SHAREHOLDERS' EQUITY - AOCI Components (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
After-tax amounts:
Accumulated other comprehensive income (loss)	$ 16,550	$ 2,300
Unrealized Appreciation on Available for sale Securities
Pre-tax amounts:
Accumulated other comprehensive income (loss) before tax	44,023	31,700	$ 33,051
After-tax amounts:
Accumulated other comprehensive income (loss)	29,071	20,070	20,899
Defined Benefit Pension Plan
Pre-tax amounts:
Accumulated other comprehensive income (loss) before tax	(21,693)	(28,873)	(34,112)
After-tax amounts:
Accumulated other comprehensive income (loss)	(12,521)	(17,770)	(21,103)
Accumulated Other Comprehensive (Loss) Income
Pre-tax amounts:
Accumulated other comprehensive income (loss) before tax	22,330	2,827	(1,061)
After-tax amounts:
Accumulated other comprehensive income (loss)	$ 16,550	$ 2,300	$ (204)