Accounting Changes Consolidated Statement of Operations (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Selling, general and administrative expenses	$ 329,070	$ 293,441	$ 264,337
Earnings before income taxes	77,488	55,997	34,665
Income tax expense	26,346	20,386	9,670
Net earnings	51,142	35,611	24,995
Basic net earnings per share	$ 1.95	$ 1.37	$ 0.97
Diluted net earnings per share	$ 1.93	$ 1.36	$ 0.97
Effect of Change [Member]
Selling, general and administrative expenses		4,375	12,345
Earnings before income taxes		(4,375)	(12,345)
Income tax expense		(1,662)	(4,691)
Net earnings		(2,713)	(7,654)
Basic net earnings per share		$ (0.11)	$ (0.30)
Diluted net earnings per share		$ (0.11)	$ (0.30)
Previously Reported [Member]
Selling, general and administrative expenses		289,066	251,992
Earnings before income taxes		60,372	47,010
Income tax expense		22,048	14,361
Net earnings		$ 38,324	$ 32,649
Basic net earnings per share		$ 1.48	$ 1.27
Diluted net earnings per share		$ 1.47	$ 1.27