LOANS AND LEASES, NET - Past Due Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Financing Receivable, Past Due [Line Items]
Loans and leases	$ 3,590,474	$ 3,658,847
Performing Financial Instruments
Financing Receivable, Past Due [Line Items]
Total past due	53,738	40,825
Current	3,793,983	3,759,365
Loans and leases	3,847,721	3,800,190
Performing Financial Instruments | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	26,861	9,157
Performing Financial Instruments | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	7,488	7,242
Performing Financial Instruments | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	19,389	24,426
Performing Financial Instruments | Loans Held for Investment
Financing Receivable, Past Due [Line Items]
Total past due	53,675	37,984
Current	3,529,622	3,613,429
Loans and leases	3,583,297	3,651,413
Performing Financial Instruments | Loans Held for Investment | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	26,798	8,035
Performing Financial Instruments | Loans Held for Investment | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	7,488	6,487
Performing Financial Instruments | Loans Held for Investment | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	19,389	23,462
Nonperforming Financial Instruments
Financing Receivable, Past Due [Line Items]
Loans and leases	23,983	26,521
Non-accrual balance	16,602	14,422
Nonperforming Financial Instruments | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	7,381	12,099
Nonperforming Financial Instruments | Loans Held for Investment
Financing Receivable, Past Due [Line Items]
Loans and leases	23,983	25,557
Non-accrual balance	16,602	14,422
Nonperforming Financial Instruments | Loans Held for Investment | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	7,381	11,135
National Lending | Performing Financial Instruments
Financing Receivable, Past Due [Line Items]
Total past due	51,678	36,903
Current	2,587,854	2,412,689
Loans and leases	2,639,532	2,449,592
National Lending | Performing Financial Instruments | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	26,422	6,963
National Lending | Performing Financial Instruments | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	5,876	6,487
National Lending | Performing Financial Instruments | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	19,380	23,453
National Lending | Performing Financial Instruments | Loans held for sale
Financing Receivable, Past Due [Line Items]
Total past due	63	2,841
Current	264,361	145,936
Loans and leases	264,424	148,777
National Lending | Performing Financial Instruments | Loans held for sale | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	63	1,122
National Lending | Performing Financial Instruments | Loans held for sale | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	755
National Lending | Performing Financial Instruments | Loans held for sale | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	964
National Lending | Performing Financial Instruments | Term lending
Financing Receivable, Past Due [Line Items]
Total past due	27,746	17,170
Current	667,601	624,572
Loans and leases	695,347	641,742
National Lending | Performing Financial Instruments | Term lending | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	12,300	2,162
National Lending | Performing Financial Instruments | Term lending | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	2,767	910
National Lending | Performing Financial Instruments | Term lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	12,679	14,098
National Lending | Performing Financial Instruments | Asset based lending
Financing Receivable, Past Due [Line Items]
Total past due	26	0
Current	250,607	250,465
Loans and leases	250,633	250,465
National Lending | Performing Financial Instruments | Asset based lending | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	26	0
National Lending | Performing Financial Instruments | Asset based lending | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Asset based lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Factoring
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	285,776	296,507
Loans and leases	285,776	296,507
National Lending | Performing Financial Instruments | Factoring | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Factoring | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Factoring | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Lease financing
Financing Receivable, Past Due [Line Items]
Total past due	6,408	4,030
Current	217,307	173,885
Loans and leases	223,715	177,915
National Lending | Performing Financial Instruments | Lease financing | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	3,757	1,160
National Lending | Performing Financial Instruments | Lease financing | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	758	1,134
National Lending | Performing Financial Instruments | Lease financing | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	1,893	1,736
National Lending | Performing Financial Instruments | Insurance premium finance
Financing Receivable, Past Due [Line Items]
Total past due	11,313	8,687
Current	337,986	352,418
Loans and leases	349,299	361,105
National Lending | Performing Financial Instruments | Insurance premium finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	7,065	1,999
National Lending | Performing Financial Instruments | Insurance premium finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,117	2,881
National Lending | Performing Financial Instruments | Insurance premium finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	3,131	3,807
National Lending | Performing Financial Instruments | SBA/USDA
Financing Receivable, Past Due [Line Items]
Total past due	1,008	338
Current	89,261	88,493
Loans and leases	90,269	88,831
National Lending | Performing Financial Instruments | SBA/USDA | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	979	83
