Consolidated Condensed Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Other Comprehensive Income [Abstract]
Net earnings	$ 5,484	$ 8,857	$ 7,442	$ 6,249	$ 1,187	$ 6,880	$ 7,834	$ 3,260	$ 28,032	$ 19,161	$ 28,662
Other comprehensive income :
Foreign currency translation adjustment									393	(267)	(282)
Employee benefit funded status adjustment, net of tax									225	(1,162)	1,730
Comprehensive income									$ 28,650	$ 17,732	$ 30,110