COMMITMENTS AND CONTINGENT LIABILITIES - SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) $ in Thousands	6 Months Ended
Mar. 31, 2019 USD ($)
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 63,800
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	378,193
2020	366,341
2021	230,054
2022	181,129
2023	159,346
Thereafter	669,927
Energy Services
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	263,496
2020	194,521
2021	66,551
2022	36,560
2023	26,139
Thereafter	8,023
Energy Services \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	212,509
2020	98,677
2021	12,253
2022	0
2023	0
Thereafter	0
Energy Services \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	16,112
2020	26,227
2021	15,648
2022	11,749
2023	6,953
Thereafter	2,599
Energy Services \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	34,875
2020	69,617
2021	38,650
2022	24,811
2023	19,186
Thereafter	$ 5,424
Energy Services \| Minimum
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	1 year
Energy Services \| Maximum
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	10 years
Natural Gas Distribution
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	$ 114,697
2020	171,820
2021	163,503
2022	144,569
2023	133,207
Thereafter	661,904
Natural Gas Distribution \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	50,881
2020	44,346
2021	34,879
2022	34,844
2023	35,939
Thereafter	38,281
Natural Gas Distribution \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	18,400
2020	33,881
2021	24,162
2022	15,696
2023	9,037
Thereafter	6,613
Natural Gas Distribution \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	45,416
2020	93,593
2021	104,462
2022	94,029
2023	88,231
Thereafter	$ 617,010

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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