Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 712,563	$ 562,481	$ 569,977
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	645,649	617,547	694,403
Impairment loss	11,812	0	1,783
Non-cash compensation expense	40,117	35,361	32,911
Income from unconsolidated joint ventures	(2,222)	(11,232)	(8,074)
Gain on sale of investment in unconsolidated joint venture	0	0	(59,370)
Distributions of net cash flow from operations of unconsolidated joint ventures	6,703	26,858	24,955
(Gains) losses on investments in securities	1,865	(3,678)	(2,273)
Non-cash portion of interest expense	21,303	(1,284)	(35,052)
Settlement of accreted debt discount on redemption of unsecured senior notes	(483)	(1,980)	0
Losses (gains) from early extinguishments of debt	16,490	(496)	371
Gains on sales of real estate	(182,356)	(7,663)	(80,606)
Change in assets and liabilities:
Tenant and other receivables, net	29,204	2,433	3,688
Note receivable	(13)	0	0
Accrued rental income, net	(43,662)	(58,355)	(28,127)
Prepaid expenses and other assets	12,472	51,425	52,923
Accounts payable and accrued expenses	1,353	10,482	15,666
Accrued interest payable	5,237	(160,521)	53,547
Other liabilities	4,955	(44,970)	(106,071)
Tenant leasing costs	(130,742)	(104,429)	(96,103)
Total adjustments	437,682	349,498	464,571
Net cash provided by operating activities	1,150,245	911,979	1,034,548
Cash flows from investing activities:
Acquisitions of real estate	0	(15,953)	(78,000)
Construction in progress	(694,791)	(608,404)	(500,350)
Building and other capital improvements	(189,771)	(222,482)	(150,640)
Tenant improvements	(210,034)	(205,331)	(230,298)
Proceeds from sales of real estate	455,409	29,810	122,750
Capital contributions to unconsolidated joint ventures	(345,717)	(109,015)	(575,795)
Capital distributions from unconsolidated joint ventures	0	251,000	20,440
Proceeds from sale of investment in unconsolidated joint venture	0	0	55,707
Deposit on capital lease	(13,615)	0	0
Issuance of related party note receivable	(80,000)	0	0
Issuance of note receivable	(19,455)	0	0
Investments in securities, net	(902)	(1,669)	(1,161)
Net cash used in investing activities	(1,098,876)	(882,044)	(1,337,347)
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	2,300,000	0
Repayments of mortgage notes payable	(18,634)	(1,317,653)	(1,326,865)
Proceeds from unsecured senior notes	996,410	847,935	1,989,790
Redemption of unsecured senior notes	(699,517)	(848,020)	0
Borrowings on unsecured line of credit	745,000	580,000	25,000
Repayments of unsecured line of credit	(790,000)	(535,000)	(25,000)
Proceeds from unsecured term loan	500,000	0	0
Repayments of mezzanine notes payable	0	(306,000)	0
Repayments of outside members’ notes payable	0	(70,424)	0
Payments on capital lease obligations	(1,353)	(493)	(745)
Payments on real estate financing transactions	(960)	(2,840)	(5,260)
Deposit on mortgage note payable interest rate lock	0	(23,200)	0
Return of deposit on mortgage note payable interest rate lock	0	23,200	0
Deferred financing costs	(8,362)	(50,705)	(16,121)
Debt prepayment and extinguishment costs	(15,973)	(12,784)	0
Net proceeds from equity transactions	(730)	241	(271)
Dividends and distributions	(587,628)	(526,578)	(671,626)
Contributions from noncontrolling interests in property partnerships	46,701	52,009	11,951
Distributions to noncontrolling interests in property partnerships	(82,501)	(54,342)	(55,474)
Net cash provided by (used in) financing activities	82,453	55,346	(74,621)
Net increase (decrease) in cash and cash equivalents	133,822	85,281	(377,420)
Cash and cash equivalents and cash held in escrows, beginning of year	505,369	420,088	797,508
Cash and cash equivalents and cash held in escrows, end of year	639,191	505,369	420,088
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of year	434,767	356,914	723,718
Cash held in escrows, beginning of period	70,602	63,174	73,790
Cash and cash equivalents, end of year	543,359	434,767	356,914
Cash held in escrows,end of period	95,832	70,602	63,174
Supplemental disclosures:
Cash paid for interest	416,019	598,486	433,591
Interest capitalized	65,766	61,070	39,200
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(135,431)	(124,891)	(206,721)
Change in real estate included in accounts payable and accrued expenses	(44,866)	27,978	(1,481)
Real estate acquired through capital lease	12,397	28,962	21,000
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	0	109,576	0
Dividends and distributions declared but not paid	165,114	139,040	130,308
Conversions of noncontrolling interests to stockholders’ equity	2,880	16,916	6,461
Issuance of restricted securities to employees and directors	37,052	35,989	33,615
