SHAREHOLDERS' EQUITY - AOCI Components (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018
After-tax amounts:
Accumulated other comprehensive income (loss)	$ (16,085)	$ 16,550
Unrealized Appreciation on Equity Securities
Pre-tax amounts:
Accumulated other comprehensive income (loss)	0	44,023
After-tax amounts:
Accumulated other comprehensive income (loss)	0	29,071
Defined Benefit Pension Plan
Pre-tax amounts:
Accumulated other comprehensive income (loss)	(20,818)	(21,693)
After-tax amounts:
Accumulated other comprehensive income (loss)	(16,085)	(12,521)
Accumulated Other Comprehensive Income (Loss)
Pre-tax amounts:
Accumulated other comprehensive income (loss)	(20,818)	22,330
After-tax amounts:
Accumulated other comprehensive income (loss)	$ (16,085)	$ 16,550