CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 119,929	$ (8,508)	$ (20,296)
Other comprehensive loss:
Cumulative translation adjustment	(2,257)	(1,333)	(802)
Unrealized loss on derivative instruments, net of tax:
Change in fair value of derivative instruments	0	(87)	(116)
Less: reclassification adjustments for losses included in net income	0	0	(220)
Defined benefit pension and other postretirement benefit plans, net of tax:
Prior service costs arising during the period	0	(43)	(659)
Net loss arising during the period	(8,452)	(5,036)	(30,159)
Less: amortization of prior service cost included in net periodic benefit cost	6,879	5,679	4,163
Other comprehensive loss	(3,830)	(820)	(27,793)
Comprehensive income (loss)	$ 116,099	$ (9,328)	$ (48,089)