National Lending | Performing Financial Instruments | SBA/USDA | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | SBA/USDA | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	29	255
National Lending | Performing Financial Instruments | Other commercial finance
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	99,617	99,665
Loans and leases	99,617	99,665
National Lending | Performing Financial Instruments | Other commercial finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Other commercial finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Other commercial finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Commercial finance
Financing Receivable, Past Due [Line Items]
Total past due	46,501	30,225
Current	1,948,155	1,886,005
Loans and leases	1,994,656	1,916,230
National Lending | Performing Financial Instruments | Commercial finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	24,127	5,404
National Lending | Performing Financial Instruments | Commercial finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	4,642	4,925
National Lending | Performing Financial Instruments | Commercial finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	17,732	19,896
National Lending | Performing Financial Instruments | Consumer credit products
Financing Receivable, Past Due [Line Items]
Total past due	1,701	1,423
Current	114,142	105,371
Loans and leases	115,843	106,794
National Lending | Performing Financial Instruments | Consumer credit products | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	953	627
National Lending | Performing Financial Instruments | Consumer credit products | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	430	557
National Lending | Performing Financial Instruments | Consumer credit products | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	318	239
National Lending | Performing Financial Instruments | Other consumer finance
Financing Receivable, Past Due [Line Items]
Total past due	3,476	3,015
Current	151,296	158,389
Loans and leases	154,772	161,404
National Lending | Performing Financial Instruments | Other consumer finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,342	932
National Lending | Performing Financial Instruments | Other consumer finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	804	1,005
National Lending | Performing Financial Instruments | Other consumer finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	1,330	1,078
National Lending | Performing Financial Instruments | Consumer finance
Financing Receivable, Past Due [Line Items]
Total past due	5,177	4,438
Current	265,438	263,760
Loans and leases	270,615	268,198
National Lending | Performing Financial Instruments | Consumer finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	2,295	1,559
National Lending | Performing Financial Instruments | Consumer finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,234	1,562
National Lending | Performing Financial Instruments | Consumer finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	1,648	1,317
National Lending | Performing Financial Instruments | Tax services
Financing Receivable, Past Due [Line Items]
Total past due	0	2,240
Current	101,739	0
Loans and leases	101,739	2,240
National Lending | Performing Financial Instruments | Tax services | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Tax services | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Tax services | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	2,240
National Lending | Performing Financial Instruments | Warehouse finance
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Current	272,522	262,924
Loans and leases	272,522	262,924
National Lending | Performing Financial Instruments | Warehouse finance | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Warehouse finance | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Performing Financial Instruments | Warehouse finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
National Lending | Nonperforming Financial Instruments
Financing Receivable, Past Due [Line Items]
Loans and leases	23,974	25,513
Non-accrual balance	16,593	14,378
National Lending | Nonperforming Financial Instruments | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	7,381	11,135
National Lending | Nonperforming Financial Instruments | Loans held for sale
Financing Receivable, Past Due [Line Items]
Loans and leases	0	964
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Loans held for sale | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	964
National Lending | Nonperforming Financial Instruments | Term lending
Financing Receivable, Past Due [Line Items]
Loans and leases	13,688	14,387
Non-accrual balance	12,372	12,146
National Lending | Nonperforming Financial Instruments | Term lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	1,316	2,241
National Lending | Nonperforming Financial Instruments | Asset based lending
Financing Receivable, Past Due [Line Items]
Loans and leases	583	0
Non-accrual balance	583	0
National Lending | Nonperforming Financial Instruments | Asset based lending | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Factoring
Financing Receivable, Past Due [Line Items]
Loans and leases	205	1,669
Non-accrual balance	205	1,669
National Lending | Nonperforming Financial Instruments | Factoring | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Lease financing
Financing Receivable, Past Due [Line Items]
Loans and leases	2,015	1,838
Non-accrual balance	729	308
National Lending | Nonperforming Financial Instruments | Lease financing | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	1,286	1,530
National Lending | Nonperforming Financial Instruments | Insurance premium finance
Financing Receivable, Past Due [Line Items]
Loans and leases	3,131	3,807
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Insurance premium finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	3,131	3,807
National Lending | Nonperforming Financial Instruments | SBA/USDA
Financing Receivable, Past Due [Line Items]
Loans and leases	2,704	255
