.4 million to Noncontrolling interests - Common Units of Boston Properties, Inc. and Noncontrolling Interest - Redeemable Partnership Units of Boston Properties Limited Partnership and $70,000 to Noncontrolling Interests - Property Partnerships of Boston Properties, Inc. and Noncontrolling Interests in Property Partnerships of Boston Properties Limited Partnership on the corresponding Consolidated Balance Sheets. The Company made the policy election, when it is the lessee, to not apply the revenue recognition requirements of Topic 842 to short-term leases. This policy election is made by class of underlying assets and as described below, the Company considers real estate to be a class of underlying assets, and will not be further delineating it into specific uses of the real estate asset as the risk profiles are similar in nature. The Company will recognize the lease payments in net income on a straight-line basis over the lease term. Lease payments from operating leases are recognized on a straight-line basis over the term of the leases. The cumulative difference between lease revenue recognized under this method and the contractual lease payment terms is recorded as deferred rent receivable on our consolidated balance sheets. The Company reviews its trade accounts receivable, including its straight-line rent receivable, related to base rents, straight-line rent, expense reimbursements and other revenues for collectability. The Company analyzes its accounts receivable, customer credit worthiness and current economic trends when evaluating the adequacy of the collectability of the lessee’s total accounts receivable balance on a lease-by-lease basis. In addition, tenants in bankruptcy are analyzed and considerations are made in connection with the expected recovery of pre-petition and post-petition claims. If a lessee’s accounts receivable balance is considered uncollectible the Company will write-off the receivable balances associated with the lease to Lease revenue and cease to recognize lease income, including straight-line rent unless cash is received. If the Company subsequently determines that it is probable it will collect substantially all the remaining lessee’s lease payments under the lease term, the Company will then reinstate the straight-line balance adjusting for the amount related to the period when the lease payments were considered not probable. The Company’s reported net earnings are directly affected by management’s estimate of the collectability of its trade accounts receivable. In January 2018, the FASB issued ASU 2018-01, “Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842” (“ASU 2018-01”), which provides an optional transition practical expedient to not evaluate, under Topic 842, existing or expired land easements that were not previously accounted for as leases under the leases guidance in Topic 840. An entity that elects this practical expedient should evaluate new or modified land easements under Topic 842 beginning at the date that the entity adopts Topic 842. An entity that does not elect this practical expedient should evaluate all existing or expired land easements in connection with the adoption of the new lease requirements in Topic 842 to assess whether they meet the definition of a lease. The effective date and transition requirements for ASU 2018-01 are the same as the effective date and transition requirements in ASU 2016-02. The Company adopted ASU 2018-01 on January 1, 2019. Lessee For leases in which the Company is the lessee (generally ground leases), on January 1, 2019, the Company recognized a right-of-use asset and a lease liability of approximately $151.8 million and $199.3 million , respectively. The leases liability was equal to the present value of the minimum lease payments in accordance with Topic ASC 840. In addition, the Company did not know the rate implicit in any of its ground leases that were classified as operating leases, and accordingly used the Company’s incremental borrowing rate (“IBR”) to determine the net present value of the minimum lease payments. In order to determine the IBR, the Company utilized a market-based approach to estimate the incremental borrowing rate for each individual lease. The approach required significant judgment. Therefore, the Company utilized different data sets to estimate base IBRs via an analysis of the following weighted-components: • The interpolated rates from yields on outstanding U.S. Treasury issuances for up to 30 years and for years 31 and beyond, longer-term publicly traded educational institution debt issued by high credit quality educational institutions with maturity dates up to 2116, • Observable mortgage rates spread over U.S. Treasury issuances, and • Unlevered property yields and discount rates. The Company then applied adjustments to account for considerations related to term and interpolated the IBR. The Company has four non-cancelable ground lease obligations, which were classified as operating leases, with various initial term expiration dates through 2114. The Company recognizes ground rent expense on a straight-line basis over the term of the respective ground lease agreements. None of the amounts disclosed below for these ground leases contain variable payments, extension options or residual value guarantees. One of the ground leases does have an extension option. However, lease payments for this ground lease are based on fair market value and as such have not been included in the analysis below. The Company has four finance lease obligations with various initial term expiration dates through 2036. The following table provides lease cost information for the Company’s operating and finance leases for the three and six months ended June 30, 2019 (in thousands): Three months ended June 30, 2019 Six months ended June 30, 2019 Lease costs Operating lease costs $ 3,656 $ 7,333 Finance lease costs Amortization of right of use asset (1) $ (14 ) $ 2 Interest on lease liabilities (2) $ 12 $ 24 _______________ (1) The finance leases relate to either land, buildings or assets that remain in development. The Company’s policy is not to depreciate finance lease assets related to land because it is assumed to have an indefinite life. For assets under development, depreciation may commence once the asset is placed in-service and depreciation would be recognized in accordance with the Company’s policy. (2) Three of the finance leases relate to assets under development and as such, the entire interest amount was capitalized. The following table provides other quantitative information for the Company’s operating and finance leases as of June 30, 2019 : June 30, 2019 Other information Weighted-average remaining lease term (in years) Operating leases 51 Finance leases 5 Weighted-average discount rate Operating leases 5.7 % Finance leases 4.1 % The following table provides a maturity analysis for the Company’s future contractual minimum lease payments to be made by the Company as of December 31, 2018, under non-cancelable ground leases which expire on various dates through 2114: Years Ending December 31, (in thousands) 2019 $ 11,425 2020 18,425 2021 25,310 2022 8,894 2023 9,084 Thereafter 567,232 The following table provides a maturity analysis for the Company's future minimum lease payments, as of December 31, 2018, related to the four capital leases, through 2036: Years Ending December 31, (in thousands) 2019 $ 1,441 2020 12,682 2021 2,123 2022 1,253 2023 944 Thereafter 73,241 Total expected minimum lease payments 91,684 Interest portion (27,497 ) Present value of expected net minimum lease payments $ 64,187 The following table provides a maturity analysis for the Company’s lease liabilities related to its operating and finance leases as of June 30, 2019 (in thousands): Operating Finance (1) July 1, 2019 - December 31, 2019 $ 4,872 $ 2,494 2020 10,050 121,499 2021 24,953 2,096 2022 18,041 1,632 2023 10,326 1,039 Thereafter 567,232 73,241 Total lease payments 635,474 202,001 Less: interest portion (436,130 ) (29,099 ) Present value of lease payments $ 199,344 $ 172,902 _______________ (1) Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million , respectively, related to purchase options that the Company is reasonably certain that it will exercise.
Lessor, Operating Leases	Lessor The Company leases primarily Class A office, retail and residential space to tenants. These leases may contain extension and termination options that are predominately at the sole discretion of the tenant, provided certain conditions are satisfied. In a few instances, the leases also contain purchase options, which would be exercisable at fair market value. Also, certain of the Company’s leases include rental payments that are based on a percentage of the tenant sales in excess of contractual amounts. ASU 2018-11 provides lessors a practical expedient to not separate nonlease components from the associated lease component if certain criteria stated above are met for each class of underlying assets. The guidance in Topic 842 defines “underlying asset” as “an asset that is the subject of a lease for which a right to use that asset has been conveyed to a lessee. The underlying asset could be a physically distinct portion of a single asset.” Based on the above guidance, t he Company considers real estate assets as a class of underlying assets and will not be further delineating it into specific uses of the real estate asset as the risk profiles are similar in nature. Lease components are elements of an arrangement that provide the customer with the right to use an identified asset. Nonlease components are distinct elements of a contract that are not related to securing the use of the leased asset and revenue is recognized in accordance with ASC 606. The Company considers common area maintenance (CAM) and service income associated with tenant work orders to be nonlease components because they represent delivery of a separate service but are not considered a cost of securing the identified asset. In the case of the Company’s business, the identified asset would be the leased real estate (office, retail or residential). The Company assessed and concluded that the timing and pattern of transfer for nonlease components and the associated lease component are the same. The Company determined that the predominate component was the lease component and as such its leases will continue to qualify as operating leases and the Company has made a policy election to account for and present the lease component and the nonlease component as a single component in the revenue section of the Consolidated Statements of Operations labeled Lease. Prior to the adoption of Topic 842, nonlease components had been included within Recoveries from Tenants Revenue, Parking and Other Revenue and Development and Management Services Revenue on the Company’s Consolidated Statements of Operations. In addition, under ASU 2016-02, lessors will only capitalize incremental direct leasing costs. As a result, starting January 1, 2019, the Company no longer capitalizes non-incremental legal costs and internal leasing wages. These costs are expensed as incurred. The expensing of these items is included within General and Administrative Expense on the Consolidated Statements of Operations. The following table summarizes the components of lease revenue recognized during the three and six months ended June 30, 2019 included within the Company’s Consolidated Statements of Operations (in thousands): Lease Revenue Three months ended June 30, 2019 Six months ended June 30, 2019 Fixed Contractual Payments $ 557,820 $ 1,111,806 Variable lease payments 122,369 247,634 $ 680,189 $ 1,359,440 The Company’s properties are leased to tenants under operating leases with initial term expiration dates ranging from 2019 to 2049. The future contractual minimum lease payments to be received (excluding operating expense reimbursements) by the Company as of December 31, 2018, under non-cancelable operating leases which expire on various dates through 2049: Years Ending December 31, (in thousands) 2019 $ 2,088,171 2020 2,106,963 2021 2,015,031 2022 1,838,699 2023 1,736,636 Thereafter 12,295,464 The future contractual lease payments to be received (excluding operating expense reimbursements) by the Company as of June 30, 2019 , under non-cancelable operating leases which expire on various dates through 2049: (in thousands) July 1, 2019 - December 31, 2019 $ 1,053,967 2020 2,144,485 2021 2,111,755 2022 1,982,534 2023 1,910,896 Thereafter 14,416,019

Investments in Unconsolidated J

Investments in Unconsolidated Joint Ventures	6 Months Ended
	Jun. 30, 2019
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 June 30, 2019 and December 31, 2018 : Nominal % Ownership Carrying Value of Investment (1) Entity Properties June 30, 2019 December 31, 2018 (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (5,518 ) $ (6,424 ) The Metropolitan Square Associates LLC Metropolitan Square 20.0 % 5,827 2,644 BP/CRF 901 New York Avenue LLC 901 New York Avenue 25.0 % (2) (12,859 ) (13,640 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 37,521 38,214 Annapolis Junction NFM LLC Annapolis Junction 50.0 % (4) 25,290 25,268 540 Madison Venture LLC 540 Madison Avenue 60.0 % (5) 9,200 66,391 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (5,451 ) (5,026 ) 501 K Street LLC 1001 6th Street 50.0 % (6) 42,473 42,557 Podium Developer LLC The Hub on Causeway - Podium 50.0 % 58,637 69,302 Residential Tower Developer LLC The Hub on Causeway - Residential 50.0 % 48,201 47,505 Hotel Tower Developer LLC The Hub on Causeway - Hotel Air Rights 50.0 % 3,626 3,022 Office Tower Developer LLC 100 Causeway Street 50.0 % (7) 69,551 23,804 1265 Main Office JV LLC 1265 Main Street 50.0 % 4,125 3,918 BNY Tower Holdings LLC Dock 72 50.0 % 91,134 82,520 CA-Colorado Center Limited Partnership Colorado Center 50.0 % 254,122 253,495 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % (7) 70,122 69,724 BP-M 3HB Venture LLC 3 Hudson Boulevard 25.0 % 47,966 46,993 SMBP Venture LP Santa Monica Business Park 55.0 % 169,040 180,952 $ 913,007 $ 931,219 _______________ (1) Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets. (2) The Company’s economic ownership has increased based on the achievement of certain return thresholds. (3) The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project. (4) The joint venture owns three in-service buildings and two undeveloped land parcels. (5) The property was sold on June 27, 2019. As of June 30, 2019, the investment is comprised of undistributed cash. See note below for additional details. (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 ). Certain of the Company’s unconsolidated joint venture agreements provide that, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exceptions, under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. Under certain of the Company’s joint venture agreements, if certain return thresholds are achieved, the partners will be entitled to an additional promoted interest or payments. The Company classifies distributions received from equity method investees within its consolidated statements of cash flows using the nature of the distribution approach, which classifies the distributions received on the basis of the nature of the activity or activities of the investee that generated the distribution as either a return on investment (classified as cash inflows from operating activities) or a return of investment (classified as cash inflows from investing activities). The combined summarized balance sheets of the Company’s unconsolidated joint ventures are as follows: June 30, 2019 December 31, 2018 (in thousands) ASSETS Real estate and development in process, net (1) $ 3,551,504 $ 3,545,906 Other assets 515,923 543,512 Total assets $ 4,067,427 $ 4,089,418 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 1,991,290 $ 2,017,609 Other liabilities (2) 656,902 582,006 Members’/Partners’ equity 1,419,235 1,489,803 Total liabilities and members’/partners’ equity $ 4,067,427 $ 4,089,418 Company’s share of equity $ 574,662 $ 622,498 Basis differentials (3) 338,345 308,721 Carrying value of the Company’s investments in unconsolidated joint ventures (4) $ 913,007 $ 931,219 _______________ (1) At June 30, 2019 , this amount includes right of use assets - finance leases and right of use assets - operating leases totaling approximately $248.9 million and $12.5 million , respectively. (2) At June 30, 2019 , this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.2 million and $17.2 million , respectively. (3) This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At June 30, 2019 and December 31, 2018 , there was an aggregate basis differential of approximately $313.3 million and $316.7 million , respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities. (4) Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018 , 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 June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Total revenue (1) $ 80,204 $ 57,096 $ 163,159 $ 113,582 Expenses Operating 30,134 22,868 60,633 45,717 Depreciation and amortization 24,818 14,527 53,464 29,252 Total expenses 54,952 37,395 114,097 74,969 Other income (expense) Interest expense (20,803 ) (14,708 ) (41,560 ) (29,132 ) Gain on sale of real estate (2) 34,572 — 34,572 — Net income $ 39,021 $ 4,993 $ 42,074 $ 9,481 Company’s share of net income $ 22,376 $ 2,105 $ 23,960 $ 3,931 Basis differential (2) (3) 25,588 (1,336 ) 24,217 (2,701 ) Income from unconsolidated joint ventures $ 47,964 $ 769 $ 48,177 $ 1,230 _______________ (1) Includes straight-line rent adjustments of approximately $7.6 million and $3.2 million for the three months ended June 30, 2019 and 2018 , respectively, and $13.4 million and $5.0 million for the six months ended June 30, 2019 and 2018 , respectively. (2) Represents the total gain on sale of 540 Madison Avenue recognized by the joint venture, as described below. During 2008, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture resulting in a basis differential between the carrying value of the Company’s investment in the joint venture and the joint venture’s basis in the assets and liabilities of the property. As a result of the historical basis difference, the Company recognized a gain on sale of real estate totaling approximately $47.8 million , which consists of its share of the gain on sale reported by the joint venture as well as an adjustment for the basis differential. The gain on sale is included in Income from Unconsolidated Joint Ventures in the Company’s Consolidated Statements of Operations. (3) Includes straight-line rent adjustments of approximately $0.5 million and $0.7 million for the three months ended June 30, 2019 and 2018 , respectively, and $1.1 million and $1.4 million for the six months ended June 30, 2019 and 2018 , respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.4 million for the three months ended June 30, 2019 and 2018 , respectively, and $0.8 million and $0.8 million for the six months ended June 30, 2019 and 2018 , respectively. On January 24, 2019, a joint venture in which the Company has a 50% interest extended the loan collateralized by its Annapolis Junction Building Six property. At the time of the extension, the outstanding balance of the loan totaled approximately $13.0 million and was scheduled to mature on November 17, 2019, with one , one -year extension option, subject to certain conditions. The extended loan has a total commitment amount of approximately $14.3 million , bears interest at a variable rate equal to LIBOR plus 2.00% per annum and matures on November 17, 2020. Annapolis Junction Building Six is a Class A office property with approximately 119,000 net rentable square feet located in Annapolis, Maryland. On April 26, 2019, a joint venture in which the Company has a 50% interest obtained construction financing with a total commitment of $255.0 million collateralized by its 7750 Wisconsin Avenue development project located in Bethesda, Maryland. The construction financing bears interest at a variable rate equal to LIBOR plus 1.25% per annum and matures on April 26, 2023, with two , one -year extension options, subject to certain conditions. As of June 30, 2019 , there have been no amounts drawn under the loan. 7750 Wisconsin Avenue is a 734,000 net rentable square foot build-to-suit Class A office project and below-grade parking garage. On May 28, 2019, joint ventures in which the Company has a 50% interest and that own The Hub on Causeway - Podium and 100 Causeway Street development projects entered into an infrastructure development assistance agreement (the “IDAA”) with the Commonwealth of Massachusetts and the City of Boston. Per the IDAA, the Hub on Causeway - Podium development project will be reimbursed for certain costs of public infrastructure improvements using the proceeds of up to $30.0 million in aggregate principal amount of municipal bonds issued by the Commonwealth of Massachusetts. As of June 30, 2019, the joint venture had not received any reimbursements of costs for the public infrastructure improvements. In addition, the joint venture that owns the Hub on Causeway - Podium development project modified its construction loan agreement with the lender requiring the joint venture to pay down the construction loan balance using the proceeds received from the reimbursement of costs of the public infrastructure improvements. On June 15, 2019, the joint venture partially placed in-service The Hub on Causeway - Podium development project, an approximately 385,000 net rentable square foot project containing retail and office space located in Boston, Massachusetts. On June 27, 2019, a joint venture in which the Company has a 60% interest completed the sale of 540 Madison Avenue in New York City for a gross sale price of approximately $310.3 million , including the assumption by the buyer of the mortgage loan collateralized by the property totaling $120.0 million . The mortgage loan bore interest at a variable rate equal to LIBOR plus 1.10% per annum and was scheduled to mature on June 5, 2023. Net cash proceeds totaled approximately $178.7 million , of which the Company’s share was approximately $107.1 million , after the payment of transaction costs. During 2008, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture. As a result, the Company recognized a gain on sale of real estate totaling approximately $47.8 million , which is included in Income from Unconsolidated Joint Ventures in the accompanying Consolidated Statements of Operations. 540 Madison Avenue is an approximately 284,000

Unsecured Senior Notes

Unsecured Senior Notes	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Unsecured Senior Notes	6. Unsecured Senior Notes The following summarizes the unsecured senior notes outstanding as of June 30, 2019 (dollars in thousands): Coupon/Stated Rate Effective Rate(1) Principal Amount Maturity Date(2) 10 Year Unsecured Senior Notes 5.625 % 5.708 % $ 700,000 November 15, 2020 10 Year Unsecured Senior Notes 4.125 % 4.289 % 850,000 May 15, 2021 11 Year Unsecured Senior Notes 3.850 % 3.954 % 1,000,000 February 1, 2023 10.5 Year Unsecured Senior Notes 3.125 % 3.279 % 500,000 September 1, 2023 10.5 Year Unsecured Senior Notes 3.800 % 3.916 % 700,000 February 1, 2024 7 Year Unsecured Senior Notes 3.200 % 3.350 % 850,000 January 15, 2025 10 Year Unsecured Senior Notes 3.650 % 3.766 % 1,000,000 February 1, 2026 10 Year Unsecured Senior Notes 2.750 % 3.495 % 1,000,000 October 1, 2026 10 Year Unsecured Senior Notes 4.500 % 4.628 % 1,000,000 December 1, 2028 10 Year Unsecured Senior Notes 3.400 % 3.505 % 850,000 June 21, 2029 Total principal 8,450,000 Net unamortized discount (18,802 ) Deferred financing costs, net (40,490 ) Total $ 8,390,708 _______________ (1) Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs. (2) No principal amounts are due prior to maturity. On June 21, 2019, Boston Properties Limited Partnership completed a public offering of $850.0 million in aggregate principal amount of its 3.400% unsecured senior notes due 2029. The notes were priced at 99.815% of the principal amount to yield an effective rate (including financing fees) of approximately 3.505% per annum to maturity. The notes will mature on June 21, 2029, unless earlier redeemed. The aggregate net proceeds from the offering were approximately $841.3 million after deducting underwriting discounts and transaction expenses. The indenture relating to the unsecured senior notes contains certain financial restrictions and requirements, including (1) a leverage ratio not to exceed 60%, (2) a secured debt leverage ratio not to exceed 50%, (3) an interest coverage ratio of greater than 1.50 and (4) an unencumbered asset value of not less than 150% of unsecured debt. At June 30, 2019 , Boston Properties Limited Partnership was in compliance with each of these financial restrictions and requirements.

