Unaudited Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 6,393	$ 6,788	$ 14,569	$ 11,766
Foreign currency translation adjustment	0	672	0	1,743
Deferred gain on equity securities	0	238	0	464
Current period cash flow hedging activity, net of $283 and $369 tax benefit in the three and six months ended June 30, 2017, respectively.	0	(620)	0	(859)
Reclassification of hedging activities into earnings, net of $77 and $89 tax benefit in the three and six months ended June 30, 2017, respectively.	0	134	0	140
Reclassification of pension and postretirement adjustments into earnings, net of $26 and $61 tax benefit in the three and six months ended June 30, 2018, respectively, net of $140 and $190 tax benefit in the three and six months ended June 30, 2017, respectively.	105	148	245	324
Total other comprehensive income	105	572	245	1,812
Comprehensive income	$ 6,498	$ 7,360	$ 14,814	$ 13,578