Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net earnings	$ 78,573	$ 90,071	$ 55,972
Other comprehensive (loss)/income, net of tax:
Net foreign currency translation adjustment	(2,982)	5,404	(1,390)
Net change in postretirement benefit plan, net of taxes of $434, $207, and $49 at December 31, 2018, 2017 and 2016, respectively	1,022	(197)	(345)
Other comprehensive (loss)/income	(1,960)	5,207	(1,735)
Comprehensive income	$ 76,613	$ 95,278	$ 54,237