Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Lease agreement term (in years)	1 year
Balance Sheet
Cash and cash equivalents	$ 243,547	$ 118,799	$ 106,308
Restricted cash	119,574	131,442	131,367	$ 111,300
Statement of Cash Flows
Cash, cash equivalents and restricted cash	$ 363,121	$ 250,241	$ 237,675	$ 168,968