Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net earnings	$ 133,453	$ 99,533	$ 86,896
Currency translation	(1,955)	(1,035)	(802)
Postretirement plans	49	(2,820)	908
Short-term investments	0	0	(1,213)
Comprehensive income	131,547	95,678	85,789
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Tax	$ 100	$ 1,800	$ 2,100