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Organization (Details 2) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Corporate Office Properties, L.P. [Member] | Common Units [Member] |  |
Forms of ownership in Operating Partnership and ownership percentage by the entity |  |
Percentage ownership in operating partnership | 98.80% | 96.90%

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- Definition Percentage investment held by the managing member or general partner of the limited liability company (LLC) or limited partnership (LP). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 272 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055 + Details
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