CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Comprehensive income (loss):
Net income (loss)	$ 20,783	$ (58,273)	$ 12,775	$ (83,951)
Other comprehensive income before income tax effect:
Net loss on foreign currency cash flow hedges reclassified as income	(46)	(46)	(140)	(139)
Defined benefit plans and other postretirement benefits:
Amortization of prior service benefit during the period	(670)	(667)	(1,652)	(2,001)
Amortization of net loss during the period	2,145	1,919	4,865	5,758
Other comprehensive income before income tax effect	1,429	1,206	3,073	3,618
Income tax effect	(382)	(382)	(1,145)	(1,147)
Other comprehensive income	1,047	824	1,928	2,471
Total comprehensive income (loss)	$ 21,830	$ (57,449)	$ 14,703	$ (81,480)