LOANS AND LEASES RECEIVABLE, NET - Allowance for Loan Losses and Recorded Investment in Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2019	Sep. 30, 2018
Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 13,040	$ 7,534	$ 5,635
Provision (recovery) for loan losses	55,650	29,433	10,589
Charge offs	(42,854)	(25,964)	(8,997)
Recoveries	3,313	2,037	307
Ending balance	29,149	13,040	7,534
Ending balance: individually evaluated for impairment				$ 1,875	$ 0
Ending balance: collectively evaluated for impairment				27,274	13,040
Total	13,040	13,040	7,534	29,149	13,040
Loans:
Ending balance: individually evaluated for impairment				33,639	15,611
Ending balance: collectively evaluated for impairment				3,617,774	2,929,378
Total gross loans and leases receivable				3,651,413	2,944,989
National Lending
Loans:
Total gross loans and leases receivable				2,449,592	1,846,283
National Lending | Asset Based Lending
Allowance for Credit Losses [Roll Forward]
Beginning balance	107	0
Provision (recovery) for loan losses	8,663	(249)
Charge offs	(2,486)	0
Recoveries	159	356
Ending balance	6,443	107	0
Ending balance: individually evaluated for impairment				443	0
Ending balance: collectively evaluated for impairment				6,000	107
Total	107	107	0	6,443	107
Loans:
Ending balance: individually evaluated for impairment				16,727	1,404
Ending balance: collectively evaluated for impairment				671,793	476,513
Total gross loans and leases receivable				688,520	477,917
National Lending | Factoring
Allowance for Credit Losses [Roll Forward]
Beginning balance	64	0
Provision (recovery) for loan losses	5,849	434
Charge offs	(2,725)	(821)
Recoveries	73	451
Ending balance	3,261	64	0
Ending balance: individually evaluated for impairment				1,262	0
Ending balance: collectively evaluated for impairment				1,999	64
Total	3,261	0	0	3,261	64
Loans:
Ending balance: individually evaluated for impairment				3,824	3,331
Ending balance: collectively evaluated for impairment				292,683	280,890
Total gross loans and leases receivable				296,507	284,221
National Lending | Lease financing
Allowance for Credit Losses [Roll Forward]
Beginning balance	59	0
Provision (recovery) for loan losses	4,009	147
Charge offs	(3,473)	(135)
Recoveries	2,207	47
Ending balance	2,802	59	0
Ending balance: individually evaluated for impairment				119	0
Ending balance: collectively evaluated for impairment				2,683	59
Total	2,802	0	0	2,802	59
Loans:
Ending balance: individually evaluated for impairment				4,432	8,877
Ending balance: collectively evaluated for impairment				377,170	256,438
Total gross loans and leases receivable				381,602	265,315
National Lending | Premium Finance
Allowance for Credit Losses [Roll Forward]
Beginning balance	1,031	796
Provision (recovery) for loan losses	2,361	998
Charge offs	(2,689)	(1,078)
Recoveries	321	315
Ending balance	1,024	1,031	796
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				1,024	1,031
Total	1,031	796	796	1,024	1,031
Loans:
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				361,105	337,877
Total gross loans and leases receivable				361,105	337,877
National Lending | SBA/USDA
Allowance for Credit Losses [Roll Forward]
Beginning balance	13	0
Provision (recovery) for loan losses	370	622
Charge offs	0	(609)
Recoveries	0	0
Ending balance	383	13	0
Ending balance: individually evaluated for impairment				51	0
Ending balance: collectively evaluated for impairment				332	13
Total	13	0	0	383	13
Loans:
Ending balance: individually evaluated for impairment				3,841	0
Ending balance: collectively evaluated for impairment				84,990	59,374
Total gross loans and leases receivable				88,831	59,374
National Lending | Other Commercial Finance
Allowance for Credit Losses [Roll Forward]
Beginning balance	28	4
Provision (recovery) for loan losses	655	24
Charge offs	0	0
Recoveries	0	0
Ending balance	683	28	4
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				683	28
Total	683	4	4	683	28
Loans:
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				99,665	85,145
Total gross loans and leases receivable				99,665	85,145
National Lending | Commercial Operating
Allowance for Credit Losses [Roll Forward]
Beginning balance	1,302	800
Provision (recovery) for loan losses	21,907	1,976
Charge offs	(11,373)	(2,643)
Recoveries	2,760	1,169
Ending balance	14,596	1,302	800
Ending balance: individually evaluated for impairment				1,875	0
Ending balance: collectively evaluated for impairment				12,721	1,302
Total	1,302	800	800	14,596	1,302
Loans:
Ending balance: individually evaluated for impairment				28,824	13,612
Ending balance: collectively evaluated for impairment				1,887,406	1,496,237
Total gross loans and leases receivable				1,916,230	1,509,849
National Lending | Consumer Credit Products
Allowance for Credit Losses [Roll Forward]
Beginning balance	785	0
Provision (recovery) for loan losses	259	785
Charge offs	0	0
Recoveries	0	0
Ending balance	1,044	785	0
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				1,044	785
Total	785	785	0	1,044	785
Loans:
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				106,794	80,605
