Noncontrolling Interests (Narrative) (Details) - Boston Properties Limited Partnership	Sep. 30, 2020 shares
Noncontrolling Interest [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operating Partnership (OP) Units (in shares)	16,120,074
Long-Term Incentive Plan (LTIP) Units (in shares)	1,338,400
OPP Units 2012 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Outperformance awards in LTIP Units (in shares)	105,080
MYLTIP 2013
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2013 MYLTIP	64,468
MYLTIP 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2014 MYLTIP	23,100
MYLTIP 2015 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2015 MYLTIP	24,966
MYLTIP 2016 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2016 MYLTIP	89,791
MYLTIP 2017 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2017 MYLTIP	116,078
MYLTIP 2018
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2018 MYLTIP	336,195
MYLTIP 2019 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2019 MYLTIPS	219,916
MYLTIP 2020 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
2020 MYLTIP	203,278