Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income	$ 651,999	$ 712,563	$ 562,481
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	677,764	645,649	617,547
Amortization of right-of-use assets - operating leases	2,412
Impairment losses	24,038	11,812	0
Non-cash compensation expense	40,958	40,117	35,361
Income from unconsolidated joint ventures	(46,592)	(2,222)	(11,232)
Distributions of net cash flow from operations of unconsolidated joint ventures	17,155	6,703	26,858
(Gains) losses from investments in securities	(6,417)	1,865	(3,678)
Non-cash portion of interest expense	22,254	21,303	(1,284)
Settlement of accreted debt discount on redemption of unsecured senior notes	(763)	(483)	(1,980)
Losses (gains) from early extinguishments of debt	29,540	16,490	(496)
Gains on sales of real estate	(709)	(182,356)	(7,663)
Change in assets and liabilities:
Tenant and other receivables, net	(24,876)	29,204	2,433
Note receivable	4	(13)	0
Accrued rental income, net	(56,817)	(43,662)	(58,355)
Prepaid expenses and other assets	2,965	12,472	51,425
Lease liabilities - operating leases	1,616
Accounts payable and accrued expenses	12,627	1,353	10,482
Accrued interest payable	858	5,237	(160,521)
Other liabilities	(49,569)	4,955	(44,970)
Tenant leasing costs	(117,282)	(130,742)	(104,429)
Total adjustments	529,166	437,682	349,498
Net cash provided by operating activities	1,181,165	1,150,245	911,979
Cash flows from investing activities:
Acquisitions of real estate	(149,031)	0	(15,953)
Construction in progress	(546,060)	(694,791)	(608,404)
Building and other capital improvements	(180,556)	(189,771)	(222,482)
Tenant improvements	(251,831)	(210,034)	(205,331)
Right of use assets - finance leases	(5,152)	0	0
Proceeds from sales of real estate	90,824	455,409	29,810
Capital contributions to unconsolidated joint ventures	(87,392)	(345,717)	(109,015)
Capital distributions from unconsolidated joint ventures	136,807	0	251,000
Cash and cash equivalents deconsolidated	(24,112)	0	0
Deposit on capital lease	0	(13,615)	0
Issuance of related party note receivable	0	(80,000)	0
Issuance of note receivable	0	(19,455)	0
Proceeds from note receivable	3,544	0	0
Investments in securities, net	(2,132)	(902)	(1,669)
Net cash used in investing activities	(1,015,091)	(1,098,876)	(882,044)
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	0	2,300,000
Repayments of mortgage notes payable	(46,173)	(18,634)	(1,317,653)
Proceeds from unsecured senior notes	1,548,106	996,410	847,935
Redemption of unsecured senior notes	(699,237)	(699,517)	(848,020)
Borrowings on unsecured line of credit	380,000	745,000	580,000
Repayments of unsecured line of credit	(380,000)	(790,000)	(535,000)
Proceeds from unsecured term loan	0	500,000	0
Repayments of mezzanine notes payable	0	0	(306,000)
Repayments of outside members’ notes payable	0	0	(70,424)
Payments on finance lease obligations	(502)	0	0
Payments on capital lease obligations	0	(1,353)	(493)
Payments on real estate financing transactions	0	(960)	(2,840)
Deposit on mortgage note payable interest rate lock	0	0	(23,200)
Return of deposit on mortgage note payable interest rate lock	0	0	23,200
Deferred financing costs	(13,213)	(8,362)	(50,705)
Debt prepayment and extinguishment costs	(28,716)	(15,973)	(12,784)
Net proceeds from equity transactions	13,710	(730)	241
Dividends and distributions	(666,294)	(587,628)	(526,578)
Contributions from noncontrolling interests in property partnerships	35,816	46,701	52,009
Distributions to noncontrolling interests in property partnerships	(69,913)	(82,501)	(54,342)
Acquisition of noncontrolling interest in property partnership	(186,963)	0	0
Net cash (used in) provided by financing activities	(113,379)	82,453	55,346
Net increase (decrease) in cash and cash equivalents	52,695	133,822	85,281
Cash and cash equivalents and cash held in escrows, beginning of year	639,191	505,369	420,088
Cash and cash equivalents and cash held in escrows, end of year	691,886	639,191	505,369
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of year	543,359	434,767	356,914
Cash held in escrows, beginning of period	95,832	70,602	63,174
Cash and cash equivalents, end of year	644,950	543,359	434,767
Cash held in escrows,end of period	46,936	95,832	70,602
Supplemental disclosures:
Cash paid for interest	439,059	416,019	598,486
Interest capitalized	54,911	65,766	61,070
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(129,831)	(135,431)	(124,891)
Change in real estate included in accounts payable and accrued expenses	89,245	(44,866)	27,978
Real estate acquired through capital leases	0	12,397	28,962
Real estate acquired through capital lease	287,540	0	0
Prepaid rent reclassified to right of use asset	15,000	0	0
Building and other capital improvements deconsolidated	(12,767)	0	0
Right of use asset - finance lease deconsolidated	(135,004)	0	0
Investment in unconsolidated joint venture recorded on deconsolidation	29,246	0	0
Lease liability - finance lease deconsolidation	119,534	0	0
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	0	0	109,576
Dividends and distributions declared but not paid	170,713	165,114	139,040
Conversions of noncontrolling interests to stockholders’ equity	4,885	2,880	16,916
Issuance of restricted securities to employees and directors	37,622	37,052	35,989
