Consolidated Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net earnings	$ 9,534	$ 11,358	$ 21,388	$ 22,182
Other comprehensive income:
Foreign currency translation adjustments	445	395	(182)	137
Pension and postretirement benefits, net of tax	1	360	2	349
Comprehensive income	$ 9,980	$ 12,113	$ 21,208	$ 22,668