Earnings Per Share (Details) (USD $) In Millions	3 Months Ended	9 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Numerator
Net income	$ 28.7	$ 50.5	$ 36.0	$ 253.9
Effect of dilutive securities
Interest expense and amortization of issuance costs associated with convertible senior notes				23.1
Numerator for diluted earnings per share after assumed conversions	$ 28.7	$ 50.5	$ 36.0	$ 277.0
Denominator
Denominator for basic earnings (loss) per share - weighted average common shares	318.7	318.2	319.0	318.0
Effect of dilutive securities:
Employee stock awards	0.3	0.9	0.3	0.6
Convertible senior notes				38.3
Denominator for diluted earnings per share adjusted weighted average common shares	319.0	319.1	319.3	356.9
Earnings per share (Textuals) [Abstract]
Number of shares excluded from computation of earnings per share	9.6	9.5	9.5	9.7

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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