Accumulated Other Comprehensive Loss - Components of and Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income
Balance at beginning of period	$ (10,893)	$ (11,635)
Other comprehensive income before reclassifications	421	291
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(21)	61	83
Amounts reclassified from accumulated other comprehensive loss, tax	(21)	(46)
Net current period other comprehensive income, net of tax	482	374
Accumulated other comprehensive (loss) income	(10,411)	(11,261)
Unrecognized pension and postretirement benefits
Accumulated Other Comprehensive Income
Balance at beginning of period	(11,597)	(10,495)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(21)	61	83
Net current period other comprehensive income, net of tax	61	83
Accumulated other comprehensive (loss) income	(11,536)	(10,412)
Foreign currency
Accumulated Other Comprehensive Income
Balance at beginning of period	704	(1,140)
Other comprehensive income before reclassifications	421	291
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(21)	0	0
Net current period other comprehensive income, net of tax	421	291
Accumulated other comprehensive (loss) income	$ 1,125	$ (849)