REVENUE - DISAGGREGATED REVENUE - PRODUCT (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 321,191	$ 364,551
Alternative revenue programs	(2,537)	(3,465)
Derivative instruments	147,423	370,864
Revenues out of scope	146,019	359,016
Total operating revenues	467,210	723,567
Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	257,875	288,167
Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	40,130	54,686
Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,940	8,661
Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,894	5,605
Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,650	1,202
Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,714	7,704
ES
Disaggregation of Revenue [Line Items]
Total operating revenues	9,500	20,000
Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenues	452,376	709,314
Operating Segments | NJNG
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	257,538	287,830
Alternative revenue programs	(2,537)	(3,465)
Derivative instruments	38,092	73,044
Revenues out of scope	35,555	69,579
Total operating revenues	293,093	357,409
Operating Segments | NJNG | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	257,875	288,167
Operating Segments | NJNG | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | NJNG | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | NJNG | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | NJNG | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | NJNG | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | CEV
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9,364	8,906
Alternative revenue programs	0	0
Derivative instruments	25,931	3,886
Revenues out of scope	25,931	3,886
Total operating revenues	35,295	12,792
Operating Segments | CEV | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | CEV | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | CEV | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | CEV | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | CEV | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,650	1,202
Operating Segments | CEV | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,714	7,704
Operating Segments | ES
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	16,268	27,848
Alternative revenue programs	0	0
Derivative instruments	83,400	293,934
Revenues out of scope	84,533	285,551
Total operating revenues	100,801	313,399
Operating Segments | ES | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | ES | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	16,268	27,848
Operating Segments | ES | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | ES | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | ES | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | ES | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | S&T
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	23,187	25,714
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	23,187	25,714
Operating Segments | S&T | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | S&T | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	23,862	26,838
Operating Segments | S&T | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | S&T | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | S&T | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Operating Segments | S&T | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Corporate, Non-Segment
Disaggregation of Revenue [Line Items]
Revenues out of scope	0	0
Total operating revenues	14,834	14,253
Corporate, Non-Segment | HSO
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	14,834	14,253
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	14,834	14,253
Corporate, Non-Segment | HSO | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Corporate, Non-Segment | HSO | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Corporate, Non-Segment | HSO | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,940	8,661
Corporate, Non-Segment | HSO | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,894	5,605
Corporate, Non-Segment | HSO | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Corporate, Non-Segment | HSO | 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	(1,012)	(1,474)
Revenues out of scope	1,133	(8,383)
Total operating revenues		(9,857)
Eliminations | NJNG
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(337)	(337)
Revenues out of scope	0	0
Eliminations | CEV
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Revenues out of scope	0	0
Eliminations | ES
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Revenues out of scope	1,133	(8,383)
Eliminations | S&T
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(675)	(1,124)
Revenues out of scope	0	0
Eliminations | HSO
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	(13)
Revenues out of scope	$ 0	$ 0