Lessee - Leases Narrative (Details) $ in Thousands			3 Months Ended
		Mar. 31, 2024 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Mar. 28, 2024 USD ($) ft²	Dec. 31, 2023 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Payments			$ 1,241	$ 251
Operating Lease, Right-of-Use Asset	[1]	$ 344,255	$ 344,255			$ 324,298
171 Dartmouth Street air rights [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract					90 years
Lessee, Operating Lease, Discount Rate					6.57%
Net Present Value and Operating Lease Liability					$ 23,200
Operating Lease, Right-of-Use Asset					$ 23,900
Operating lease costs		$ 0
Land Subject to Ground Leases | ft²					61,000
171 Dartmouth Street air rights [Member] | Base Rental Payment [Member]
Lessee, Lease, Description [Line Items]
Operating Leases, Future Minimum Payments Due					$ 250
171 Dartmouth Street air rights [Member] | Additional Rental Payment
Lessee, Lease, Description [Line Items]
Operating Leases, Future Minimum Payments Due					$ 500

[1] See Note 4.