Consolidated Statements of Comprehensive Income Statement (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Other Comprehensive Income [Abstract]
Net earnings	$ 6,380	$ 9,049	$ 6,281	$ 2,907	$ 5,484	$ 8,857	$ 7,442	$ 6,249	$ 24,617	$ 28,032	$ 19,161
Other comprehensive income :
Foreign currency translation adjustment									172	393	(267)
Employee benefit funded status adjustment, net of tax									6,252	225	(1,162)
Comprehensive income									$ 31,041	$ 28,650	$ 17,732