Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		2.8
Numerator:
Net Income (Loss) Attributable to Parent	$ 189.3	$ 206.9
Denominator:
Denominator for basic earnings per share — weighted average common shares	375.8	373.3
Effect of dilutive securities:
Employee stock awards (shares)	8.0	4.1
Denominator for diluted earnings per share — adjusted weighted average common shares	383.8	377.4
Basic net income per common share attributable to Parent (in dollars per share)	$ 0.50	$ 0.55
Diluted net income per common share attributable to Parent (in dollars per share)	$ 0.49	$ 0.55