Variable Interest Entity - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2021
Variable Interest Entity [Line Items]
Proceeds from issuance of securitized long-term debt by AEK		$ 95,000,000	$ 0	$ 0
Long-term debt, fair value		5,402,591,000
AEK | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Long-term debt		$ 95,000,000
AEK | Variable Interest Entity, Primary Beneficiary | Securitized Utility Tariff Property
Variable Interest Entity [Line Items]
Proceeds from sale of intangible assets	$ 92,300,000
Intangible asset, useful life		10 years
Intangible assets, amortization period		5 years 2 months 8 days
Senior Notes
Variable Interest Entity [Line Items]
Debt face amount					$ 2,200,000,000
Series 2023-A Securitized Utility Tariff Bonds Due March 2033 | Senior Notes | AEK | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Debt face amount	$ 95,000,000
Debt instrument, interest rate	5.155%
Debt instrument, term	10 years
Proceeds from issuance of securitized long-term debt by AEK	$ 93,700,000
Long-term debt		$ 95,000,000
Long-term debt, fair value		$ 92,300,000