Net Earnings Per Share Net Earnings Per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator for earnings per share:
Earnings from continuing operations	$ 55,949	$ 64,390	$ 147,179	$ 145,818
Loss from discontinued operations	(44)	329	(2,042)	(475)
Net earnings for basic and diluted earnings per share	$ 55,905	$ 64,719	$ 145,137	$ 145,343
Denominator for earnings per share:
Weighted average number of common shares outstanding (in shares)	150,878	158,665	152,820	159,225
Assumed exercises of stock options and vesting of restricted stock awards, net of shares assumed reacquired under the treasury stock method (in shares)	1,449	2,133	1,938	2,586
Weighted average diluted shares outstanding (in shares)	152,327	160,798	154,758	161,811