Earnings Per Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 252.6	$ 268.2	$ 552.1	$ 1,626.5
Less: Distributed and undistributed income available to participating securities, Basic				(0.2)
Net income attributable to common stockholders, basic	252.6	268.2	552.1	1,626.3
Less: Distributed and undistributed income available to participating securities, Diluted				(0.2)
Net income attributable to common stockholders, diluted	$ 1,327.0	$ 268.2	$ 1,626.5	$ 1,626.3
Basic weighted average shares outstanding	257.3	256.1	256.2	255.7
Effect of dilutive stock options and non- participating securities	1.3	4.5	2.9	4.3
Diluted weighted average shares outstanding	258.6	260.6	259.1	260.0
Basic earnings per share attributable to common stockholders	$ 0.98	$ 1.05	$ 2.15	$ 6.36
Diluted earnings per share attributable to common stockholders	$ 0.98	$ 1.03	$ 2.13	$ 6.25