Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of shares excluded from computation of earnings per share			6.4	8.7
Earnings Per Share Reconciliation [Abstract]
Net income	$ 195.1	$ 147.9	$ 352.8	$ 290.4
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Denominator for basic earnings per share - weighted average common shares	370.2	365.8	369.7	365.4
Employee stock awards (shares)	3.5	3.6	3.9	3.4
Denominator for diluted earnings per share - adjusted weighted average common shares	373.7	369.4	373.6	368.8
Basic net income per common share (in dollars per share)	$ 0.53	$ 0.40	$ 0.95	$ 0.79
Net income per common share assuming dilution (in dollars per share)	$ 0.52	$ 0.40	$ 0.94	$ 0.79