REVENUE - DISAGGREGATED REVENUE - TYPE (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 364,551	$ 284,090
Revenues out of scope	359,016	391,752
Total operating revenues	723,567	675,842
Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	234,411	168,055
Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	103,043	91,068
Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	26,199	22,675
Interruptible and off-tariff
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	898	2,292
Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenues	719,158	666,342
Home Services and Other
Disaggregation of Revenue [Line Items]
Revenues out of scope	0	0
Total operating revenues	14,253	13,852
Home Services and Other \| Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	14,180	13,775
Home Services and Other \| Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	73	77
Home Services and Other \| Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Home Services and Other \| Interruptible and off-tariff
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Natural Gas Distribution \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	287,830	223,459
Revenues out of scope	69,579	50,976
Total operating revenues	357,409	274,435
Natural Gas Distribution \| Operating Segments \| Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	216,938	151,308
Natural Gas Distribution \| Operating Segments \| Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	43,795	47,184
Natural Gas Distribution \| Operating Segments \| Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	26,199	22,675
Natural Gas Distribution \| Operating Segments \| Interruptible and off-tariff
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	898	2,292
Clean Energy Ventures \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,906	7,316
Revenues out of scope	3,886	2,867
Total operating revenues	12,792	10,183
Clean Energy Ventures \| Operating Segments \| Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,293	2,972
Clean Energy Ventures \| Operating Segments \| Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,613	4,344
Clean Energy Ventures \| Operating Segments \| Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Clean Energy Ventures \| Operating Segments \| Interruptible and off-tariff
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Energy Services
Disaggregation of Revenue [Line Items]
Total operating revenues	20,000	22,100
Energy Services \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27,848	27,879
Revenues out of scope	285,551	337,909
Total operating revenues	313,399	365,788
Energy Services \| Operating Segments \| Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Energy Services \| Operating Segments \| Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27,848	27,879
Energy Services \| Operating Segments \| Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Energy Services \| Operating Segments \| Interruptible and off-tariff
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Storage and Transportation \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	25,714	11,584
Revenues out of scope	0	0
Total operating revenues	25,714	11,584
Storage and Transportation \| Operating Segments \| Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Storage and Transportation \| Operating Segments \| Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	25,714	11,584
Storage and Transportation \| Operating Segments \| Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Storage and Transportation \| Operating Segments \| Interruptible and off-tariff
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 0	$ 0

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