REVENUE - DISAGGREGATED REVENUE - TYPE (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
Revenues out of scope	163,955	129,408
Total operating revenues	604,854	488,361
Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	300,082	241,473
Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	103,738	87,039
Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	34,677	27,325
Interruptible, off-tariff and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,402	3,116
Operating Segments
Disaggregation of Revenue [Line Items]
Total operating revenues	588,848	472,728
NJNG | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	374,621	296,065
Revenues out of scope	35,280	37,363
Total operating revenues	409,901	333,428
NJNG | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	284,101	223,819
NJNG | Operating Segments | Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	53,441	41,805
NJNG | Operating Segments | Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	34,677	27,325
NJNG | Operating Segments | Interruptible, off-tariff and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,402	3,116
CEV | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9,352	8,722
Revenues out of scope	22,408	17,684
Total operating revenues	31,760	26,406
CEV | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	2,110
CEV | Operating Segments | Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9,352	6,612
CEV | Operating Segments | Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
CEV | Operating Segments | Interruptible, off-tariff and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
ES
Disaggregation of Revenue [Line Items]
Total operating revenues	4,900	4,900
ES | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12,840	11,947
Revenues out of scope	106,267	74,361
Total operating revenues	119,107	86,308
ES | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
ES | Operating Segments | Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12,840	11,947
ES | Operating Segments | Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
ES | Operating Segments | Interruptible, off-tariff and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
S&T | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	28,080	26,586
Revenues out of scope	0	0
Total operating revenues	28,080	26,586
S&T | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
S&T | Operating Segments | Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	28,080	26,586
S&T | Operating Segments | Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
S&T | Operating Segments | Interruptible, off-tariff and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
HSO | Corporate, Non-Segment
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	16,006	15,633
Revenues out of scope	0	0
Total operating revenues	16,006	15,633
HSO | Corporate, Non-Segment | Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	15,981	15,544
HSO | Corporate, Non-Segment | Commercial and industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	25	89
HSO | Corporate, Non-Segment | Firm transportation
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
HSO | Corporate, Non-Segment | Interruptible, off-tariff and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 0	$ 0