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(Common Units) (Narrative) (Details) $ / shares in Units, $ in Thousands					12 Months Ended
	Feb. 06, 2020 USD ($) shares	Sep. 03, 2019 shares	Feb. 09, 2019 USD ($) shares	Feb. 04, 2018 USD ($) shares	Dec. 31, 2020 USD ($) yr $ / shares shares	Dec. 31, 2019 USD ($) shares
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)		4,917
Boston Properties Limited Partnership
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount \| $					$ 1,643,024	$ 2,468,753
Unvested MYLTIP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
unvested MYLTIP distributions as compared to total distributions (percentage)					10.00%
MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target	83.80%
Value of MYLTIP Awards \| $	$ 17,600
Forfeitures, in units	270,942
MYLTIP 2017 [Member] \| Boston Properties Limited Partnership
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Noncontrolling Interest, Outstanding					116,078
MYLTIP 2016 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target			69.50%
Value of MYLTIP Awards \| $			$ 13,600
Forfeitures, in units			364,980
MYLTIP 2016 [Member] \| Boston Properties Limited Partnership
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Noncontrolling Interest, Outstanding					89,791
MYLTIP 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target				22.00%
Value of MYLTIP Awards \| $				$ 3,600
Forfeitures, in units				337,847
MYLTIP 2015 [Member] \| Boston Properties Limited Partnership
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Noncontrolling Interest, Outstanding					24,966
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)					856,811	144,481
Restriction on redemption of OP Unit to Common Stock (in years) \| yr					1
Redemption of OP Unit equivalent to Common Stock (in shares)					1
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount \| $					$ 1,600,000
Closing price of common stock (in dollars per share) \| $ / shares					$ 94.53
Vested 2012 OPP units and MYLTIPS
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)					88,168	92,678