SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Assets of VIE's) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 126,545	$ 99,977	$ 1,267,586	$ 773,830
Loans and leases	3,658,847	2,944,739
Allowance for loan and lease losses	(29,149)	(13,040)
Accrued interest receivable	20,400	22,016
Foreclosed real estate and repossessed assets	29,494	31,638
Other assets	54,832	35,090
Total assets	6,182,890	5,835,067	$ 5,228,332
Accrued expenses and other liabilities	130,656	133,838
Noncontrolling interest	4,047	$ 3,574
VIE's Aggregated Disclosure
Variable Interest Entity [Line Items]
Cash and cash equivalents	2,064
Loans and leases	139,544
Allowance for loan and lease losses	(702)
Accrued interest receivable	763
Rental equipment	0
Foreclosed real estate and repossessed assets	1,372
Other assets	5,647
Total assets	148,688
Accrued expenses and other liabilities	3,258
Noncontrolling interest	4,047
Net assets less noncontrolling interest	$ 141,383