Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net Income (Loss) Attributable to Parent	$ 351.0	$ 229.2	$ 540.3	$ 436.1
Denominator:
Denominator for basic earnings per share — weighted average common shares	376.8	374.4	376.3	373.8
Effect of dilutive securities:
Employee stock awards (shares)	7.1	4.5	7.5	4.3
Denominator for diluted earnings per share — adjusted weighted average common shares	383.9	378.9	383.8	378.1
Basic net income per common share attributable to Parent (in dollars per share)	$ 0.93	$ 0.61	$ 1.44	$ 1.17
Diluted net income per common share attributable to Parent (in dollars per share)	$ 0.91	$ 0.60	$ 1.41	$ 1.15