Business Segment Information (Reconciliation of Equity Affiliates' Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Equity affiliates' income	$ 88.2	$ 46.2	$ 146.4	$ 99.1
India Finance Act 2020	33.8		33.8
Segment Total
Segment Reporting Information [Line Items]
Equity affiliates' income	54.4	46.2	112.6	99.1
Segment Reconciling Items
Segment Reporting Information [Line Items]
India Finance Act 2020	$ 33.8	$ 0.0	$ 33.8	$ 0.0