COPT Defense Properties Quarterly report [Sections 13 or 15(d)]

Interest Rate Derivatives - Effect of Interest Rate Derivatives on Consolidated Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of (Loss) Income Recognized in AOCI on Derivatives	$ 67	$ (2,582)	$ 261	$ 1,309
Amount of Income Reclassified from AOCI into Interest Expense on Statement of Operations	368	1,170	1,296	3,522
Interest rate swaps
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of (Loss) Income Recognized in AOCI on Derivatives	67	(2,582)	261	1,309
Interest rate swaps \| Interest expense
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of Income Reclassified from AOCI into Interest Expense on Statement of Operations	$ 368	$ 1,170	$ 1,296	$ 3,522