(Common Units) (Narrative) (Details) $ / shares in Units, $ in Thousands		9 Months Ended
	Feb. 09, 2019 USD ($) shares	Sep. 30, 2019 USD ($) shares yr $ / shares	Dec. 31, 2018 USD ($)
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)		41,577
Redemption of OP units issued on conversion of LTIP Units (in shares)		39,377
Restriction on redemption of OP Unit to Common Stock (in years) | yr		1
Redemption of OP Unit equivalent to Common Stock (in shares)		1
Common units of operating partnership if converted value | $		$ 2,300,000
Closing price of common stock (in dollars per share) | $ / shares		$ 129.66
2016 MYLTIP [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
2016 MYLTIP Units Forfeited	364,980
Boston Properties Limited Partnership
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Common units of operating partnership if converted value | $		$ 2,335,272	$ 2,000,591
Boston Properties Limited Partnership | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
MYLTIP distribution prior to measurement date		10.00%
Boston Properties Limited Partnership | 2017 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP (in units)		394,921
Boston Properties Limited Partnership | 2018 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP (in units)		336,195
Boston Properties Limited Partnership | 2019 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS (in units)		220,734