Income Taxes - Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
U.S. federal	$ 3,406	$ 1,748	$ 2,726
State and local	72	374	189
Foreign	8,304	4,150	9,028
Total current	11,782	6,272	11,943
Deferred tax (benefit) expense:
U.S. federal	9,495	(1,416)	(4,588)
State and local	(369)	(356)	(87)
Foreign	(3,297)	304	(466)
Total deferred	5,829	(1,468)	(5,141)
Total provision for income taxes	$ 17,611	$ 4,804	$ 6,802