FAIR VALUE MEASUREMENTS - Quantitative Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Sep. 30, 2018
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Foreclosed Assets, net	$ 31,548	$ 31,638
Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Range of estimated selling cost	4.00%
Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Range of estimated selling cost	10.00%
Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	$ 0	0
Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	3,284,648	2,927,755
Impaired Loans [Member] | Level 3 [Member] | Valuation, Market Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	1,485	4,825
Foreclosed Assets [Member] | Level 3 [Member] | Valuation, Market Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	31,548	31,638
Nonrecurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	33,033	36,463
Nonrecurring [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	33,033	36,463
Nonrecurring [Member] | Finance Leases Portfolio Segment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		2,869
Nonrecurring [Member] | Finance Leases Portfolio Segment [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		0
Nonrecurring [Member] | Finance Leases Portfolio Segment [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		0
Nonrecurring [Member] | Finance Leases Portfolio Segment [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		2,869
Nonrecurring [Member] | Commercial Portfolio Segment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	1,485	4,825
Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	1,485	4,825
Nonrecurring [Member] | National Lending [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	1,485	4,825
Nonrecurring [Member] | National Lending [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | National Lending [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | National Lending [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	1,485	4,825
Nonrecurring [Member] | Agricultural Operating [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		4,825
Nonrecurring [Member] | Agricultural Operating [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		0
Nonrecurring [Member] | Agricultural Operating [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		0
Nonrecurring [Member] | Agricultural Operating [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value		4,825
Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	1,485
Nonrecurring [Member] | Impaired Loans [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0
Nonrecurring [Member] | Impaired Loans [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0
Nonrecurring [Member] | Impaired Loans [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	1,485
Nonrecurring [Member] | Asset Based Lending [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	761	57
Nonrecurring [Member] | Asset Based Lending [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Asset Based Lending [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Asset Based Lending [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	761	57
Nonrecurring [Member] | Factoring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	724	1,899
Nonrecurring [Member] | Factoring [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Factoring [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	0	0
Nonrecurring [Member] | Factoring [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value	724	1,899
Nonrecurring [Member] | Foreclosed Assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Foreclosed Assets, net	31,548	31,638
Nonrecurring [Member] | Foreclosed Assets [Member] | Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Foreclosed Assets, net	0	0
Nonrecurring [Member] | Foreclosed Assets [Member] | Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Foreclosed Assets, net	0	0
Nonrecurring [Member] | Foreclosed Assets [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Foreclosed Assets, net	$ 31,548	$ 31,638