Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net earnings	$ 49,343	$ 47,177	$ 27,790
Other comprehensive income :
Foreign currency translation adjustment	1,096	(58)	(484)
Pension and postretirement benefits, net of tax	(208)	(97)	13,657
Comprehensive income	$ 50,231	$ 47,022	$ 40,963