Variable Interest Entity - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023	Jun. 30, 2023
Variable Interest Entity [Line Items]
Long-term debt, fair value	$ 6,892,431	$ 5,402,591
Securitized Utility Tariff Bonds | Senior Notes | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Debt face amount			$ 95,000
Long-term debt	89,300
Long-term debt, fair value	$ 89,200