Share-Based Payments - Exercisable Options (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Information concerning outstanding and exercisable options
Aggregate intrinsic value of stock options exercised		$ 0.9	$ 1.2
Allocated Share-based Compensation Expense	$ 63.8	73.1	$ 83.8
Unrecognized compensation expense	$ 74.6	$ 94.3
Vesting period	3 years
Employee Stock Option
Information concerning outstanding and exercisable options
Number of stock options granted during the period	0	0
Performance Earnings Program
Information concerning outstanding and exercisable options
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 27.53	$ 37.69	$ 38.15
Restricted Stock Units (RSUs)
Information concerning outstanding and exercisable options
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 27.73	$ 36.83	$ 37.96

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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