DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Derivatives, Fair Value [Line Items]
Asset Derivatives, current	$ 35,251	$ 23,310
Asset Derivatives, noncurrent	3,403	3,349
Liability Derivatives, current	87,145	33,865
Liability Derivatives, noncurrent	13,497	13,352
Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Asset Derivatives	38,654	26,659
Liability Derivatives	100,642	47,217
Derivatives not designated as hedging instruments: \| Physical commodity contracts \| Natural Gas Distribution
Derivatives, Fair Value [Line Items]
Asset Derivatives, current	36	78
Liability Derivatives, current	16	76
Derivatives not designated as hedging instruments: \| Physical commodity contracts \| Energy Services
Derivatives, Fair Value [Line Items]
Asset Derivatives, current	2,818	6,454
Asset Derivatives, noncurrent	333	1,264
Liability Derivatives, current	24,592	20,438
Liability Derivatives, noncurrent	13,237	12,003
Derivatives not designated as hedging instruments: \| Financial commodity contracts \| Natural Gas Distribution
Derivatives, Fair Value [Line Items]
Asset Derivatives, current	2,046	71
Liability Derivatives, current	13	282
Derivatives not designated as hedging instruments: \| Financial commodity contracts \| Energy Services
Derivatives, Fair Value [Line Items]
Asset Derivatives, current	30,226	16,671
Asset Derivatives, noncurrent	3,068	2,037
Liability Derivatives, current	62,521	12,965
Liability Derivatives, noncurrent	260	1,346
Derivatives not designated as hedging instruments: \| Foreign currency contracts \| Energy Services
Derivatives, Fair Value [Line Items]
Asset Derivatives, current	125	36
Asset Derivatives, noncurrent	2	48
Liability Derivatives, current	3	104
Liability Derivatives, noncurrent	$ 0	$ 3

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