Real Estate (Narrative) (Details) $ in Thousands						5 Months Ended	7 Months Ended	10 Months Ended	12 Months Ended
	Dec. 14, 2021 USD ($) ft² shares	Oct. 25, 2021 USD ($) ft² Buildings	Aug. 02, 2021 USD ($) ft² a Buildings	Jun. 02, 2021 USD ($) ft² Buildings	Apr. 19, 2021 USD ($) a ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Oct. 24, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 15, 2021	Dec. 08, 2021 ft²	Dec. 03, 2021 ft²	Oct. 19, 2021 ft²	Apr. 16, 2021 ft²	Feb. 25, 2021 ft²	Feb. 01, 2021 ft²
Real Estate Properties [Line Items]
Assumption of mortgage notes payable									$ 200,311	$ 0	$ 0
Issuance of operating partnership units for 360 Park Avenue South									99,689	0	0
Secured Debt						$ 3,267,914	$ 3,267,914		3,267,914	2,909,081
Total revenue									2,888,621	2,765,686	2,960,562
Proceeds from sales of real estate									179,887	519,303	90,824
Net income									631,932	1,018,691	651,999
153 & 211 Second Avenue [Member]
Real Estate Properties [Line Items]
Payments to Acquire Real Estate				$ 100,200
Number of real estate properties | Buildings				2
Leased percentage				100.00%
Net Rentable Area (in sf) | ft²				137,000
Total revenue							5,500
Operating Income (Loss)							(2,100)
Shady Grove Innovation District [Member]
Real Estate Properties [Line Items]
Payments to Acquire Real Estate			$ 118,500
Net Rentable Area (in sf) | ft²			435,000
Number of buildings | Buildings			7
Area of Land | a			31
Total revenue						1,200
Operating Income (Loss)						(1,500)
360 Park South Avenue
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²	450,000
Number of floors	20
Noncash or Part Noncash Acquisition, Value of Assets Acquired	$ 300,700
Assumption of mortgage notes payable	200,300
Issuance of operating partnership units for 360 Park Avenue South	99,700
number of investors												2
Ownership Percentage												42.21%
Debt - Total loan amount	$ 220,000
11251 Roger Bacon Drive
Real Estate Properties [Line Items]
Leased percentage					100.00%
Net Rentable Area (in sf) | ft²					65,000
Area of Land | a					2.6
Asset Acquisition, Price of Acquisition, Expected					$ 5,600
One Five Nine East 53rd Street
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²																		220,000
Noncontrolling Interest, Ownership Percentage by Parent																		55.00%
3625 - 3635 Peterson Way
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²																218,000
Reston Next
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²															1,100,000
200 West Street
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²														138,000
6595 Springfield Center Drive
Real Estate Properties [Line Items]
Gains (Losses) on Sales of Investment Real Estate									8,100
181, 191 and 201 Spring Street
Real Estate Properties [Line Items]
Number of real estate properties | Buildings		3
Net Rentable Area (in sf) | ft²		333,000
Contractual Sales Price		$ 191,500
Proceeds from sales of real estate		179,900
Gains (Losses) on Sales of Investment Real Estate		115,600
Net income								$ 5,700		7,200	7,000
Construction in Progress | 180 CityPoint
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²																	329,000
Construction in Progress | 880 Winter Street [Member]
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²																	224,000
Construction in Progress | The Prudential Center Observatory
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²																	59,000
Construction in Progress | 103 CityPoint
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²													113,000
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Assumption of mortgage notes payable									200,311	0	0
Issuance of operating partnership units for 360 Park Avenue South									99,689	0	0
Secured Debt						$ 3,267,914	$ 3,267,914		3,267,914	2,909,081
Total revenue									2,888,621	2,765,686	2,960,562
Proceeds from sales of real estate									179,887	519,303	90,824
Net income									$ 641,771	$ 1,038,739	$ 661,722
Boston Properties Limited Partnership | 360 Park South Avenue
Real Estate Properties [Line Items]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Shares Issued | shares	866,503
Boston Properties Limited Partnership | 181, 191 and 201 Spring Street
Real Estate Properties [Line Items]
Gains (Losses) on Sales of Investment Real Estate		$ 117,100