Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net income	$ 631,932	$ 1,018,691	$ 651,999
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	717,336	683,751	677,764
Amortization of right of use assets - operating leases	3,516	2,234	2,412
Impairment of Real Estate	0	0	24,038
Non-cash compensation expense	50,860	44,142	40,958
Loss (income) from unconsolidated joint ventures	2,570	85,110	(46,592)
Distributions of net cash flow from operations of unconsolidated joint ventures	21,542	31,892	17,155
Gains from investments in securities	(5,626)	(5,261)	(6,417)
Allowance for current expected credit losses	(1,207)	1,849	0
Non-cash portion of interest expense	23,368	23,384	22,254
Settlement of accreted debt discount on redemption of unsecured senior notes	(8,500)	0	(763)
Loss from early extinguishment of debt	45,182	0	29,540
Gains on sales of real estate	(123,660)	(618,982)	(709)
Change in assets and liabilities:
Tenant and other receivables, net	4,820	22,550	(24,876)
Notes receivable, net	(545)	(19)	4
Accrued rental income, net	(101,548)	(97,099)	(56,817)
Prepaid expenses and other assets	(20,811)	12,488	2,965
Lease liabilities - finance leases	0	(568)	0
Lease liabilities - operating leases	(23,599)	1,533	1,616
Accounts payable and accrued expenses	20,025	(4,059)	12,627
Accrued interest payable	(10,839)	16,211	858
Other liabilities	(28,739)	17,629	(49,569)
Tenant leasing costs	(62,850)	(79,772)	(117,282)
Total adjustments	501,295	138,149	529,166
Net cash provided by operating activities	1,133,227	1,156,840	1,181,165
Cash flows from investing activities:
Acquisitions of real estate	(222,260)	(137,976)	(149,031)
Construction in progress	(513,878)	(482,507)	(546,060)
Building and other capital improvements	(150,998)	(160,126)	(180,556)
Tenant improvements	(263,952)	(234,423)	(251,831)
Right of use assets - finance leases	0	0	(5,152)
Proceeds from sales of real estate	179,887	519,303	90,824
Capital contributions to unconsolidated joint ventures	(98,152)	(172,436)	(87,392)
Capital distributions from unconsolidated joint ventures	122	55,298	136,807
Cash and cash equivalents deconsolidated	0	0	(24,112)
Issuance of notes receivable, net	0	(9,800)	0
Proceeds from note receivable	10,035	6,397	(3,544)
Proceeds from sale of investment in unconsolidated joint venture	17,789	0	0
Investments in securities, net	1,451	2,551	(2,132)
Net cash used in investing activities	(1,039,956)	(613,719)	(1,015,091)
Cash flows from financing activities:
Proceeds from mortgage notes payable	1,201,388	0	0
Repayments of mortgage notes payable	(832,296)	(17,168)	(46,173)
Proceeds from unsecured senior notes	1,695,996	1,248,125	1,548,106
Redemption of unsecured senior notes	(1,841,500)	0	(699,237)
Borrowings on unsecured line of credit	770,000	265,000	380,000
Repayments of unsecured line of credit	(625,000)	(265,000)	(380,000)
Repayment of unsecured term loan	(500,000)	0	0
Redemption of preferred stock	(200,000)	0	0
Payments on finance lease obligations	1,250	0	502
Deferred financing costs	(20,757)	(10,416)	(13,213)
Debt issuance costs	(16,186)	0	0
Debt prepayment and extinguishment costs	(43,036)	0	(28,716)
Net proceeds from equity transactions	24,214	3,277	13,710
Dividends and distributions	(683,753)	(688,904)	(666,294)
Contributions from noncontrolling interests in property partnerships	18,002	8,219	35,816
Distributions to noncontrolling interests in property partnerships	(259,764)	(58,811)	(69,913)
Acquisition of noncontrolling interest in property partnership	0	0	(186,963)
Net cash provided by (used in) financing activities	(1,311,442)	484,322	(113,379)
Net increase (decrease) in cash and cash equivalents and cash held in escrows	(1,218,171)	1,027,443	52,695
Cash and cash equivalents and cash held in escrows, beginning of period	1,719,329	691,886	639,191
