Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net earnings	$ 14,150	$ 14,916	$ 26,036	$ 30,088
Other comprehensive income (loss), net of tax:
Net foreign currency translation adjustment	(707)	550	548	(2,130)
Net change in postretirement benefit plan, net of taxes of $(6) and $2 for the three months ended June 30, 2016 and 2015, and $(5) and $3 for the six months ended June 30, 2016 and 2015.	(426)	(3)	(430)	(6)
Total other comprehensive income (loss)	(1,133)	547	118	(2,136)
Comprehensive income	$ 13,017	$ 15,463	$ 26,154	$ 27,952