Other Assets and Accrued Liabilities - Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Other Liabilities Disclosure [Abstract]
Prepaid rent	$ 0		$ 11,245
Prepaid maintenance expenses	3,499		3,981
Interest rate swaps	2,275		4,930
Contract asset	43,879		37,957
Other	4,133		2,049
Prepaid expenses and other	$ 53,786	$ 48,582	$ 60,162