LOANS AND LEASES RECEIVABLE, NET - Past Due Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Past Due [Line Items]
Total gross loans and leases	$ 3,658,847	$ 2,944,739
Impaired financing receivable, interest income, accrual method	560	160
National Lending
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	433	0
National Lending | Asset Based Lending
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	344	0
National Lending | Factoring
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	5	0
National Lending | Lease financing
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	17	0
National Lending | Commercial Operating
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	366	0
National Lending | Other Consumer Finance
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	67	0
National Lending | Consumer
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	67	0
National Lending | SBA/USDA
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	0	0
Community Banking
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	127	160
Community Banking | Commercial and Multi-Family Real Estate
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	14	19
Community Banking | 1-4 Family Real Estate
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	6	14
Community Banking | Agricultural operating loans
Financing Receivable, Past Due [Line Items]
Impaired financing receivable, interest income, accrual method	107	127
Accruing and Non-accruing Loans and Lease
Financing Receivable, Past Due [Line Items]
Total past due	40,825
Current	3,759,365
Total gross loans and leases	3,800,190
Accruing and Non-accruing Loans and Lease | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	9,157
Accruing and Non-accruing Loans and Lease | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	7,242
Accruing and Non-accruing Loans and Lease | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	24,426
Accruing and Non-accruing Loans and Lease | Loans Held for Investment
Financing Receivable, Past Due [Line Items]
Total past due	37,984	38,851
Current	3,613,429	2,906,138
Total gross loans and leases	3,651,413	2,944,989
Accruing and Non-accruing Loans and Lease | Loans Held for Investment | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	8,035	24,022
Accruing and Non-accruing Loans and Lease | Loans Held for Investment | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	6,487	5,297
Accruing and Non-accruing Loans and Lease | Loans Held for Investment | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	23,462	9,532
Accruing and Non-accruing Loans and Lease | National Lending
Financing Receivable, Past Due [Line Items]
Total past due	36,903	38,667
Current	2,412,689	1,807,616
Total gross loans and leases	2,449,592	1,846,283
Accruing and Non-accruing Loans and Lease | National Lending | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	6,963	23,917
Accruing and Non-accruing Loans and Lease | National Lending | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	6,487	5,297
Accruing and Non-accruing Loans and Lease | National Lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	23,453	9,453
Accruing and Non-accruing Loans and Lease | National Lending | Loans Held for Sale
Financing Receivable, Past Due [Line Items]
Total past due	2,841
Current	145,936
Total gross loans and leases	148,777
Accruing and Non-accruing Loans and Lease | National Lending | Loans Held for Sale | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,122
Accruing and Non-accruing Loans and Lease | National Lending | Loans Held for Sale | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	755
Accruing and Non-accruing Loans and Lease | National Lending | Loans Held for Sale | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	964
Accruing and Non-accruing Loans and Lease | National Lending | Asset Based Lending
Financing Receivable, Past Due [Line Items]
Total past due	12,123	3,480
Current	676,397	474,437
Total gross loans and leases	688,520	477,917
Accruing and Non-accruing Loans and Lease | National Lending | Asset Based Lending | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	109	1,235
Accruing and Non-accruing Loans and Lease | National Lending | Asset Based Lending | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	243	2,151
Accruing and Non-accruing Loans and Lease | National Lending | Asset Based Lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	11,771	94
Accruing and Non-accruing Loans and Lease | National Lending | Factoring
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	296,507	284,221
Total gross loans and leases	296,507	284,221
Accruing and Non-accruing Loans and Lease | National Lending | Factoring | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Factoring | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Factoring | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Lease financing
Financing Receivable, Past Due [Line Items]
Total past due	9,077	19,995
Current	372,525	245,320
Total gross loans and leases	381,602	265,315
Accruing and Non-accruing Loans and Lease | National Lending | Lease financing | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	3,213	16,542
Accruing and Non-accruing Loans and Lease | National Lending | Lease financing | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,801	532
Accruing and Non-accruing Loans and Lease | National Lending | Lease financing | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	4,063	2,921
Accruing and Non-accruing Loans and Lease | National Lending | Commercial Operating
Financing Receivable, Past Due [Line Items]
Total past due	30,225	30,406
Current	1,886,005	1,479,443
Total gross loans and leases	1,916,230	1,509,849
Accruing and Non-accruing Loans and Lease | National Lending | Commercial Operating | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	5,404	20,708
Accruing and Non-accruing Loans and Lease | National Lending | Commercial Operating | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	4,925	3,702
Accruing and Non-accruing Loans and Lease | National Lending | Commercial Operating | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	19,896	5,996
Accruing and Non-accruing Loans and Lease | National Lending | Consumer Credit Products
Financing Receivable, Past Due [Line Items]
