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

Quarterly report [Sections 13 or 15(d)]

Debt, Net - Schedule of Debt (Details)

Debt, Net - Schedule of Debt (Details)	9 Months Ended
Debt, Net - Schedule of Debt (Details)	Sep. 30, 2026 USD ($) extension $ / shares	Mar. 16, 2026	Dec. 31, 2025 USD ($)
Debt
Long-term debt, gross	$ 2,599,000,000		$ 2,791,300,000
Net unamortized discounts and commissions	(16,002,000)		(19,382,000)
Net deferred financing costs	(3,265,000)		(4,084,000)
Total debt, net	2,579,733,000		2,767,834,000
Mortgage and Other Secured Debt
Debt
Long-term debt, gross	170,000,000		142,239,000
Revolving Development Facility \| Mortgage and Other Secured Debt
Debt
Long-term debt, gross	$ 170,000,000		96,000,000
Weighted average interest rate	5.20%
Extension option period	12 months
Extension fee percentage	0.25%
Revolving Development Facility \| Mortgage and Other Secured Debt \| Minimum
Debt
Variable rate, spread over SOFR	1.25%
Revolving Development Facility \| Mortgage and Other Secured Debt \| Maximum
Debt
Variable rate, spread over SOFR	1.90%
Variable-rate secured debt \| Mortgage and Other Secured Debt
Debt
Long-term debt, gross	$ 0		10,160,000
Fixed-rate mortgage debt \| Mortgage and Other Secured Debt
Debt
Long-term debt, gross	0		36,079,000
Credit Agreement \| Line of credit \| Revolving Credit Facility
Debt
Long-term debt, gross	$ 234,000,000		54,000,000
Weighted average interest rate	4.80%
Extension option period	6 months
Extension fee percentage	0.0625%
Number of extensions \| extension	2
Credit Agreement \| Line of credit \| Revolving Credit Facility \| Minimum
Debt
Variable rate, spread over SOFR	0.725%
Credit Agreement \| Line of credit \| Revolving Credit Facility \| Maximum
Debt
Variable rate, spread over SOFR	1.40%
Credit Agreement \| Term loan facility \| Term loan facility
Debt
Long-term debt, gross	$ 50,000,000		50,000,000
Extension option period	12 months
Extension fee percentage	0.125%
Effective interest rate	4.80%
Credit Agreement \| Term loan facility \| Term loan facility \| Minimum
Debt
Variable rate, spread over SOFR	0.85%
Credit Agreement \| Term loan facility \| Term loan facility \| Maximum
Debt
Variable rate, spread over SOFR	1.70%
5.25%, $345,000 aggregate principal \| Unsecured Senior Notes
Debt
Interest rate	5.25%
Aggregate principal	$ 345,000,000
Long-term debt, gross	$ 345,000,000		345,000,000
Effective interest rate	5.80%
Exchange rate of notes	0.0336253
Exchange price (in dollars per share) \| $ / shares	$ 29.74
2.00%, $400,000 aggregate principal \| Unsecured Senior Notes
Debt
Interest rate	2.00%
Aggregate principal	$ 400,000,000
Long-term debt, gross	$ 400,000,000		400,000,000
Effective interest rate	2.10%
4.50%, $400,000 aggregate principal \| Unsecured Senior Notes
Debt
Interest rate	4.50%
Aggregate principal	$ 400,000,000
Long-term debt, gross	$ 400,000,000		400,000,000
Effective interest rate	4.80%
2.75%, $600,000 aggregate principal \| Unsecured Senior Notes
Debt
Interest rate	2.75%
Aggregate principal	$ 600,000,000
Long-term debt, gross	$ 600,000,000		600,000,000
Effective interest rate	2.90%
2.90%, $400,000 aggregate principal \| Unsecured Senior Notes
Debt
Interest rate	2.90%
Aggregate principal	$ 400,000,000
Long-term debt, gross	$ 400,000,000		400,000,000
Effective interest rate	3.00%
2.25%, $400,000 aggregate principal \| Unsecured Senior Notes
Debt
Interest rate	2.25%	2.25%
Aggregate principal	$ 400,000,000
Long-term debt, gross	0		400,000,000
Unsecured note payable \| Unsecured note payable
Debt
Long-term debt, gross	$ 0		$ 61,000