REVENUE - DISAGGREGATED REVENUE - PRODUCT (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 1,351,305	$ 1,229,949	$ 1,111,520
Alternative revenue programs	(28,747)	1,087	27,257
Derivative instruments	713,854	560,628	834,387
Revenues out of scope	685,107	566,590	851,474
Total operating revenues	2,036,412	1,796,539	1,962,994
Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,091,000	861,882	845,392
Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	154,066	260,374	169,834
Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	37,327	36,231	35,210
Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	25,561	26,404	22,428
Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	17,575	15,111	12,636
Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27,240	32,913	31,733
ES
Disaggregation of Revenue [Line Items]
Total operating revenues	19,700	137,200	48,500
Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenues	1,973,826	1,734,162	1,905,561
Operating Segments | NJNG
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,089,879	860,532	844,043
Alternative revenue programs	(28,747)	1,087	27,257
Derivative instruments	240,364	156,863	139,984
Revenues out of scope	211,617	157,950	167,241
Total operating revenues	1,301,496	1,018,482	1,011,284
Operating Segments | NJNG | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,091,000	861,882	845,392
Operating Segments | NJNG | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | NJNG | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | NJNG | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | NJNG | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | NJNG | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | CEV
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	44,815	48,024	44,369
Alternative revenue programs	0	0	0
Derivative instruments	67,686	82,539	79,762
Revenues out of scope	67,686	82,539	79,762
Total operating revenues	112,501	130,563	124,131
Operating Segments | CEV | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | CEV | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | CEV | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | CEV | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | CEV | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	17,575	15,111	12,636
Operating Segments | CEV | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27,240	32,913	31,733
Operating Segments | ES
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	47,653	164,165	76,975
Alternative revenue programs	0	0	0
Derivative instruments	405,804	321,226	614,641
Revenues out of scope	405,804	326,101	604,471
Total operating revenues	453,457	490,266	681,446
Operating Segments | ES | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | ES | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	47,653	164,165	76,975
Operating Segments | ES | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | ES | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | ES | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | ES | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | S&T
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	106,372	94,851	88,700
Alternative revenue programs	0	0	0
Derivative instruments	0	0	0
Revenues out of scope	0	0	0
Total operating revenues	106,372	94,851	88,700
Operating Segments | S&T | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | S&T | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	106,413	96,209	92,859
Operating Segments | S&T | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | S&T | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | S&T | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Operating Segments | S&T | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate, Non-Segment
Disaggregation of Revenue [Line Items]
Revenues out of scope	0	0	0
Total operating revenues	62,586	62,377	57,433
Corporate, Non-Segment | HSO
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	62,586	62,377	57,433
Alternative revenue programs	0	0	0
Derivative instruments	0	0	0
Revenues out of scope	0	0	0
Total operating revenues	62,586	62,377	57,433
Corporate, Non-Segment | HSO | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate, Non-Segment | HSO | Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate, Non-Segment | HSO | Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	37,327	36,231	35,210
Corporate, Non-Segment | HSO | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	25,561	26,404	22,428
Corporate, Non-Segment | HSO | Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Corporate, Non-Segment | HSO | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Eliminations
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(1,464)	(2,966)	(5,713)
Revenues out of scope		4,875	(10,170)
Eliminations | NJNG
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(1,121)	(1,350)	(1,349)
Revenues out of scope		0	0
Eliminations | CEV
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Revenues out of scope		0	0
Eliminations | ES
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Revenues out of scope		4,875	(10,170)
Eliminations | S&T
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(41)	(1,358)	(4,159)
Revenues out of scope		0	0
Eliminations | HSO
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ (302)	(258)	(205)
Revenues out of scope		$ 0	$ 0