Boston Properties Limited Partnership
Net income	661,722	730,312	571,198
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	669,956	637,891	609,407
Amortization of right-of-use assets - operating leases	2,412
Impairment losses	22,272	10,181	0
Non-cash compensation expense	40,958	40,117	35,361
Income from unconsolidated joint ventures	(46,592)	(2,222)	(11,232)
Distributions of net cash flow from operations of unconsolidated joint ventures	17,155	6,703	26,858
(Gains) losses from investments in securities	(6,417)	1,865	(3,678)
Non-cash portion of interest expense	22,254	21,303	(1,284)
Settlement of accreted debt discount on redemption of unsecured senior notes	(763)	(483)	(1,980)
Losses (gains) from early extinguishments of debt	29,540	16,490	(496)
Gains on sales of real estate	(858)	(190,716)	(8,240)
Change in assets and liabilities:
Tenant and other receivables, net	(24,876)	29,204	2,433
Note receivable	4	(13)	0
Accrued rental income, net	(56,817)	(43,662)	(58,355)
Prepaid expenses and other assets	2,965	12,472	51,425
Lease liabilities - operating leases	1,616
Accounts payable and accrued expenses	12,627	1,353	10,482
Accrued interest payable	858	5,237	(160,521)
Other liabilities	(49,569)	4,955	(44,970)
Tenant leasing costs	(117,282)	(130,742)	(104,429)
Total adjustments	519,443	419,933	340,781
Net cash provided by operating activities	1,181,165	1,150,245	911,979
Cash flows from investing activities:
Acquisitions of real estate	(149,031)	0	(15,953)
Construction in progress	(546,060)	(694,791)	(608,404)
Building and other capital improvements	(180,556)	(189,771)	(222,482)
Tenant improvements	(251,831)	(210,034)	(205,331)
Right of use assets - finance leases	(5,152)	0	0
Proceeds from sales of real estate	90,824	455,409	29,810
Capital contributions to unconsolidated joint ventures	(87,392)	(345,717)	(109,015)
Capital distributions from unconsolidated joint ventures	136,807	0	251,000
Cash and cash equivalents deconsolidated	(24,112)	0	0
Deposit on capital lease	0	(13,615)	0
Issuance of related party note receivable	0	(80,000)	0
Issuance of note receivable	0	(19,455)	0
Proceeds from note receivable	3,544	0	0
Investments in securities, net	(2,132)	(902)	(1,669)
Net cash used in investing activities	(1,015,091)	(1,098,876)	(882,044)
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	0	2,300,000
Repayments of mortgage notes payable	(46,173)	(18,634)	(1,317,653)
Proceeds from unsecured senior notes	1,548,106	996,410	847,935
Redemption of unsecured senior notes	(699,237)	(699,517)	(848,020)
Borrowings on unsecured line of credit	380,000	745,000	580,000
Repayments of unsecured line of credit	(380,000)	(790,000)	(535,000)
Proceeds from unsecured term loan	0	500,000	0
Repayments of mezzanine notes payable	0	0	(306,000)
Repayments of outside members’ notes payable	0	0	(70,424)
Payments on finance lease obligations	(502)
Payments on capital lease obligations		(1,353)	(493)
Payments on real estate financing transactions	0	(960)	(2,840)
Deposit on mortgage note payable interest rate lock	0	0	(23,200)
Return of deposit on mortgage note payable interest rate lock	0	0	23,200
Deferred financing costs	(13,213)	(8,362)	(50,705)
Debt prepayment and extinguishment costs	(28,716)	(15,973)	(12,784)
Net proceeds from equity transactions	13,710	(730)	241
Dividends and distributions	(666,294)	(587,628)	(526,578)
Contributions from noncontrolling interests in property partnerships	35,816	46,701	52,009
Distributions to noncontrolling interests in property partnerships	(69,913)	(82,501)	(54,342)
Acquisition of noncontrolling interest in property partnership	(186,963)	0
Net cash (used in) provided by financing activities	(113,379)	82,453	55,346
Net increase (decrease) in cash and cash equivalents	52,695	133,822	85,281
Cash and cash equivalents and cash held in escrows, beginning of year	639,191	505,369	420,088
Cash and cash equivalents and cash held in escrows, end of year	691,886	639,191	505,369
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of year	543,359	434,767	356,914
Cash held in escrows, beginning of period	95,832	70,602	63,174
Cash and cash equivalents, end of year	644,950	543,359	434,767
Cash held in escrows,end of period	46,936	95,832	70,602
Supplemental disclosures:
Cash paid for interest	439,059	416,019	598,486
Interest capitalized	54,911	65,766	61,070
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(129,253)	(135,431)	(123,714)
Change in real estate included in accounts payable and accrued expenses	89,245	44,866	27,978
Real estate acquired through capital leases	0	12,397	28,962
Real estate acquired through capital lease	287,540	0	0
Prepaid rent reclassified to right of use asset	15,000	0	0
Building and other capital improvements deconsolidated	(12,767)	0	0
Right of use asset - finance lease deconsolidated	(135,004)	0	0
Investment in unconsolidated joint venture recorded on deconsolidation	29,246	0	0
Lease liability - finance lease deconsolidation	119,534	0	0
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	0	0	109,576
Dividends and distributions declared but not paid	170,713	165,114	139,040
Conversions of noncontrolling interests to stockholders’ equity	4,885	2,880	16,916
Issuance Of Restricted Units To Employees And Directors	$ 37,622	$ 37,052	$ 35,989