Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net earnings	$ 27,790	$ 34,571	$ 32,295
Other comprehensive income :
Foreign currency translation adjustment	(484)	1,844	(328)
Pension and postretirement benefits, net of tax	13,657	(1,102)	1,473
Comprehensive income	$ 40,963	$ 35,313	$ 33,440