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Basis Of Presentation And Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Entity Information [Line Items]
Payroll and related costs from management services contracts	$ 1,970	$ 0	$ 4,855	$ 0
Direct reimbursements of payroll and related costs from management services contracts	1,970	0	4,855	0
Net Cash Provided by (Used in) Operating Activities			560,846	364,809
Cumulative effect of a change in accounting principle			5,496	(2,035)
Net Cash Provided by (Used in) Investing Activities			485,801	547,678
Net Cash Provided by (Used in) Financing Activities			(146,646)	(302,561)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect			(221,691)	(119,692)
Interest Expense	92,204	95,143	182,424	190,677
Boston Properties Limited Partnership
Entity Information [Line Items]
Payroll and related costs from management services contracts	1,970	0	4,855	0
Direct reimbursements of payroll and related costs from management services contracts	1,970	0	4,855	0
Net Cash Provided by (Used in) Operating Activities			560,846	364,809
Cumulative effect of a change in accounting principle			4,933	(272)
Net Cash Provided by (Used in) Investing Activities			485,801	547,678
Net Cash Provided by (Used in) Financing Activities			(146,646)	(302,561)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect			(221,691)	(119,692)
Interest Expense	92,204	$ 95,143	182,424	190,677
Dividends In Excess Of Earnings [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle			4,933	(272)
Noncontrolling Interests [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle			563	(1,763)
Noncontrolling Interests [Member] | Boston Properties Limited Partnership
Entity Information [Line Items]
Cumulative effect of a change in accounting principle			563	(1,763)
Accounting Standards Update 2014-09 [Member]
Entity Information [Line Items]
Payroll and related costs from management services contracts	2,000		4,900
Direct reimbursements of payroll and related costs from management services contracts	2,000		4,900
Cumulative effect of a change in accounting principle			4,900
Accounting Standards Update 2014-09 [Member] | Boston Properties Limited Partnership
Entity Information [Line Items]
Cumulative effect of a change in accounting principle			4,900
Accounting Standards Update 2014-09 [Member] | Noncontrolling Interests [Member]
Entity Information [Line Items]
Cumulative effect of a change in accounting principle			600
Accounting Standards Update 2014-09 [Member] | Noncontrolling Interests [Member] | Boston Properties Limited Partnership
Entity Information [Line Items]
Cumulative effect of a change in accounting principle			$ 600
Accounting Standards Update 2016-18 [Member]
Entity Information [Line Items]
Net Cash Provided by (Used in) Operating Activities				(7,500)
Net Cash Provided by (Used in) Investing Activities				8,200
Net Cash Provided by (Used in) Financing Activities				100
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect				$ 15,800
Accounting Standards Update 2017-12 [Member]
Entity Information [Line Items]
Interest Expense	$ 1,700

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