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	7. Commitments and Contingencies General In the normal course of business, the Company guarantees its performance of services or indemnifies third parties against its negligence. In addition, in the normal course of business, the Company guarantees to certain tenants the obligations of its subsidiaries for the payment of tenant improvement allowances and brokerage commissions in connection with their leases and limited costs arising from delays in delivery of their premises. The Company has letter of credit and performance obligations related to lender and development requirements that total approximately $18.4 million . Certain of the Company’s joint venture agreements include provisions whereby, at certain specified times, each partner has the right to initiate a purchase or sale of its interest in the joint ventures. With limited exception, under these provisions, the Company is not compelled to purchase the interest of its outside joint venture partners. From time to time, under certain of the Company’s joint venture agreements, if certain return thresholds are achieved, either the Company or its partners will be entitled to an additional promoted interest or payments (See Note 8 ). From time to time, the Company (or ventures in which the Company has an ownership interest) has agreed, and may in the future agree, to (1) guarantee portions of the principal, interest and other amounts in connection with their borrowings, (2) provide customary environmental indemnifications and nonrecourse carve-outs (e.g., guarantees against fraud, misrepresentation and bankruptcy) in connection with their borrowings and (3) provide guarantees to lenders, tenants and other third parties for the completion of development projects. The Company has agreements with its outside partners whereby the partners agree to reimburse the joint venture for their share of any payments made under the guarantee. In some cases, the Company earns a fee from the applicable joint venture for providing the guarantee. In connection with the refinancing of 767 Fifth Avenue’s (the General Motors Building) secured loan by the Company’s consolidated joint venture entity, 767 Venture, LLC, the Company guaranteed the consolidated entity’s obligation to fund various reserves for tenant improvement costs and allowances, leasing commissions and free rent obligations in lieu of cash deposits. As of June 30, 2019 , the maximum funding obligation under the guarantee was approximately $79.8 million . The Company earns a fee from the joint venture for providing the guarantee and has an agreement with the outside partners to reimburse the joint venture for their share of any payments made under the guarantee. As of June 30, 2019 , no amounts related to the guarantee are recorded as liabilities in the Company’s consolidated financial statements. Pursuant to the lease agreement with Marriott, the Company has guaranteed the completion of the office building and parking garage on behalf of its 7750 Wisconsin Avenue joint venture and has also agreed to provide any financing guaranty that may be required with respect to third-party construction financing. The Company earns 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 unavailability or insufficiency of third-party construction financing. In addition, the Company has guaranteed to Marriott, as hotel manager, the completion of a hotel being developed by an affiliate of The Bernstein Companies (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. To secure such financing arrangements, affiliates of The Bernstein Companies are required to provide certain security, which varies depending on the specific loan, by pledges of their equity interest in the office property, a fee mortgage on the hotel property, or both. As of June 30, 2019 , no amounts related to the contingent aspect of any of the guarantees are recorded as liabilities in the Company’s consolidated financial statements. In connection with the sale and development of the Company’s 6595 Springfield Center Drive development project, the Company has guaranteed the completion of the project and the payment of certain cost overruns in accordance with the development management agreement with the buyer. Although the project has been sold and the lease with the federal government tenant has been assigned to the buyer, pursuant to the terms of the Federal Government lease, the Federal Government tenant is not obligated to release the prior owner/landlord from such landlord’s obligations under the lease until completion of the construction. As a result, the entity which previously owned the land remains liable to the Federal Government tenant for the completion of the construction obligations under the lease. The buyer is obligated to fund the balance of the costs to meet such construction obligations, subject to the Company’s obligation to fund cost overruns (if any), as noted above. An affiliate of the buyer has provided a guaranty of the obligations of the buyer to fund such construction costs and the buyer has agreed to use commercially reasonable efforts to require the construction lender to provide certain remedies to the Company in the event the buyer does not fund such construction obligations. As of June 30, 2019 , 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 currently consists of an approximately 115,000 net rentable square foot Class A office property that will be demolished and 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 (See Note 3 ). In 2009, the Company filed a general unsecured creditor’s claim against Lehman Brothers, Inc. for approximately $45.3 million related to its rejection of a lease at 399 Park Avenue in New York City. On January 10, 2014, the trustee for the liquidation of the business of Lehman Brothers allowed the Company’s claim in the amount of approximately $45.2 million . During 2014, 2015, 2016, 2017 and 2018, the Company received distributions of approximately $7.7 million , $8.1 million , $1.4 million , $0.4 million and $0.3 million , respectively. The Company has a remaining claim of approximately $27.2 million . The Company will continue to evaluate whether to attempt to sell the remaining claim or wait until the trustee distributes proceeds from the Lehman Brothers estate. Given the inherent uncertainties in bankruptcy proceedings, there can be no assurance as to the timing or amount of additional proceeds, if any, that the Company may ultimately realize on the remaining claim, whether by sale to a third party or by one or more distributions from the trustee. Accordingly, the Company has not recorded any estimated recoveries associated with this gain contingency within its Consolidated Financial Statements at June 30, 2019 . 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.” In 2019, the program trigger is $180 million and the coinsurance is 19% , however, both will increase in subsequent years pursuant to TRIA. 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, 2020, 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 . The mortgages on the Company’s properties typically contain requirements concerning the financial ratings of the insurers who provide policies covering the property. The Company provides the lenders on a regular basis with the identity of the insurance companies in the Company’s insurance programs. The ratings of some of the Company’s insurers are below the rating requirements in some of the Company’s loan agreements and the lenders for these loans could attempt to claim that an event of default has occurred under the loan. The Company believes it could obtain insurance with insurers which satisfy the rating requirements. Additionally, in the future, the Company’s ability to obtain debt financing secured by individual properties, or the terms of such financing, may be adversely affected if lenders generally insist on ratings for insurers or amounts of insurance which are difficult to obtain or which result in a commercially unreasonable premium. There can be no assurance that a deficiency in the financial ratings of one or more of the Company’s insurers will not have a material adverse effect on the Company. The Company continues to monitor the state of the insurance market in general, and the scope and costs of coverage for acts of terrorism and California earthquake risk in particular, but the Company cannot anticipate what coverage will be available on commercially reasonable terms in future policy years. There are other types of losses, such as from wars, for which the Company cannot obtain insurance at all or at a reasonable cost. With respect to such losses and losses from acts of terrorism, earthquakes or other catastrophic events, if the Company experiences a loss that is uninsured or that exceeds policy limits, the Company could lose the capital invested in the damaged properties, as well as the anticipated future revenues from those properties. Depending on the specific circumstances of each affected property, it is possible that the Company could be liable for mortgage indebtedness or other obligations related to the property. Any such loss could materially and adversely affect the Company’s business and financial condition and results of operations.

Noncontrolling Interests

Noncontrolling Interests	6 Months Ended
	Jun. 30, 2019
Noncontrolling Interest [Abstract]
Noncontrolling Interests	8. Noncontrolling Interests Noncontrolling interests relate to the interests in Boston Properties Limited Partnership not owned by Boston Properties, Inc. and interests in consolidated property partnerships not wholly-owned by the Company. As of June 30, 2019 , the noncontrolling interests in Boston Properties Limited Partnership consisted of 16,828,230 OP Units, 1,189,117 LTIP Units (including 118,067 2012 OPP Units, 68,659 2013 MYLTIP Units, 23,100 2014 MYLTIP Units, 28,724 2015 MYLTIP Units and 98,706 2016 MYLTIP Units), 394,921 2017 MYLTIP Units, 336,195 2018 MYLTIP Units and 220,734 2019 MYLTIP Units held by parties other than Boston Properties, Inc. Noncontrolling Interest—Common Units During the six months ended June 30, 2019 , 34,967 OP Units were presented by the holders for redemption (including 33,767 OP Units issued upon conversion of LTIP Units, 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and 2016 MYLTIP Units) and were redeemed by Boston Properties, Inc. in exchange for an equal number of shares of Common Stock. At June 30, 2019 , Boston Properties Limited Partnership had outstanding 394,921 2017 MYLTIP Units, 336,195 2018 MYLTIP Units and 220,734 2019 MYLTIP Units. Prior to the applicable measurement date (February 6, 2020 for the 2017 MYLTIP Units, February 5, 2021 for the 2018 MYLTIP Units and February 4, 2022 for the 2019 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 9, 2019, the measurement period for the Company’s 2016 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 69.5% of target or an aggregate of approximately $13.6 million (after giving effect to voluntary employee separations). As a result, an aggregate of 364,980 2016 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 MYLTIP Units, 2014 MYLTIP Units and 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) paid in 2019 : Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 28, 2019 July 31, 2019 $0.95 $0.095 March 29, 2019 April 30, 2019 $0.95 $0.095 December 31, 2018 January 30, 2019 $0.95 $0.095 The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and, after the February 4, 2018 measurement date, the 2015 MYLTIP Units) and its distributions on the 2015 MYLTIP Units (prior to the February 4, 2018 measurement date), 2016 MYLTIP Units, 2017 MYLTIP Units and 2018 MYLTIP Units (after the February 6, 2018 issuance date) that occurred during the first and second quarters of 2018: Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 29, 2018 July 31, 2018 $0.80 $0.080 March 29, 2018 April 30, 2018 $0.80 $0.080 December 31, 2017 January 30, 2018 $0.80 $0.080 A holder of an OP Unit may present the OP Unit to Boston Properties Limited Partnership for redemption at any time (subject to restrictions agreed upon at the time of issuance of OP Units to particular holders that may restrict such redemption right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, Boston Properties Limited Partnership must redeem the OP Unit for cash equal to the then value of a share of common stock of Boston Properties, Inc. Boston Properties, Inc. may, in its sole discretion, elect to assume and satisfy the redemption obligation by paying either cash or issuing one share of Common Stock. The value of the OP Units not owned by Boston Properties, Inc. and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units), assuming that all conditions had been met for the conversion thereof, had all of such units been redeemed at June 30, 2019 was approximately $2.3 billion based on the last reported price of a share of Common Stock on the New York Stock Exchange of $129.00 per share on June 28, 2019. Noncontrolling Interests—Property Partnerships The noncontrolling interests in property partnerships consist of the outside equity interests in ventures that are consolidated with the financial results of the Company because the Company exercises control over the entities that own the properties. The equity interests in these ventures that are not owned by the Company, totaling approximately $1.7 billion at June 30, 2019 and December 31, 2018 , are included in Noncontrolling Interests—Property Partnerships in the accompanying Consolidated Balance Sheets. On May 12, 2016, the partners in the Company’s consolidated entity that owns Salesforce Tower located in San Francisco, California amended the venture agreement. Under the original venture agreement, if the Company elected to fund the construction of Salesforce Tower without a construction loan (or a construction loan of less than 50% of project costs) and the venture commenced vertical construction of the project, then the partner’s capital funding obligation would be limited, in which event the Company would fund up to 2.5% of the total project costs (i.e., 50% of the partner’s 5% interest in the venture) in the form of a loan to the partner. This loan would bear interest at the then prevailing market interest rates for construction loans. Under the amended agreement, the partners agreed to structure this funding by the Company as preferred equity rather than a loan. The preferred equity contributed by the Company earned a preferred return equal to LIBOR plus 3.00% per annum and was payable to the Company out of any distributions to which the partner would otherwise be entitled until such preferred equity and preferred return was repaid to the Company. The Company contributed an aggregate of approximately $22.6 million of preferred equity to the venture. Also, under the joint venture agreement, (a) from and after the stabilization date, the partner had the right to cause the Company to purchase all (but not less than all) of the partner’s interest and (b) from and after the third anniversary of the stabilization date, the Company had the right to acquire all (but not less than all) of the partner’s interest, in each case at an agreed upon purchase price or appraised value. In addition, if certain threshold returns were achieved the partner would be entitled to receive an additional promoted interest with respect to cash flow distributions. The term stabilization date was defined in the agreement to generally mean the first date after completion upon which Salesforce Tower is (1) at least 90% leased and (2) 50% occupied by tenants that are paying rent. Salesforce Tower is an approximately 1,421,000 net rentable square foot Class A office property. On January 18, 2019, the Company and its partner amended the venture agreement. Per the amendment, the partner exercised its right to cause the Company to purchase on April 1, 2019 its 5% ownership interest and promoted profits interest in the venture for cash totaling approximately $210.9 million , which amount was reduced by approximately $24.1 million , consisting of the repayment of the Company’s preferred equity and preferred return as provided for in the venture agreement. On April 1, 2019, the Company completed the acquisition of its partner’s 5% ownership interest and promoted profits interest in the consolidated entity for cash totaling approximately $210.9 million , which amount was reduced by approximately $24.1 million to $186.8 million to reflect the repayment of the Company's preferred equity and preferred return in the venture, as described above. The Company now owns 100% of Salesforce Tower. The Company has accounted for the transaction as an equity transaction for financial reporting purposes and has reflected the difference between the fair value of the total consideration paid and the related carrying value of the noncontrolling interest - property partnership totaling approximately $162.5 million as a decrease to Additional Paid-in Capital and Partners’ Capital in the Consolidated Balance Sheets of Boston Properties, Inc. and Boston Properties Limited Partnership, respectively.

Stockholders' Equity _ Partners

Stockholders' Equity / Partners' Capital	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Stockholders' Equity / Partners' Capital	9. Stockholders’ Equity / Partners’ Capital As of June 30, 2019 , Boston Properties, Inc. had 154,563,130 shares of Common Stock outstanding. As of June 30, 2019 , Boston Properties, Inc. owned 1,725,805 general partnership units and 152,837,325 limited partnership units of Boston Properties Limited Partnership. On June 2, 2017, Boston Properties, Inc. renewed its “at the market” (“ATM”) stock offering program through which it may sell from time to time up to an aggregate of $600.0 million of its common stock through sales agents over a three -year period. This program 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 six months ended June 30, 2019, Boston Properties, Inc. issued 29,704 shares of Common Stock upon the exercise of options to purchase Common Stock. During the six months ended June 30, 2019 , Boston Properties, Inc. issued 34,967 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 2019 and during the first and second quarters of 2018: Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) June 28, 2019 July 31, 2019 $0.95 $0.95 March 29, 2019 April 30, 2019 $0.95 $0.95 December 31, 2018 January 30, 2019 $0.95 $0.95 June 29, 2018 July 31, 2018 $0.80 $0.80 March 29, 2018 April 30, 2018 $0.80 $0.80 December 31, 2017 January 30, 2018 $0.80 $0.80 Preferred Stock As of June 30, 2019 , 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., 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 2019 and the first and second quarters of 2018: Record Date Payment Date Dividend (Per Share) August 2, 2019 August 15, 2019 $32.8125 May 3, 2019 May 15, 2019 $32.8125 February 4, 2019 February 15, 2019 $32.8125 August 3, 2018 August 15, 2018 $32.8125 May 4, 2018 May 15, 2018 $32.8125 February 2, 2018 February 15, 2018 $32.8125

