LOANS RECEIVABLE, NET - Asset Classification of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	$ 1,326,832	$ 925,894
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	1,265,560	876,194
Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	17,272	8,015
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	3,387	32,710
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	40,613	8,975
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
1-4 Family Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	196,706	162,298
1-4 Family Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	195,838	161,255
1-4 Family Real Estate [Member] | Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	525	200
1-4 Family Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	247	666
1-4 Family Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	96	177
1-4 Family Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial and Multi-Family Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	585,510	422,932
Commercial and Multi-Family Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	574,730	421,577
Commercial and Multi-Family Real Estate [Member] | Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	10,200	72
Commercial and Multi-Family Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	201	962
Commercial and Multi-Family Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	379	321
Commercial and Multi-Family Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	61,800	63,612
Agricultural Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	27,376	34,421
Agricultural Real Estate [Member] | Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	2,006	2,934
Agricultural Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	2,939	25,675
Agricultural Real Estate [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	29,479	582
Agricultural Real Estate [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	163,004	37,094
Consumer [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	163,004	37,094
Consumer [Member] | Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Consumer [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Consumer [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Consumer [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial Operating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	35,759	31,271
Commercial Operating [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	35,759	30,574
Commercial Operating [Member] | Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	184
Commercial Operating [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Commercial Operating [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	513
Commercial Operating [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Agricultural Operating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	33,594	37,083
Agricultural Operating [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	18,394	19,669
Agricultural Operating [Member] | Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	4,541	4,625
Agricultural Operating [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	5,407
Agricultural Operating [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	10,659	7,382
Agricultural Operating [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Premium Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	250,459	171,604
Premium Finance [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	250,459	171,604
Premium Finance [Member] | Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Premium Finance [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Premium Finance [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	0	0
Premium Finance [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans receivable	$ 0	$ 0