Cash and cash equivalents and cash held in escrows, end of period	501,158	1,719,329	691,886
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of period	1,668,742	644,950	543,359
Cash held in escrows, beginning of period	50,587	46,936	95,832
Cash and cash equivalents, end of period	452,692	1,668,742	644,950
Cash held in escrows,end of period	48,466	50,587	46,936
Supplemental disclosures:
Cash paid for interest	465,442	433,492	439,059
Interest capitalized	53,097	53,881	54,911
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(239,317)	(99,494)	(129,831)
Change in real estate included in accounts payable and accrued expenses	(25,183)	(19,848)	89,245
Right-of-use assets obtained in exchange for operating lease liabilities	26,887	0	287,540
Prepaid rent reclassified to right of use asset	0	0	15,000
Accrued rental income, net deconsolidated	0	(4,558)	0
Tenant leasing costs, net deconsolidated	0	(3,462)	0
Building and other capital improvements, net deconsolidated	0	(111,889)	(12,767)
Tenant improvements, net deconsolidated	0	(12,331)	0
Construction in progress, net deconsolidated	(299,947)	0	0
Prepaid expenses and other assets, net deconsolidated	(5,011)	0	0
Right of use asset - finance lease deconsolidated	0	0	(135,004)
Lease liability - finance lease deconsolidated	0	0	119,534
Investment in unconsolidated joint venture recorded upon deconsolidation	107,132	347,898	29,246
Issuance of operating partnership units for 360 Park Avenue South	99,689	0	0
Assumption of mortgage notes payable	200,311	0	0
Mortgage notes payable - deconsolidated	(198,381)	0	0
Dividends and distributions declared but not paid	169,859	171,082	170,713
Conversions of noncontrolling interests to stockholders’ equity	18,386	29,698	4,885
Issuance of restricted securities to employees and non-employee directors	44,405	42,607	37,622
Boston Properties Limited Partnership
Net income	641,771	1,038,739	661,722
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	709,035	676,666	669,956
Amortization of right of use assets - operating leases	3,516	2,234	2,412
Impairment of Real Estate	0	0	22,272
Non-cash compensation expense	50,860	44,142	40,958
Loss (income) from unconsolidated joint ventures	2,570	85,110	(46,592)
Distributions of net cash flow from operations of unconsolidated joint ventures	21,542	31,892	17,155
Gains from investments in securities	(5,626)	(5,261)	(6,417)
Allowance for current expected credit losses	(1,207)	1,849	0
Non-cash portion of interest expense	23,368	23,384	22,254
Settlement of accreted debt discount on redemption of unsecured senior notes	(8,500)	0	(763)
Loss from early extinguishment of debt	45,182	0	29,540
Gains on sales of real estate	(125,198)	(631,945)	(858)
Change in assets and liabilities:
Tenant and other receivables, net	4,820	22,550	(24,876)
Notes receivable, net	(545)	(19)	4
Accrued rental income, net	(101,548)	(97,099)	(56,817)
Prepaid expenses and other assets	(20,811)	12,488	2,965
Lease liabilities - finance leases	0	(568)	0
Lease liabilities - operating leases	(23,599)	1,533	1,616
Accounts payable and accrued expenses	20,025	(4,059)	12,627
Accrued interest payable	(10,839)	16,211	858
Other liabilities	(28,739)	17,629	(49,569)
Tenant leasing costs	(62,850)	(79,772)	(117,282)
Total adjustments	491,456	118,101	519,443
Net cash provided by operating activities	1,133,227	1,156,840	1,181,165
Cash flows from investing activities:
Acquisitions of real estate	(222,260)	(137,976)	(149,031)
Construction in progress	(513,878)	(482,507)	(546,060)
Building and other capital improvements	(150,998)	(160,126)	(180,556)
Tenant improvements	(263,952)	(234,423)	(251,831)
Right of use assets - finance leases	0	0	(5,152)
Proceeds from sales of real estate	179,887	519,303	90,824
