Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Condensed Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net earnings	$ 13,976	$ 15,178	$ 44,063	$ 33,804
Other comprehensive income (loss), net of tax:
Net foreign currency translation adjustment	375	(1,739)	(1,754)	(1,934)
Net change in postretirement benefit plan, net of taxes of $1 and $1 for the three months ended September 30, 2015 and 2014, and $5 and $3 for the nine months ended September 30, 2015 and 2014.	(3)	(2)	(9)	(6)
Other comprehensive income (loss)	372	(1,741)	(1,763)	(1,940)
Comprehensive income	$ 14,348	$ 13,437	$ 42,300	$ 31,864