Basis of Condensed Consolidated Financial Statements (Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 97,884	$ 118,804	$ 149,411
Restricted cash included in other assets	10,355		13,532
Restricted cash included in prepaid expenses and other current assets	1,070		0
Total cash, cash equivalents and restricted cash	$ 109,309	$ 132,154	$ 162,943	$ 89,974