Earnings Per Share (Schedule of Calculation of Numerator and Denominator in Earnings Per Share)(Details) (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Income from continuing operations	$ 42,418	$ 37,609	$ 82,748	$ 71,781
Loss from discontinued operations, net of tax		(991)		(257)
NET INCOME	42,418	36,618	82,748	71,524
Income from continuing operations, basic	$ 0.40	$ 0.33	$ 0.77	$ 0.63
Loss from discontinued operations, net of tax, basic		$ (0.01)
Net income	$ 0.40	$ 0.32	$ 0.77	$ 0.63
Loss from discontinued operations, net of tax, diluted		$ (0.01)
Income from continuing operations, diluted	$ 0.39	$ 0.33	$ 0.76	$ 0.62
Net income	$ 0.39	$ 0.32	$ 0.76	$ 0.62
Basic [Member]
Income from continuing operations	42,418	37,609	82,748	71,781
Loss from discontinued operations, net of tax		(991)		(257)
NET INCOME	42,418	36,618	82,748	71,524
Weighted average common shares outstanding	106,977	112,980	107,828	114,163
Income from continuing operations, basic	$ 0.40	$ 0.33	$ 0.77	$ 0.63
Loss from discontinued operations, net of tax, basic		$ (0.01)
Net income	$ 0.40	$ 0.32	$ 0.77	$ 0.63
Diluted [Member]
Income from continuing operations	42,418	37,609	82,748	71,781
Loss from discontinued operations, net of tax		(991)		(257)
NET INCOME	$ 42,418	$ 36,618	$ 82,748	$ 71,524
Weighted average shares and assumed conversions	107,728	113,873	108,631	115,106
Loss from discontinued operations, net of tax, diluted		$ (0.01)
Income from continuing operations, diluted	$ 0.39	$ 0.33	$ 0.76	$ 0.62
Net income	$ 0.39	$ 0.32	$ 0.76	$ 0.62
Stock options [Member]
Effect of dilutive securities	622	770	657	804
Restricted stock-based compensation [Member]
Effect of dilutive securities	129	123	146	139