Non-accrual balance	2,704	255
National Lending | Nonperforming Financial Instruments | SBA/USDA | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Other commercial finance
Financing Receivable, Past Due [Line Items]
Loans and leases	0	0
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Other commercial finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Commercial finance
Financing Receivable, Past Due [Line Items]
Loans and leases	22,326	21,956
Non-accrual balance	16,593	14,378
National Lending | Nonperforming Financial Instruments | Commercial finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	5,733	7,578
National Lending | Nonperforming Financial Instruments | Consumer credit products
Financing Receivable, Past Due [Line Items]
Loans and leases	318	239
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Consumer credit products | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	318	239
National Lending | Nonperforming Financial Instruments | Other consumer finance
Financing Receivable, Past Due [Line Items]
Loans and leases	1,330	1,078
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Other consumer finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	1,330	1,078
National Lending | Nonperforming Financial Instruments | Consumer finance
Financing Receivable, Past Due [Line Items]
Loans and leases	1,648	1,317
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Consumer finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	1,648	1,317
National Lending | Nonperforming Financial Instruments | Tax services
Financing Receivable, Past Due [Line Items]
Loans and leases	0	2,240
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Tax services | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	2,240
National Lending | Nonperforming Financial Instruments | Warehouse finance
Financing Receivable, Past Due [Line Items]
Loans and leases	0	0
Non-accrual balance	0	0
National Lending | Nonperforming Financial Instruments | Warehouse finance | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
Community Banking | Performing Financial Instruments
Financing Receivable, Past Due [Line Items]
Total past due	1,997	1,081
Current	941,768	1,200,740
Loans and leases	943,765	1,201,821
Community Banking | Performing Financial Instruments | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	376	1,072
Community Banking | Performing Financial Instruments | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,612	0
Community Banking | Performing Financial Instruments | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	9	9
Community Banking | Performing Financial Instruments | Commercial real estate and operating
Financing Receivable, Past Due [Line Items]
Total past due	0	565
Current	682,399	883,367
Loans and leases	682,399	883,932
Community Banking | Performing Financial Instruments | Commercial real estate and operating | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	565
Community Banking | Performing Financial Instruments | Commercial real estate and operating | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Community Banking | Performing Financial Instruments | Commercial real estate and operating | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Community Banking | Performing Financial Instruments | Consumer one to four family real estate and other
Financing Receivable, Past Due [Line Items]
Total past due	429	467
Current	220,159	258,958
Loans and leases	220,588	259,425
Community Banking | Performing Financial Instruments | Consumer one to four family real estate and other | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	346	458
Community Banking | Performing Financial Instruments | Consumer one to four family real estate and other | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	74	0
Community Banking | Performing Financial Instruments | Consumer one to four family real estate and other | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	9	9
Community Banking | Performing Financial Instruments | Agricultural real estate and operating
Financing Receivable, Past Due [Line Items]
Total past due	1,568	49
Current	39,210	58,415
Loans and leases	40,778	58,464
Community Banking | Performing Financial Instruments | Agricultural real estate and operating | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	30	49
Community Banking | Performing Financial Instruments | Agricultural real estate and operating | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	1,538	0
Community Banking | Performing Financial Instruments | Agricultural real estate and operating | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Community Banking | Nonperforming Financial Instruments
Financing Receivable, Past Due [Line Items]
Loans and leases	9	44
Non-accrual balance	9	44
Community Banking | Nonperforming Financial Instruments | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
Community Banking | Nonperforming Financial Instruments | Commercial real estate and operating
Financing Receivable, Past Due [Line Items]
Loans and leases	0	0
Non-accrual balance	0	0
Community Banking | Nonperforming Financial Instruments | Commercial real estate and operating | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
Community Banking | Nonperforming Financial Instruments | Consumer one to four family real estate and other
Financing Receivable, Past Due [Line Items]
Loans and leases	9	44
Non-accrual balance	9	44
Community Banking | Nonperforming Financial Instruments | Consumer one to four family real estate and other | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	0	0
Community Banking | Nonperforming Financial Instruments | Agricultural real estate and operating
Financing Receivable, Past Due [Line Items]
Loans and leases	0	0
Non-accrual balance	0	0
Community Banking | Nonperforming Financial Instruments | Agricultural real estate and operating | Greater Than 90 Days
Financing Receivable, Past Due [Line Items]
Non-accrual balance	$ 0	$ 0