Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Number of shares excluded from computation of earnings per share	0.0	8.9
Earnings Per Share Reconciliation [Abstract]
Net income	$ 157.7	$ 142.5
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Denominator for basic earnings per share - weighted average common shares	369.3	364.9
Employee stock awards (shares)	4.2	3.2
Denominator for diluted earnings per share - adjusted weighted average common shares	373.5	368.1
Basic net income per common share (in dollars per share)	$ 0.43	$ 0.39
Net income per common share assuming dilution (in dollars per share)	$ 0.42	$ 0.39