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Equity - COPT and Subsidiaries (Details) (USD $)
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0 Months Ended | 1 Months Ended | 12 Months Ended | 0 Months Ended | 0 Months Ended | 12 Months Ended | 0 Months Ended | |||||||||
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Mar. 19, 2013
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Oct. 31, 2012
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Jul. 16, 2013
Common Stock Issued to Public Under At-the-Market Program
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Dec. 31, 2013
Common Stock Issued to Public Under At-the-Market Program
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Jun. 27, 2012
Series L Preferred Units
Public Offering
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Aug. 06, 2012
Series G Preferred Shares
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Dec. 31, 2013
Preferred Shares
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Dec. 31, 2012
Preferred Shares
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Dec. 31, 2013
Series H
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Dec. 31, 2013
Series K
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Dec. 31, 2013
Series L Cumulative Preferred Stock
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Jun. 27, 2012
Series L Cumulative Preferred Stock
Public Offering
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Apr. 22, 2013
Series J
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| Preferred Stock | ||||||||||||||||
| Number of shares issued | 9,431,667 | 2,000,000 | 531,667 | 6,900,000 | ||||||||||||
| Preferred Stock, Shares Authorized | 25,000,000 | |||||||||||||||
| Number of preferred shares of beneficial interest authorized (in dollars per share) | $ 0.01 | |||||||||||||||
| Aggregate Liquidation Preference | $ 249,083,000 | $ 333,833,000 | $ 50,000,000 | $ 26,583,000 | $ 172,500,000 | |||||||||||
| Annual dividend yield | 8.00% | 7.50% | 5.60% | 7.375% | 7.625% | |||||||||||
| Annual dividend per share (in dollars per share) | $ 1.87500 | $ 2.80000 | $ 1.84375 | |||||||||||||
| Number of common shares to be issued on conversion of each preferred share | 0.8163 | |||||||||||||||
| Net proceeds from issuance of Series L preferred shares | 0 | 165,652,000 | 0 | 165,700,000 | ||||||||||||
| Number of Series L preferred units of operating partnerships received in exchange for offering proceeds (in units) | 6,900,000 | |||||||||||||||
| Preferred stock, redemption price per share | $ 25 | $ 25 | ||||||||||||||
| Stock redeemed or called during period (in units/ shares) | 84,750,000 | 55,000,000 | 55,000,000 | 84,800,000 | ||||||||||||
| Issuance costs associated with redeemed preferred shares | 1,800,000 | 2,900,000 | ||||||||||||||
| Common Shares | ||||||||||||||||
| Shares issued to the public | 4,485,000 | 8,600,000 | 4,600,000 | 1,500,000 | 6,900,000 | 6,900,000 | ||||||||||
| Per share value of common and preferred shares issued to the public (in dollars per share) | $ 26.34 | $ 24.75 | $ 25.00 | |||||||||||||
| Net proceeds from issue of shares after underwriter discounts but before offering expenses | 118,100,000 | 204,900,000 | 117,961,000 | 145,367,000 | 38,500,000 | 165,652,000 | ||||||||||
| At-market-stock, offering program established, aggregate value | 150,000,000.0 | |||||||||||||||
| Issuance of stock, weighted average price per share | $ 26.05 | |||||||||||||||
| Payments of stock issuance costs | 586,000 | |||||||||||||||
| At-market stock, offering program established, remaining capacity | $ 110,900,000 | |||||||||||||||
| Number of common shares for each converted common unit (in shares) | 1 | |||||||||||||||
| Number of operating partnerships units converted into common shares (in units) | 311,343 | 234,246 | 100,939 | |||||||||||||
| Dividends declared per common share | $ 1.1000 | $ 1.1 | $ 1.65 | |||||||||||||