Total past due	1,423	963
Current	105,371	79,642
Total gross loans and leases	106,794	80,605
Accruing and Non-accruing Loans and Lease | National Lending | Consumer Credit Products | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	627	532
Accruing and Non-accruing Loans and Lease | National Lending | Consumer Credit Products | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	557	284
Accruing and Non-accruing Loans and Lease | National Lending | Consumer Credit Products | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	239	147
Accruing and Non-accruing Loans and Lease | National Lending | Other Consumer Finance
Financing Receivable, Past Due [Line Items]
Total past due	3,015	6,225
Current	158,389	183,531
Total gross loans and leases	161,404	189,756
Accruing and Non-accruing Loans and Lease | National Lending | Other Consumer Finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	932	2,677
Accruing and Non-accruing Loans and Lease | National Lending | Other Consumer Finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,005	1,311
Accruing and Non-accruing Loans and Lease | National Lending | Other Consumer Finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	1,078	2,237
Accruing and Non-accruing Loans and Lease | National Lending | Consumer
Financing Receivable, Past Due [Line Items]
Total past due	4,438	7,188
Current	263,760	263,173
Total gross loans and leases	268,198	270,361
Accruing and Non-accruing Loans and Lease | National Lending | Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,559	3,209
Accruing and Non-accruing Loans and Lease | National Lending | Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,562	1,595
Accruing and Non-accruing Loans and Lease | National Lending | Consumer | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	1,317	2,384
Accruing and Non-accruing Loans and Lease | National Lending | Tax Services
Financing Receivable, Past Due [Line Items]
Total past due	2,240	1,073
Current	0	0
Total gross loans and leases	2,240	1,073
Accruing and Non-accruing Loans and Lease | National Lending | Tax Services | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Tax Services | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Tax Services | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	2,240	1,073
Accruing and Non-accruing Loans and Lease | National Lending | Warehouse Agreement Borrowings
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	262,924	65,000
Total gross loans and leases	262,924	65,000
Accruing and Non-accruing Loans and Lease | National Lending | Warehouse Agreement Borrowings | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Warehouse Agreement Borrowings | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Warehouse Agreement Borrowings | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Premium Finance
Financing Receivable, Past Due [Line Items]
Total past due	8,687	5,864
Current	352,418	332,013
Total gross loans and leases	361,105	337,877
Accruing and Non-accruing Loans and Lease | National Lending | Premium Finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,999	1,864
Accruing and Non-accruing Loans and Lease | National Lending | Premium Finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	2,881	1,019
Accruing and Non-accruing Loans and Lease | National Lending | Premium Finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	3,807	2,981
Accruing and Non-accruing Loans and Lease | National Lending | SBA/USDA
Financing Receivable, Past Due [Line Items]
Total past due	338	1,067
Current	88,493	58,307
Total gross loans and leases	88,831	59,374
Accruing and Non-accruing Loans and Lease | National Lending | SBA/USDA | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	83	1,067
Accruing and Non-accruing Loans and Lease | National Lending | SBA/USDA | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | SBA/USDA | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	255	0
Accruing and Non-accruing Loans and Lease | National Lending | Other Commercial Finance
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	99,665	85,145
Total gross loans and leases	99,665	85,145
Accruing and Non-accruing Loans and Lease | National Lending | Other Commercial Finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Other Commercial Finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | National Lending | Other Commercial Finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | Community Banking
Financing Receivable, Past Due [Line Items]
Total past due	1,081	184
Current	1,200,740	1,098,522
Total gross loans and leases	1,201,821	1,098,706
Accruing and Non-accruing Loans and Lease | Community Banking | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,072	105
Accruing and Non-accruing Loans and Lease | Community Banking | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | Community Banking | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	9	79
Accruing and Non-accruing Loans and Lease | Community Banking | Commercial and Multi-Family Real Estate
Financing Receivable, Past Due [Line Items]
Total past due	565	0
Current	883,367	790,890
Total gross loans and leases	883,932	790,890
Accruing and Non-accruing Loans and Lease | Community Banking | Commercial and Multi-Family Real Estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	565	0
Accruing and Non-accruing Loans and Lease | Community Banking | Commercial and Multi-Family Real Estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | Community Banking | Commercial and Multi-Family Real Estate | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | Community Banking | 1-4 Family Real Estate
Financing Receivable, Past Due [Line Items]
Total past due	467	184
Current	258,958	247,134
Total gross loans and leases	259,425	247,318
Accruing and Non-accruing Loans and Lease | Community Banking | 1-4 Family Real Estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	458	105
Accruing and Non-accruing Loans and Lease | Community Banking | 1-4 Family Real Estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | Community Banking | 1-4 Family Real Estate | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	9	79
Accruing and Non-accruing Loans and Lease | Community Banking | Agricultural operating loans
Financing Receivable, Past Due [Line Items]
