Business Segment Information (Reconciliation of Equity Affiliates' Income) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Equity affiliates' income	$ 69.8	$ 88.2	$ 139.1	$ 146.4
India Finance Act 2020		33.8
Segment Total
Segment Reporting Information [Line Items]
Equity affiliates' income	69.8	54.4	139.1	112.6
Segment Reconciling Items
Segment Reporting Information [Line Items]
India Finance Act 2020	$ 0.0	$ 33.8	$ 0.0	$ 33.8

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

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