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v3.3.1.900

Equity - COPT and Subsidiaries (Details) - USD ($) |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jun. 16, 2014 | Jul. 15, 2013 | Nov. 30, 2014 | Oct. 31, 2012 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Preferred Stock |  |  |  |  |  |  |
Number of shares issued |  |  |  |  | 7,431,667 |  |
Aggregate liquidation preference |  |  |  |  | $ 199,083,000 | $ 199,083,000 |
Stock redeemed or called during period value |  |  |  |  |  | 50,000,000 | $ 84,750,000
Common Shares |  |  |  |  |  |  |
Shares issued to the public |  |  | 5,520,000 |  |  |  |
Per share value of common and preferred shares issued to the public (in dollars per share) |  |  | $ 27.30 |  |  |  |
Net proceeds from issue of shares after underwriter discounts but before offering expenses |  |  | $ 148,900,000 |  |  | $ 148,666,000 | $ 117,961,000
Number of common shares for each converted common unit (in shares) |  |  |  |  | 1 |  |
Number of operating partnerships units converted into common shares (in units) |  |  |  |  | 160,160 | 140,149 | 311,343
Dividends declared per common share |  |  |  |  | $ 1.1000 | $ 1.10 | $ 1.10
Common Stock Issued to Public Under At-the-Market Program [Member] |  |  |  |  |  |  |
Common Shares |  |  |  |  |  |  |
Shares issued to the public |  | 1,500,000.0 |  |  | 890,241 |  | 1,500,000
At-market-stock, offering program established, aggregate value |  |  |  | $ 150,000,000.0 |  |  |
Issuance of stock, weighted average price per share |  |  |  |  | $ 30.29 |  |
Payments of stock issuance costs |  | $ 600,000 |  |  | $ 400,000 |  |
At-market stock, offering program established, remaining capacity |  |  |  |  | 84,000,000 |  |
Share Price |  | $ 26.05 |  |  |  |  |
Proceeds from Issuance of Common Stock, Net of Issuance Costs |  | $ 38,500,000 |  |  | $ 26,600,000 |  |
Preferred Shares [Member] |  |  |  |  |  |  |
Preferred Stock |  |  |  |  |  |  |
Number of preferred shares authorized |  |  |  |  | 25,000,000 |  |
Number of preferred shares of beneficial interest authorized (in dollars per share) |  |  |  |  | $ 0.01 |  |
Series H [Member] |  |  |  |  |  |  |
Preferred Stock |  |  |  |  |  |  |
Annual dividend yield | 7.50% |  |  |  |  |  |
Preferred stock, redemption price per share | $ 25 |  |  |  |  |  |
Stock redeemed or called during period value | $ 50,000,000 |  |  |  |  |  |
Issuance costs associated with redeemed preferred shares | $ 1,800,000 |  |  |  |  |  |
Series K [Member] |  |  |  |  |  |  |
Preferred Stock |  |  |  |  |  |  |
Number of shares issued |  |  |  |  | 531,667 |  |
Aggregate liquidation preference |  |  |  |  | $ 26,583,000 |  |
Annual dividend yield |  |  |  |  | 5.60% |  |
Annual dividend per share (in dollars per share) |  |  |  |  | $ 2.80000 |  |
Number of common shares to be issued on conversion of each preferred share |  |  |  |  | 0.8163 |  |
Series L [Member] |  |  |  |  |  |  |
Preferred Stock |  |  |  |  |  |  |
Number of shares issued |  |  |  |  | 6,900,000 |  |
Aggregate liquidation preference |  |  |  |  | $ 172,500,000 |  |
Annual dividend yield |  |  |  |  | 7.375% |  |
Annual dividend per share (in dollars per share) |  |  |  |  | $ 1.84375 |  |

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