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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 178.5	$ 252.6	$ 465.1	$ 552.1
Less: Distributed and undistributed income available to participating securities, Basic			(0.1)
Distributed and undistributed income available to common stockholders, Basic	178.5	252.6	465.0	552.1
Less: Distributed and undistributed income available to participating securities, Diluted			(0.1)
Distributed and undistributed income available to common stockholders, Diluted	$ 178.5	$ 252.6	$ 465.0	$ 552.1
Basic weighted average shares outstanding	259.4	257.3	258.9	256.2
Effect of dilutive stock options and non- participating securities	1.0	1.3	1.3	2.9
Diluted weighted average shares outstanding	260.4	258.6	260.2	259.1
Basic earnings per share attributable to common stockholders	$ 0.69	$ 0.98	$ 1.80	$ 2.15
Diluted earnings per share attributable to common stockholders	$ 0.69	$ 0.98	$ 1.79	$ 2.13

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount of earnings (loss) distributed and earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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