INCOME TAXES - DEFERRED TAX ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Deferred tax assets
Investment tax credits	$ 150,182	$ 192,238
State net operating losses	28,136	38,762
Deferred revenue	14,085	14,107
Fair value of derivatives	3,020	5,397
Impairment of equity method investment	14,004	14,004
Postemployment benefits	2,841	855
Incentive compensation	7,611	10,142
Amortization of intangibles	5,543	6,248
Overrecovered natural gas costs	2,975	9,072
Allowance for doubtful accounts	4,978	3,744
Other	7,919	7,226
Total deferred tax assets	241,294	301,795
Less: Valuation allowance	(5,454)	(5,621)
Total deferred tax assets net of valuation allowance	235,840	296,174
Deferred tax liabilities
Property-related items	(588,101)	(563,403)
Remediation costs	(20,953)	(21,656)
Investments in equity investees	(30,044)	(28,704)
Conservation incentive program	(6,344)	(14,379)
Other	(7,989)	(6,065)
Total deferred tax liabilities	(653,431)	(634,207)
Total net deferred tax liabilities	(417,591)	(338,033)
Tax credit carryforward	149,700	191,600
NJNG
Deferred tax liabilities
Tax credit carryforward	$ 500	$ 700