Business Segment and Geographic Information (Reconciliation of Equity Affiliates' Income) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
India Finance Act 2020		$ 33.8
Equity affiliates' income	$ 294.1	264.8	$ 215.4
Segment Reconciling Items
Segment Reporting Information [Line Items]
India Finance Act 2020	0.0	33.8	0.0
Segment Total
Segment Reporting Information [Line Items]
Equity affiliates' income	$ 294.1	$ 231.0	$ 215.4

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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