Basis of Presentation and Consolidation - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 213,091	$ 371,684	$ 365,046	$ 504,423
Restricted cash included in Other current assets	11,683	19,200	4,715	18,499
Restricted cash included in Other assets	2,124	1,422	1,068	1,327
Total cash, cash equivalents and restricted cash	$ 226,898	$ 392,306	$ 370,829	$ 524,249