Earnings Per Share _ Common Uni

Earnings Per Share / Common Unit	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share / Common Unit	10. Earnings Per Share / Common Unit Boston Properties, Inc. The following table provides a reconciliation of both the net income attributable to Boston Properties, Inc. common shareholders and the number of common shares used in the computation of basic earnings per share (“EPS”), which is calculated by dividing net income attributable to Boston Properties, Inc. common shareholders by the weighted-average number of common shares outstanding during the period. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are also participating securities. As such, unvested restricted common stock of Boston Properties, Inc. and Boston Properties Limited Partnership’s LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic EPS of Boston Properties, Inc. using the two -class method. Participating securities are included in the computation of diluted EPS of Boston Properties, Inc. using the if-converted method if the impact is dilutive. Because the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units required, and the 2017-2019 MYLTIP Units require, Boston Properties, Inc. to outperform absolute and relative return thresholds, unless such thresholds have been met by the end of the applicable reporting period, Boston Properties, Inc. excludes such units from the diluted EPS calculation. Other potentially dilutive common shares, including stock options, restricted stock and other securities of Boston Properties Limited Partnership that are exchangeable for Boston Properties, Inc.’s Common Stock, and the related impact on earnings, are considered when calculating diluted EPS. Three months ended June 30, 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 $ 164,318 154,555 $ 1.06 Allocation of undistributed earnings to participating securities (48 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,555 $ 1.06 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,874 $ 1.06 Three months ended June 30, 2018 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 $ 128,681 154,415 $ 0.83 Allocation of undistributed earnings to participating securities (16 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 128,665 154,415 $ 0.83 Effect of Dilutive Securities: Stock Based Compensation — 156 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 128,665 154,571 $ 0.83 Six months ended June 30, 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 $ 262,431 154,540 $ 1.70 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 262,431 154,859 $ 1.69 Six months ended June 30, 2018 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 $ 304,682 154,400 $ 1.97 Allocation of undistributed earnings to participating securities (142 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 304,540 154,400 $ 1.97 Effect of Dilutive Securities: Stock Based Compensation — 238 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 304,540 154,638 $ 1.97 Boston Properties Limited Partnership The following table provides a reconciliation of both the net income attributable to Boston Properties Limited Partnership common unitholders and the number of common units used in the computation of basic earnings per common unit, which is calculated by dividing net income attributable to Boston Properties Limited Partnership common unitholders by the weighted-average number of common units outstanding during the period. Unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are also participating securities. As such, unvested restricted common stock of Boston Properties, Inc. and Boston Properties Limited Partnership’s LTIP Units, 2012 OPP Units and MYLTIP Units are considered participating securities. Participating securities are included in the computation of basic earnings per common unit using the two -class method. Participating securities are included in the computation of diluted earnings per common unit using the if-converted method if the impact is dilutive. Because the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units and 2016 MYLTIP Units required, and the 2017-2019 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 17,647,000 and 17,501,000 redeemable common units for the three months ended June 30, 2019 and 2018 , respectively, and 17,627,000 and 17,492,000 redeemable common units for the six months ended June 30, 2019 and 2018 , respectively. Three months ended June 30, 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 $ 185,715 172,202 $ 1.08 Allocation of undistributed earnings to participating securities (54 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,202 $ 1.08 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,521 $ 1.08 Three months ended June 30, 2018 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 $ 145,961 171,916 $ 0.85 Allocation of undistributed earnings to participating securities (18 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 145,943 171,916 $ 0.85 Effect of Dilutive Securities: Stock Based Compensation — 156 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 145,943 172,072 $ 0.85 Six months ended June 30, 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 $ 299,097 172,167 $ 1.74 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 299,097 172,486 $ 1.73 Six months ended June 30, 2018 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 $ 346,868 171,892 $ 2.02 Allocation of undistributed earnings to participating securities (158 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 346,710 171,892 $ 2.02 Effect of Dilutive Securities: Stock Based Compensation — 238 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 346,710 172,130 $ 2.01

Stock Option and Incentive Plan

Stock Option and Incentive Plan	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	11. Stock Option and Incentive Plan On February 5, 2019, Boston Properties, Inc.’s Compensation Committee approved the 2019 MYLTIP awards under Boston Properties, Inc.’s 2012 Stock Option and Incentive Plan (the “2012 Plan”) to certain officers and employees of Boston Properties, Inc. The 2019 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 Nareit Office Index adjusted to include Vornado Realty Trust. Earned awards will range from zero to a maximum of 220,734 LTIP Units depending on Boston Properties, Inc.’s TSR relative to the Nareit Office Index adjusted to include Vornado Realty Trust, with a target of approximately 110,367 LTIP Units and linear interpolation between zero and maximum. Earned awards (if any) will vest 50% on February 4, 2022 and 50% on February 4, 2023, 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 4, 2022, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2019 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 2019 MYLTIP awards have an aggregate value of approximately $13.5 million , which amount will generally be amortized into earnings over the four year plan period under the graded vesting method. On February 9, 2019, the measurement period for the Company’s 2016 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 69.5% of target or an aggregate of approximately $13.6 million (after giving effect to voluntary employee separations). As a result, an aggregate of 364,980 2016 MYLTIP Units that had been previously granted were automatically forfeited. During the six months ended June 30, 2019 , Boston Properties, Inc. issued 26,503 shares of restricted common stock and Boston Properties Limited Partnership issued 181,919 LTIP Units and 220,734 2019 MYLTIP Units to employees and non-employee directors under the 2012 Plan. Employees and non-employee directors paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit and 2019 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. 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 six months ended June 30, 2019 were valued at approximately $3.5 million ( $131.27 per share weighted-average). The LTIP Units granted were valued at approximately $22.1 million (approximately $121.50 per unit weighted-average fair value) using a Monte Carlo simulation method model. The per unit fair values of the LTIP Units granted were estimated on the dates of grant and for a substantial majority of such units were valued using the following assumptions: an expected life of 5.7 years , a risk-free interest rate of 2.68% and an expected price volatility of 27.0% . Because the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units, 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 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, non-qualified stock options, LTIP Units, 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units, 2015 MYLTIP Units, 2016 MYLTIP Units, 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units was approximately $10.1 million and $7.9 million for the three months ended June 30, 2019 and 2018 , respectively, and approximately $24.9 million and $22.1 million for the six months ended June 30, 2019 and 2018 , respectively. At June 30, 2019 , there was (1) an aggregate of approximately $33.2 million of unrecognized compensation expense related to unvested restricted stock, LTIP Units and 2016 MYLTIP Units and (2) an aggregate of approximately $17.9 million of unrecognized compensation expense related to unvested 2017 MYLTIP Units, 2018 MYLTIP Units and 2019 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 2.6 years.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Segment Information	12. Segment Information The following tables present reconciliations of Net Income Attributable to Boston Properties, Inc. Common Shareholders to the Company’s share of Net Operating Income and Net Income Attributable to Boston Properties Limited Partnership Common Unitholders to the Company’s share of Net Operating Income for the three and six months ended June 30, 2019 and 2018 . Boston Properties, Inc. Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 164,318 $ 128,681 $ 262,431 $ 304,682 Add: Preferred dividends 2,625 2,625 5,250 5,250 Noncontrolling interest—common units of Boston Properties Limited Partnership 19,036 14,859 30,627 35,311 Noncontrolling interests in property partnerships 17,482 14,400 36,312 31,634 Interest expense 102,357 92,204 203,366 182,424 Impairment loss — — 24,038 — Net operating income from unconsolidated joint ventures 24,715 16,227 50,064 32,287 Depreciation and amortization expense 177,411 156,417 342,005 322,214 Transaction costs 417 474 877 495 Payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 General and administrative expense 35,071 28,468 76,833 64,362 Less: Net operating income attributable to noncontrolling interests in property partnerships 45,562 43,049 92,647 88,958 Gains from investments in securities 1,165 505 4,134 379 Interest and other income 3,615 2,579 7,368 4,227 Gains on sales of real estate 1,686 18,292 781 114,689 Income from unconsolidated joint ventures 47,964 769 48,177 1,230 Direct reimbursements of payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 Development and management services revenue 9,986 9,305 19,263 17,710 Company’s share of Net Operating Income $ 433,454 $ 379,856 $ 859,433 $ 751,466 Boston Properties Limited Partnership Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,715 $ 145,961 $ 299,097 $ 346,868 Add: Preferred distributions 2,625 2,625 5,250 5,250 Noncontrolling interests in property partnerships 17,482 14,400 36,312 31,634 Interest expense 102,357 92,204 203,366 182,424 Impairment loss — — 22,272 — Net operating income from unconsolidated joint ventures 24,715 16,227 50,064 32,287 Depreciation and amortization expense 175,199 154,474 337,881 318,327 Transaction costs 417 474 877 495 Payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 General and administrative expense 35,071 28,468 76,833 64,362 Less: Net operating income attributable to noncontrolling interests in property partnerships 45,562 43,049 92,647 88,958 Gains from investments in securities 1,165 505 4,134 379 Interest and other income 3,615 2,579 7,368 4,227 Gains on sales of real estate 1,835 18,770 930 117,677 Income from unconsolidated joint ventures 47,964 769 48,177 1,230 Direct reimbursements of payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 Development and management services revenue 9,986 9,305 19,263 17,710 Company’s share of Net Operating Income $ 433,454 $ 379,856 $ 859,433 $ 751,466 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 from investments in securities, interest and other income, gains on sales of real estate, income from unconsolidated joint ventures, direct reimbursements of payroll and related costs from management services contracts and development and management services revenue. The Company believes NOI is useful to investors as a performance measure and believes it provides useful information to investors regarding the Company’s 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 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’ percentage ownership interests and, in some cases, after priority allocations, income allocation to private REIT shareholders and their share of fees due to the Company). The Company’s share of NOI from unconsolidated joint ventures does not include its share of gains on sale of real estate from unconsolidated joint ventures which is included within income from unconsolidated joint ventures in the Company’s Consolidated Statements of Operations. Management utilizes its share of NOI in assessing its performance as the Company has several significant joint ventures and, in some cases, the Company exercises significant influence over, but does not control, the joint venture, in which case GAAP requires that the Company account for the joint venture entity using the equity method of accounting and the Company does not consolidate it for financial reporting purposes. In other cases, GAAP requires that the Company consolidate the venture even though the Company’s partner(s) owns a significant percentage interest. As a result, the presentations of the Company’s share of NOI should not be considered a substitute for, and should only be considered together with and as a supplement to, the Company’s financial information presented in accordance with GAAP. Asset information by segment is not reported because the Company does not use this measure to assess performance. Therefore, depreciation and amortization expense is not allocated among segments. Preferred dividends/distributions, interest expense, impairment loss, depreciation and amortization expense, transaction costs, payroll and related costs from management services contracts, corporate general and administrative expense, gains from investments in securities, interest and other income, gains on sales of real estate, direct reimbursements of payroll and related costs from management services contracts and development and management services revenue are not included in NOI and are provided as reconciling items to the Company’s reconciliations of its share of NOI to net income attributable to common shareholders/unitholders. The Company’s segments are based on the Company’s method of internal reporting which classifies its operations by geographic area. The Company’s segments by geographic area are Boston, Los Angeles, New York, San Francisco and Washington, DC. The Company also presents information for each segment by property type including Office, Residential and Hotel. Beginning in 2019, the Company modified the presentation of its geographic area classification for all periods presented to include the Los Angeles geographic area to align with its method of internal reporting. The Company expanded its presence in the Los Angeles geographic area with its equity method investment in Santa Monica Business Park located in Santa Monica, California. As of June 30, 2019, the Company has equity interests in a portfolio of 27 office and retail properties in the Los Angeles geographic area aggregating approximately 2.3 million net rentable square feet, all of which are owned through investments in unconsolidated joint ventures. The Company is presenting the Los Angeles geographic area as a reportable segment to align with its method of internal reporting given the increased significance as a result of commencing a full reporting period of ownership of the Santa Monica Business Park portfolio. The inclusion of the Los Angeles geographic area has also resulted in a change in the reported measure of segment profit or loss from NOI to the Company’s share of NOI. This change has been reflected in all periods presented and the impact of the change can been seen within the tables below. The Company has not presented rental revenue and rental expenses for properties owned through investments in unconsolidated joint ventures, including those in the Los Angeles geographic area, as the Company accounts for these properties using the equity method of accounting. Information by geographic area (dollars in thousands): For the three months ended June 30, 2019 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 217,961 $ — $ 251,556 $ 131,506 $ 96,486 $ 697,509 Residential 3,222 — — — 5,777 8,999 Hotel 14,844 — — — — 14,844 Total 236,027 — 251,556 131,506 102,263 721,352 % of Grand Totals 32.72 % — % 34.87 % 18.23 % 14.18 % 100.00 % Rental Expenses: Office 77,660 — 96,809 43,708 35,672 253,849 Residential 1,279 — — — 2,843 4,122 Hotel 9,080 — — — — 9,080 Total 88,019 — 96,809 43,708 38,515 267,051 % of Grand Totals 32.96 % — % 36.25 % 16.37 % 14.42 % 100.00 % Net operating income $ 148,008 $ — $ 154,747 $ 87,798 $ 63,748 $ 454,301 % of Grand Totals 32.58 % — % 34.06 % 19.33 % 14.03 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,031 ) — (35,531 ) — — (45,562 ) Add: Company’s share of net operating income from unconsolidated joint ventures 818 15,454 1,696 — 6,747 24,715 Company’s share of net operating income $ 138,795 $ 15,454 $ 120,912 $ 87,798 $ 70,495 $ 433,454 % of Grand Totals 32.01 % 3.57 % 27.90 % 20.26 % 16.26 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the three months ended June 30, 2018 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 207,810 $ — $ 234,006 $ 93,482 $ 98,505 $ 633,803 Residential 1,195 — — — 3,604 4,799 Hotel 14,607 — — — — 14,607 Total 223,612 — 234,006 93,482 102,109 653,209 % of Grand Totals 34.23 % — % 35.83 % 14.31 % 15.63 % 100.00 % Rental Expenses: Office 77,147 — 91,838 31,214 34,678 234,877 Residential 706 — — — 2,207 2,913 Hotel 8,741 — — — — 8,741 Total 86,594 — 91,838 31,214 36,885 246,531 % of Grand Totals 35.12 % — % 37.26 % 12.66 % 14.96 % 100.00 % Net operating income $ 137,018 $ — $ 142,168 $ 62,268 $ 65,224 $ 406,678 % of Grand Totals 33.69 % — % 34.96 % 15.31 % 16.04 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (8,418 ) — (34,751 ) 120 — (43,049 ) Add: Company’s share of net operating income from unconsolidated joint ventures 781 6,902 1,706 — 6,838 16,227 Company’s share of net operating income $ 129,381 $ 6,902 $ 109,123 $ 62,388 $ 72,062 $ 379,856 % of Grand Totals 34.06 % 1.82 % 28.73 % 16.42 % 18.97 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2019 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 435,372 $ — $ 510,187 $ 255,561 $ 192,831 $ 1,393,951 Residential 5,923 — — — 10,791 16,714 Hotel 23,782 — — — — 23,782 Total 465,077 — 510,187 255,561 203,622 1,434,447 % of Grand Totals 32.42 % — % 35.56 % 17.82 % 14.20 % 100.00 % Rental Expenses: Office 157,160 — 193,780 84,833 71,819 507,592 Residential 2,485 — — — 5,411 7,896 Hotel 16,943 — — — — 16,943 Total 176,588 — 193,780 84,833 77,230 532,431 % of Grand Totals 33.17 % — % 36.39 % 15.93 % 14.51 % 100.00 % Net operating income $ 288,489 $ — $ 316,407 $ 170,728 $ 126,392 $ 902,016 % of Grand Totals 31.98 % — % 35.08 % 18.93 % 14.01 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (19,404 ) — (72,795 ) (448 ) — (92,647 ) Add: Company’s share of net operating income from unconsolidated joint ventures 1,590 31,162 3,482 — 13,830 50,064 Company’s share of net operating income $ 270,675 $ 31,162 $ 247,094 $ 170,280 $ 140,222 $ 859,433 % of Grand Totals 31.49 % 3.63 % 28.75 % 19.81 % 16.32 % 100.00 % _______________ (1) Rental Revenue is equal to total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2018 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 412,807 $ — $ 476,404 $ 183,375 $ 197,817 $ 1,270,403 Residential 2,347 — — — 6,611 8,958 Hotel 23,709 — — — — 23,709 Total 438,863 — 476,404 183,375 204,428 1,303,070 % of Grand Totals 33.68 % — % 36.56 % 14.07 % 15.69 % 100.00 % Rental Expenses: Office 157,471 — 185,600 58,842 71,021 472,934 Residential 1,220 — — — 3,965 5,185 Hotel 16,814 — — — — 16,814 Total 175,505 — 185,600 58,842 74,986 494,933 % of Grand Totals 35.46 % — % 37.50 % 11.89 % 15.15 % 100.00 % Net operating income $ 263,358 $ — $ 290,804 $ 124,533 $ 129,442 $ 808,137 % of Grand Totals 32.59 % — % 35.98 % 15.41 % 16.02 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (16,547 ) — (72,697 ) 286 — (88,958 ) Add: Company’s share of net operating income from unconsolidated joint ventures 1,315 13,976 3,367 — 13,629 32,287 Company’s share of net operating income $ 248,126 $ 13,976 $ 221,474 $ 124,819 $ 143,071 $ 751,466 % of Grand Totals 33.02 % 1.86 % 29.47 % 16.61 % 19.04 % 100.00 % _______________ (1) Rental Revenue is equal to total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	13. Subsequent Events On July 16, 2019, the Company executed a 75 -year ground lease with The George Washington University for land parcels at 2100 Pennsylvania Avenue located in Washington, DC and commenced development of an approximately 480,000 net rentable square foot Class A office property pursuant to a development agreement that the Company entered into with The George Washington University in 2016. The development agreement provided for the execution of the ground lease upon completion of the entitlement process and relocation of existing tenants. Also in 2016, the Company made a deposit of $15.0 million that, upon execution of the ground lease, will be credited against ground rent payable under the ground lease. In 2017, the Company entered into a 16-year lease with a tenant for approximately 300,000

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Boston Properties, Inc. does not have any other significant assets, liabilities or operations, other than its investment in Boston Properties Limited Partnership, nor does it have employees of its own. Boston Properties Limited Partnership, not Boston Properties, Inc., generally executes all significant business relationships other than transactions involving securities of Boston Properties, Inc. All majority-owned subsidiaries and joint ventures over which the Company has financial and operating control and variable interest entities (“VIEs”) in which the Company has determined it is the primary beneficiary are included in the consolidated financial statements. All significant intercompany balances and transactions have been eliminated in consolidation. The Company accounts for all other unconsolidated joint ventures using the equity method of accounting. Accordingly, the Company’s share of the earnings of these joint ventures and companies is included in consolidated net income. 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, 2018
Fair Value of Financial Instruments	The Company follows the authoritative guidance for fair value measurements when valuing its financial instruments for disclosure purposes. Boston Properties Limited Partnership determines the fair value of its unsecured senior notes using market prices. The inputs used in determining the fair value of Boston Properties Limited Partnership’s unsecured senior notes is categorized at a Level 1 basis (as defined in Accounting Standards Codification (“ASC”) 820 “Fair Value Measurements and Disclosures” (“ASC 820”)) due to the fact that it uses quoted market rates to value these instruments. However, the inputs used in determining the fair value could be categorized at a Level 2 basis (as defined in ASC 820) if trading volumes are low. The Company determines the fair value of its related party note receivable, note receivable and mortgage notes payable using discounted cash flow analysis by discounting the spread between the future contractual interest payments and hypothetical future interest payments on note receivables / mortgage debt based on current market rates for similar securities. In determining the current market rates, the Company adds its estimates of market spreads to the quoted yields on federal government treasury securities with similar maturity dates to its debt. The inputs used in determining the fair value of the Company’s related party note receivable, note receivable, and mortgage notes payable are categorized at a Level 3 basis (as defined in ASC 820) due to the fact that the Company considers the rates used in the valuation techniques to be unobservable inputs. To the extent that there are outstanding borrowings under the unsecured line of credit or unsecured term loan, the Company utilizes a discounted cash flow methodology in order to estimate the fair value. To the extent that credit spreads have changed since the origination, the net present value of the difference between future contractual interest payments and future interest payments based on the Company’s estimate of a current market rate would represent the difference between the book value and the fair value. The Company’s estimate of a current market rate is based upon the rate, considering current market conditions and Boston Properties Limited Partnership’s specific credit profile, at which it estimates it could obtain similar borrowings. To the extent there are outstanding borrowings, this current market rate is estimated and therefore would be primarily based upon a Level 3 input.
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 nine entities that are VIEs.
New Accounting Pronouncements	New Accounting Pronouncements Adopted Leases On January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” (“ASU 2016-02” or “Topic 842”). For information pertaining to the Company’s adoption and disclosures with respect to leases, see Note 4 .

