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Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2022
Income Tax Contingency [Line Items]
Effective income tax rate	11.00%	5.90%
Regulatory liabilities	$ 1,339,967		$ 1,358,907
Regulatory excess deferred taxes
Income Tax Contingency [Line Items]
Deferred tax liabilities, net	458,400
Regulatory liabilities	506,406		545,021
Regulatory excess deferred taxes | Other Current Liabilities
Income Tax Contingency [Line Items]
Deferred tax liabilities, net	160,600		$ 159,800
Regulatory excess deferred taxes, to be returned, tranche one
Income Tax Contingency [Line Items]
Deferred tax liabilities, net	368,800
Regulatory excess deferred taxes, to be returned, tranche two
Income Tax Contingency [Line Items]
Regulatory liabilities	74,500
Regulatory excess deferred taxes, to be returned, tranche three
Income Tax Contingency [Line Items]
Deferred tax liabilities, net	$ 15,100
Minimum | Regulatory excess deferred taxes, to be returned, tranche one
Income Tax Contingency [Line Items]
Return basis, term	35 months
Minimum | Regulatory excess deferred taxes, to be returned, tranche two
Income Tax Contingency [Line Items]
Return basis, term	15 years
Maximum | Regulatory excess deferred taxes, to be returned, tranche one
Income Tax Contingency [Line Items]
Return basis, term	60 months
Maximum | Regulatory excess deferred taxes, to be returned, tranche two
Income Tax Contingency [Line Items]
Return basis, term	69 years

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

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