Boston Properties Limited Partnership
Net income	730,312	571,198	583,773
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	637,891	609,407	682,776
Impairment loss	10,181	0	1,783
Non-cash compensation expense	40,117	35,361	32,911
Income from unconsolidated joint ventures	(2,222)	(11,232)	(8,074)
Gain on sale of investment in unconsolidated joint venture	0	0	(59,370)
Distributions of net cash flow from operations of unconsolidated joint ventures	6,703	26,858	24,955
(Gains) losses on investments in securities	1,865	(3,678)	(2,273)
Non-cash portion of interest expense	21,303	(1,284)	(35,052)
Settlement of accreted debt discount on redemption of unsecured senior notes	(483)	(1,980)	0
Losses (gains) from early extinguishments of debt	16,490	(496)	371
Gains on sales of real estate	(190,716)	(8,240)	(82,775)
Change in assets and liabilities:
Tenant and other receivables, net	29,204	2,433	3,688
Note receivable	(13)	0	0
Accrued rental income, net	(43,662)	(58,355)	(28,127)
Prepaid expenses and other assets	12,472	51,425	52,923
Accounts payable and accrued expenses	1,353	10,482	15,666
Accrued interest payable	5,237	(160,521)	53,547
Other liabilities	4,955	(44,970)	(106,071)
Tenant leasing costs	(130,742)	(104,429)	(96,103)
Total adjustments	419,933	340,781	450,775
Net cash provided by operating activities	1,150,245	911,979	1,034,548
Cash flows from investing activities:
Acquisitions of real estate	0	(15,953)	(78,000)
Construction in progress	(694,791)	(608,404)	(500,350)
Building and other capital improvements	(189,771)	(222,482)	(150,640)
Tenant improvements	(210,034)	(205,331)	(230,298)
Proceeds from sales of real estate	455,409	29,810	122,750
Capital contributions to unconsolidated joint ventures	(345,717)	(109,015)	(575,795)
Capital distributions from unconsolidated joint ventures	0	251,000	20,440
Proceeds from sale of investment in unconsolidated joint venture	0	0	55,707
Deposit on capital lease	(13,615)	0	0
Issuance of related party note receivable	(80,000)	0	0
Issuance of note receivable	(19,455)	0	0
Investments in securities, net	(902)	(1,669)	(1,161)
Net cash used in investing activities	(1,098,876)	(882,044)	(1,337,347)
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	2,300,000	0
Repayments of mortgage notes payable	(18,634)	(1,317,653)	(1,326,865)
Proceeds from unsecured senior notes	996,410	847,935	1,989,790
Redemption of unsecured senior notes	(699,517)	(848,020)	0
Borrowings on unsecured line of credit	745,000	580,000	25,000
Repayments of unsecured line of credit	(790,000)	(535,000)	(25,000)
Proceeds from unsecured term loan	500,000	0	0
Repayments of mezzanine notes payable	0	(306,000)	0
Repayments of outside members’ notes payable	0	(70,424)	0
Payments on capital lease obligations	(1,353)	(493)	(745)
Payments on real estate financing transactions	(960)	(2,840)	(5,260)
Deposit on mortgage note payable interest rate lock	0	(23,200)	0
Return of deposit on mortgage note payable interest rate lock	0	23,200	0
Deferred financing costs	(8,362)	(50,705)	(16,121)
Debt prepayment and extinguishment costs	(15,973)	(12,784)	0
Net proceeds from equity transactions	(730)	241	(271)
Dividends and distributions	(587,628)	(526,578)	(671,626)
Contributions from noncontrolling interests in property partnerships	46,701	52,009	11,951
Distributions to noncontrolling interests in property partnerships	(82,501)	(54,342)	(55,474)
Net cash provided by (used in) financing activities	82,453	55,346	(74,621)
Net increase (decrease) in cash and cash equivalents	133,822	85,281	(377,420)
Cash and cash equivalents and cash held in escrows, beginning of year	505,369	420,088	797,508
Cash and cash equivalents and cash held in escrows, end of year	639,191	505,369	420,088
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of year	434,767	356,914	723,718
Cash held in escrows, beginning of period	70,602	63,174	73,790
Cash and cash equivalents, end of year	543,359	434,767	356,914
Cash held in escrows,end of period	95,832	70,602	63,174
Supplemental disclosures:
Cash paid for interest	416,019	598,486	433,591
Interest capitalized	65,766	61,070	39,237
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(135,431)	(123,714)	(202,388)
Change in real estate included in accounts payable and accrued expenses	(44,866)	27,978	(1,481)
Real estate acquired through capital lease	12,397	28,962	21,000
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	0	109,576	0
Dividends and distributions declared but not paid	165,114	139,040	130,308
Conversions of noncontrolling interests to stockholders’ equity	2,880	16,916	6,461
Issuance Of Restricted Units To Employees And Directors	$ 37,052	$ 35,989	$ 33,615