Total gross loans and leases receivable				106,794	80,605
National Lending | Other Consumer Finance
Allowance for Credit Losses [Roll Forward]
Beginning balance	2,820	0
Provision (recovery) for loan losses	8,563	4,263
Charge offs	(6,346)	(1,443)
Recoveries	81	0
Ending balance	5,118	2,820	0
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				5,118	2,820
Total	2,820	2,820	0	5,118	2,820
Loans:
Ending balance: individually evaluated for impairment				1,472	0
Ending balance: collectively evaluated for impairment				159,932	189,756
Total gross loans and leases receivable				161,404	189,756
National Lending | Consumer
Allowance for Credit Losses [Roll Forward]
Beginning balance	3,605	0
Provision (recovery) for loan losses	8,822	5,048
Charge offs	(6,346)	(1,443)
Recoveries	81	0
Ending balance	6,162	3,605	0
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				6,162	3,605
Total	6,162	0	0	6,162	3,605
Loans:
Ending balance: individually evaluated for impairment				1,472	0
Ending balance: collectively evaluated for impairment				266,726	270,361
Total gross loans and leases receivable				268,198	270,361
National Lending | Tax Services
Allowance for Credit Losses [Roll Forward]
Beginning balance	0	5
Provision (recovery) for loan losses	24,873	21,344
Charge offs	(25,095)	(21,802)
Recoveries	222	453
Ending balance	0	0	5
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				0	0
Total	0	5	5	0	0
Loans:
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				2,240	1,073
Total gross loans and leases receivable				2,240	1,073
National Lending | Warehouse Agreement Borrowings
Allowance for Credit Losses [Roll Forward]
Beginning balance	65	0
Provision (recovery) for loan losses	198	65
Charge offs	0	0
Recoveries	0	0
Ending balance	263	65	0
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				263	65
Total	65	65	0	263	65
Loans:
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				262,924	65,000
Total gross loans and leases receivable				262,924	65,000
National Lending | National Lending
Allowance for Credit Losses [Roll Forward]
Beginning balance	4,972	805
Provision (recovery) for loan losses	55,800	28,433
Charge offs	(42,814)	(25,888)
Recoveries	3,063	1,622
Ending balance	21,021	4,972	805
Ending balance: individually evaluated for impairment				1,875	0
Ending balance: collectively evaluated for impairment				19,146	4,972
Total	4,972	4,972	805	21,021	4,972
Loans:
Ending balance: individually evaluated for impairment				30,296	13,612
Ending balance: collectively evaluated for impairment				2,419,296	1,832,671
Total gross loans and leases receivable				2,449,592	1,846,283
Community Banking
Allowance for Credit Losses [Roll Forward]
Beginning balance	8,068	6,203
Provision (recovery) for loan losses	(150)	1,527
Charge offs	(40)	(76)
Recoveries	250	414
Ending balance	8,128	8,068	6,203
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				8,128	8,068
Total	8,068	8,068	6,203	8,128	8,068
Loans:
Ending balance: individually evaluated for impairment				3,343	1,999
Ending balance: collectively evaluated for impairment				1,198,478	1,096,707
Total gross loans and leases receivable				1,201,821	1,098,706
Community Banking | Commercial and Multi-Family Real Estate
Allowance for Credit Losses [Roll Forward]
Beginning balance	6,220	2,820
Provision (recovery) for loan losses	(12)	3,400
Charge offs	0	0
Recoveries	0	0
Ending balance	6,208	6,220	2,820
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				6,208	6,220
Total	6,220	2,820	2,820	6,208	6,220
Loans:
Ending balance: individually evaluated for impairment				258	451
Ending balance: collectively evaluated for impairment				883,674	790,439
Total gross loans and leases receivable				883,932	790,890
Community Banking | 1-4 Family Real Estate
Allowance for Credit Losses [Roll Forward]
Beginning balance	632	809
Provision (recovery) for loan losses	461	(104)
Charge offs	(40)	(76)
Recoveries	0	3
Ending balance	1,053	632	809
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				1,053	632
Total	632	632	809	1,053	632
Loans:
Ending balance: individually evaluated for impairment				100	94
Ending balance: collectively evaluated for impairment				259,325	247,224
Total gross loans and leases receivable				259,425	247,318
Community Banking | Agricultural operating loans
Allowance for Credit Losses [Roll Forward]
Beginning balance	1,216	2,574
Provision (recovery) for loan losses	(599)	(1,769)
Charge offs	0	0
Recoveries	250	411
Ending balance	867	1,216	2,574
Ending balance: individually evaluated for impairment				0	0
Ending balance: collectively evaluated for impairment				867	1,216
Total	1,216	1,216	2,574	867	1,216
Loans:
Ending balance: individually evaluated for impairment				2,985	1,454
Ending balance: collectively evaluated for impairment				55,479	59,044
Total gross loans and leases receivable				$ 58,464	60,498
Unallocated
Allowance for Credit Losses [Roll Forward]
Beginning balance	0	527
Provision (recovery) for loan losses		(527)
Charge offs		0
Recoveries		0
Ending balance		0	527
Total	$ 0	$ 527	$ 527		$ 0