Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 527,322	$ 430,278
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	480,210	463,288
Non-cash compensation expense	31,700	27,260
Loss (income) from unconsolidated joint ventures	3,083	(7,035)
Distributions of net cash flow from operations of unconsolidated joint ventures	3,988	8,563
Gains from investments in securities	(1,454)	(2,716)
Gains from early extinguishments of debt	0	(14,354)
Non-cash portion of interest expense	15,922	(6,667)
Gains on sales of real estate	(122,552)	(6,791)
Change in assets and liabilities:
Tenant and other receivables, net	1,578	12,528
Accrued rental income, net	(41,519)	(36,012)
Prepaid expenses and other assets	(51,938)	(13,633)
Accounts payable and accrued expenses	6,354	7,861
Accrued interest payable	8,860	(144,833)
Other liabilities	(1,561)	(65,073)
Tenant leasing costs	(89,366)	(67,699)
Total adjustments	243,305	154,687
Net cash provided by operating activities	770,627	584,965
Cash flows from investing activities:
Acquisitions of real estate	0	(15,953)
Construction in progress	(530,389)	(452,283)
Building and other capital improvements	(140,969)	(162,395)
Tenant improvements	(129,450)	(152,749)
Proceeds from sales of real estate	175,577	29,810
Capital contributions to unconsolidated joint ventures	(314,075)	(89,874)
Capital distributions from unconsolidated joint ventures	0	251,000
Issuance of related party note receivable	(80,000)	0
Investments in securities, net	(761)	(1,451)
Net cash used in investing activities	(1,020,067)	(593,895)
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	2,300,000
Repayments of mortgage notes payable	(14,677)	(1,313,890)
Borrowings on unsecured line of credit	580,000	470,000
Repayments of unsecured line of credit	(455,000)	(470,000)
Proceeds from unsecured term loan	500,000	0
Repayments of mezzanine notes payable	0	(306,000)
Repayments of outside members’ notes payable	0	(70,424)
Payments on capital lease obligations	0	(463)
Payments on real estate financing transactions	(960)	(1,306)
Deposit on mortgage note payable interest rate lock	0	(23,200)
Return of deposit on mortgage note payable interest rate lock	0	23,200
Deferred financing costs	(263)	(44,083)
Debt prepayment and extinguishment costs	0	(90)
Net proceeds from equity transactions	(333)	241
Dividends and distributions	(421,264)	(394,900)
Contributions from noncontrolling interests in property partnerships	37,148	38,196
Distributions to noncontrolling interests in property partnerships	(56,796)	(41,605)
Net cash provided by financing activities	167,855	165,676
Net increase (decrease) in cash and cash equivalents and cash held in escrows	(81,585)	156,746
Cash and cash equivalents and cash held in escrows, beginning of period	505,369	420,088
Cash and cash equivalents and cash held in escrows, end of period	423,784	576,834
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	434,767	356,914
Cash held in escrows, beginning of period	70,602	63,174
Cash and Cash Equivalents, end of period	322,502	493,055
Cash held in escrows, end of period	101,282	83,779
Supplemental disclosures:
Cash paid for interest	303,203	477,189
Interest capitalized	51,594	43,286
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(100,118)	(103,972)
Additions to real estate included in accounts payable and accrued expenses	(11,746)	36,609
Real estate acquired through capital lease	0	28,962
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	0	109,576
Dividends and distributions declared but not paid	165,118	130,434
Conversions of noncontrolling interests to stockholders’ equity / partners' capital	2,112	16,812
Issuance of restricted securities to employees	37,342	35,711
Boston Properties Limited Partnership
Cash flows from operating activities:
Net income	537,428	437,041
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	474,383	457,102
Non-cash compensation expense	31,700	27,260
Loss (income) from unconsolidated joint ventures	3,083	(7,035)
Distributions of net cash flow from operations of unconsolidated joint ventures	3,988	8,563
Gains from investments in securities	(1,454)	(2,716)
Gains from early extinguishments of debt	0	(14,354)
Non-cash portion of interest expense	15,922	(6,667)
Gains on sales of real estate	(126,831)	(7,368)
Change in assets and liabilities:
Tenant and other receivables, net	1,578	12,528
Accrued rental income, net	(41,519)	(36,012)
Prepaid expenses and other assets	(51,938)	(13,633)
Accounts payable and accrued expenses	6,354	7,861
Accrued interest payable	8,860	(144,833)
Other liabilities	(1,561)	(65,073)
Tenant leasing costs	(89,366)	(67,699)
Total adjustments	233,199	147,924
Net cash provided by operating activities	770,627	584,965
Cash flows from investing activities:
Acquisitions of real estate	0	(15,953)
Construction in progress	(530,389)	(452,283)
Building and other capital improvements	(140,969)	(162,395)
Tenant improvements	(129,450)	(152,749)
Proceeds from sales of real estate	175,577	29,810
Capital contributions to unconsolidated joint ventures	(314,075)	(89,874)
Capital distributions from unconsolidated joint ventures	0	251,000
Issuance of related party note receivable	(80,000)	0
Investments in securities, net	(761)	(1,451)
Net cash used in investing activities	(1,020,067)	(593,895)
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	2,300,000
Repayments of mortgage notes payable	(14,677)	(1,313,890)
Borrowings on unsecured line of credit	580,000	470,000
Repayments of unsecured line of credit	(455,000)	(470,000)
Proceeds from unsecured term loan	500,000	0
Repayments of mezzanine notes payable	0	(306,000)
Repayments of outside members’ notes payable	0	(70,424)
Payments on capital lease obligations	0	(463)
Payments on real estate financing transactions	(960)	(1,306)
Deposit on mortgage note payable interest rate lock	0	(23,200)
Return of deposit on mortgage note payable interest rate lock	0	23,200
Deferred financing costs	(263)	(44,083)
Debt prepayment and extinguishment costs	0	(90)
Net proceeds from equity transactions	(333)	241
Dividends and distributions	(421,264)	(394,900)
Contributions from noncontrolling interests in property partnerships	37,148	38,196
Distributions to noncontrolling interests in property partnerships	(56,796)	(41,605)
Net cash provided by financing activities	167,855	165,676
Net increase (decrease) in cash and cash equivalents and cash held in escrows	(81,585)	156,746
Cash and cash equivalents and cash held in escrows, beginning of period	505,369	420,088
Cash and cash equivalents and cash held in escrows, end of period	423,784	576,834
Reconciliation of cash and cash equivalents and cash held in escrows:
Cash and cash equivalents, beginning of period	434,767	356,914
Cash held in escrows, beginning of period	70,602	63,174
Cash and Cash Equivalents, end of period	322,502	493,055
Cash held in escrows, end of period	101,282	83,779
Supplemental disclosures:
Cash paid for interest	303,203	477,189
Interest capitalized	51,594	43,286
Non-cash investing and financing activities:
Write-off of fully depreciated real estate	(100,118)	(102,795)
Additions to real estate included in accounts payable and accrued expenses	(11,746)	36,609
Real estate acquired through capital lease	0	28,962
Outside members’ notes payable contributed to noncontrolling interests in property partnerships	0	109,576
Dividends and distributions declared but not paid	165,118	130,434
Conversions of noncontrolling interests to stockholders’ equity / partners' capital	2,112	16,812
Issuance of restricted securities to employees	$ 37,342	$ 35,711