Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 83,300	$ 30,960	$ (39,800)
Other comprehensive income
Defined benefit plans	3,250	1,670	250
Foreign currency translation	(6,880)	6,050	(12,620)
Derivative instruments	4,110	(650)	(730)
Total other comprehensive income (loss)	480	7,070	(13,100)
Total comprehensive income (loss)	$ 83,780	$ 38,030	$ (52,900)