INCOME TAXES - INCOME TAX RECONCILIATION (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory income tax expense	$ 73,735	$ 31,747	$ 41,896
Change resulting from:
Investment/production tax credits	(300)	(322)	(322)
Cost of removal of assets placed in service prior to 1981	(3,533)	(5,366)	(5,362)
AFUDC equity	(2,361)	(786)	(4,933)
State income taxes, net of federal benefit	13,072	6,124	11,965
NJ Unitary method change	0	0	(15,345)
Valuation allowance	(1,372)	5,974	13,604
Tax Act - utility excess deferred income taxes amortized	(3,573)	(3,573)	(3,573)
Other	527	(512)	(1,436)
Income tax provision	$ 76,195	$ 33,286	$ 36,494
Effective income tax rate	21.70%	22.00%	18.30%

Effective Income Tax Rate Reconciliation, Equity In Allowance For Funds Used During Construction

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Effective Income Tax Rate Reconciliation, Tax Act, Utility Excess Deferred Income Taxes Amortized

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

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