Consolidated Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net earnings	$ 14,861	$ 12,721	$ 36,249	$ 34,903
Other comprehensive income:
Foreign currency translation adjustments	450	(646)	268	(509)
Pension and postretirement benefits, net of tax	(11)	(16)	(9)	333
Comprehensive income	$ 15,300	$ 12,059	$ 36,508	$ 34,727