Earnings 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
Anti-dilutive shares			5,800,000	2,300,000
Net Income (Numerator)
Basic earnings - net income	$ 43,304	$ 18,741	$ 247,917	$ 132,917
5.125% convertible senior notes, net of tax (in dollars)	2,358	2,377	7,074	7,131
Diluted earnings - net income (in dollars)	$ 45,662	$ 21,118	$ 254,991	$ 140,048
Shares (Denominator)
Weighted average common shares outstanding - basic	218,674,000	216,881,000	218,389,000	216,600,000
Dilutive stock option effect (in shares)	703,000	1,280,000	1,312,000	1,619,000
5.125% convertible senior notes, net of tax (in shares)	16,382,000	16,382,000	16,382,000	16,382,000
Weighted average common shares outstanding - diluted	235,759,000	234,543,000	236,083,000	234,601,000
Per Share Amount
Basic earnings per share (in dollars per share)	$ 0.20	$ 0.09	$ 1.14	$ 0.61
Diluted earnings per share (in dollars per share)	$ 0.19	$ 0.09	$ 1.08	$ 0.60