(Common Units) (Narrative) (Details) $ / shares in Units, $ in Millions				12 Months Ended
	Feb. 04, 2018 USD ($) shares	Feb. 03, 2017 USD ($) shares	Feb. 04, 2016 USD ($) shares	Dec. 31, 2018 USD ($) shares yr $ / shares	Dec. 31, 2017 shares	May 02, 2016 shares
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Conversion of LTIP Units to OP Units (in units)						625,043
MYLTIP 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target		27.70%
Value of MYLTIP Awards | $		$ 3.5
MYLTIP Units forfeited		447,386
2012 OPP and 2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Conversion of LTIP Units to OP Units (in units)						32,349
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares)				83,136	495,637
Redemption of OP units issued on conversion of LTIP Units (in shares)				48,389	36,486
MYLTIP Units distribution as percentage of OP Unit distribution prior to measurement date				10.00%
Restriction on redemption of OP Unit to Common Stock (in years) | yr				1
Redemption of OP Unit equivalence to Common Stock (in shares)				1
Common units of operating partnership if converted value | $				$ 2,000.0
Closing price of common stock (in dollars per share) | $ / shares				$ 112.55
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 | $	$ 3.6
MYLTIP Units forfeited	337,847
MYLTIP 2013
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Final awards percentage of target			109.50%
Value of MYLTIP Awards | $			$ 13.5
MYLTIP Units forfeited			205,762
Boston Properties Limited Partnership | MYLTIP 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP				23,187
Boston Properties Limited Partnership | MYLTIP 2016 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIP				471,579
Boston Properties Limited Partnership | MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP				398,871
Boston Properties Limited Partnership | MYLTIP 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIP				28,724
Boston Properties Limited Partnership | MYLTIP 2018
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP				341,366