LOANS RECEIVABLE, NET - Past Due Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	$ 44,376	$ 3,226
Current	1,281,771	922,585
Non-accrual loans	685	83
Total loans receivable	1,326,832	925,894
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	4,391	1,549
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	3,079	659
Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	36,906	1,018
1-4 Family Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	449	30
Current	196,257	162,185
Non-accrual loans	0	83
Total loans receivable	196,706	162,298
1-4 Family Real Estate [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	370	0
1-4 Family Real Estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	79	30
1-4 Family Real Estate [Member] | Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Commercial and Multi-Family Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Current	584,825	422,932
Non-accrual loans	685	0
Total loans receivable	585,510	422,932
Commercial and Multi-Family Real Estate [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Commercial and Multi-Family Real Estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Commercial and Multi-Family Real Estate [Member] | Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	34,198	0
Current	27,602	63,612
Non-accrual loans	0	0
Total loans receivable	61,800	63,612
Agricultural Real Estate [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Agricultural Real Estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Agricultural Real Estate [Member] | Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	34,198	0
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	4,476	53
Current	158,528	37,041
Non-accrual loans	0	0
Total loans receivable	163,004	37,094
Consumer [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	2,512	0
Consumer [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	558	0
Consumer [Member] | Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,406	53
Commercial Operating [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	505
Current	35,759	30,766
Non-accrual loans	0	0
Total loans receivable	35,759	31,271
Commercial Operating [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	151
Commercial Operating [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	354
Commercial Operating [Member] | Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Agricultural Operating [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	97	0
Current	33,497	37,083
Non-accrual loans	0	0
Total loans receivable	33,594	37,083
Agricultural Operating [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Agricultural Operating [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	0	0
Agricultural Operating [Member] | Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	97	0
Premium Finance [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	5,156	2,638
Current	245,303	168,966
Non-accrual loans	0	0
Total loans receivable	250,459	171,604
Premium Finance [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,509	1,398
Premium Finance [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	2,442	275
Premium Finance [Member] | Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	$ 1,205	$ 965