Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
U.S. federal	$ (79)	$ 9,564	$ 2,737
Foreign	16,871	22,552	26,275
State and local	77	8	319
Total current	16,869	32,124	29,331
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
U.S. federal	(8,390)	2,365	23,478
Foreign	(10,463)	392	(4,138)
State and local	199	(255)	(154)
Total deferred	(18,654)	2,502	19,186
Provision for income taxes	$ (1,785)	$ 34,626	$ 48,517