Deferred Costs (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred leasing costs	$ 415,824	$ 443,341
Less: accumulated amortization	(220,267)	(217,140)
Deferred costs, net	$ 195,557	$ 226,201