Other Assets and Accrued Liabilities - Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Prepaid rent	$ 9,929		$ 10,519
Prepaid maintenance expenses	3,806		3,062
Interest rate swaps	4,577		2,411
Deferred contract costs	37,947		0
Other	7,904		1,119
Prepaid expenses and other	$ 64,163	$ 53,688	$ 17,111