Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net earnings	$ 11,886	$ 15,172
Other comprehensive income (loss), net of tax:
Net foreign currency translation adjustment	1,255	(2,680)
Net change in postretirement benefit plan, net of taxes of $1 and $2 for the three months ended March 31, 2016 and 2015.	(4)	(3)
Other comprehensive income (loss)	1,251	(2,683)
Comprehensive income	$ 13,137	$ 12,489