FAIR VALUES OF FINANCIAL INSTRUMENTS - Quantitative Information (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Range of estimated selling cost (in hundredths)		4.00%
Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Range of estimated selling cost (in hundredths)		10.00%
Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value of Impaired Loans, Net and Foreclosed Assets, Net		$ 1,318,402	$ 926,803
Impaired Loans [Member] | Level 3 [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value of Impaired Loans, Net and Foreclosed Assets, Net		$ 0	68
Valuation techniques	[1]	Appraised values
Foreclosed Assets [Member] | Level 3 [Member] | Market Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value of Impaired Loans, Net and Foreclosed Assets, Net		$ 292	$ 76
Valuation techniques	[1]	Appraised values

[1] The Company generally relies on external appraisers to develop this information. Management reduced the appraised value by estimated selling costs in a range of 4% to 10%.