Leases (Policies)

Leases (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Lessee	For leases in which the Company is the lessee (generally ground leases), on January 1, 2019, the Company recognized a right-of-use asset and a lease liability of approximately $151.8 million and $199.3 million , respectively. The leases liability was equal to the present value of the minimum lease payments in accordance with Topic ASC 840. In addition, the Company did not know the rate implicit in any of its ground leases that were classified as operating leases, and accordingly used the Company’s incremental borrowing rate (“IBR”) to determine the net present value of the minimum lease payments. In order to determine the IBR, the Company utilized a market-based approach to estimate the incremental borrowing rate for each individual lease. The approach required significant judgment. Therefore, the Company utilized different data sets to estimate base IBRs via an analysis of the following weighted-components: • The interpolated rates from yields on outstanding U.S. Treasury issuances for up to 30 years and for years 31 and beyond, longer-term publicly traded educational institution debt issued by high credit quality educational institutions with maturity dates up to 2116, • Observable mortgage rates spread over U.S. Treasury issuances, and • Unlevered property yields and discount rates. The Company then applied adjustments to account for considerations related to term and interpolated the IBR. The Company has four non-cancelable ground lease obligations, which were classified as operating leases, with various initial term expiration dates through 2114. The Company recognizes ground rent expense on a straight-line basis over the term of the respective ground lease agreements. None of the amounts disclosed below for these ground leases contain variable payments, extension options or residual value guarantees. One of the ground leases does have an extension option. However, lease payments for this ground lease are based on fair market value and as such have not been included in the analysis below.
Lessor	ASU 2018-11 provides lessors a practical expedient to not separate nonlease components from the associated lease component if certain criteria stated above are met for each class of underlying assets. The guidance in Topic 842 defines “underlying asset” as “an asset that is the subject of a lease for which a right to use that asset has been conveyed to a lessee. The underlying asset could be a physically distinct portion of a single asset.” Based on the above guidance, t he Company considers real estate assets as a class of underlying assets and will not be further delineating it into specific uses of the real estate asset as the risk profiles are similar in nature. Lease components are elements of an arrangement that provide the customer with the right to use an identified asset. Nonlease components are distinct elements of a contract that are not related to securing the use of the leased asset and revenue is recognized in accordance with ASC 606. The Company considers common area maintenance (CAM) and service income associated with tenant work orders to be nonlease components because they represent delivery of a separate service but are not considered a cost of securing the identified asset. In the case of the Company’s business, the identified asset would be the leased real estate (office, retail or residential). The Company assessed and concluded that the timing and pattern of transfer for nonlease components and the associated lease component are the same. The Company determined that the predominate component was the lease component and as such its leases will continue to qualify as operating leases and the Company has made a policy election to account for and present the lease component and the nonlease component as a single component in the revenue section of the Consolidated Statements of Operations labeled Lease. Prior to the adoption of Topic 842, nonlease components had been included within Recoveries from Tenants Revenue, Parking and Other Revenue and Development and Management Services Revenue on the Company’s Consolidated Statements of Operations.

Basis Of Presentation And Sum_3

Basis Of Presentation And Summary Of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Carrying Value Of Indebtedness And Corresponding Estimate Of Fair Value	The following table presents the aggregate carrying value of the Company’s related party note receivable, note receivable, mortgage notes payable, net, unsecured senior notes, net, unsecured line of credit and unsecured term loan, net and the Company’s corresponding estimate of fair value as of June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 December 31, 2018 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Related party note receivable $ 80,000 $ 80,321 $ 80,000 $ 80,000 Note receivable 19,718 18,205 19,468 19,468 $ 99,718 $ 98,526 $ 99,468 $ 99,468 Mortgage notes payable, net $ 2,956,833 $ 3,013,338 $ 2,964,572 $ 2,903,925 Unsecured senior notes, net 8,390,708 8,745,888 7,544,697 7,469,338 Unsecured line of credit — — — — Unsecured term loan, net 498,700 500,673 498,488 500,783 Total $ 11,846,241 $ 12,259,899 $ 11,007,757 $ 10,874,046

Real Estate (Tables)

Real Estate (Tables)	6 Months Ended
	Jun. 30, 2019
Entity Information [Line Items]
Schedule of Real Estate Properties [Table Text Block]	Boston Properties, Inc. Real estate consisted of the following at June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 December 31, 2018 Land $ 5,056,046 $ 5,072,568 Right of use assets - finance leases 187,269 — Right of use assets - operating leases 149,839 — Land held for future development (1) 272,332 200,498 Buildings and improvements 13,271,691 13,356,751 Tenant improvements 2,486,269 2,396,932 Furniture, fixtures and equipment 44,462 44,351 Construction in progress 812,408 578,796 Total 22,280,316 21,649,896 Less: Accumulated depreciation (5,050,606 ) (4,897,777 ) $ 17,229,710 $ 16,752,119 _______________ (1) Includes pre-development costs.
Finance Lease, Liability, Maturity [Table Text Block]	The following table provides a maturity analysis for the Company’s lease liabilities related to its operating and finance leases as of June 30, 2019 (in thousands): Operating Finance (1) July 1, 2019 - December 31, 2019 $ 4,872 $ 2,494 2020 10,050 121,499 2021 24,953 2,096 2022 18,041 1,632 2023 10,326 1,039 Thereafter 567,232 73,241 Total lease payments 635,474 202,001 Less: interest portion (436,130 ) (29,099 ) Present value of lease payments $ 199,344 $ 172,902 _______________ (1) Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million , respectively, related to purchase options that the Company is reasonably certain that it will exercise.
Boston Properties Limited Partnership
Entity Information [Line Items]
Schedule of Real Estate Properties [Table Text Block]	Boston Properties Limited Partnership Real estate consisted of the following at June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 December 31, 2018 Land $ 4,955,593 $ 4,971,475 Right of use assets - finance leases 187,269 — Right of use assets - operating leases 149,839 — Land held for future development (1) 272,332 200,498 Buildings and improvements 12,976,345 13,059,488 Tenant improvements 2,486,269 2,396,932 Furniture, fixtures and equipment 44,462 44,351 Construction in progress 812,408 578,796 Total 21,884,517 21,251,540 Less: Accumulated depreciation (4,949,822 ) (4,800,475 ) $ 16,934,695 $ 16,451,065 _______________ (1) Includes pre-development costs.
Platform 16 [Member]
Entity Information [Line Items]
Finance Lease, Liability, Maturity [Table Text Block]	As of January 24, 2019, the lease payments from the finance lease related to the remaining parcels made available for lease to the Company are as follows (in thousands): Period from January 24, 2019 through December 31, 2019 $ 17,918 2020 109,460 Total expected minimum lease payments 127,378 Interest portion (4,815 ) Present value of expected net lease payments $ 122,563

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	The following table provides a maturity analysis for the Company’s lease liabilities related to its operating and finance leases as of June 30, 2019 (in thousands): Operating Finance (1) July 1, 2019 - December 31, 2019 $ 4,872 $ 2,494 2020 10,050 121,499 2021 24,953 2,096 2022 18,041 1,632 2023 10,326 1,039 Thereafter 567,232 73,241 Total lease payments 635,474 202,001 Less: interest portion (436,130 ) (29,099 ) Present value of lease payments $ 199,344 $ 172,902
Lease, Cost [Table Text Block]	The following table provides lease cost information for the Company’s operating and finance leases for the three and six months ended June 30, 2019 (in thousands): Three months ended June 30, 2019 Six months ended June 30, 2019 Lease costs Operating lease costs $ 3,656 $ 7,333 Finance lease costs Amortization of right of use asset (1) $ (14 ) $ 2 Interest on lease liabilities (2) $ 12 $ 24 _______________ (1) The finance leases relate to either land, buildings or assets that remain in development. The Company’s policy is not to depreciate finance lease assets related to land because it is assumed to have an indefinite life. For assets under development, depreciation may commence once the asset is placed in-service and depreciation would be recognized in accordance with the Company’s policy. (2) Three of the finance leases relate to assets under development and as such, the entire interest amount was capitalized. The following table provides other quantitative information for the Company’s operating and finance leases as of June 30, 2019 : June 30, 2019 Other information Weighted-average remaining lease term (in years) Operating leases 51 Finance leases 5 Weighted-average discount rate Operating leases 5.7 % Finance leases 4.1 %
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	The following table provides a maturity analysis for the Company’s future contractual minimum lease payments to be made by the Company as of December 31, 2018, under non-cancelable ground leases which expire on various dates through 2114: Years Ending December 31, (in thousands) 2019 $ 11,425 2020 18,425 2021 25,310 2022 8,894 2023 9,084 Thereafter 567,232
Capital Leases in Financial Statements of Lessee Disclosure [Text Block]	The following table provides a maturity analysis for the Company's future minimum lease payments, as of December 31, 2018, related to the four capital leases, through 2036: Years Ending December 31, (in thousands) 2019 $ 1,441 2020 12,682 2021 2,123 2022 1,253 2023 944 Thereafter 73,241 Total expected minimum lease payments 91,684 Interest portion (27,497 ) Present value of expected net minimum lease payments $ 64,187
Finance Lease, Liability, Maturity [Table Text Block]	The following table provides a maturity analysis for the Company’s lease liabilities related to its operating and finance leases as of June 30, 2019 (in thousands): Operating Finance (1) July 1, 2019 - December 31, 2019 $ 4,872 $ 2,494 2020 10,050 121,499 2021 24,953 2,096 2022 18,041 1,632 2023 10,326 1,039 Thereafter 567,232 73,241 Total lease payments 635,474 202,001 Less: interest portion (436,130 ) (29,099 ) Present value of lease payments $ 199,344 $ 172,902 _______________ (1) Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million , respectively, related to purchase options that the Company is reasonably certain that it will exercise.
Operating Lease, Lease Income [Table Text Block]	The following table summarizes the components of lease revenue recognized during the three and six months ended June 30, 2019 included within the Company’s Consolidated Statements of Operations (in thousands): Lease Revenue Three months ended June 30, 2019 Six months ended June 30, 2019 Fixed Contractual Payments $ 557,820 $ 1,111,806 Variable lease payments 122,369 247,634 $ 680,189 $ 1,359,440
Lessor, Operating Lease, Payments to be Received, Maturity [Table Text Block]	The future contractual minimum lease payments to be received (excluding operating expense reimbursements) by the Company as of December 31, 2018, under non-cancelable operating leases which expire on various dates through 2049: Years Ending December 31, (in thousands) 2019 $ 2,088,171 2020 2,106,963 2021 2,015,031 2022 1,838,699 2023 1,736,636 Thereafter 12,295,464 The future contractual lease payments to be received (excluding operating expense reimbursements) by the Company as of June 30, 2019 , under non-cancelable operating leases which expire on various dates through 2049: (in thousands) July 1, 2019 - December 31, 2019 $ 1,053,967 2020 2,144,485 2021 2,111,755 2022 1,982,534 2023 1,910,896 Thereafter 14,416,019

Investments in Unconsolidated_2

Investments in Unconsolidated Joint Ventures (Tables)	6 Months Ended
	Jun. 30, 2019
Investments In Unconsolidated Joint Ventures [Abstract]
Investments In Unconsolidated Joint Ventures	The investments in unconsolidated joint ventures consist of the following at June 30, 2019 and December 31, 2018 : Nominal % Ownership Carrying Value of Investment (1) Entity Properties June 30, 2019 December 31, 2018 (in thousands) Square 407 Limited Partnership Market Square North 50.0 % $ (5,518 ) $ (6,424 ) The Metropolitan Square Associates LLC Metropolitan Square 20.0 % 5,827 2,644 BP/CRF 901 New York Avenue LLC 901 New York Avenue 25.0 % (2) (12,859 ) (13,640 ) WP Project Developer LLC Wisconsin Place Land and Infrastructure 33.3 % (3) 37,521 38,214 Annapolis Junction NFM LLC Annapolis Junction 50.0 % (4) 25,290 25,268 540 Madison Venture LLC 540 Madison Avenue 60.0 % (5) 9,200 66,391 500 North Capitol Venture LLC 500 North Capitol Street, NW 30.0 % (5,451 ) (5,026 ) 501 K Street LLC 1001 6th Street 50.0 % (6) 42,473 42,557 Podium Developer LLC The Hub on Causeway - Podium 50.0 % 58,637 69,302 Residential Tower Developer LLC The Hub on Causeway - Residential 50.0 % 48,201 47,505 Hotel Tower Developer LLC The Hub on Causeway - Hotel Air Rights 50.0 % 3,626 3,022 Office Tower Developer LLC 100 Causeway Street 50.0 % (7) 69,551 23,804 1265 Main Office JV LLC 1265 Main Street 50.0 % 4,125 3,918 BNY Tower Holdings LLC Dock 72 50.0 % 91,134 82,520 CA-Colorado Center Limited Partnership Colorado Center 50.0 % 254,122 253,495 7750 Wisconsin Avenue LLC 7750 Wisconsin Avenue 50.0 % (7) 70,122 69,724 BP-M 3HB Venture LLC 3 Hudson Boulevard 25.0 % 47,966 46,993 SMBP Venture LP Santa Monica Business Park 55.0 % 169,040 180,952 $ 913,007 $ 931,219 _______________ (1) Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets. (2) The Company’s economic ownership has increased based on the achievement of certain return thresholds. (3) The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project. (4) The joint venture owns three in-service buildings and two undeveloped land parcels. (5) The property was sold on June 27, 2019. As of June 30, 2019, the investment is comprised of undistributed cash. See note below for additional details. (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: June 30, 2019 December 31, 2018 (in thousands) ASSETS Real estate and development in process, net (1) $ 3,551,504 $ 3,545,906 Other assets 515,923 543,512 Total assets $ 4,067,427 $ 4,089,418 LIABILITIES AND MEMBERS’/PARTNERS’ EQUITY Mortgage and notes payable, net $ 1,991,290 $ 2,017,609 Other liabilities (2) 656,902 582,006 Members’/Partners’ equity 1,419,235 1,489,803 Total liabilities and members’/partners’ equity $ 4,067,427 $ 4,089,418 Company’s share of equity $ 574,662 $ 622,498 Basis differentials (3) 338,345 308,721 Carrying value of the Company’s investments in unconsolidated joint ventures (4) $ 913,007 $ 931,219 _______________ (1) At June 30, 2019 , this amount includes right of use assets - finance leases and right of use assets - operating leases totaling approximately $248.9 million and $12.5 million , respectively. (2) At June 30, 2019 , this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.2 million and $17.2 million , respectively. (3) This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At June 30, 2019 and December 31, 2018 , there was an aggregate basis differential of approximately $313.3 million and $316.7 million , respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities. (4) Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018 , 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 June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Total revenue (1) $ 80,204 $ 57,096 $ 163,159 $ 113,582 Expenses Operating 30,134 22,868 60,633 45,717 Depreciation and amortization 24,818 14,527 53,464 29,252 Total expenses 54,952 37,395 114,097 74,969 Other income (expense) Interest expense (20,803 ) (14,708 ) (41,560 ) (29,132 ) Gain on sale of real estate (2) 34,572 — 34,572 — Net income $ 39,021 $ 4,993 $ 42,074 $ 9,481 Company’s share of net income $ 22,376 $ 2,105 $ 23,960 $ 3,931 Basis differential (2) (3) 25,588 (1,336 ) 24,217 (2,701 ) Income from unconsolidated joint ventures $ 47,964 $ 769 $ 48,177 $ 1,230 _______________ (1) Includes straight-line rent adjustments of approximately $7.6 million and $3.2 million for the three months ended June 30, 2019 and 2018 , respectively, and $13.4 million and $5.0 million for the six months ended June 30, 2019 and 2018 , respectively. (2) Represents the total gain on sale of 540 Madison Avenue recognized by the joint venture, as described below. During 2008, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture resulting in a basis differential between the carrying value of the Company’s investment in the joint venture and the joint venture’s basis in the assets and liabilities of the property. As a result of the historical basis difference, the Company recognized a gain on sale of real estate totaling approximately $47.8 million , which consists of its share of the gain on sale reported by the joint venture as well as an adjustment for the basis differential. The gain on sale is included in Income from Unconsolidated Joint Ventures in the Company’s Consolidated Statements of Operations. (3) Includes straight-line rent adjustments of approximately $0.5 million and $0.7 million for the three months ended June 30, 2019 and 2018 , respectively, and $1.1 million and $1.4 million for the six months ended June 30, 2019 and 2018 , respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.4 million for the three months ended June 30, 2019 and 2018 , respectively, and $0.8 million and $0.8 million for the six months ended June 30, 2019 and 2018

Unsecured Senior Notes (Tables)

Unsecured Senior Notes (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule of Unsecured Senior Notes	The following summarizes the unsecured senior notes outstanding as of June 30, 2019 (dollars in thousands): Coupon/Stated Rate Effective Rate(1) Principal Amount Maturity Date(2) 10 Year Unsecured Senior Notes 5.625 % 5.708 % $ 700,000 November 15, 2020 10 Year Unsecured Senior Notes 4.125 % 4.289 % 850,000 May 15, 2021 11 Year Unsecured Senior Notes 3.850 % 3.954 % 1,000,000 February 1, 2023 10.5 Year Unsecured Senior Notes 3.125 % 3.279 % 500,000 September 1, 2023 10.5 Year Unsecured Senior Notes 3.800 % 3.916 % 700,000 February 1, 2024 7 Year Unsecured Senior Notes 3.200 % 3.350 % 850,000 January 15, 2025 10 Year Unsecured Senior Notes 3.650 % 3.766 % 1,000,000 February 1, 2026 10 Year Unsecured Senior Notes 2.750 % 3.495 % 1,000,000 October 1, 2026 10 Year Unsecured Senior Notes 4.500 % 4.628 % 1,000,000 December 1, 2028 10 Year Unsecured Senior Notes 3.400 % 3.505 % 850,000 June 21, 2029 Total principal 8,450,000 Net unamortized discount (18,802 ) Deferred financing costs, net (40,490 ) Total $ 8,390,708 _______________ (1) Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs. (2) No principal amounts are due prior to maturity.

