Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Condensed Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net earnings	$ 14,916	$ 9,732	$ 30,088	$ 18,626
Other comprehensive income (loss), net of tax:
Net foreign currency translation adjustment	550	(176)	(2,130)	(194)
Net change in postretirement benefit plan, net of taxes of $2 and $1 for the three months ended June 30, 2015 and 2014, and $3 and $2 for the six months ended June 30, 2015 and 2014.	(3)	(2)	(6)	(4)
Other comprehensive income (loss)	547	(178)	(2,136)	(198)
Comprehensive income	$ 15,463	$ 9,554	$ 27,952	$ 18,428