Real Estate (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) ft²	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) ft²	Jun. 30, 2022 USD ($)	Jun. 01, 2023 ft²	Apr. 29, 2023 ft²	Jan. 30, 2023 ft²	Jan. 05, 2023 ft²
Real Estate Properties [Line Items]
Depreciation and amortization | $	$ 202,577	$ 183,146	$ 411,311	$ 360,770
Construction in Progress
Real Estate Properties [Line Items]
Net Rentable Area (in sf)	3,100,000		3,100,000
290 Binney
Real Estate Properties [Line Items]
Net Rentable Area (in sf)								566,000
Leased percentage								100.00%
300 Binney Street
Real Estate Properties [Line Items]
Net Rentable Area (in sf)							195,000
Depreciation and amortization | $			$ 11,000
300 Binney Street | Construction in Progress
Real Estate Properties [Line Items]
Net Rentable Area (in sf)							236,000
Leased percentage							100.00%
2100 Pennsylvania Avenue
Real Estate Properties [Line Items]
Net Rentable Area (in sf)						476,000
View Boston
Real Estate Properties [Line Items]
Net Rentable Area (in sf)					63,000