Business Segment and Geographic Information (Reconciliation of Equity Affiliates' Income) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Equity method investment impairment charge										$ 0.0	$ 0.0	$ (79.5)
Tax reform repatriation - equity method investment											(28.5)
Equity affiliates' income		$ 59.9	$ 56.4	$ 46.2	$ 52.9	$ 59.2	$ 58.1	$ 43.7	$ 13.8	215.4	174.8	80.1
Segment Reconciling Items
Segment Reporting Information [Line Items]
Equity method investment impairment charge										0.0	0.0	(79.5)
Tax reform repatriation - equity method investment										0.0	(28.5)	0.0
Segment Total
Segment Reporting Information [Line Items]
Equity affiliates' income	[1]									$ 215.4	$ 203.3	$ 159.6

[1] Refer to the Reconciliations to Consolidated Results section below.