Net Earnings Per Share Net Earnings Per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011		Jun. 30, 2012	Jun. 30, 2011
Numerator for earnings per share:
Earnings from continuing operations	$ 42,405	$ 29,823	[1]	$ 91,230	$ 81,426	[1]
Loss from discontinued operations	(1,312)	(514)	[1]	(1,998)	(802)	[1]
Net earnings for basic and diluted earnings per share	$ 41,093	$ 29,309	[1]	$ 89,232	$ 80,624	[1]
Denominator for earnings per share:
Weighted average number of common shares outstanding (in shares)	153,172	159,796	[1]	153,829	159,599	[1]
Assumed exercises of stock options and vesting of restricted stock awards, net of shares assumed reacquired under the treasury stock method (in shares)	1,861	2,754	[1]	2,154	2,828	[1]
Weighted average diluted shares outstanding (in shares)	155,033	162,550	[1]	155,983	162,427	[1]

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