Business and Basis of Presentation - Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 210,997	$ 538,908	$ 630,016	$ 474,233
Restricted cash classified in:
Prepaid expenses and other current assets	2,295	15,148	15,158	25,121
Other assets	0	3,002	3,002	0
Cash and cash equivalents	0	10,000	0	0
Cash and cash equivalents and restricted cash	$ 213,292	$ 567,058	$ 648,176	$ 499,354