Consolidated Statements of Comprehensive Income Statement (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net earnings	$ 6,001	$ 10,231	$ 8,814	$ 4,632	$ 6,380	$ 9,049	$ 6,281	$ 2,907	$ 29,678	$ 24,617	$ 28,032
Other comprehensive income :
Foreign currency translation adjustment									(1,721)	172	393
Pension and postretirement benefits, net of tax									(2,611)	6,252	225
Comprehensive income									$ 25,346	$ 31,041	$ 28,650