COMMITMENTS AND CONTINGENT LIABILITIES - SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) $ in Thousands	9 Months Ended
Jun. 30, 2020 USD ($)
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 125,700
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	390,340
2021	211,831
2022	173,022
2023	129,053
2024	108,389
Thereafter	618,045
Energy Services
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	251,378
2021	69,838
2022	43,184
2023	26,427
2024	19,336
Thereafter	41,535
Energy Services \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	161,351
2021	1,264
2022	0
2023	0
2024	0
Thereafter	0
Energy Services \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	23,483
2021	12,975
2022	10,116
2023	4,063
2024	2,173
Thereafter	1,329
Energy Services \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	66,544
2021	55,599
2022	33,068
2023	22,364
2024	17,163
Thereafter	40,206
Natural Gas Distribution
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	138,962
2021	141,993
2022	129,838
2023	102,626
2024	89,053
Thereafter	576,510
Natural Gas Distribution \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	13,273
2021	0
2022	0
2023	0
2024	0
Thereafter	0
Natural Gas Distribution \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	36,062
2021	34,483
2022	23,424
2023	13,409
2024	9,154
Thereafter	4,077
Natural Gas Distribution \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2020	89,627
2021	107,510
2022	106,414
2023	89,217
2024	79,899
Thereafter	$ 572,433
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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Storage and Pipeline Capacity, Term of Contract

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Minimum amount of purchase arrangement maturing after the fifth fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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Minimum amount of purchase arrangement maturing in the fourth fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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Minimum amount of purchase arrangement maturing in the next fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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Minimum amount of purchase arrangement maturing in the second fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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Minimum amount of purchase arrangement maturing in the third fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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