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	6 Months Ended
	Jun. 30, 2019
Noncontrolling Interest [Line Items]
Distributions Declared to OP, LTIP, OPP and MYLTIP Units [Table Text Block]	The following table presents Boston Properties, Inc.’s dividends per share and Boston Properties Limited Partnership’s distributions per OP Unit and LTIP Unit paid or declared in 2019 and during the first and second quarters of 2018: Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) June 28, 2019 July 31, 2019 $0.95 $0.95 March 29, 2019 April 30, 2019 $0.95 $0.95 December 31, 2018 January 30, 2019 $0.95 $0.95 June 29, 2018 July 31, 2018 $0.80 $0.80 March 29, 2018 April 30, 2018 $0.80 $0.80 December 31, 2017 January 30, 2018 $0.80 $0.80
Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Distributions Declared to OP, LTIP, OPP and MYLTIP Units [Table Text Block]	The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and 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) paid in 2019 : Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 28, 2019 July 31, 2019 $0.95 $0.095 March 29, 2019 April 30, 2019 $0.95 $0.095 December 31, 2018 January 30, 2019 $0.95 $0.095 The following table presents Boston Properties Limited Partnership’s distributions on the OP Units and LTIP Units (including the 2012 OPP Units, 2013 MYLTIP Units, 2014 MYLTIP Units and, after the February 4, 2018 measurement date, the 2015 MYLTIP Units) and its distributions on the 2015 MYLTIP Units (prior to the February 4, 2018 measurement date), 2016 MYLTIP Units, 2017 MYLTIP Units and 2018 MYLTIP Units (after the February 6, 2018 issuance date) that occurred during the first and second quarters of 2018: Record Date Payment Date Distributions per OP Unit and LTIP Unit Distributions per MYLTIP Unit June 29, 2018 July 31, 2018 $0.80 $0.080 March 29, 2018 April 30, 2018 $0.80 $0.080 December 31, 2017 January 30, 2018 $0.80 $0.080

Stockholders' Equity _ Partne_2

Stockholders' Equity / Partners' Capital Tables (Tables)	6 Months Ended
	Jun. 30, 2019
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 2019 and during the first and second quarters of 2018: Record Date Payment Date Dividend (Per Share) Distribution (Per Unit) June 28, 2019 July 31, 2019 $0.95 $0.95 March 29, 2019 April 30, 2019 $0.95 $0.95 December 31, 2018 January 30, 2019 $0.95 $0.95 June 29, 2018 July 31, 2018 $0.80 $0.80 March 29, 2018 April 30, 2018 $0.80 $0.80 December 31, 2017 January 30, 2018 $0.80 $0.80
Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Dividends Declared [Table Text Block]	The following table presents Boston Properties Inc.’s dividends per share on its outstanding Series B Preferred Stock paid or declared during 2019 and the first and second quarters of 2018: Record Date Payment Date Dividend (Per Share) August 2, 2019 August 15, 2019 $32.8125 May 3, 2019 May 15, 2019 $32.8125 February 4, 2019 February 15, 2019 $32.8125 August 3, 2018 August 15, 2018 $32.8125 May 4, 2018 May 15, 2018 $32.8125 February 2, 2018 February 15, 2018 $32.8125

Earnings Per Share _ Common U_2

Earnings Per Share / Common Unit (Tables)	6 Months Ended
	Jun. 30, 2019
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share	Three months ended June 30, 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 $ 164,318 154,555 $ 1.06 Allocation of undistributed earnings to participating securities (48 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,555 $ 1.06 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 164,270 154,874 $ 1.06 Three months ended June 30, 2018 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 $ 128,681 154,415 $ 0.83 Allocation of undistributed earnings to participating securities (16 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 128,665 154,415 $ 0.83 Effect of Dilutive Securities: Stock Based Compensation — 156 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 128,665 154,571 $ 0.83 Six months ended June 30, 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 $ 262,431 154,540 $ 1.70 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 262,431 154,859 $ 1.69 Six months ended June 30, 2018 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 $ 304,682 154,400 $ 1.97 Allocation of undistributed earnings to participating securities (142 ) — — Net income attributable to Boston Properties, Inc. common shareholders $ 304,540 154,400 $ 1.97 Effect of Dilutive Securities: Stock Based Compensation — 238 — Diluted Earnings: Net income attributable to Boston Properties, Inc. common shareholders $ 304,540 154,638 $ 1.97
Boston Properties Limited Partnership
Entity Information [Line Items]
Computation Of Basic And Diluted Earnings Per Share	Three months ended June 30, 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 $ 185,715 172,202 $ 1.08 Allocation of undistributed earnings to participating securities (54 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,202 $ 1.08 Effect of Dilutive Securities: Stock Based Compensation — 319 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,661 172,521 $ 1.08 Three months ended June 30, 2018 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 $ 145,961 171,916 $ 0.85 Allocation of undistributed earnings to participating securities (18 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 145,943 171,916 $ 0.85 Effect of Dilutive Securities: Stock Based Compensation — 156 — Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 145,943 172,072 $ 0.85 Six months ended June 30, 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 $ 299,097 172,167 $ 1.74 Effect of Dilutive Securities: Stock Based Compensation — 319 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 299,097 172,486 $ 1.73 Six months ended June 30, 2018 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 $ 346,868 171,892 $ 2.02 Allocation of undistributed earnings to participating securities (158 ) — — Net income attributable to Boston Properties Limited Partnership common unitholders $ 346,710 171,892 $ 2.02 Effect of Dilutive Securities: Stock Based Compensation — 238 (0.01 ) Diluted Earnings: Net income attributable to Boston Properties Limited Partnership common unitholders $ 346,710 172,130 $ 2.01

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Schedule Of Reconciliation Of Net Operating Income To Net Income	The following tables present reconciliations of Net Income Attributable to Boston Properties, Inc. Common Shareholders to the Company’s share of Net Operating Income and Net Income Attributable to Boston Properties Limited Partnership Common Unitholders to the Company’s share of Net Operating Income for the three and six months ended June 30, 2019 and 2018 . Boston Properties, Inc. Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Net income attributable to Boston Properties, Inc. common shareholders $ 164,318 $ 128,681 $ 262,431 $ 304,682 Add: Preferred dividends 2,625 2,625 5,250 5,250 Noncontrolling interest—common units of Boston Properties Limited Partnership 19,036 14,859 30,627 35,311 Noncontrolling interests in property partnerships 17,482 14,400 36,312 31,634 Interest expense 102,357 92,204 203,366 182,424 Impairment loss — — 24,038 — Net operating income from unconsolidated joint ventures 24,715 16,227 50,064 32,287 Depreciation and amortization expense 177,411 156,417 342,005 322,214 Transaction costs 417 474 877 495 Payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 General and administrative expense 35,071 28,468 76,833 64,362 Less: Net operating income attributable to noncontrolling interests in property partnerships 45,562 43,049 92,647 88,958 Gains from investments in securities 1,165 505 4,134 379 Interest and other income 3,615 2,579 7,368 4,227 Gains on sales of real estate 1,686 18,292 781 114,689 Income from unconsolidated joint ventures 47,964 769 48,177 1,230 Direct reimbursements of payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 Development and management services revenue 9,986 9,305 19,263 17,710 Company’s share of Net Operating Income $ 433,454 $ 379,856 $ 859,433 $ 751,466 Boston Properties Limited Partnership Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (in thousands) Net income attributable to Boston Properties Limited Partnership common unitholders $ 185,715 $ 145,961 $ 299,097 $ 346,868 Add: Preferred distributions 2,625 2,625 5,250 5,250 Noncontrolling interests in property partnerships 17,482 14,400 36,312 31,634 Interest expense 102,357 92,204 203,366 182,424 Impairment loss — — 22,272 — Net operating income from unconsolidated joint ventures 24,715 16,227 50,064 32,287 Depreciation and amortization expense 175,199 154,474 337,881 318,327 Transaction costs 417 474 877 495 Payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 General and administrative expense 35,071 28,468 76,833 64,362 Less: Net operating income attributable to noncontrolling interests in property partnerships 45,562 43,049 92,647 88,958 Gains from investments in securities 1,165 505 4,134 379 Interest and other income 3,615 2,579 7,368 4,227 Gains on sales of real estate 1,835 18,770 930 117,677 Income from unconsolidated joint ventures 47,964 769 48,177 1,230 Direct reimbursements of payroll and related costs from management services contracts 2,403 1,970 5,798 4,855 Development and management services revenue 9,986 9,305 19,263 17,710 Company’s share of Net Operating Income $ 433,454 $ 379,856 $ 859,433 $ 751,466
Schedule Of Segment Information By Geographic Area And Property Type	Information by geographic area (dollars in thousands): For the three months ended June 30, 2019 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 217,961 $ — $ 251,556 $ 131,506 $ 96,486 $ 697,509 Residential 3,222 — — — 5,777 8,999 Hotel 14,844 — — — — 14,844 Total 236,027 — 251,556 131,506 102,263 721,352 % of Grand Totals 32.72 % — % 34.87 % 18.23 % 14.18 % 100.00 % Rental Expenses: Office 77,660 — 96,809 43,708 35,672 253,849 Residential 1,279 — — — 2,843 4,122 Hotel 9,080 — — — — 9,080 Total 88,019 — 96,809 43,708 38,515 267,051 % of Grand Totals 32.96 % — % 36.25 % 16.37 % 14.42 % 100.00 % Net operating income $ 148,008 $ — $ 154,747 $ 87,798 $ 63,748 $ 454,301 % of Grand Totals 32.58 % — % 34.06 % 19.33 % 14.03 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (10,031 ) — (35,531 ) — — (45,562 ) Add: Company’s share of net operating income from unconsolidated joint ventures 818 15,454 1,696 — 6,747 24,715 Company’s share of net operating income $ 138,795 $ 15,454 $ 120,912 $ 87,798 $ 70,495 $ 433,454 % of Grand Totals 32.01 % 3.57 % 27.90 % 20.26 % 16.26 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the three months ended June 30, 2018 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 207,810 $ — $ 234,006 $ 93,482 $ 98,505 $ 633,803 Residential 1,195 — — — 3,604 4,799 Hotel 14,607 — — — — 14,607 Total 223,612 — 234,006 93,482 102,109 653,209 % of Grand Totals 34.23 % — % 35.83 % 14.31 % 15.63 % 100.00 % Rental Expenses: Office 77,147 — 91,838 31,214 34,678 234,877 Residential 706 — — — 2,207 2,913 Hotel 8,741 — — — — 8,741 Total 86,594 — 91,838 31,214 36,885 246,531 % of Grand Totals 35.12 % — % 37.26 % 12.66 % 14.96 % 100.00 % Net operating income $ 137,018 $ — $ 142,168 $ 62,268 $ 65,224 $ 406,678 % of Grand Totals 33.69 % — % 34.96 % 15.31 % 16.04 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (8,418 ) — (34,751 ) 120 — (43,049 ) Add: Company’s share of net operating income from unconsolidated joint ventures 781 6,902 1,706 — 6,838 16,227 Company’s share of net operating income $ 129,381 $ 6,902 $ 109,123 $ 62,388 $ 72,062 $ 379,856 % of Grand Totals 34.06 % 1.82 % 28.73 % 16.42 % 18.97 % 100.00 % _______________ (1) Rental Revenue is equal to Total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2019 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 435,372 $ — $ 510,187 $ 255,561 $ 192,831 $ 1,393,951 Residential 5,923 — — — 10,791 16,714 Hotel 23,782 — — — — 23,782 Total 465,077 — 510,187 255,561 203,622 1,434,447 % of Grand Totals 32.42 % — % 35.56 % 17.82 % 14.20 % 100.00 % Rental Expenses: Office 157,160 — 193,780 84,833 71,819 507,592 Residential 2,485 — — — 5,411 7,896 Hotel 16,943 — — — — 16,943 Total 176,588 — 193,780 84,833 77,230 532,431 % of Grand Totals 33.17 % — % 36.39 % 15.93 % 14.51 % 100.00 % Net operating income $ 288,489 $ — $ 316,407 $ 170,728 $ 126,392 $ 902,016 % of Grand Totals 31.98 % — % 35.08 % 18.93 % 14.01 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (19,404 ) — (72,795 ) (448 ) — (92,647 ) Add: Company’s share of net operating income from unconsolidated joint ventures 1,590 31,162 3,482 — 13,830 50,064 Company’s share of net operating income $ 270,675 $ 31,162 $ 247,094 $ 170,280 $ 140,222 $ 859,433 % of Grand Totals 31.49 % 3.63 % 28.75 % 19.81 % 16.32 % 100.00 % _______________ (1) Rental Revenue is equal to total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations. For the six months ended June 30, 2018 : Boston Los Angeles New York San Francisco Washington, DC Total Rental Revenue: (1) Office $ 412,807 $ — $ 476,404 $ 183,375 $ 197,817 $ 1,270,403 Residential 2,347 — — — 6,611 8,958 Hotel 23,709 — — — — 23,709 Total 438,863 — 476,404 183,375 204,428 1,303,070 % of Grand Totals 33.68 % — % 36.56 % 14.07 % 15.69 % 100.00 % Rental Expenses: Office 157,471 — 185,600 58,842 71,021 472,934 Residential 1,220 — — — 3,965 5,185 Hotel 16,814 — — — — 16,814 Total 175,505 — 185,600 58,842 74,986 494,933 % of Grand Totals 35.46 % — % 37.50 % 11.89 % 15.15 % 100.00 % Net operating income $ 263,358 $ — $ 290,804 $ 124,533 $ 129,442 $ 808,137 % of Grand Totals 32.59 % — % 35.98 % 15.41 % 16.02 % 100.00 % Less: Net operating income attributable to noncontrolling interests in property partnerships (16,547 ) — (72,697 ) 286 — (88,958 ) Add: Company’s share of net operating income from unconsolidated joint ventures 1,315 13,976 3,367 — 13,629 32,287 Company’s share of net operating income $ 248,126 $ 13,976 $ 221,474 $ 124,819 $ 143,071 $ 751,466 % of Grand Totals 33.02 % 1.86 % 29.47 % 16.61 % 19.04 % 100.00 % _______________ (1) Rental Revenue is equal to total Revenue per the Company’s Consolidated Statements of Operations, less Development and Management Services Revenue and Direct Reimbursements of Payroll and Related Costs from Management Services Contracts Revenue per the Consolidated Statements of Operations.

Organization (Details)

Organization (Details) ft² in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019ft²Real_Estate_PropertiesseriesBuildingsyrshares	Dec. 31, 2018shares
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.60%	89.70%
Restriction on redemption of OP units from date of issuance (years) | yr	1
One OP unit is equivalent to one share of Common Stock (in shares) | shares	1
OP unit conversion rate (in shares) | shares	1
Number Of Series Of Preferred Units Outstanding | series	1
Office Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	10
Commercial Real Estate Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	193
Net Rentable Area (in sf) | ft²	50.9
Total Properties Under Construction [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	12
Net Rentable Area (in sf) | ft²	5.7
Total Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	174
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
Retail Properties [ Member]
Real Estate Properties [Line Items]
Number of real estate properties | Buildings	12
Hotel Property [ Member]
Real Estate Properties [Line Items]
Number of real estate properties	1
Series B Cumulative Redeemable Preferred Stock [Member]
Real Estate Properties [Line Items]
Ratio of depository shares to shares of Series B Preferred Stock	0.01
Series B, Shares Outstanding (in shares) | shares	80,000	80,000
Series B, Dividend Rate, Percentage	5.25%
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Real Estate Properties [Line Items]
Series B, Shares Outstanding (in shares) | shares	8,000,000
Series B Preferred Units [Member]
Real Estate Properties [Line Items]
Series B, Shares Outstanding (in shares) | shares	80,000

Basis Of Presentation And Sum_4

Basis Of Presentation And Summary Of Significant Accounting Policies (Carrying Value Of note receivable, Indebtedness And Corresponding Estimate Of Fair Value) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Summary Of Significant Accounting Policies [Line Items]
Document Period End Date	Jun. 30, 2019
Related party note receivable	$ 80,000	$ 80,000
Note receivable	19,718	19,468
Mortgage notes payable, net	2,956,833	2,964,572
Unsecured senior notes, net	8,390,708	7,544,697
Unsecured line of credit	0	0
Unsecured term loan, net	$ 498,700	498,488
Number of VIEs that are consolidated	6
Carrying Amount [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable	$ 80,000	80,000
Note receivable	19,718	19,468
Note and Related Party Receivables	99,718	99,468
Mortgage notes payable, net	2,956,833	2,964,572
Unsecured senior notes, net	8,390,708	7,544,697
Unsecured line of credit	0	0
Unsecured term loan, net	498,700	498,488
Total	11,846,241	11,007,757
Estimated Fair Value [Member]
Summary Of Significant Accounting Policies [Line Items]
Related party note receivable	80,321	80,000
Note receivable	18,205	19,468
Note and Related Party Receivables	98,526	99,468
Mortgage notes payable, net	3,013,338	2,903,925
Unsecured senior notes, net	8,745,888	7,469,338
Unsecured line of credit	0	0
Unsecured term loan, net	500,673	500,783
Total	$ 12,259,899	$ 10,874,046

Basis Of Presentation And Sum_5

Basis Of Presentation And Summary Of Significant Accounting Policies Narrative (Details)	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Number of VIEs that are consolidated	6
In-service Properties [Member]
Schedule of Equity Method Investments [Line Items]
Number of VIEs that are consolidated	5

Real Estate Properties Table (D

Real Estate Properties Table (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Real estate
Document Period End Date		Jun. 30, 2019
Land		$ 5,056,046		$ 5,072,568
Right of use assets - finance leases		187,269		0
Right of use assets - operating leases		149,839	$ 151,800	0
Land held for future development	[1]	272,332		200,498
Buildings and improvements		13,271,691		13,356,751
Tenant improvements		2,486,269		2,396,932
Furniture, fixtures and equipment		44,462		44,351
Construction in progress		812,408		578,796
Total		22,280,316		21,649,896
Accumulated depreciation		(5,050,606)		(4,897,777)
Total real estate		$ 17,229,710		16,752,119
Boston Properties Limited Partnership
Real estate
Document Period End Date		Jun. 30, 2019
Land		$ 4,955,593		4,971,475
Right of use assets - finance leases		187,269		0
Right of use assets - operating leases		149,839		0
Land held for future development	[1]	272,332		200,498
Buildings and improvements		12,976,345		13,059,488
Tenant improvements		2,486,269		2,396,932
Furniture, fixtures and equipment		44,462		44,351
Construction in progress		812,408		578,796
Total		21,884,517		21,251,540
Accumulated depreciation		(4,949,822)		(4,800,475)
Total real estate		$ 16,934,695		$ 16,451,065
[1]	Includes pre-development costs.

