CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 5,096	$ 12,933	$ (183,498)	$ 29,463
Other comprehensive income (loss), net of tax
Translation adjustments	1,092	442	1,477	3,133
Minimum pension liability adjustments	704	7,418	1,408	8,333
Cash flow hedge adjustments	(36)	100	32	(427)
Total other comprehensive income (loss), net of tax	1,760	7,960	2,917	11,039
Comprehensive income (loss)	$ 6,856	$ 20,893	$ (180,581)	$ 40,502