Net Income Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Numerator:
Income from continuing operations (in dollars)	$ 76,221	$ 136,972	$ 265,392	$ 295,777
Loss from discontinued operations		$ (757)		$ (1,848)
Denominator:
Average number of common shares outstanding	62,414,000	52,920,000	59,601,000	53,224,000
Effect of dilutive securities:
Stock awards and warrants (in shares)	345,000	473,000	370,000	548,000
Weighted average shares, diluted (in shares)	62,759,000	53,393,000	59,971,000	53,772,000
Income from continuing operations, basic (in dollars per share)	$ 1.22	$ 2.59	$ 4.45	$ 5.56
Loss from discontinued operations, basic (in dollars per share)		$ (0.02)		$ (0.04)
Net income per share, basic (in dollars per share)	$ 1.22	$ 2.57	$ 4.45	$ 5.52
Income from continuing operations, diluted (in dollars per share)	$ 1.21	$ 2.57	$ 4.43	$ 5.50
Loss from discontinued operations, diluted (in dollars per share)		$ (0.02)		$ (0.03)
Net income per share, diluted (in dollars per share)	$ 1.21	$ 2.55	$ 4.43	$ 5.47
Anti-dilutive securities excluded from earnings per share calculation (in shares)	38,083	30,755	32,086	27,802