(Common Units) (Narrative) (Details) - Class of Stock [Domain] $ / shares in Units, $ in Millions				6 Months Ended
	Apr. 30, 2015 $ / shares	Feb. 06, 2015 USD ($) shares	Jan. 28, 2015 $ / shares	Jun. 30, 2015 USD ($) yr $ / shares shares	Jun. 30, 2014 USD ($)	Jun. 17, 2015 $ / shares
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Cumulative non-cash adjustment to the accretion of the changes in the redemption value of the noncontrolling interest | $					$ 2.4
OP Units and LTIP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distributions made to OP and LTIP units per unit (in dollars per share)			$ 0.65
Distribution declared to OP and LTIP units by Boston Properties, Inc. (in dollars per share)						$ 0.65
MYLTIP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distribution paid to outperformance awards, OPP Units and MYLTIP Units (in dollars per share)	$ 0.065
Distribution declared to outperformance awards OPP Units by Boston Properties, Inc. (in dollars per share)						$ 0.065
2012 OPP Units and MYLTIP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distribution paid to outperformance awards, OPP Units and MYLTIP Units (in dollars per share)			0.065
OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
OP Units for redemption (in shares) | shares				321,700
Redemption of OP units issued on conversion of LTIP Units (in shares) | shares				57,701
Outperformance Awards LTIP Units distribution as percentage of OP Unit distribution prior to measurement date				10.00%
Distributions made to OP and LTIP units per unit (in dollars per share)	0.65
Restriction on redemption of OP Unit to Common Stock (in years) | yr				1
Redemption of OP Unit equivalence to Common Stock (in shares) | shares				1
Common units of operating partnership if converted value | $				$ 2,200.0
Closing price of common stock (in dollars per share)				$ 121.04
OPP Units 2012 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distributions made to OP and LTIP units per unit (in dollars per share)	$ 0.42
2013 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP (in shares) | shares				309,818
MYLTIP 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP (in shares) | shares				476,320
2015 MYLTIP [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIPS (in shares) | shares				368,415
Quarter 4 2014 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date				Jan. 28, 2015
Quarter 4 2014 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date				Jan. 28, 2015
Holders of record date				Dec. 31, 2014
Quarter 1 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date				Apr. 30, 2015
Quarter 1 2015 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date				Apr. 30, 2015
Holders of record date				Mar. 31, 2015
Quarter 2 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date				Jul. 31, 2015
Dividends payable, date declared				Jun. 17, 2015
Quarter 2 2015 [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Dividend payable date				Jul. 31, 2015
Holders of record date				Jun. 30, 2015
Dividends payable, date declared				Jun. 17, 2015
special dividend [Member] | OP Units [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Distributions made to OP and LTIP units per unit (in dollars per share)			$ 4.50
OPP Units 2012 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards earned | $		$ 32.1
Potential maximum amount of Outperformance Awards earned (percent)		80.00%
Potential Awards Earned | $		$ 40.0
2012 OPP Units Forfeited (in shares) | shares		174,549