COMMITMENTS AND CONTINGENT LIABILITIES - SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) $ in Thousands	9 Months Ended
Jun. 30, 2021 USD ($)
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 157,500
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	396,110
2022	229,771
2023	194,456
2024	196,554
2025	181,273
Thereafter	1,474,287
Energy Services
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	214,837
2022	60,013
2023	35,818
2024	30,384
2025	26,732
Thereafter	41,898
Energy Services \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	134,318
2022	0
2023	0
2024	0
2025	0
Thereafter	0
Energy Services \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	22,028
2022	13,610
2023	7,044
2024	4,524
2025	3,151
Thereafter	1,148
Energy Services \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	58,491
2022	46,403
2023	28,774
2024	25,860
2025	23,581
Thereafter	40,750
Annual pipeline obligation to be paid over 10 year period	4,000
Natural Gas Distribution
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	181,273
2022	169,758
2023	158,638
2024	166,170
2025	154,541
Thereafter	1,432,389
Natural Gas Distribution \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	23,788
2022	0
2023	0
2024	0
2025	0
Thereafter	0
Natural Gas Distribution \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	37,285
2022	33,026
2023	15,695
2024	9,181
2025	1,966
Thereafter	2,184
Natural Gas Distribution \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2021	120,200
2022	136,732
2023	142,943
2024	156,989
2025	152,575
Thereafter	$ 1,430,205
Minimum \| Energy Services
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	1 year
Maximum \| Energy Services
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	10 years

Current Charges Recoverable Through Basic Gas Supply Service as shown for the reporting period

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Purchase Obligation, To Be Paid, After Year Four

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Recorded Unconditional Purchase Obligation, To Be Paid Annual By Counterparty Over 10 Year Period

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Storage and Pipeline Capacity, Term of Contract

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Amount of purchase arrangement to be paid in fourth fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of purchase arrangement to be paid in second fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of purchase arrangement to be paid in third fiscal year following current fiscal year. Includes, but is not limited to, recorded and unrecorded purchase obligations, long-term purchase commitment, and short-term purchase commitment. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of recorded unconditional purchase obligation to be paid in remainder of current fiscal year.

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