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

Quarterly report [Sections 13 or 15(d)]

Subsequent Events (Details)

Subsequent Events (Details) ft² in Thousands					9 Months Ended
Subsequent Events (Details) ft² in Thousands	Oct. 30, 2025 USD ($) ft²	Oct. 16, 2025 USD ($)	Oct. 06, 2025 USD ($) extension	Oct. 02, 2025 USD ($)	Sep. 30, 2025 USD ($) extension
Credit Agreement \| Line of Credit \| Revolving Credit Facility
Subsequent Event [Line Items]
Aggregate commitment					$ 600,000,000.0
Number of extensions \| extension					2
Extension option period					6 months
Extension fee percentage					0.0625%
Credit Agreement \| Line of Credit \| Revolving Credit Facility \| Minimum
Subsequent Event [Line Items]
Variable rate, spread over SOFR					0.725%
Credit Agreement \| Line of Credit \| Revolving Credit Facility \| Maximum
Subsequent Event [Line Items]
Variable rate, spread over SOFR					1.40%
Credit Agreement \| Term Loan Facility \| Term Loan Facility
Subsequent Event [Line Items]
Interest rate					5.68%
Number of extensions \| extension					2
Extension option period					12 months
Extension fee percentage					0.125%
Credit Agreement \| Term Loan Facility \| Term Loan Facility \| Minimum
Subsequent Event [Line Items]
Variable rate, spread over SOFR					0.85%
Credit Agreement \| Term Loan Facility \| Term Loan Facility \| Maximum
Subsequent Event [Line Items]
Variable rate, spread over SOFR					1.70%
Subsequent Event \| 15050 Conference Center Drive
Subsequent Event [Line Items]
Square footage of real estate properties (in square feet) \| ft²	142
Asset acquisition, percentage leased	100.00%
Purchase price	$ 40,000,000
Subsequent Event \| Unsecured Senior Notes due October 2030 \| Senior Notes
Subsequent Event [Line Items]
Debt instrument, face amount				$ 400,000,000.0
Interest rate				4.50%
Initial offering price, percentage				0.9946
Proceeds from issuance of debt				$ 395,500,000
Basis point used in determining redemption price prior to maturity				0.15%
Subsequent Event \| Unsecured Senior Notes due October 2030 \| Senior Notes \| Redemption on or after September 15, 2030
Subsequent Event [Line Items]
Redemption price, percentage				100.00%
Subsequent Event \| Credit Agreement \| Line of Credit \| Revolving Credit Facility
Subsequent Event [Line Items]
Aggregate commitment			$ 800,000,000.0
Number of extensions \| extension			2
Extension option period			6 months
Extension fee percentage			0.0625%
Subsequent Event \| Credit Agreement \| Line of Credit \| Revolving Credit Facility \| Minimum
Subsequent Event [Line Items]
Variable rate, spread over SOFR			0.725%
Commitment fee percentage			0.125%
Subsequent Event \| Credit Agreement \| Line of Credit \| Revolving Credit Facility \| Maximum
Subsequent Event [Line Items]
Variable rate, spread over SOFR			1.40%
Commitment fee percentage			0.30%
Subsequent Event \| Credit Agreement \| Term Loan Facility \| Term Loan Facility
Subsequent Event [Line Items]
Number of extensions \| extension			2
Extension option period			12 months
Extension fee percentage			0.125%
Subsequent Event \| Credit Agreement \| Term Loan Facility \| Term Loan Facility \| Minimum
Subsequent Event [Line Items]
Variable rate, spread over SOFR			0.85%
Subsequent Event \| Credit Agreement \| Term Loan Facility \| Term Loan Facility \| Maximum
Subsequent Event [Line Items]
Variable rate, spread over SOFR			1.70%
Subsequent Event \| Revolving Development Facility \| Line of Credit \| Secured Debt
Subsequent Event [Line Items]
Aggregate commitment		$ 200,000,000.0
Extension option period		12 months
Extension fee percentage		0.25%
Right to increase maximum commitment, amount		$ 250,000,000.0
Subsequent Event \| Revolving Development Facility \| Line of Credit \| Secured Debt \| Minimum
Subsequent Event [Line Items]
Variable rate, spread over SOFR		1.25%
Commitment fee percentage		0.125%
Subsequent Event \| Revolving Development Facility \| Line of Credit \| Secured Debt \| Maximum
Subsequent Event [Line Items]
Variable rate, spread over SOFR		1.90%
Commitment fee percentage		0.30%