Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Loss
Net loss	$ (204,285)	$ (48,103)	$ (44,904)
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	3,353	(132)	(1,990)
Unrealized pension actuarial gains (losses), net of tax	1,285	(7,263)	3,655
Total other comprehensive loss, net of tax	$ (199,647)	$ (55,498)	$ (43,239)