Accounting Changes Consolidated Statement of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net earnings	$ 51,142	$ 35,611	$ 24,995
Pension liabilities	(14,150)	(22,510)	6,581
Effect of Change [Member]
Net earnings		(2,713)	(7,654)
Pension liabilities		2,713	7,654
Previously Reported [Member]
Net earnings		38,324	32,649
Pension liabilities		$ (25,223)	$ (1,073)