LOANS AND LEASES, NET - Summary of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018	Aug. 01, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	$ 3,435,016	$ 2,944,989
Allowance for loan and lease losses	(48,672)	(13,040)
Net Deferred Loan Origination Fees	2,964	(250)
Total Loans Receivable, Net	3,389,308	2,931,699
Financing Receivable | Asset based lending
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	572,210	477,917
Financing Receivable | Factoring
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	287,955	284,221
Financing Receivable | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	321,414	265,315
Financing Receivable | Insurance premium finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	307,875	337,877
Financing Receivable | SBA/USDA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	77,481	59,374
Financing Receivable | Other commercial finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	98,956	85,145
Financing Receivable | Commercial finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	1,665,891	1,509,849
Financing Receivable | Consumer credit products
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	139,617	80,605
Financing Receivable | Other consumer finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	170,824	189,756
Financing Receivable | Consumer finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	310,441	270,361
Financing Receivable | Tax services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	84,824	1,073
Financing Receivable | Warehouse finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	186,697	65,000
Financing Receivable | National Lending
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	2,247,853	1,846,283
Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	1,187,163	1,098,706
Loans Receivable | Commercial real estate and operating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	869,917	790,890
Loans Receivable | 1-4 Family Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	257,079	247,318
Loans Receivable | Agricultural real estate and operating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans Receivable	60,167	$ 60,498
Crestmark Bancorp, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables acquired	591,100
Acquired loans and leases from Crestmark acquisition			$ 1,060,000
Credit discounts	$ (8,700)		(12,300)
Interest rate mark discounts			$ (6,000)