Basis of Presentation and Major Accounting Policies (Allowance for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Allowance for Credit Losses
Beginning balance	$ 26.3	$ 22.9	$ 24.1
Provision for credit losses	10.3	10.7	8.2
Write-offs charged against the allowance	(7.5)	(8.5)	(7.9)
Currency translation and other	1.1	1.2	(1.5)
Ending balance	30.2	$ 26.3	$ 22.9
Variable Interest Entity, Not Primary Beneficiary | World Energy, LLC
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit loss	$ 300.0