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SEC Schedule, Article 12-28, Real Estate and Accumulated Depreciation Roll Forward (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]      
Balance at the beginning of the year $ 22,844,697 $ 21,605,545 $ 21,058,714
Additions to / improvements of real estate 996,989 1,671,898 1,043,379
Assets sold/written-off (538,383) (432,746) (496,548)
Balance at the end of the year 23,303,303 22,844,697 21,605,545
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward]      
Balance at the beginning of the year 5,239,179 4,871,102 4,566,570
Depreciation expense 573,898 564,938 533,342
Assets sold/written-off (311,440) (196,861) (228,810)
Balance at the end of the year 5,501,637 5,239,179 4,871,102
Boston Properties Limited Partnership      
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]      
Balance at the beginning of the year 22,449,476 21,207,189 20,647,236
Additions to / improvements of real estate 996,989 1,671,898 1,043,379
Assets sold/written-off (519,971) (429,611) (483,426)
Balance at the end of the year 22,926,494 22,449,476 21,207,189
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward]      
Balance at the beginning of the year 5,135,289 4,773,800 4,473,895
Depreciation expense 566,813 557,130 525,584
Assets sold/written-off (305,991) (195,641) (225,679)
Balance at the end of the year $ 5,396,111 $ 5,135,289 $ 4,773,800