Deferred Costs - Deferred Costs (Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of Deferred Costs Net [Abstract]
Leasing costs, Total Cost	$ 154,481	$ 146,135
Total Cost	158,076	149,730
Leasing costs, Accumulated Amortization	(59,046)	(56,942)
Total, Accumulated Amortization	(61,381)	(58,388)
Leasing costs, Deferred Costs, net	95,435	89,193
Financing costs, Deferred Costs, net	11,141
Deferred Costs	96,695	91,342
Revolving Credit Facility [Member]
Components of Deferred Costs Net [Abstract]
Financing costs, Total Cost	3,595	3,595
Financing costs, Accumulated Amortization	(2,335)	(1,446)
Financing costs, Deferred Costs, net	$ 1,260	$ 2,149