INCOME TAXES - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Provision at statutory rate			$ 9,541	$ 11,857
Tax-exempt income			(1,824)	(3,728)
State income taxes			2,143	2,003
Interim period effective rate adjustment			(3,968)	(1,277)
Tax credit investments, net - federal			(9,568)	0
Tax Reform rate adjustment			0	3,635
IRC 162(m) nondeductible compensation			1,561	0
Other, net			29	(258)
Income tax expense	$ (395)	$ 6,548	$ (2,086)	$ 12,232
Effective tax rate			(4.40%)	25.31%

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

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Effective Income Tax Rate Reconciliation, Tax Credit, Tax Cuts and Jobs Act of 2017

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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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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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