EMPLOYEE BENEFIT PLANS - SUMMARY OF CHANGE IN FUNDED STATUS AND LIABILITIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Postemployment employee benefit liability
Noncurrent	$ (82,867)	$ (169,267)
Pension
Change in Benefit Obligation
Benefit obligation at beginning of year	395,547	397,164
Service cost	8,291	8,730	$ 8,223
Interest cost	9,632	9,112	10,587
Plan participants’ contributions	59	27
Actuarial (gain)	(109,320)	(7,319)
Benefits paid, net of retiree subsidies received	(13,386)	(12,167)
Benefit obligation at end of year	290,823	395,547	397,164
Change in plan assets
Fair value of plan assets at beginning of year	355,284	307,968
Actual (loss) return on plan assets	(58,239)	58,874
Employer contributions	628	548
Benefits paid, net of plan participants’ contributions	(13,326)	(12,106)
Fair value of plan assets at end of year	284,347	355,284	307,968
Funded status	(6,476)	(40,263)
Postemployment employee benefit asset
Noncurrent	4,388	0
Postemployment employee benefit liability
Current	(578)	(587)
Noncurrent	(10,286)	(39,676)
Total	(6,476)	(40,263)
OPEB
Change in Benefit Obligation
Benefit obligation at beginning of year	244,674	245,862
Service cost	4,305	4,844	4,854
Interest cost	6,355	6,071	7,026
Plan participants’ contributions	423	451
Actuarial (gain)	(77,775)	(4,715)
Benefits paid, net of retiree subsidies received	(4,765)	(7,839)
Benefit obligation at end of year	173,217	244,674	245,862
Change in plan assets
Fair value of plan assets at beginning of year	114,183	96,406
Actual (loss) return on plan assets	(15,996)	18,144
Employer contributions	6,082	7,198
Benefits paid, net of plan participants’ contributions	(4,533)	(7,565)
Fair value of plan assets at end of year	99,736	114,183	$ 96,406
Funded status	(73,481)	(130,491)
Postemployment employee benefit asset
Noncurrent	0	0
Postemployment employee benefit liability
Current	(900)	(900)
Noncurrent	(72,581)	(129,591)
Total	$ (73,481)	$ (130,491)