Concentrations of Credit Risk - Additional Information (Details) Pures in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2025 USD ($)
Customer Concentration Risk [Member] | Utility Companies and Their Marketing Affiliates [Member]
Concentration Risk [Line Items]
Accounts Receivable, after Allowance for Credit Loss	$ 52.3
Customer Concentration Risk [Member] | Five Largest Counterparties [Member]
Concentration Risk [Line Items]
Accounts Receivable, after Allowance for Credit Loss	$ 25.6
Gas Utility [Member]
Concentration Risk [Line Items]
Number of Customer Serves | Pures	1.7