Total past due	49	0
Current	58,415	60,498
Total gross loans and leases	58,464	60,498
Accruing and Non-accruing Loans and Lease | Community Banking | Agricultural operating loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	49	0
Accruing and Non-accruing Loans and Lease | Community Banking | Agricultural operating loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Accruing and Non-accruing Loans and Lease | Community Banking | Agricultural operating loans | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Non-performing Loans and Leases
Financing Receivable, Past Due [Line Items]
Non-accrual loans	14,422
Total gross loans and leases	26,521
Non-performing Loans and Leases | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	12,099
Non-performing Loans and Leases | Loans Held for Investment
Financing Receivable, Past Due [Line Items]
Non-accrual loans	14,422	2,864
Total gross loans and leases	25,557	10,201
Non-performing Loans and Leases | Loans Held for Investment | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	11,135	7,337
Non-performing Loans and Leases | National Lending
Financing Receivable, Past Due [Line Items]
Non-accrual loans	14,378	2,864
Total gross loans and leases	25,513	10,122
Non-performing Loans and Leases | National Lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	11,135	7,258
Non-performing Loans and Leases | National Lending | Loans Held for Sale
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0
Total gross loans and leases	964
Non-performing Loans and Leases | National Lending | Loans Held for Sale | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	964
Non-performing Loans and Leases | National Lending | Asset Based Lending
Financing Receivable, Past Due [Line Items]
Non-accrual loans	11,332	0
Total gross loans and leases	11,814	94
Non-performing Loans and Leases | National Lending | Asset Based Lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	482	94
Non-performing Loans and Leases | National Lending | Factoring
Financing Receivable, Past Due [Line Items]
Non-accrual loans	1,669	0
Total gross loans and leases	1,669	0
Non-performing Loans and Leases | National Lending | Factoring | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Non-performing Loans and Leases | National Lending | Lease financing
Financing Receivable, Past Due [Line Items]
Non-accrual loans	1,122	2,864
Total gross loans and leases	4,411	3,590
Non-performing Loans and Leases | National Lending | Lease financing | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	3,289	726
Non-performing Loans and Leases | National Lending | Commercial Operating
Financing Receivable, Past Due [Line Items]
Non-accrual loans	14,378	2,864
Total gross loans and leases	21,956	6,665
Non-performing Loans and Leases | National Lending | Commercial Operating | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	7,578	3,801
Non-performing Loans and Leases | National Lending | Consumer Credit Products
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	239	147
Non-performing Loans and Leases | National Lending | Consumer Credit Products | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	239	147
Non-performing Loans and Leases | National Lending | Other Consumer Finance
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	1,078	2,237
Non-performing Loans and Leases | National Lending | Other Consumer Finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	1,078	2,237
Non-performing Loans and Leases | National Lending | Consumer
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	1,317	2,384
Non-performing Loans and Leases | National Lending | Consumer | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	1,317	2,384
Non-performing Loans and Leases | National Lending | Tax Services
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	2,240	1,073
Non-performing Loans and Leases | National Lending | Tax Services | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	2,240	1,073
Non-performing Loans and Leases | National Lending | Warehouse Agreement Borrowings
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	0	0
Non-performing Loans and Leases | National Lending | Warehouse Agreement Borrowings | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Non-performing Loans and Leases | National Lending | Premium Finance
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	3,807	2,981
Non-performing Loans and Leases | National Lending | Premium Finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	3,807	2,981
Non-performing Loans and Leases | National Lending | SBA/USDA
Financing Receivable, Past Due [Line Items]
Non-accrual loans	255	0
Total gross loans and leases	255	0
Non-performing Loans and Leases | National Lending | SBA/USDA | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Non-performing Loans and Leases | National Lending | Other Commercial Finance
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	0	0
Non-performing Loans and Leases | National Lending | Other Commercial Finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Non-performing Loans and Leases | Community Banking
Financing Receivable, Past Due [Line Items]
Non-accrual loans	44	0
Total gross loans and leases	44	79
Non-performing Loans and Leases | Community Banking | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	79
Non-performing Loans and Leases | Community Banking | Commercial and Multi-Family Real Estate
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	0	0
Non-performing Loans and Leases | Community Banking | Commercial and Multi-Family Real Estate | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Non-performing Loans and Leases | Community Banking | 1-4 Family Real Estate
Financing Receivable, Past Due [Line Items]
Non-accrual loans	44	0
Total gross loans and leases	44	79
Non-performing Loans and Leases | Community Banking | 1-4 Family Real Estate | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	79
Non-performing Loans and Leases | Community Banking | Agricultural operating loans
Financing Receivable, Past Due [Line Items]
Non-accrual loans	0	0
Total gross loans and leases	0	0
Non-performing Loans and Leases | Community Banking | Agricultural operating loans | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual loans	$ 0	$ 0