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Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Allowance for doubtful accounts- AR | $ 607 | $ 603
Allowance for deferred rent receivable | 364 | 373
Accumulated amortization of deferred leasing costs | $ 29,560 | $ 65,988
Common Shares of beneficial interest, par value (in dollars per share) | $ 0.01 | $ 0.01
Common Shares of beneficial interest, shares authorized | 150,000,000 | 125,000,000
Common Shares of beneficial interest, shares issued | 101,292,299 | 98,498,651
Common Shares of beneficial interest, shares outstanding | 101,292,299 | 98,498,651
Corporate Office Properties, L.P. [Member] |  |
Allowance for doubtful accounts- AR | $ 607 | $ 603
Allowance for deferred rent receivable | 364 | 373
Accumulated amortization of deferred leasing costs | $ 29,560 | $ 65,988
Redeemable preferred units of general partner outstanding, in units |  | 531,667
General Partner [Member] | Corporate Office Properties, L.P. [Member] |  |
Preferred Units, Outstanding | 0 | 6,900,000
Common Shares of beneficial interest, shares outstanding | 101,292,299 | 98,498,651
Limited Partner [Member] | Corporate Office Properties, L.P. [Member] |  |
Preferred Units, Outstanding | 352,000 | 352,000
Common Shares of beneficial interest, shares outstanding | 3,250,878 | 3,590,391

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