Real Estate Narrative (Details)

Real Estate Narrative (Details) $ in Thousands	Jun. 28, 2019USD ($)ft²	Jun. 03, 2019USD ($)	May 09, 2019ft²	Jan. 24, 2019USD ($)ft²a	Jan. 23, 2019USD ($)	Jun. 02, 2019USD ($)	Jun. 30, 2019USD ($)	Jun. 27, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 02, 2019USD ($)	Jun. 30, 2019USD ($)	Jun. 27, 2019USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Apr. 18, 2019USD ($)ft²	Jan. 10, 2019USD ($)ft²
Real Estate [Line Items]
Document Period End Date											Jun. 30, 2019
Accelerated depreciation							$ 177,411		$ 156,417		$ 342,005		$ 322,214
Right of use assets - finance leases							187,269				187,269			$ 0
Proceeds from sales of real estate											60,398		141,249
Gains (loss) on sales of real estate							1,686		18,292		$ 781		114,689
Boston Properties Limited Partnership
Real Estate [Line Items]
Document Period End Date											Jun. 30, 2019
Accelerated depreciation							175,199		154,474		$ 337,881		318,327
Right of use assets - finance leases							187,269				187,269			0
Proceeds from sales of real estate											60,398		141,249
Gains (loss) on sales of real estate							1,835		18,770		930		117,677
325 Main Street [Member]
Real Estate [Line Items]
Term of Lease Signed (in years)			15-year
Net Rentable Area (in sf) | ft²			115,000
Accelerated depreciation							9,900
325 Main Street [Member] | Boston Properties Limited Partnership
Real Estate [Line Items]
Accelerated depreciation							$ 9,500
Platform 16 [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²				1,100,000
Finance Lease fixed purchase price				$ 134,800
Right of use assets - finance leases				$ 122,600
Lessee, Finance Lease, Term of Contract				65 years
Area of Land | a				5.6
Carnegie Center [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²																1,700,000
Aggregate purchase price																$ 51,500
Deferred purchase price																$ 8,600
164 exington Road [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²	64,000
Gross Sale Price	$ 4,000
Proceeds from sales of real estate	3,800
Net income (loss)								$ (100)	(100)			$ (100)	(100)
Gains (loss) on sales of real estate	2,500
164 exington Road [Member] | Boston Properties Limited Partnership
Real Estate [Line Items]
Gains (loss) on sales of real estate	$ 2,600
2600 Tower Oaks Boulevard [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²				179,000
Gross Sale Price				$ 22,700
Proceeds from sales of real estate				$ 21,400
Net income (loss)					$ (200)				(100)				(300)
Gains (loss) on sales of real estate											(600)
Impairment loss														3,100
2600 Tower Oaks Boulevard [Member] | Boston Properties Limited Partnership
Real Estate [Line Items]
Impairment loss														$ 1,500
One Tower Center [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²															410,000
Gross Sale Price															$ 38,000
Proceeds from sales of real estate		$ 36,600
Net income (loss)						$ (100)			$ (700)	$ (900)			$ (1,300)
Gains (loss) on sales of real estate		$ (800)
Impairment loss											24,000
One Tower Center [Member] | Boston Properties Limited Partnership
Real Estate [Line Items]
Impairment loss											$ 22,300
Future Office Building [Member] | 325 Main Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²			420,000
Square Footage Of Signed Lease | ft²			379,000
Future Retail Building [Member] | 325 Main Street [Member]
Real Estate [Line Items]
Net Rentable Area (in sf) | ft²			41,000

Real Estate Finance Lease Liabi

Real Estate Finance Lease Liability, Maturity - Platform 16 (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Jan. 24, 2019	Dec. 31, 2018
Real estate
2019		$ 2,494
2020	[1]	121,499
Total expected minimum lease payments		202,001
Interest portion		(29,099)
Present value of expected net lease payments		$ 172,902		$ 0
Platform 16 [Member]
Real estate
2019			$ 17,918
2020			109,460
Total expected minimum lease payments			127,378
Interest portion			(4,815)
Present value of expected net lease payments			$ 122,563
[1]	Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million , respectively, related to purchase options that the Company is reasonably certain that it will exercise.

Leases Narrative (Details)

Leases Narrative (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Finance leases under development	3	3
Cumulative effect of a change in accounting principle		$ 4,379,000	$ (5,496,000)
Right of use assets - operating leases	$ 149,839,000	149,839,000		$ 151,800,000	$ 0
Lease liabilities - operating leases	$ 199,344,000	199,344,000		$ 199,300,000	0
Lessee, Finance Lease, Description	four
Boston Properties Limited Partnership
Right of use assets - operating leases	$ 149,839,000	149,839,000			0
Lease liabilities - operating leases	199,344,000	199,344,000			$ 0
Dividends In Excess Of Earnings [Member]
Cumulative effect of a change in accounting principle		3,864,000	(4,933,000)
Dividends In Excess Of Earnings [Member] | Boston Properties Limited Partnership
Cumulative effect of a change in accounting principle		3,900,000
Noncontrolling Interests - Common units [Member]
Cumulative effect of a change in accounting principle		445,000	$ (563,000)
Noncontrolling Interests - Common units [Member] | Boston Properties Limited Partnership
Cumulative effect of a change in accounting principle		400,000
Noncontrolling interest - property partnerships [Member]
Cumulative effect of a change in accounting principle	$ 0	70,000
Noncontrolling interest - property partnerships [Member] | Boston Properties Limited Partnership
Cumulative effect of a change in accounting principle		$ 70,000

Leases Lessee, Lease Costs and

Leases Lessee, Lease Costs and Other Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)		Jun. 30, 2019USD ($)
Leases [Abstract]
Finance leases under development	3		3
Operating lease costs	$ 3,656		$ 7,333
Finance Lease, Amortization of right of use asset	(14)	[1]	2	[1]
Finance Lease, Interest on lease liabilities	$ 12	[2]	$ 24	[2]
Operating Lease, Weighted Average Remaining Lease Term	51 years		51 years
Finance Lease, Weighted Average Remaining Lease Term	5 years		5 years
Operating Lease, Weighted Average Discount Rate, Percent	5.70%		5.70%
Finance Lease, Weighted Average Discount Rate, Percent	4.10%		4.10%
[1]	The finance leases relate to either land, buildings or assets that remain in development. The Company’s policy is not to depreciate finance lease assets related to land because it is assumed to have an indefinite life. For assets under development, depreciation may commence once the asset is placed in-service and depreciation would be recognized in accordance with the Company’s policy.
[2]	of the finance leases relate to assets under development and as such, the entire interest amount was capitalized.

Leases Future Minimum Lease Pay

Leases Future Minimum Lease Payments for Ground Leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 11,425
2020	18,425
2021	25,310
2022	8,894
2023	9,084
Thereafter	$ 567,232

Leases Future Minimum Lease P_2

Leases Future Minimum Lease Payments, Capital Leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 1,441
2020	12,682
2021	2,123
2022	1,253
2023	944
Thereafter	73,241
Total expected minimum lease payments	91,684
Interest portion	(27,497)
Present value of expected net minimum lease payments	$ 64,187

Leases Lease Liability Maturity

Leases Lease Liability Maturity Schedule (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Leases
July 1, 2019 - December 31, 2019		$ 4,872
2020		10,050
2021		24,953
2022		18,041
2023		10,326
Thereafter		567,232
Total lease payments		635,474
Less: interest portion		(436,130)
Present value of lease payments		199,344	$ 199,300	$ 0
Finance Leases
July 1, 2019 - December 31, 2019		2,494
2020	[1]	121,499
2021		2,096
2022		1,632
2023		1,039
Thereafter	[1]	73,241
Total expected minimum lease payments		202,001
Interest portion		(29,099)
Present value of expected net lease payments		172,902		$ 0
Lessee, Finance Lease, Option to Extend, Reasonably Certain 2024		38,700
Lessee, Finance Lease, Option to Extend, Reasonably Certain 2020		$ 119,800
[1]	Finance lease payments in 2020 and 2024 include approximately $119.8 million and $38.7 million , respectively, related to purchase options that the Company is reasonably certain that it will exercise.

Leases Lessor, Lease Income Tab

Leases Lessor, Lease Income Table (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Leases [Abstract]
Fixed Contractual Payments	$ 557,820		$ 1,111,806
Variable lease payments	122,369		247,634
Lease	$ 680,189	$ 0	$ 1,359,440	$ 0

Leases Lessor , Future Minimum

Leases Lessor , Future Minimum Rents (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
July 1, 2019 - December 31, 2019	$ 1,053,967
2019		$ 2,088,171
2020	2,144,485	2,106,963
2021	2,111,755	2,015,031
2022	1,982,534	1,838,699
2023	1,910,896	1,736,636
Thereafter	$ 14,416,019	$ 12,295,464

Investments in Unconsolidated_3

Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) $ in Thousands		Jun. 27, 2019ft²	Apr. 26, 2019USD ($)ft²yr	Jun. 30, 2019USD ($)ft²Land_ParcelsBuildingspayments		Dec. 31, 2018USD ($)
Schedule of Equity Method Investments [Line Items]
Carrying Value of investment				$ (355,984)		$ (503,726)
Carrying value of the Company's investments in unconsolidated joint ventures				$ 936,835		956,309
Square 407 Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties				Market Square North
Ownership Percentage				50.00%
Carrying Value of investment	[1]			$ (5,518)		(6,424)
The Metropolitan Square Associates LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				Metropolitan Square
Ownership Percentage				20.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 5,827		2,644
BP/CRF 901 New York Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				901 New York Avenue
Ownership Percentage	[2]			25.00%
Carrying Value of investment	[1]			$ (12,859)		(13,640)
WP Project Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				Wisconsin Place Land and Infrastructure
Ownership Percentage	[3]			33.30%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 37,521		38,214
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				Annapolis Junction
Ownership Percentage	[4]			50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 25,290		25,268
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]
Debt Instrument, Basis Spread on Variable Rate		1.10%
Properties				540 Madison Avenue
Ownership Percentage		60.00%		60.00%	[5]
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 9,200		66,391
Net Rentable Area (in sf) | ft²		284,000
500 North Capitol Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				500 North Capitol Street, NW
Ownership Percentage				30.00%
Carrying Value of investment	[1]			$ (5,451)		(5,026)
501 K Street LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				1001 6th Street
Ownership Percentage	[6]			50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 42,473		42,557
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%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 58,637		69,302
Residential Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				The Hub on Causeway - Residential
Ownership Percentage				50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 48,201		47,505
Hotel Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				The Hub on Causeway - Hotel Air Rights
Ownership Percentage				50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 3,626		3,022
Office Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				100 Causeway Street
Ownership Percentage	[7]			50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 69,551		23,804
1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				1265 Main Street
Ownership Percentage				50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 4,125		3,918
BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				Dock 72
Ownership Percentage				50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 91,134		82,520
CA-Colorado Center Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties				Colorado Center
Ownership Percentage				50.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 254,122		253,495
7750 Wisconsin Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Construction Loan Facility Borrowing Capacity			$ 255,000
Number of extensions			2
Extension Option (in years) | yr			1
Debt Instrument, Basis Spread on Variable Rate			1.25%
Properties				7750 Wisconsin Avenue
Ownership Percentage			50.00%	50.00%	[7]
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 70,122		69,724
Net Rentable Area (in sf) | ft²			734,000
BP-M 3HB Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties				3 Hudson Boulevard
Ownership Percentage				25.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 47,966		46,993
SMBP Venture LP [Member]
Schedule of Equity Method Investments [Line Items]
Properties				Santa Monica Business Park
Ownership Percentage				55.00%
Carrying value of the Company's investments in unconsolidated joint ventures	[1]			$ 169,040		180,952
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value of investment				23,800		25,100
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value of investment				(656,902)	[8]	(582,006)
Carrying value of the Company's investments in unconsolidated joint ventures	[1],[9]			$ 913,007		$ 931,219
[1]	Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[2]	The Company’s economic ownership has increased based on the achievement of certain return thresholds.
[3]	The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.3% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.
[4]	The joint venture owns three in-service buildings and two
[5]	The property was sold on June 27, 2019. As of June 30, 2019, the investment is comprised of undistributed cash. See note below for additional details.
[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]	At June 30, 2019 , this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.2 million and $17.2 million , respectively.
[9]	Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018

Investments in Unconsolidated_4

Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands		Jun. 30, 2019		Jan. 01, 2019	Dec. 31, 2018
ASSETS
Real estate and development in process, net		$ 17,229,710			$ 16,752,119
Liabilities and Members'/Partners' Equity [Abstract]
Mortgage notes payable, net		2,956,833			2,964,572
Other Liabilities		355,984			503,726
Total liabilities and equity / capital		21,268,275			20,256,477
Carrying value of the Company's investments in unconsolidated joint ventures		936,835			956,309
Right of use assets - finance leases		187,269			0
Right of use assets - operating leases		149,839		$ 151,800	0
Lease liabilities - finance leases		172,902			0
Lease liabilities - operating leases		199,344		$ 199,300	0
Unconsolidated Joint Ventures [Member]
ASSETS
Real estate and development in process, net		3,551,504	[1]		3,545,906
Other assets		515,923			543,512
Total assets		4,067,427			4,089,418
Liabilities and Members'/Partners' Equity [Abstract]
Mortgage notes payable, net		1,991,290			2,017,609
Other Liabilities		656,902	[2]		582,006
Members'/Partners' equity		1,419,235			1,489,803
Total liabilities and equity / capital		4,067,427			4,089,418
Company's share of equity		574,662			622,498
Basis differentials	[3]	338,345			308,721
Carrying value of the Company's investments in unconsolidated joint ventures	[4],[5]	913,007			931,219
Unconsolidated Joint Ventures [Member]
Liabilities and Members'/Partners' Equity [Abstract]
Other Liabilities		(23,800)			(25,100)
Right of use assets - finance leases		248,900
Right of use assets - operating leases		12,500
Lease liabilities - finance leases		393,200
Lease liabilities - operating leases		17,200
Colorado Center [Member] | Unconsolidated Joint Ventures [Member]
Liabilities and Members'/Partners' Equity [Abstract]
Basis differentials		$ 313,300			$ 316,700
[1]	At June 30, 2019 , this amount includes right of use assets - finance leases and right of use assets - operating leases totaling approximately $248.9 million and $12.5 million , respectively.
[2]	At June 30, 2019 , this amount includes lease liabilities - finance leases and lease liabilities - operating leases totaling approximately $393.2 million and $17.2 million , respectively.
[3]	This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At June 30, 2019 and December 31, 2018 , there was an aggregate basis differential of approximately $313.3 million and $316.7 million , respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities.
[4]	Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018 , respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[5]	Investments with deficit balances aggregating approximately $23.8 million and $25.1 million at June 30, 2019 and December 31, 2018

Investments in Unconsolidated_5

Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		Jun. 27, 2019	Jun. 30, 2019		Jun. 30, 2018	Jun. 30, 2019		Jun. 30, 2018
Schedule of Equity Method Investments [Line Items]
Document Period End Date						Jun. 30, 2019
Total revenue			$ 733,741		$ 664,484	$ 1,459,508		$ 1,325,635
Expenses
Depreciation and amortization			177,411		156,417	342,005		322,214
Total expenses			482,353		433,860	957,944		886,859
Other expense
Interest expense			(102,357)		(92,204)	(203,366)		(182,424)
Gains (loss) on sales of real estate			1,686		18,292	781		114,689
Net income			203,461		160,565	334,620		376,877
Income from unconsolidated joint ventures			47,964		769	48,177		1,230
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]		80,204		57,096	163,159		113,582
Expenses
Operating			30,134		22,868	60,633		45,717
Depreciation and amortization			24,818		14,527	53,464		29,252
Total expenses			54,952		37,395	114,097		74,969
Other expense
Interest expense			(20,803)		(14,708)	(41,560)		(29,132)
Gains (loss) on sales of real estate			34,572	[2]	0	34,572	[2]	0
Net income			39,021		4,993	42,074		9,481
Company's share of net income (loss)			22,376		2,105	23,960		3,931
Basis differential	[2],[3]		25,588		(1,336)	24,217		(2,701)
Income from unconsolidated joint ventures			47,964		769	48,177		1,230
Straight-line rent adjustments			7,600		3,200	13,400		5,000
540 Madison Venture LLC [Member]
Other expense
Equity Method Investment, Realized Gain (Loss) on Disposal		$ 47,800
Colorado Center [Member] | Unconsolidated Joint Ventures [Member]
Other expense
Straight-line rent adjustments			500		700	1,100		1,400
"Above" and "below" market rent adjustments, net			$ 400		$ 400	$ 800		$ 800
[1]	Includes straight-line rent adjustments of approximately $7.6 million and $3.2 million for the three months ended June 30, 2019 and 2018 , respectively, and $13.4 million and $5.0 million for the six months ended June 30, 2019 and 2018 , respectively.
[2]	Represents the total gain on sale of 540 Madison Avenue recognized by the joint venture, as described below. During 2008, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture resulting in a basis differential between the carrying value of the Company’s investment in the joint venture and the joint venture’s basis in the assets and liabilities of the property. As a result of the historical basis difference, the Company recognized a gain on sale of real estate totaling approximately $47.8 million , which consists of its share of the gain on sale reported by the joint venture as well as an adjustment for the basis differential. The gain on sale is included in Income from Unconsolidated Joint Ventures in the Company’s Consolidated Statements of Operations.
[3]	Includes straight-line rent adjustments of approximately $0.5 million and $0.7 million for the three months ended June 30, 2019 and 2018 , respectively, and $1.1 million and $1.4 million for the six months ended June 30, 2019 and 2018 , respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million and $0.4 million for the three months ended June 30, 2019 and 2018 , respectively, and $0.8 million and $0.8 million for the six months ended June 30, 2019 and 2018

Investments in Unconsolidated_6

Investments in Unconsolidated Joint Ventures Narrative (Details) $ in Thousands	Jun. 27, 2019USD ($)ft²	May 28, 2019USD ($)	Apr. 26, 2019USD ($)ft²yr	Jan. 24, 2019USD ($)ft²	Jun. 30, 2019USD ($)		Jun. 15, 2019ft²	Dec. 31, 2018USD ($)
Schedule of Equity Method Investments [Line Items]
Mortgage notes payable, net					$ 2,956,833			$ 2,964,572
Annapolis Junction Building Six [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage				50.00%
Mortgage notes payable, net				$ 13,000
Debt Instrument, Basis Spread on Variable Rate				2.00%
Number of extensions				1
Extension Option (in years)				1
Debt instrument, borrowing capacity				$ 14,300
Net Rentable Area (in sf) | ft²				119,000
7750 Wisconsin Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			50.00%		50.00%	[1]
Construction Loan Facility Borrowing Capacity			$ 255,000
Debt Instrument, Basis Spread on Variable Rate			1.25%
Number of extensions			2
Extension Option (in years) | yr			1
Net Rentable Area (in sf) | ft²			734,000
The Hub on Causeway - Podium and One hundred Causeway [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
Repayments of Construction Loans Payable		$ 30,000
Hub on Causeway - Podium [Member]
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²							385,000
540 Madison Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	60.00%				60.00%	[2]
Contractual Sales Price	$ 310,300
Loans Assumed	$ 120,000
Debt Instrument, Basis Spread on Variable Rate	1.10%
Proceeds from Sale of Equity Method Investments	$ 178,700
Equity Method Investment, Realized Gain (Loss) on Disposal	$ 47,800
Net Rentable Area (in sf) | ft²	284,000
Company's Share [Member] | 540 Madison Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Sale of Equity Method Investments	$ 107,100
[1]	This entity is a VIE (See Note 2 ).
[2]	The property was sold on June 27, 2019. As of June 30, 2019, the investment is comprised of undistributed cash. See note below for additional details.

