Consolidated Statements of Comprehensive Income - 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 earnings	$ 6,154	$ 10,614	$ 13,700	$ 19,363
Other comprehensive income:
Foreign currency translation adjustment	(808)	1,049	(387)	1,340
Pension and postretirement benefits, net of tax	5,711	71	5,772	154
Comprehensive income	$ 11,057	$ 11,734	$ 19,085	$ 20,857