LOANS AND LEASES RECEIVABLE, NET - Summary of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Aug. 01, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	$ 3,651,413	$ 2,944,989
Net deferred loan origination fees (costs)	7,434	(250)
Total gross loans and leases	3,658,847	2,944,739
Allowance for Loan Losses	(29,149)	(13,040)
Total Loans Receivable, Net	3,629,698	2,931,699
Interest rate mark discounts	700
National Lending
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	2,449,592	1,846,283
National Lending | Asset Based Lending
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	688,520	477,917
National Lending | Factoring
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	296,507	284,221
National Lending | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	381,602	265,315
National Lending | Premium Finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	361,105	337,877
National Lending | SBA/USDA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	88,831	59,374
National Lending | Other Commercial Finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	99,665	85,145
National Lending | Commercial Operating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	1,916,230	1,509,849
National Lending | Consumer Credit Products
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	106,794	80,605
National Lending | Other Consumer Finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	161,404	189,756
National Lending | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	268,198	270,361
National Lending | Tax Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	2,240	1,073
National Lending | Warehouse Agreement Borrowings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	262,924	65,000
Community Banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	1,201,821	1,098,706
Community Banking | Commercial and Multi-Family Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	883,932	790,890
Community Banking | 1-4 Family Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	259,425	247,318
Community Banking | Agricultural operating loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans and leases receivable	58,464	$ 60,498
Crestmark Bancorp, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables acquired	312,500
Credit discounts	5,600		$ 12,300
Interest rate mark discounts	$ 2,600		6,000
Gross contractual amount			$ 1,060,000