Accumulated Other Comprehensive Income (Loss) - Components of and Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, tax	$ (5,000)	$ (100)
Accumulated Other Comprehensive Income
Balance at beginning of period	(10,893)	(11,635)
Other comprehensive income (loss) before reclassifications	(281)	1,545
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	13,168	234
Net current period other comprehensive income (loss), net of tax	12,887	1,779
Cumulative impact of adopting ASU 2018-02			$ (1,700)
Accumulated other comprehensive income (loss)	294	(9,856)
Unrecognized pension and postretirement benefits
Accumulated Other Comprehensive Income
Balance at beginning of period	(11,597)	(10,495)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	13,168	234
Net current period other comprehensive income (loss), net of tax	13,168	234
Cumulative impact of adopting ASU 2018-02			(1,700)
Accumulated other comprehensive income (loss)	(129)	(10,261)
Foreign currency
Accumulated Other Comprehensive Income
Balance at beginning of period	704	(1,140)
Other comprehensive income (loss) before reclassifications	(281)	1,545
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0
Net current period other comprehensive income (loss), net of tax	(281)	1,545
Cumulative impact of adopting ASU 2018-02			$ 0
Accumulated other comprehensive income (loss)	$ 423	$ 405