Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 29,406	$ (8,385)	$ 20,766	$ (4,001)
Other comprehensive income (loss) - net of tax:
Adjustment to accrued pension liability	498	499	997	1,228
Change in unrealized net (loss) gain on foreign currency	(4,723)	395	(6,196)	3,630
Unrealized gain (loss) on cash flow hedge derivatives	204	204	240	(144)
Other comprehensive (loss) income	(4,021)	1,098	(4,959)	4,714
Total comprehensive income (loss)	$ 25,385	$ (7,287)	$ 15,807	$ 713