Unsecured Senior Notes (Details

Unsecured Senior Notes (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2019	Jun. 21, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total		$ 8,390,708		$ 7,544,697
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Total		8,390,708		$ 7,544,697
Boston Properties Limited Partnership | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		8,450,000
Net unamortized discount		18,802
Deferred financing costs, net		40,490
Total		$ 8,390,708
Boston Properties Limited Partnership | Senior Notes [Member] | 10 Year Unsecured Senior Notes 5.708% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.625%
Debt Instrument, Interest Rate, Effective Percentage	[1]	5.708%
Long-term Debt, Gross		$ 700,000
Debt Instrument, Maturity Date	[2]	Nov. 15, 2020
Boston Properties Limited Partnership | Senior Notes [Member] | 10 Year Unsecured Senior Notes 4.289% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.125%
Debt Instrument, Interest Rate, Effective Percentage	[1]	4.289%
Long-term Debt, Gross		$ 850,000
Debt Instrument, Maturity Date	[2]	May 15, 2021
Boston Properties Limited Partnership | Senior Notes [Member] | 11 Year Unsecured Senior Notes 3.954%[Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.85%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.954%
Long-term Debt, Gross		$ 1,000,000
Debt Instrument, Maturity Date	[2]	Feb. 1, 2023
Boston Properties Limited Partnership | Senior Notes [Member] | 10.5 year Unsecured Senior Notes 3.279% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.125%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.279%
Long-term Debt, Gross		$ 500,000
Debt Instrument, Maturity Date	[2]	Sep. 1, 2023
Boston Properties Limited Partnership | Senior Notes [Member] | 10.5 Year Unsecured Senior Notes 3.916%[Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.80%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.916%
Long-term Debt, Gross		$ 700,000
Debt Instrument, Maturity Date	[2]	Feb. 1, 2024
Boston Properties Limited Partnership | Senior Notes [Member] | 7 Year Unsecured Senior Notes 3.350% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.20%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.35%
Long-term Debt, Gross		$ 850,000
Debt Instrument, Maturity Date	[2]	Jan. 15, 2025
Boston Properties Limited Partnership | Senior Notes [Member] | 10 Year Unsecured Senior Notes 3.766%[Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.65%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.766%
Long-term Debt, Gross		$ 1,000,000
Debt Instrument, Maturity Date	[2]	Feb. 1, 2026
Boston Properties Limited Partnership | Senior Notes [Member] | 10 Year Unsecured Senior Notes 3.495% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.75%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.495%
Long-term Debt, Gross		$ 1,000,000
Debt Instrument, Maturity Date	[2]	Oct. 1, 2026
Boston Properties Limited Partnership | Senior Notes [Member] | 10 Year Unsecured Senior Notes 4.628%[Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.50%
Debt Instrument, Interest Rate, Effective Percentage	[1]	4.628%
Long-term Debt, Gross		$ 1,000,000
Debt Instrument, Maturity Date	[2]	Dec. 1, 2028
Boston Properties Limited Partnership | Senior Notes [Member] | 10 Year Unsecured Senior Notes 3.505% [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.40%	3.40%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.505%	3.505%
Long-term Debt, Gross		$ 850,000	$ 850,000
Debt Instrument, Maturity Date	[2]	Jun. 21, 2029
[1]	Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs.
[2]	No principal amounts are due prior to maturity.

Unsecured Senior Notes Narrativ

Unsecured Senior Notes Narrative (Details) - USD ($) $ in Thousands		Jun. 21, 2019	Jun. 30, 2019	Jun. 30, 2018
Debt Instrument [Line Items]
Proceeds from unsecured senior notes			$ 848,428	$ 0
Boston Properties Limited Partnership
Debt Instrument [Line Items]
Proceeds from unsecured senior notes			848,428	$ 0
Boston Properties Limited Partnership | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 8,450,000
Debt Instrument, Covenant Description			The indenture relating to the unsecured senior notes contains certain financial restrictions and requirements, including (1) a leverage ratio not to exceed 60%, (2) a secured debt leverage ratio not to exceed 50%, (3) an interest coverage ratio of greater than 1.50 and (4) an unencumbered asset value of not less than 150% of unsecured debt.
Boston Properties Limited Partnership | Senior Notes [Member] | 10 Year Unsecured Senior Notes 3.505% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 850,000	$ 850,000
Senior Notes Pricing		99.815%
Debt Instrument, Interest Rate, Stated Percentage		3.40%	3.40%
Debt Instrument, Interest Rate, Effective Percentage	[1]	3.505%	3.505%
Proceeds from unsecured senior notes		$ 841,300
[1]	Yield on issuance date including the effects of discounts on the notes, settlements of interest rate contracts and the amortization of financing costs.

Commitments And Contingencies (

Commitments And Contingencies (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019USD ($)ft²	Dec. 31, 2009USD ($)	May 09, 2019ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Jan. 10, 2014USD ($)
Commitments And Contingencies [Line Items]
Letter of credit and performance obligations	$ 18.4
Document Period End Date	Jun. 30, 2019
Property insurance program per occurrence limits	$ 1,000
Per occurrence limit for NBCR Coverage	1,000
Value of program trigger	$ 180
Coinsurance of program trigger	19.00%
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
Annual aggregate limit of the earthquake insurance which covers San Francisco and Los Angeles regions	240
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco and Los Angeles	20
767 Venture, LLC [Member]
Commitments And Contingencies [Line Items]
Maximum funding obligation	79.8
Property insurance program per occurrence limits	1,625
Lehman [Member]
Commitments And Contingencies [Line Items]
Bankruptcy claim, amount filed by general creditor		$ 45.3
Bankruptcy claim amount allowed by court to creditor									$ 45.2
Bankruptcy Claims, Amount of Claims Settled				$ 0.3	$ 0.4	$ 1.4	$ 8.1	$ 7.7
Bankruptcy remaining claim amount allowed by court to creditor	27.2
325 Main Street [Member]
Commitments And Contingencies [Line Items]
Net Rentable Area (in sf) | ft²			115,000
601 Lexington Avenue [Member]
Commitments And Contingencies [Line Items]
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP	$ 250
Boston Properties Limited Partnership
Commitments And Contingencies [Line Items]
Document Period End Date	Jun. 30, 2019
Operating partnership guarantee to cover liabilities of IXP	$ 20
Residential Real Estate [Member] | 325 Main Street [Member]
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 [Member]
Commitments And Contingencies [Line Items]
Net Rentable Area (in sf) | ft²			420,000
Future Retail Building [Member] | 325 Main Street [Member]
Commitments And Contingencies [Line Items]
Net Rentable Area (in sf) | ft²			41,000
home ownership units [Member] | Residential Real Estate [Member] | 325 Main Street [Member]
Commitments And Contingencies [Line Items]
Affordable Housing requirement			20.00%

Noncontrolling Interests (Narra

Noncontrolling Interests (Narrative) (Details) - Boston Properties Limited Partnership	Jun. 30, 2019shares
Noncontrolling Interests [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operating Partnership (OP) Units (in shares)	16,828,230
Long-Term Incentive Plan (LTIP) Units (in shares)	1,189,117
OPP Units 2012 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards in LTIP Units (in shares)	118,067
2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP (in units)	68,659
2014 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP (in units)	23,100
2015 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIPS (in units)	28,724
2016 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIPs (in units)	98,706
2017 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP (in units)	394,921
2018 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP	336,195
2019 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS	220,734

(Common Units) (Narrative) (Det

(Common Units) (Narrative) (Details) $ / shares in Units, $ in Thousands	Feb. 09, 2019USD ($)shares	Jun. 30, 2019USD ($)sharesyr	Jun. 28, 2019$ / shares	Dec. 31, 2018USD ($)
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)		34,967
Redemption of OP units issued on conversion of LTIP Units (in shares)		33,767
Restriction on redemption of OP Unit to Common Stock (in years) | yr		1
Redemption of OP Unit equivalent to Common Stock (in shares)		1
Common units of operating partnership if converted value | $		$ 2,300,000
Closing price of common stock (in dollars per share) | $ / shares			$ 129
2016 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target	69.50%
Value of MYLTIP Awards | $	$ 13,600
2016 MYLTIP Units Forfeited	364,980
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 | $		$ 2,324,238		$ 2,000,591
Boston Properties Limited Partnership | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
MYLTIP distribution prior to measurement date		10.00%
Boston Properties Limited Partnership | 2017 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP (in units)		394,921
Boston Properties Limited Partnership | 2018 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP		336,195
Boston Properties Limited Partnership | 2019 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS		220,734

Noncontrolling Interests Common

Noncontrolling Interests Common units distributions (Details) - Boston Properties Limited Partnership - $ / shares	Apr. 30, 2019	Jan. 30, 2019	Jul. 31, 2018	Apr. 30, 2018	Jan. 30, 2018	Jun. 10, 2019
Dividends Payable [Line Items]
Distributions Declared To OP And LTIP Units Per Unit						$ 0.95
Distributions Declared To MYLTIP Units Per Unit (in dollars per unit)						$ 0.095
Distributions made to OP and LTIP units per unit (in dollars per unit)	$ 0.95	$ 0.95	$ 0.80	$ 0.80	$ 0.80
Distribution paid to MYLTIP Units (in dollars per unit)	$ 0.095	$ 0.095	$ 0.080	$ 0.080	$ 0.080

Noncontrolling Interests (Prope

Noncontrolling Interests (Property Partnerships) (Narrative) (Details) $ in Thousands	Apr. 01, 2019USD ($)	May 12, 2016ft²	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Noncontrolling Interest [Line Items]
Noncontrolling Interest in Limited Partnerships			$ 1,696,221	$ 1,696,221		$ 1,711,445
Payments to Noncontrolling Interests				39,401	$ 44,033
Acquisition of noncontrolling interest in property partnerships			(187,006)	(187,006)
Salesforce Tower [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Portion of project costs covered by a construction loan		50.00%
Portion of costs funded (in percentage)		50.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		5.00%
Debt Instrument, Basis Spread on Variable Rate		3.00%
Stabilization definition for Salesforce Tower		The term stabilization date was defined in the agreement to generally mean the first date after completion upon which Salesforce Tower is (1) at least 90% leased and (2) 50% occupied by tenants that are paying rent.
Net Rentable Area (in sf) | ft²		1,421,000
Salesforce Tower [Member] | Parent Company [Member] | Consolidated Properties [Member]
Noncontrolling Interest [Line Items]
Costs funded (in percentage)		2.50%
Preferred equity funded			$ 22,600	$ 22,600
Salesforce Tower [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	5.00%
Payments to Noncontrolling Interests	$ 210,900
Repayment of Preferred Equity	24,100
Net Payments To Minority Shareholders	$ 186,800
Amount of property owned	100.00%
Acquisition of noncontrolling interest in property partnerships	$ 162,500

Stockholders' Equity _ Partne_3

Stockholders' Equity / Partners' Capital Narrative (Details)	Jun. 02, 2017USD ($)yr	Jun. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Mar. 27, 2018$ / shares	Jun. 03, 2014USD ($)
Class of Stock [Line Items]
Common stock, shares outstanding		154,563,130	154,458,478
General Partners' Capital Account, Units Outstanding		1,725,805
Limited Partners' Capital Account, Units Outstanding		152,837,325
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		29,704
Shares of Common Stock in connection with the redemption of an equal number of OP Units (in shares)		34,967
Common Stock, Value, Issued | $		$ 1,546,000	$ 1,545,000
ATM Program [Member]
Class of Stock [Line Items]
At the market stock offering program, aggregate value of common stock | $	$ 600,000,000				$ 600,000,000
At Market Stock Offering Program Maximum Length Of Sale In Years | yr	3
Common Stock, Value, Issued | $		$ 0
Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		80,000	80,000
Series B, Dividend Rate, Percentage		5.25%
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares		$ 2,500	$ 2,500	$ 2,500
Ratio of depository shares to shares of Series B Preferred Stock		0.01
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		8,000,000
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares		$ 25		$ 25
Boston Properties Limited Partnership
Class of Stock [Line Items]
General Partners' Capital Account, Units Outstanding		1,725,805	1,722,336
Limited Partners' Capital Account, Units Outstanding		152,837,325	152,736,142
Boston Properties Limited Partnership | Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		80,000	80,000
Series B, Liquidation Preference Per Share (dollars per share) | $ / shares		$ 2,500	$ 2,500

Stockholders' Equity _ Partne_4

Stockholders' Equity / Partners' Capital Stockholders' Equity / Partners' Capital Dividends / Distributions (Details) - $ / shares	May 15, 2019	Apr. 30, 2019	Feb. 15, 2019	Jan. 30, 2019	Aug. 15, 2018	Jul. 31, 2018	May 15, 2018	Apr. 30, 2018	Feb. 15, 2018	Jan. 30, 2018	Jun. 10, 2019
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit											$ 0.95
Dividends, Per Share / Unit		$ 0.95		$ 0.95		$ 0.80		$ 0.80		$ 0.80
Boston Properties Limited Partnership
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit											0.95
Dividends, Per Share / Unit		$ 0.95		$ 0.95		$ 0.80		$ 0.80		$ 0.80
Series B Cumulative Redeemable Preferred Stock [Member]
Entity Information [Line Items]
Dividends Payable, Amount Per Share / Unit											$ 32.8125
Dividends, Per Share / Unit	$ 32.8125		$ 32.8125		$ 32.8125		$ 32.8125		$ 32.8125

Earnings Per Share _ Common U_3

Earnings Per Share / Common Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Basic Earnings:
Net income attributable to the Company's common shareholders / unitholders	$ 164,318	$ 128,681	$ 262,431	$ 304,682
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	154,555,000	154,415,000	154,540,000	154,400,000
Net income (in dollars per share / unit)	$ 1.06	$ 0.83	$ 1.70	$ 1.97
Allocation of undistributed earnings to participating securities	$ (48)	$ (16)		$ (142)
Allocation of undistributed earnings to participating securities (in shares)	0	0		0
Allocation of undistributed earnings to participating securities (in dollars per shares / units)	$ 0	$ 0		$ 0
Net income attributable to the Company's common shareholders / unitholders	$ 164,270	$ 128,665		$ 304,540
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	154,555,000	154,415,000		154,400,000
Net income attributable to the Company's common shareholders / unitholders (in dollars per share / unit)	$ 1.06	$ 0.83		$ 1.97
Effect of Dilutive Securities:
Stock Based Compensation, Income (Numerator)	$ 0	$ 0	$ 0	$ 0
Stock Based Compensation, Income (in shares / units)	319,000	156,000	319,000	238,000
Stock Based Compensation, Income (in dollars per share / unit)	$ 0	$ 0	$ (0.01)	$ 0
Diluted Earnings:
Net income attributable to the Company's common shareholders / unitholders (Numerator)	$ 164,270	$ 128,665	$ 262,431	$ 304,540
Net income attributable to to the Company's shareholders / unitholder (number of shares)	154,874,000	154,571,000	154,859,000	154,638,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 1.06	$ 0.83	$ 1.69	$ 1.97
Boston Properties Limited Partnership
Entity Information [Line Items]
Redeemable Common Units	17,647,000	17,501,000	17,627,000	17,492,000
Basic Earnings:
Net income attributable to the Company's common shareholders / unitholders	$ 185,715	$ 145,961	$ 299,097	$ 346,868
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	172,202,000	171,916,000	172,167,000	171,892,000
Net income (in dollars per share / unit)	$ 1.08	$ 0.85	$ 1.74	$ 2.02
Allocation of undistributed earnings to participating securities	$ (54)	$ (18)		$ (158)
Allocation of undistributed earnings to participating securities (in shares)	0	0		0
Allocation of undistributed earnings to participating securities (in dollars per shares / units)	$ 0	$ 0		$ 0
Net income attributable to the Company's common shareholders / unitholders	$ 185,661	$ 145,943		$ 346,710
Net income attributable to the Company's common shareholders / unitholders (in shares / units)	172,202,000	171,916,000		171,892,000
Net income attributable to the Company's common shareholders / unitholders (in dollars per share / unit)	$ 1.08	$ 0.85		$ 2.02
Effect of Dilutive Securities:
Stock Based Compensation, Income (Numerator)	$ 0	$ 0	$ 0	$ 0
Stock Based Compensation, Income (in shares / units)	319,000	156,000	319,000	238,000
Stock Based Compensation, Income (in dollars per share / unit)	$ 0	$ 0	$ (0.01)	$ (0.01)
Diluted Earnings:
Net income attributable to the Company's common shareholders / unitholders (Numerator)	$ 185,661	$ 145,943	$ 299,097	$ 346,710
Net income attributable to to the Company's shareholders / unitholder (number of shares)	172,521,000	172,072,000	172,486,000	172,130,000
Diluted Earnings: Net income, Per Share Amount (in dollars per share / unit)	$ 1.08	$ 0.85	$ 1.73	$ 2.01

