Supplemental Disclosure of Cash Flow Information - Cash and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 126,637	$ 222,647
Restricted cash	39,015	37,189
Long-term restricted cash	25,010	22,710
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows	$ 190,662	$ 282,546	$ 214,174	$ 277,322