INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Federal:
Current	$ 5,278	$ (4,023)	$ 12,153
Deferred	(14,831)	5,895	(5,040)
Federal income tax expense	(9,553)	1,872	7,113
State:
Current	5,649	2,611	4,366
Deferred	530	634	(1,246)
State tax expense	6,179	3,245	3,120
Income tax (benefit) expense	(3,374)	5,117	10,233
Deferred tax assets:
Bad debts	6,805	3,224
Deferred compensation	1,626	3,495
Stock based compensation	4,296	3,758
Net unrealized losses on securities available for sale	0	10,663
Valuation adjustments	6,596	6,991
General business credits	27,935	12,243
Accrued expenses	3,767	3,144
Other assets	3,144	1,629
Gross deferred tax assets	54,169	45,147
Deferred tax liabilities:
Premises and equipment	(3,084)	(347)
Intangibles	(1,812)	(4,231)
Net unrealized gains on securities available for sale	(2,146)	0
Deferred income	(179)	(2,070)
Leased assets	(24,996)	(17,985)
Leased assets	(3,068)	(1,777)
Gross deferred tax liabilities	(35,285)	(26,410)
Net deferred tax assets	18,884	18,737
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense at federal tax rate	20,568	14,082	19,303
Change in tax rate resulting from:
State income taxes net of federal benefits	5,000	2,461	2,014
162(m) disallowance	$ 2,777	$ 0	$ 0
Effective Income Tax Rate Reconciliation, 162(m) Disallowance	2.80%	0.00%	0.00%
Tax exempt income	$ (2,714)	$ (6,968)	$ (9,991)
Nondeductible acquisition costs	0	1,295	0
General business credits	(27,126)	(3,948)	0
Tax reform	0	3,849	0
Amended Crestmark Bancorp historical tax return	0	(4,644)	0
Other, net	(1,879)	(1,010)	(1,093)
Income tax (benefit) expense	$ (3,374)	$ 5,117	$ 10,233
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory federal income tax expense and rate (percent)	21.00%	24.50%	35.00%
State income taxes net of federal benefits (percent)	5.10%	4.30%	3.70%
Tax exempt income (percent)	(2.80%)	(12.10%)	(18.10%)
Nondeductible acquisition costs (percent)	0.00%	2.30%	0.00%
General business credits (percent)	(27.70%)	(6.90%)	0.00%
Tax Reform (percent)	0.00%	6.70%	0.00%
Amended Crestmark Bancorp historical tax return (percent)	0.00%	(8.10%)	0.00%
Other, net (percent)	(1.80%)	(1.70%)	(2.00%)
Total income tax expense (percent)	(3.40%)	9.00%	18.60%
Gross deferred tax on state net operating loss carryforwards	$ 2,000	$ 2,000
Operating loss carryforwards reserved	2,000	1,600
Tax credit, investment, amount	27,100	4,000	$ 0
Reconciliation for liabilities [Abstract]
Balance at beginning of fiscal year	434	645
Reductions for tax positions related to prior years	(66)	(211)
Balance at end of fiscal year	368	$ 434	$ 645
Unrecognized tax benefits that, if recognized, would impact the effective rate	291
Accrued interest related to unrecognized tax benefits	$ 77