Stock Option and Incentive Pl_2

Stock Option and Incentive Plan Stock Option and Incentive Plan (Narrative) (Details) - USD ($) $ in Millions	Feb. 09, 2019	Feb. 05, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights		Earned awards (if any) will vest 50% on February 4, 2022 and 50% on February 4, 2023, 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 4, 2022, earned awards will be calculated based on TSR performance up to the date of the change of control. The 2019 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.
2019 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Measurement, Years		three year
Minimum earned awards		0
Maximum Earned Awards		220,734
Target Tier		110,367
Value of MYLTIP Awards		$ 13.5
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards	$ 13.6
Final awards percentage of target	69.50%
2016 MYLTIP Units Forfeited	364,980

Stock Option and Incentive Pl_3

Stock Option and Incentive Plan Restricted Stock (Narrative) (Details) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)$ / sharesshares	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)$ / sharesshares	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued | shares	154,642,030		154,642,030		154,537,378
Common Stock, Value, Issued	$ 1,546		$ 1,546		$ 1,545
Stock based compensation expense	$ 10,100	$ 7,900	$ 24,900	$ 22,100
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued | shares	26,503		26,503
Employee and director payment per share (in dollars per share) | $ / shares			$ 0.01
Common Stock, Value, Issued	$ 3,500		$ 3,500
Employee's weighted average cost per share (in dollars per share) | $ / shares	$ 131.27		$ 131.27
LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of LTIP units issued			$ 22,100
Per unit fair value weighted-average (in dollars per share) | $ / shares	$ 121.50		$ 121.50
Expected life assumed to calculate per unit fair value per LTIP unit (years)			5 years 8 months 12 days
Risk-free rate			2.68%
Expected price volatility			27.00%
LTIPs (including vested 2012 OPP Awards and vested MYLTIPS) And Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting annual installments			4
Unrecognized compensation expenses	$ 33,200		$ 33,200
Unvested MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses	$ 17,900		$ 17,900
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) | shares	181,919		181,919
Boston Properties Limited Partnership | 2019 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
MYLTIP units issued (in shares) | shares	220,734		220,734
Boston Properties Limited Partnership | LTIPs and 2019 MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee and director payment per share (in dollars per share) | $ / shares			$ 0.25

Segment Information (Schedule O

Segment Information (Schedule Of Reconciliation Of Net Operating Income To Net Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income attributable to the Company's common shareholders / unitholders	$ 164,318	$ 128,681	$ 262,431	$ 304,682
Preferred Stock Dividends / Distributions	(2,625)	(2,625)	(5,250)	(5,250)
Noncontrolling interest-common units of the Operating Partnership	(19,036)	(14,859)	(30,627)	(35,311)
Noncontrolling interest in property partnerships	(17,482)	(14,400)	(36,312)	(31,634)
Interest expense	(102,357)	(92,204)	(203,366)	(182,424)
Company's share of net operating from joint ventures	(454,301)	(406,678)	(902,016)	(808,137)
Depreciation and amortization expense	(177,411)	(156,417)	(342,005)	(322,214)
Transaction costs	(417)	(474)	(877)	(495)
General and administrative expense	(35,071)	(28,468)	(76,833)	(64,362)
Gains from investments in securities	(1,165)	(505)	(4,134)	(379)
Interest and other income	(3,615)	(2,579)	(7,368)	(4,227)
Income from unconsolidated joint ventures	(47,964)	(769)	(48,177)	(1,230)
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	164,318	128,681	262,431	304,682
Preferred Stock Dividends / Distributions	2,625	2,625	5,250	5,250
Noncontrolling interest-common units of the Operating Partnership	19,036	14,859	30,627	35,311
Noncontrolling interest in property partnerships	17,482	14,400	36,312	31,634
Interest expense	102,357	92,204	203,366	182,424
Impairment loss	0	0	24,038	0
Depreciation and amortization expense	177,411	156,417	342,005	322,214
Transaction costs	417	474	877	495
Payroll and related costs from management service contracts	2,403	1,970	5,798	4,855
General and administrative expense	35,071	28,468	76,833	64,362
Gains from investments in securities	1,165	505	4,134	379
Interest and other income	3,615	2,579	7,368	4,227
(Losses) gains on sales of real estate	1,686	18,292	781	114,689
Income from unconsolidated joint ventures	47,964	769	48,177	1,230
Direct reimbursement of payroll and related costs from management service contracts	2,403	1,970	5,798	4,855
Company's Share of Net Operating Income	433,454	379,856	859,433	751,466
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	185,715	145,961	299,097	346,868
Preferred Stock Dividends / Distributions	(2,625)	(2,625)	(5,250)	(5,250)
Noncontrolling interest in property partnerships	(17,482)	(14,400)	(36,312)	(31,634)
Interest expense	(102,357)	(92,204)	(203,366)	(182,424)
Depreciation and amortization expense	(175,199)	(154,474)	(337,881)	(318,327)
Transaction costs	(417)	(474)	(877)	(495)
Payroll and related costs from management service contracts			(5,798)	(4,855)
General and administrative expense	(35,071)	(28,468)	(76,833)	(64,362)
Gains from investments in securities	(1,165)	(505)	(4,134)	(379)
Interest and other income	(3,615)	(2,579)	(7,368)	(4,227)
Income from unconsolidated joint ventures	(47,964)	(769)	(48,177)	(1,230)
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	185,715	145,961	299,097	346,868
Preferred Stock Dividends / Distributions	2,625	2,625	5,250	5,250
Noncontrolling interest in property partnerships	17,482	14,400	36,312	31,634
Interest expense	102,357	92,204	203,366	182,424
Impairment loss	0	0	22,272	0
Depreciation and amortization expense	175,199	154,474	337,881	318,327
Transaction costs	417	474	877	495
Payroll and related costs from management service contracts	2,403	1,970	5,798	4,855
General and administrative expense	35,071	28,468	76,833	64,362
Gains from investments in securities	1,165	505	4,134	379
Interest and other income	3,615	2,579	7,368	4,227
(Losses) gains on sales of real estate	1,835	18,770	930	117,677
Income from unconsolidated joint ventures	47,964	769	48,177	1,230
Direct reimbursement of payroll and related costs from management service contracts	2,403	1,970	5,798	4,855
Company's Share of Net Operating Income	433,454	379,856	859,433	751,466
Development and Management Services [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payroll and related costs from management service contracts	(2,403)	(1,970)	(5,798)	(4,855)
Direct reimbursement of payroll and related costs from management service contracts	(9,986)	(9,305)	(19,263)	(17,710)
Development and Management Services [Member] | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Direct reimbursement of payroll and related costs from management service contracts	9,986	9,305	19,263	17,710
Development and Management Services [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 service contracts	(2,403)	(1,970)
Direct reimbursement of payroll and related costs from management service contracts	(9,986)	(9,305)	(19,263)	(17,710)
Development and Management Services [Member] | Boston Properties Limited Partnership | Business Intersegment, Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Direct reimbursement of payroll and related costs from management service contracts	9,986	9,305	19,263	17,710
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 from joint ventures	45,562	43,049	92,647	88,958
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 from joint ventures	45,562	43,049	92,647	88,958
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 from joint ventures	45,562	43,049	92,647	88,958
Unconsolidated Joint Ventures [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense	(20,803)	(14,708)	(41,560)	(29,132)
Company's share of net operating from joint ventures	(24,715)	(16,227)	(50,064)	(32,287)
Depreciation and amortization expense	(24,818)	(14,527)	(53,464)	(29,252)
Income from unconsolidated joint ventures	(47,964)	(769)	(48,177)	(1,230)
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 from joint ventures	(24,715)	(16,227)	(50,064)	(32,287)
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 from joint ventures	$ (24,715)	$ (16,227)	$ (50,064)	$ (32,287)

Segment Information (Schedule_2

Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Rental Revenue: Office	[1]	$ 697,509	$ 633,803	$ 1,393,951	$ 1,270,403
Rental Revenue: Residential	[1]	8,999	4,799	16,714	8,958
Total revenue	[1]	$ 721,352	$ 653,209	$ 1,434,447	$ 1,303,070
Rental Revenue: % of Grand Totals		100.00%	100.00%	100.00%	100.00%
Rental Expenses		$ 257,971	$ 237,790	$ 515,488	$ 478,119
Rental Expenses: Total		$ 267,051	$ 246,531	$ 532,431	$ 494,933
Rental Expenses: % Of Grand Totals		100.00%	100.00%	100.00%	100.00%
Net operating Income		$ 454,301	$ 406,678	$ 902,016	$ 808,137
Net operating Income: % of Grand Totals		100.00%	100.00%	100.00%	100.00%
Company's Share of Net Operating Income: % of Grand Totals		100.00%	100.00%	100.00%	100.00%
Boston [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	[1]	$ 217,961	$ 207,810	$ 435,372	$ 412,807
Rental Revenue: Residential	[1]	3,222	1,195	5,923	2,347
Total revenue	[1]	$ 236,027	$ 223,612	$ 465,077	$ 438,863
Rental Revenue: % of Grand Totals		32.72%	34.23%	32.42%	33.68%
Rental Expenses: Total		$ 88,019	$ 86,594	$ 176,588	$ 175,505
Rental Expenses: % Of Grand Totals		32.96%	35.12%	33.17%	35.46%
Net operating Income		$ 148,008	$ 137,018	$ 288,489	$ 263,358
Net operating Income: % of Grand Totals		32.58%	33.69%	31.98%	32.59%
Company's Share of Net Operating Income: % of Grand Totals		32.01%	34.06%	31.49%	33.02%
Los Angeles [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	[1]	$ 0	$ 0	$ 0	$ 0
Rental Revenue: Residential	[1]	0	0	0	0
Total revenue	[1]	$ 0	$ 0	$ 0	$ 0
Rental Revenue: % of Grand Totals		0.00%	0.00%	0.00%	0.00%
Rental Expenses: Total		$ 0	$ 0	$ 0	$ 0
Rental Expenses: % Of Grand Totals		0.00%	0.00%	0.00%	0.00%
Net operating Income		$ 0	$ 0	$ 0	$ 0
Net operating Income: % of Grand Totals		0.00%	0.00%	0.00%	0.00%
Company's Share of Net Operating Income: % of Grand Totals		3.57%	1.82%	3.63%	1.86%
New York [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	[1]	$ 251,556	$ 234,006	$ 510,187	$ 476,404
Rental Revenue: Residential	[1]	0	0	0	0
Total revenue	[1]	$ 251,556	$ 234,006	$ 510,187	$ 476,404
Rental Revenue: % of Grand Totals		34.87%	35.83%	35.56%	36.56%
Rental Expenses: Total		$ 96,809	$ 91,838	$ 193,780	$ 185,600
Rental Expenses: % Of Grand Totals		36.25%	37.26%	36.39%	37.50%
Net operating Income		$ 154,747	$ 142,168	$ 316,407	$ 290,804
Net operating Income: % of Grand Totals		34.06%	34.96%	35.08%	35.98%
Company's Share of Net Operating Income: % of Grand Totals		27.90%	28.73%	28.75%	29.47%
San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	[1]	$ 131,506	$ 93,482	$ 255,561	$ 183,375
Rental Revenue: Residential	[1]	0	0	0	0
Total revenue	[1]	$ 131,506	$ 93,482	$ 255,561	$ 183,375
Rental Revenue: % of Grand Totals		18.23%	14.31%	17.82%	14.07%
Rental Expenses: Total		$ 43,708	$ 31,214	$ 84,833	$ 58,842
Rental Expenses: % Of Grand Totals		16.37%	12.66%	15.93%	11.89%
Net operating Income		$ 87,798	$ 62,268	$ 170,728	$ 124,533
Net operating Income: % of Grand Totals		19.33%	15.31%	18.93%	15.41%
Company's Share of Net Operating Income: % of Grand Totals		20.26%	16.42%	19.81%	16.61%
Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Office	[1]	$ 96,486	$ 98,505	$ 192,831	$ 197,817
Rental Revenue: Residential	[1]	5,777	3,604	10,791	6,611
Total revenue	[1]	$ 102,263	$ 102,109	$ 203,622	$ 204,428
Rental Revenue: % of Grand Totals		14.18%	15.63%	14.20%	15.69%
Rental Expenses: Total		$ 38,515	$ 36,885	$ 77,230	$ 74,986
Rental Expenses: % Of Grand Totals		14.42%	14.96%	14.51%	15.15%
Net operating Income		$ 63,748	$ 65,224	$ 126,392	$ 129,442
Net operating Income: % of Grand Totals		14.03%	16.04%	14.01%	16.02%
Company's Share of Net Operating Income: % of Grand Totals		16.26%	18.97%	16.32%	19.04%
Office
Segment Reporting Information [Line Items]
Rental Revenue: Hotel		$ 2,403	$ 1,970	$ 5,798	$ 4,855
Rental Expenses		253,849	234,877	507,592	472,934
Office | Boston [Member]
Segment Reporting Information [Line Items]
Rental Expenses		77,660	77,147	157,160	157,471
Office | Los Angeles [Member]
Segment Reporting Information [Line Items]
Rental Expenses		0	0	0	0
Office | New York [Member]
Segment Reporting Information [Line Items]
Rental Expenses		96,809	91,838	193,780	185,600
Office | San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Expenses		43,708	31,214	84,833	58,842
Office | Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Expenses		35,672	34,678	71,819	71,021
Residential Properties [Member]
Segment Reporting Information [Line Items]
Rental Expenses		4,122	2,913	7,896	5,185
Residential Properties [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Rental Expenses		1,279	706	2,485	1,220
Residential Properties [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Rental Expenses		0	0	0	0
Residential Properties [Member] | New York [Member]
Segment Reporting Information [Line Items]
Rental Expenses		0	0	0	0
Residential Properties [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Expenses		0	0	0	0
Residential Properties [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Expenses		2,843	2,207	5,411	3,965
Hotel [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Hotel	[1]	14,844	14,607	23,782	23,709
Rental Expenses: Hotel		9,080	8,741	16,943	16,814
Hotel [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Hotel	[1]	14,844	14,607	23,782	23,709
Rental Expenses: Hotel		9,080	8,741	16,943	16,814
Hotel [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Hotel	[1]	0	0	0	0
Rental Expenses: Hotel		0	0	0	0
Hotel [Member] | New York [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Hotel	[1]	0	0	0	0
Rental Expenses: Hotel		0	0	0	0
Hotel [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Hotel	[1]	0	0	0	0
Rental Expenses: Hotel		0	0	0	0
Hotel [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Rental Revenue: Hotel	[1]	0	0	0	0
Rental Expenses: Hotel		0	0	0	0
Noncontrolling interest - property partnerships [Member]
Segment Reporting Information [Line Items]
Net operating Income		(45,562)	(43,049)	(92,647)	(88,958)
Noncontrolling interest - property partnerships [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net operating Income		(10,031)	(8,418)	(19,404)	(16,547)
Noncontrolling interest - property partnerships [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net operating Income		0	0	0	0
Noncontrolling interest - property partnerships [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net operating Income		(35,531)	(34,751)	(72,795)	(72,697)
Noncontrolling interest - property partnerships [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net operating Income		0	120	(448)	286
Noncontrolling interest - property partnerships [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net operating Income		0	0	0	0
Unconsolidated Joint Ventures [Member]
Segment Reporting Information [Line Items]
Net operating Income		24,715	16,227	50,064	32,287
Unconsolidated Joint Ventures [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net operating Income		818	781	1,590	1,315
Unconsolidated Joint Ventures [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net operating Income		15,454	6,902	31,162	13,976
Unconsolidated Joint Ventures [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net operating Income		1,696	1,706	3,482	3,367
Unconsolidated Joint Ventures [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net operating Income		0	0	0	0
Unconsolidated Joint Ventures [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net operating Income		6,747	6,838	13,830	13,629
Company's Share [Member]
Segment Reporting Information [Line Items]
Net operating Income		433,454	379,856	859,433	751,466
Company's Share [Member] | Boston [Member]
Segment Reporting Information [Line Items]
Net operating Income		138,795	129,381	270,675	248,126
Company's Share [Member] | Los Angeles [Member]
Segment Reporting Information [Line Items]
Net operating Income		15,454	6,902	31,162	13,976
Company's Share [Member] | New York [Member]
Segment Reporting Information [Line Items]
Net operating Income		120,912	109,123	247,094	221,474
Company's Share [Member] | San Francisco [Member]
Segment Reporting Information [Line Items]
Net operating Income		87,798	62,388	170,280	124,819
Company's Share [Member] | Washington, DC [Member]
Segment Reporting Information [Line Items]
Net operating Income		$ 70,495	$ 72,062	$ 140,222	$ 143,071
[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.

Segment Information Narrative (

Segment Information Narrative (Details) - Los Angeles [Member] ft² in Millions	Jun. 30, 2019ft²Buildings
Segment Reporting Information [Line Items]
Net Rentable Area (in sf) | ft²	2.3
Number of real estate properties | Buildings	27

Subsequent Events Narrative (De

Subsequent Events Narrative (Details) - Subsequent Event [Member] - 2100 Pennsylvania Avenue [Member] $ in Millions	Jul. 16, 2019USD ($)ft²
Subsequent Event [Line Items]
Lessee, Finance Lease, Term of Contract	75 years
Net Rentable Area (in sf)	480,000
Prepaid Rent | $	$ 15
Term of Lease Signed (in years)	16-year
Square Footage Of Signed Lease	300,000