INCOME TAXES - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Provision at statutory rate			$ 27,899	$ 19,271
Tax-exempt income			(362)	(486)
State income taxes			5,543	4,135
Interim period effective rate adjustment			(3,870)	(3,116)
Tax credit investments, net - federal			(5,978)	(15,464)
Research tax credit			(355)	(323)
IRC 162(m) nondeductible compensation			505	487
Other, net			(1,104)	161
Income tax expense	$ 8,002	$ 1,133	$ 22,278	$ 4,665
Effective tax rate			16.66%	4.97%

Effective Income Tax Rate Reconciliation, IRC 162(m) Nondeductible Compensation

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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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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to state and local income tax expense (benefit).

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income (loss) exempt from income taxes.

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