COMMITMENTS AND CONTINGENT LIABILITIES - SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) $ in Thousands	3 Months Ended
Dec. 31, 2018 USD ($)
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 91,200
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	567,482
2020	269,877
2021	200,087
2022	174,225
2023	154,380
Thereafter	666,085
Energy Services
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	430,169
2020	116,581
2021	55,558
2022	34,308
2023	23,887
Thereafter	6,898
Energy Services \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	361,898
2020	34,959
2021	11,382
2022	0
2023	0
Thereafter	0
Energy Services \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	23,503
2020	21,011
2021	13,866
2022	9,229
2023	4,433
Thereafter	1,339
Energy Services \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	44,768
2020	60,611
2021	30,310
2022	25,079
2023	19,454
Thereafter	$ 5,559
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	$ 137,313
2020	153,296
2021	144,529
2022	139,917
2023	130,493
Thereafter	659,187
Natural Gas Distribution \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	46,150
2020	38,422
2021	33,861
2022	34,460
2023	35,278
Thereafter	37,067
Natural Gas Distribution \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	25,402
2020	27,318
2021	14,251
2022	12,930
2023	7,899
Thereafter	6,066
Natural Gas Distribution \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2019	65,761
2020	87,556
2021	96,417
2022	92,527
2023	87,316
Thereafter	$ 616,054

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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