Net Earnings Per Share Net Earnings Per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator for earnings per share:
Earnings from continuing operations	$ 50,158	$ 42,405	$ 101,794	$ 91,230
Loss from discontinued operations	0	(1,312)	0	(1,998)
Net earnings for basic and diluted earnings per share	$ 50,158	$ 41,093	$ 101,794	$ 89,232
Denominator for earnings per share:
Weighted average number of common shares outstanding	142,085	153,172	143,350	153,829
Assumed exercises of stock options and vesting of restricted stock awards, net of shares assumed reacquired under the treasury stock method	1,689	1,861	1,631	2,154
Weighted average diluted shares outstanding	143,774	155,033	144,981	155,983