Basic and Diluted Earnings Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Reconciliation of basic and diluted earnings per share
Net earnings from continuing operations	$ 43,457	$ 32,194	$ 78,983	$ 58,509
Earnings from discontinued operations, net		1,407		3,044
Net earnings	$ 43,457	$ 33,601	$ 78,983	$ 61,553
Basic shares:
Average shares outstanding	51,950,000	51,965,000	51,734,000	51,989,000
Basic earnings per share:
Continuing operations	$ 0.84	$ 0.62	$ 1.53	$ 1.13
Discontinued operations		$ 0.03		$ 0.05
Net earnings	$ 0.84	$ 0.65	$ 1.53	$ 1.18
Diluted shares:
Average shares outstanding	51,950,000	51,965,000	51,734,000	51,989,000
Additional shares on the potential dilution from stock options, nonvested restricted stock and performance units	1,339,000	1,076,000	1,362,000	1,050,000
Number of diluted shares outstanding	53,289,000	53,041,000	53,096,000	53,039,000
Diluted earnings per share:
Continuing operations	$ 0.82	$ 0.61	$ 1.49	$ 1.10
Discontinued operations		$ 0.02		$ 0.06
Net earnings	$ 0.82	$ 0.63	$ 1.49	$ 1.16
Basic and Diluted Earnings Per Share (Textuals)
Out-of-the money stock options associated with common stock that were anti-dilutive	200,000	1,800,000	300,000	1,800,000