Net Earnings Per Share Net Earnings Per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Numerator for earnings per share:
Earnings from continuing operations	$ 48,825	$ 51,606	[1]
Loss from discontinued operations	(686)	(291)	[1]
Net earnings for basic earnings per share	$ 48,139	$ 51,315	[1]
Denominator for earnings per share:
Weighted average number of common shares outstanding (in shares)	154,485	159,400	[1]
Assumed exercises of stock options and vesting of restricted stock awards, net of shares assumed reacquired under the treasury stock method (in shares)	2,487	2,910	[1]
Weighted average diluted shares outstanding (in shares)	156,972	162,310	[1]

[1] Amounts have been adjusted for the reclassification of certain discontinued operations to continuing operations.