REVENUE - DISAGGREGATED REVENUE - PRODUCT (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
Alternative revenue programs	(3,465)	10,654
Derivative instruments	370,864	384,554
Revenues out of scope	359,016	391,752
Total operating revenues	723,567	675,842
Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	288,167	223,796
Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	54,686	40,022
Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,661	8,467
Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,605	5,484
Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,202	846
Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	7,704	6,470
Energy Services
Disaggregation of Revenue [Line Items]
Total operating revenues	20,000	22,100
Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenues	719,158	666,342
Operating Segments | Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	287,830	223,459
Alternative revenue programs	(3,465)	10,654
Derivative instruments	73,044	40,322
Revenues out of scope	69,579	50,976
Total operating revenues	357,409	274,435
Operating Segments | Natural Gas Distribution | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	288,167	223,796
Operating Segments | Natural Gas Distribution | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Natural Gas Distribution | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Natural Gas Distribution | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Natural Gas Distribution | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Natural Gas Distribution | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Clean Energy Ventures
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,906	7,316
Alternative revenue programs	0	0
Derivative instruments	3,886	2,867
Revenues out of scope	3,886	2,867
Total operating revenues	12,792	10,183
Operating Segments | Clean Energy Ventures | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Clean Energy Ventures | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Clean Energy Ventures | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Clean Energy Ventures | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Clean Energy Ventures | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,202	846
Operating Segments | Clean Energy Ventures | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	7,704	6,470
Operating Segments | Energy Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27,848	27,879
Alternative revenue programs	0	0
Derivative instruments	293,934	341,365
Revenues out of scope	285,551	337,909
Total operating revenues	313,399	365,788
Operating Segments | Energy Services | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Energy Services | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27,848	27,879
Operating Segments | Energy Services | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Energy Services | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Energy Services | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Energy Services | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Storage and Transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	25,714	11,584
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	25,714	11,584
Operating Segments | Storage and Transportation | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Storage and Transportation | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	26,838	12,143
Operating Segments | Storage and Transportation | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Storage and Transportation | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Storage and Transportation | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | Storage and Transportation | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
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 | Home Services and Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	14,253	13,852
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	14,253	13,852
Home Services and Other | Home Services and Other | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Home Services and Other | Home Services and Other | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Home Services and Other | Home Services and Other | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,661	8,467
Home Services and Other | Home Services and Other | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,605	5,484
Home Services and Other | Home Services and Other | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Home Services and Other | Home Services and Other | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Eliminations
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(1,474)	(995)
Revenues out of scope	(8,383)	(3,456)
Eliminations | Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(337)	(337)
Revenues out of scope	0	0
Eliminations | Clean Energy Ventures
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Revenues out of scope	0	0
Eliminations | Energy Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Revenues out of scope	(8,383)	(3,456)
Eliminations | Storage and Transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(1,124)	(559)
Revenues out of scope	0	0
Eliminations | Home Services and Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(13)	(99)
Revenues out of scope	$ 0	$ 0