REVENUE - DISAGGREGATED REVENUE - PRODUCT (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 284,090	$ 225,727
Alternative revenue programs	10,654	1,568
Derivative instruments	384,554	229,138
Revenues out of scope	391,752	228,578
Total operating revenues	675,842	454,305
Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	223,796	189,364
Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	40,022	19,532
Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,467	8,259
Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,484	4,318
Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	846	690
Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,470	4,388
Energy Services
Disaggregation of Revenue [Line Items]
Total operating revenues	22,100
Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenues	666,342	444,680
Operating Segments | Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	223,459	189,364
Alternative revenue programs	10,654	1,568
Derivative instruments	40,322	4,797
Revenues out of scope	50,976	6,365
Total operating revenues	274,435	195,729
Operating Segments | Natural Gas Distribution | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	223,796	189,364
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	7,316	5,078
Alternative revenue programs	0	0
Derivative instruments	2,867	1,292
Revenues out of scope	2,867	1,292
Total operating revenues	10,183	6,370
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	846	690
Operating Segments | Clean Energy Ventures | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,470	4,388
Operating Segments | Energy Services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27,879	6,428
Alternative revenue programs	0	0
Derivative instruments	341,365	223,049
Revenues out of scope	337,909	220,921
Total operating revenues	365,788	227,349
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	27,879	6,428
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	11,584	12,447
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	11,584	12,447
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	12,143	13,104
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	13,852	12,410
Home Services and Other | Home Services and Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	13,852	12,410
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	13,852	12,410
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	8,467	8,259
Home Services and Other | Home Services and Other | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,484	4,318
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	(995)	(824)
Revenues out of scope	(3,456)	(2,128)
Eliminations | Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(337)	0
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	(3,456)	(2,128)
Eliminations | Storage and Transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(559)	(657)
Revenues out of scope	0	0
Eliminations | Home Services and Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(99)	(167)
Revenues out of scope	$ 0	$ 0