Basis of Presentation and Significant Accounting Policies - Reconciliation of Cash and Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 143,335	$ 203,404
Restricted cash and cash equivalents	5,362	7,105
Restricted cash and cash equivalents included in Other Assets	2,639	2,635
Total cash and cash equivalents and restricted cash and cash equivalents as presented in our condensed consolidated statement of cash flows	$ 151,336	$ 213,144	$ 104,713	$ 134,600