Securitization - Narrative (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Variable Interest Entity [Line Items]
Proceeds from issuance of securitized long-term debt by AEK			$ 0	$ 0	$ 95,000,000
Long-term debt, fair value			8,272,978,000
State of Texas | Extraordinary Gas Cost | Winter Storm Uri
Variable Interest Entity [Line Items]
Regulatory asset, authorized		$ 3,500,000,000
Regulatory asset, proceeds from customer rate relief bonds		$ 2,020,000,000.00
State of Texas | Extraordinary Gas Cost | Winter Storm Uri | Minimum
Variable Interest Entity [Line Items]
Regulatory asset, maturity period		12 years
State of Texas | Extraordinary Gas Cost | Winter Storm Uri | Maximum
Variable Interest Entity [Line Items]
Regulatory asset, maturity period		18 years
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Long-term debt			$ 77,003,000
Variable Interest Entity, Primary Beneficiary | Securitized Utility Tariff Property
Variable Interest Entity [Line Items]
Proceeds from sale of intangible assets	$ 92,300,000
Initial consolidation, gain (loss)	$ 0
Intangible asset, useful life	10 years
Intangible assets, amortization period			4 years 25 days
Series 2023-A Securitized Utility Tariff Bonds Due March 2033 | Senior Notes | 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			$ 77,000,000.0	85,100,000
Long-term debt, fair value			$ 78,800,000	$ 87,800,000