Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2018
Allowance for doubtful accounts
Valuation and Qualifying Accounts
Balance at Beginning of Year		$ 17.4	[1]	$ 17.1		$ 24.9
Charged to Costs and Expenses		7.0	[1]	6.1		0.1
Charged to Other Accounts		1.1	[1]	0.0		0.0
Deductions		10.3		5.8	[2]	7.9	[2]
Balance at End of Year		15.2	[1]	17.4	[1]	17.1
Valuation allowance for deferred tax assets
Valuation and Qualifying Accounts
Balance at Beginning of Year		93.8		27.0		18.6
Charged to Costs and Expenses		3.0		69.3		8.9
Charged to Other Accounts		0.2		0.0		0.0
Deductions	[2]	39.0		2.5		0.5
Balance at End of Year		$ 58.0		$ 93.8		$ 27.0

[1] Includes allowances for current and other long-term receivables.

[2] Consists of amounts written off for the allowance for doubtful accounts and adjustments resulting from our ability to utilize foreign tax credits, capital losses, or net operating loss carryforwards for which a valuation allowance had previously been recorded.