SHORT TERM DEBT AND LONG TERM DEBT SHORT TERM DEBT AND LONG TERM DEBT - Short Term Debt (Details)	12 Months Ended
	Sep. 30, 2018 USD ($) Lease	Sep. 30, 2017 USD ($)
Short-term Debt [Line Items]
Short-term debt	$ 425,759,000	$ 1,404,534,000
Pledged securities against specific FHLB advances, fair value	1,060,000,000	1,070,000,000
Loans pledged as collateral	$ 756,000,000	628,000,000
Number of capital leases | Lease	3
Number of equipment leases | Lease	2
Number of property leases | Lease	1
Leases, current	$ 64,818
Securities sold under agreements to repurchase, total	3,700,000	2,500,000
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Abstract]
Highest month-end balance	3,740,000	3,782,000
Average balance	$ 2,557,000	$ 2,225,000
Weighted average interest rate for the year	2.05%	0.98%
Weighted average interest rate at year end	2.48%	1.59%
Securities pledged as collateral for securities sold under agreement to repurchase, fair value	$ 13,900,000	$ 9,300,000
Overnight federal funds purchased [Member]
Short-term Debt [Line Items]
Short-term debt	422,000,000	987,000,000
Short-term FHLB advances [Member]
Short-term Debt [Line Items]
Short-term debt	0	415,000,000
Short-term capital lease [Member]
Short-term Debt [Line Items]
Short-term debt	65,000	62,000
Repurchase agreements [Member]
Short-term Debt [Line Items]
Short-term debt	$ 3,694,000	$ 2,472,000