COPT Defense Properties Annual report [Section 13 and 15(d), not S-K Item 405]

Annual report [Section 13 and 15(d), not S-K Item 405]

Debt, Net - Schedule of Debt (Details)

Debt, Net - Schedule of Debt (Details)		12 Months Ended
Debt, Net - Schedule of Debt (Details)	Oct. 06, 2025 USD ($)	Dec. 31, 2025 USD ($)	Oct. 02, 2025 USD ($)	Dec. 31, 2024 USD ($)	Sep. 12, 2023 USD ($)
Debt
Carrying Value		$ 2,767,834,000		$ 2,391,755,000
Net deferred financing costs		4,100,000		4,000,000.0
Mortgage and other secured debt
Debt
Carrying Value		$ 142,189,000		69,601,000
Mortgage and other secured debt \| Fixed-rate mortgage debt
Debt
Interest rate		3.82%
Carrying Value		$ 36,064,000		37,130,000
Mortgage and other secured debt \| Variable-rate secured debt
Debt
Carrying Value		$ 10,125,000		32,471,000
Variable rate, additional spread		0.0010
Variable rate, spread over SOFR		1.45%
Weighted average interest rate		5.20%
Mortgage and other secured debt \| Variable-rate secured debt \| Interest rate swaps
Debt
Weighted average interest rate		3.10%
Mortgage and other secured debt \| Revolving Development Facility
Debt
Carrying Value		$ 96,000,000		0
Weighted average interest rate		5.10%
Mortgage and other secured debt \| Revolving Development Facility \| Minimum
Debt
Variable rate, spread over SOFR		1.25%
Mortgage and other secured debt \| Revolving Development Facility \| Minimum \| Revolving Credit Facility
Debt
Variable rate, spread over SOFR		1.25%
Mortgage and other secured debt \| Revolving Development Facility \| Maximum
Debt
Variable rate, spread over SOFR		1.90%
Mortgage and other secured debt \| Revolving Development Facility \| Maximum \| Revolving Credit Facility
Debt
Variable rate, spread over SOFR		1.90%
Line of Credit \| Credit Agreement \| Revolving Credit Facility
Debt
Carrying Value		$ 54,000,000		75,000,000
Weighted average interest rate		4.60%
Line of Credit \| Credit Agreement \| Minimum \| Revolving Credit Facility
Debt
Variable rate, spread over SOFR	0.725%	0.725%
Line of Credit \| Credit Agreement \| Maximum \| Revolving Credit Facility
Debt
Variable rate, spread over SOFR	1.40%	1.40%
Term Loan Facility \| Credit Agreement \| Term Loan Facility
Debt
Interest rate		4.90%
Debt instrument, face amount	$ 125,000,000.0
Carrying Value		$ 49,911,000		124,633,000
Term Loan Facility \| Credit Agreement \| Minimum \| Term Loan Facility
Debt
Variable rate, spread over SOFR	0.85%	0.85%
Term Loan Facility \| Credit Agreement \| Maximum \| Term Loan Facility
Debt
Variable rate, spread over SOFR	1.70%	1.70%
Unsecured Senior Notes
Debt
Carrying Value		$ 2,500,000,000
Unsecured Senior Notes \| 2.25%, $400,000 aggregate principal
Debt
Interest rate		2.25%
Debt instrument, face amount		$ 400,000,000
Carrying Value		399,812,000		398,699,000
Unamortized discounts and/or commissions included in carrying value		$ 153,000		1,100,000
Effective interest rate on debt		2.50%
Unsecured Senior Notes \| 5.25%, $345,000 aggregate principal
Debt
Interest rate		5.25%			5.25%
Debt instrument, face amount		$ 345,000,000			$ 345,000,000.0
Carrying Value		339,470,000		337,588,000
Unamortized discounts and/or commissions included in carrying value		$ 4,900,000		6,600,000
Effective interest rate on debt		5.80%
Unsecured Senior Notes \| 2.00%, $400,000 aggregate principal
Debt
Interest rate		2.00%
Debt instrument, face amount		$ 400,000,000
Carrying Value		398,459,000		397,961,000
Unamortized discounts and/or commissions included in carrying value		$ 1,100,000		1,500,000
Effective interest rate on debt		2.10%
Unsecured Senior Notes \| 4.50%, $400,000 aggregate principal
Debt
Interest rate		4.50%	4.50%
Debt instrument, face amount		$ 400,000,000	$ 400,000,000.0
Carrying Value		394,326,000		0
Unamortized discounts and/or commissions included in carrying value		$ 4,300,000
Effective interest rate on debt		4.80%
Unsecured Senior Notes \| 2.75%, $600,000 aggregate principal
Debt
Interest rate		2.75%
Debt instrument, face amount		$ 600,000,000
Carrying Value		593,476,000		592,330,000
Unamortized discounts and/or commissions included in carrying value		$ 5,700,000		6,700,000
Effective interest rate on debt		2.90%
Unsecured Senior Notes \| 2.90%, $400,000 aggregate principal
Debt
Interest rate		2.90%
Debt instrument, face amount		$ 400,000,000
Carrying Value		396,130,000		395,692,000
Unamortized discounts and/or commissions included in carrying value		$ 3,200,000		3,500,000
Effective interest rate on debt		3.00%
Unsecured note payable \| Unsecured note payable
Debt
Interest rate		0.00%
Carrying Value		$ 61,000		251,000
Unamortized discounts and/or commissions included in carrying value		$ 1,000		$ 10,000