Capital contributions to unconsolidated joint ventures	(98,152)	(172,436)	(87,392)
Capital distributions from unconsolidated joint ventures	122	55,298	136,807
Cash and cash equivalents deconsolidated	0	0	(24,112)
Issuance of notes receivable, net	0	(9,800)	0
Proceeds from note receivable	10,035	6,397	3,544
Proceeds from sale of investment in unconsolidated joint venture	17,789	0	0
Investments in securities, net	1,451	2,551	(2,132)
Net cash used in investing activities	(1,039,956)	(613,719)	(1,015,091)
Cash flows from financing activities:
Proceeds from mortgage notes payable	1,201,388	0	0
Repayments of mortgage notes payable	(832,296)	(17,168)	(46,173)
Proceeds from unsecured senior notes	1,695,996	1,248,125	1,548,106
Redemption of unsecured senior notes	(1,841,500)	0	(699,237)
Borrowings on unsecured line of credit	770,000	265,000	380,000
Repayments of unsecured line of credit	(625,000)	(265,000)	(380,000)
Repayment of unsecured term loan	(500,000)	0	0
Redemption of preferred stock	(200,000)	0	0
Payments on finance lease obligations	1,250	0	(502)
Deferred financing costs	(20,757)	(10,416)	(13,213)
Debt issuance costs	(16,186)	0	0
Debt prepayment and extinguishment costs	(43,036)	0	(28,716)
Net proceeds from equity transactions	24,214	3,277	13,710
Dividends and distributions	(683,753)	(688,904)	(666,294)
Contributions from noncontrolling interests in property partnerships	18,002	8,219	35,816
Distributions to noncontrolling interests in property partnerships	(259,764)	(58,811)	(69,913)
Acquisition of noncontrolling interest in property partnership	0	0	(186,963)
Net cash provided by (used in) financing activities	(1,311,442)	484,322	(113,379)
Net increase (decrease) in cash and cash equivalents and cash held in escrows	(1,218,171)	1,027,443	52,695
Cash and cash equivalents and cash held in escrows, beginning of period	1,719,329	691,886	639,191
Cash and cash equivalents and cash held in escrows, end of period	501,158	1,719,329	691,886
Reconciliation of cash and cash equivalents and cash held in escrow
Cash and cash equivalents, beginning of period	1,668,742	644,950	543,359
Cash held in escrows, beginning of period	50,587	46,936	95,832
Cash and cash equivalents, end of period	452,692	1,668,742	644,950
Cash held in escrows,end of period	48,466	50,587	46,936
Supplemental disclosures:
Cash paid for interest	465,442	433,492	439,059
Interest capitalized	53,097	53,881	54,911
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(238,003)	(99,494)	(129,253)
Change in real estate included in accounts payable and accrued expenses	(25,183)	(19,848)	89,245
Right-of-use assets obtained in exchange for operating lease liabilities	26,887	0	287,540
Prepaid rent reclassified to right of use asset	0	0	15,000
Accrued rental income, net deconsolidated	0	(4,558)	0
Tenant leasing costs, net deconsolidated	0	(3,462)	0
Building and other capital improvements, net deconsolidated	0	(111,889)	(12,767)
Tenant improvements, net deconsolidated	0	(12,331)	0
Construction in progress, net deconsolidated	(299,947)	0	0
Prepaid expenses and other assets, net deconsolidated	(5,011)	0	0
Right of use asset - finance lease deconsolidated	0	0	(135,004)
Lease liability - finance lease deconsolidated	0	0	119,534
Investment in unconsolidated joint venture recorded upon deconsolidation	107,132	347,898	29,246
Issuance of operating partnership units for 360 Park Avenue South	99,689	0	0
Assumption of mortgage notes payable	200,311	0	0
Mortgage notes payable - deconsolidated	(198,381)	0	0
Dividends and distributions declared but not paid	169,859	171,082	170,713
Conversions of noncontrolling interests to stockholders’ equity	18,386	29,698	4,885
Issuance of restricted securities to employees and non-employee directors	$ 44,405	$ 42,607	$ 37,622