SHAREHOLDERS' EQUITY - AOCI Components (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
After-tax amounts:
Accumulated other comprehensive income (loss)	$ (12,072)	$ 16,550
Unrealized Appreciation on Equity Securities
Pre-tax amounts:
Accumulated other comprehensive income (loss) before tax		44,023
After-tax amounts:
Accumulated other comprehensive income (loss)		29,071
Defined Benefit Pension Plan
Pre-tax amounts:
Accumulated other comprehensive income (loss) before tax	(21,109)	(21,693)
After-tax amounts:
Accumulated other comprehensive income (loss)	(12,072)	(12,521)
Accumulated Other Comprehensive Income
Pre-tax amounts:
Accumulated other comprehensive income (loss) before tax	(21,109)	22,330
After-tax amounts:
Accumulated other comprehensive income (loss)	$ (12,072)	$ 16,550