Debt (Narrative) (Details) ft² in Thousands, $ in Thousands							12 Months Ended
	Dec. 10, 2025 USD ($)	Aug. 12, 2025 USD ($) ft²	Aug. 11, 2025 USD ($)	Jul. 16, 2025 USD ($) ft²	Jul. 15, 2025 USD ($)	Jan. 15, 2025 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Debt Instrument
Repayments of long-term debt							$ 1,903,513	$ 97,439	$ 148,000
Collateral property, net carrying value							6,000,000
PENN 11
Debt Instrument
Debt amount					$ 500,000
Repayments of long-term debt				$ 50,000
Basis spread on variable rate					2.06%
All-In Swapped Rate				6.28%
Proceeds from property refinancing				$ 130
4 Union Square South
Debt Instrument
Debt amount			$ 120,000
Basis spread on variable rate			1.50%
888 Seventh Avenue
Debt Instrument
Basis spread on variable rate	1.80%
Office Building | PENN 11
Debt Instrument
Stated rate (as a percent)				6.35%
Debt amount				$ 450,000
Square footage of real estate property (in sqft) | ft²				1,200
Debt term				5 years
Office Building | 4 Union Square South
Debt Instrument
Stated rate (as a percent)		5.64%
Debt amount		$ 120,000
Square footage of real estate property (in sqft) | ft²		204
Debt term		10 years
Office Building | 888 Seventh Avenue
Debt Instrument
Debt amount	$ 244,543
Additional default stated rate (as a percent)	3.00%
Default interest waived, period	90 days
Unsecured revolving credit facilities
Debt Instrument
Debt amount							$ 720,420
Senior Unsecured Notes Due 2025 | Senior unsecured notes
Debt Instrument
Repaid on loan						$ 450,000
Stated rate (as a percent)						3.50%