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Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 15, 2020
Summary Of Significant Accounting Policies [Line Items]
Interest capitalized	$ 53,881,000	$ 54,911,000	$ 65,766,000
Salaries And Related Costs Capitalized	12,900,000	10,400,000	12,500,000
Cash FDIC Insured Limit	250,000
Gains (losses) from investments in securities	5,261,000	6,417,000	(1,865,000)
Internal Leasing Salaries And Related Costs Capitalized			5,400,000
Straight Line Rent Adjustments	104,900,000	58,400,000	51,900,000
Above and below market rent adjustments, net	6,500,000	20,900,000	23,800,000
Separate Unrestricted Cash For Deferred Compensation Plan.	39,500,000	36,700,000
Adoption of ASU 2016-13 and 2018-19	(509,653,000)	(760,523,000)
Adoption of ASU 2016-13 and 2018-19	616,596,000	600,860,000
Distributions Payable, Amount Per Unit				$ 0.98
Boston Properties Limited Partnership
Summary Of Significant Accounting Policies [Line Items]
Interest capitalized	53,881,000	54,911,000	65,766,000
Gains (losses) from investments in securities	5,261,000	6,417,000	$ (1,865,000)
Adoption of ASU 2016-13 and 2018-19	4,554,639,000	3,380,175,000
Adoption of ASU 2016-13 and 2018-19	1,643,024,000	$ 2,468,753,000
Distributions Payable, Amount Per Unit				$ 0.98
Boston Properties Limited Partnership | Cumulative Effect, Period of Adoption, Adjustment
Summary Of Significant Accounting Policies [Line Items]
Adoption of ASU 2016-13 and 2018-19	1,500,000
Dividends In Excess Of Earnings [Member] | Cumulative Effect, Period of Adoption, Adjustment
Summary Of Significant Accounting Policies [Line Items]
Adoption of ASU 2016-13 and 2018-19	1,500,000
Noncontrolling Interests [Member] | Cumulative Effect, Period of Adoption, Adjustment
Summary Of Significant Accounting Policies [Line Items]
Adoption of ASU 2016-13 and 2018-19	200,000
Noncontrolling Interests [Member] | Boston Properties Limited Partnership | Cumulative Effect, Period of Adoption, Adjustment
Summary Of Significant Accounting Policies [Line Items]
Adoption of ASU 2016-13 and 2018-19	$ 200,000

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