Real Estate (Narrative) (Details) $ in Thousands			3 Months Ended
	Mar. 31, 2022 USD ($) ft²	Apr. 19, 2021 USD ($) a ft²	Mar. 31, 2022 USD ($) ft²	Mar. 31, 2021 USD ($)
Real Estate Properties [Line Items]
Proceeds from sales of real estate			$ 35,397	$ 0
Net income			176,957	128,147
Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Proceeds from sales of real estate			35,397	0
Net income			$ 179,378	131,212
11251 Roger Bacon Drive
Real Estate Properties [Line Items]
Asset Acquisition, Price of Acquisition, Expected		$ 5,600
Net Rentable Area (in sf) | ft²		65,000
Area of Land | a		2.6
Leased percentage		100.00%
195 West Street
Real Estate Properties [Line Items]
Net Rentable Area (in sf) | ft²	63,500		63,500
Contractual Sales Price	$ 37,700		$ 37,700
Proceeds from sales of real estate	35,400
Gains (Losses) on Sales of Investment Real Estate	22,700
Net income			$ 400	$ (200)
195 West Street | Boston Properties Limited Partnership
Real Estate Properties [Line Items]
Gains (Losses) on Sales of Investment Real Estate	$ 23,400