Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Marketable securities in deferred compensation plan	$ 4,481	$ 4,616
Fair value measurement on a recurring basis
Assets:
Interest rate derivatives	7,960
Total assets	12,441
Liabilities:
Deferred compensation plan liability	4,481
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,433
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	48
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total assets	4,481
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,433
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Assets:
Marketable securities in deferred compensation plan	48
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	7,960
Total assets	7,960
Liabilities:
Deferred compensation plan liability	4,481
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.
Assets:
Interest rate derivatives	7,960
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	$ 7,960