Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (loss) before taxes:
U.S.	$ (34,406)	$ (55,617)	$ (83,537)
Foreign	52,586	48,404	8,793
Income (loss) before income taxes	18,180	(7,213)	(74,744)
Current income taxes:
U.S. federal	1,383	49	480
U.S. state	127	126	195
Foreign	9,525	9,494	7,488
Total current income taxes	11,035	9,669	8,163
Deferred income taxes:
U.S. federal	1,300	263	(3,902)
U.S. state	0	0	(118)
Foreign	(4,393)	(651)	4,309
Total deferred income taxes	(3,093)	(388)	289
Income tax expense	$ 7,942	$ 9,281	$ 8,452