REVENUE - DISAGGREGATED REVENUE - PRODUCT (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 440,899	$ 358,953
Alternative revenue programs	(26,256)	(5,391)
Derivative instruments	190,211	134,799
Revenues out of scope	163,955	129,408
Total operating revenues	604,854	488,361
Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	374,858	296,402
Natural gas services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	40,920	38,575
Service contracts
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9,455	9,232
Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,551	6,562
Renewable energy certificates
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,737	2,896
Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,615	5,826
ES
Disaggregation of Revenue [Line Items]
Total operating revenues	4,900	4,900
Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenues	588,848	472,728
Operating Segments | NJNG
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	374,621	296,065
Alternative revenue programs	(26,256)	(5,391)
Derivative instruments	61,536	42,754
Revenues out of scope	35,280	37,363
Total operating revenues	409,901	333,428
Operating Segments | NJNG | Natural gas utility sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	374,858	296,402
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	9,352	8,722
Alternative revenue programs	0	0
Derivative instruments	22,408	17,684
Revenues out of scope	22,408	17,684
Total operating revenues	31,760	26,406
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	3,737	2,896
Operating Segments | CEV | Electricity sales
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5,615	5,826
Operating Segments | ES
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12,840	11,947
Alternative revenue programs	0	0
Derivative instruments	106,267	74,361
Revenues out of scope	106,267	74,361
Total operating revenues	119,107	86,308
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	12,840	11,947
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	28,080	26,586
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	28,080	26,586
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	28,080	26,628
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 | HSO
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	16,006	15,633
Alternative revenue programs	0	0
Derivative instruments	0	0
Revenues out of scope	0	0
Total operating revenues	16,006	15,633
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	9,455	9,232
Corporate, Non-Segment | HSO | Installations and maintenance
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6,551	6,562
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	(237)	(540)
Eliminations | NJNG
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(237)	(337)
Eliminations | CEV
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Eliminations | ES
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Eliminations | S&T
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	(42)
Eliminations | HSO
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 0	$ (161)