Unaudited Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 8,176	$ 4,978
Foreign currency translation adjustment	0	1,071
Deferred gain on equity securities	0	226
Current period cash flow hedging activity, net of $86 tax benefit in the three months ended March 31, 2017	0	(239)
Reclassification of hedging activities into earnings, net of $12 tax benefit in the three months ended March 31, 2017	0	6
Reclassification of pension and postretirement adjustments into earnings, net of $35 and $50 tax benefit in the three months ended March 31, 2018 and March 31, 2017, respectively	140	176
Total other comprehensive income	140	1,240
Comprehensive income	$ 8,316	$ 6,218