INCOME TAXES (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Oct. 31, 2025
Income Tax Disclosure [Abstract]
Current Federal Tax Expense (Benefit)	$ 8,484,000	$ (68,660,000)	$ 16,551,000
Current State and Local Tax Expense (Benefit)	(756,000)	(1,476,000)	(829,000)
Current Income Tax Expense (Benefit)	7,728,000	(70,136,000)	15,722,000
Deferred Federal Income Tax Expense (Benefit)	46,808,000	110,717,000	21,905,000
Deferred State and Local Income Tax Expense (Benefit)	2,699,000	(4,195,000)	2,868,000
Deferred Income Taxes and Tax Credits	49,507,000	106,522,000	$ 24,773,000
RequestedRefundFrom2022AmendedFederalTaxReturn	55,600,000
RefundFromAmendedOklahomaCorporateIncomeTaxReturn				$ 1,500,000
Reduction in income tax expense for the amortization of the regulatory liability associated with excess ADIT that was returned to customers	$ 17,600,000	$ 25,700,000
Effective Income Tax Rate Reconciliation [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 67,506,000	$ 54,439,000	$ 57,063,000
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	$ 6,155,000	$ 4,333,000	$ 3,834,000
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	1.91%	1.67%	1.41%
Tax effect of permanent differences	$ 2,302,000	$ 2,018,000	$ 1,860,000
Tax effect of permanent differences, Percent	0.0072	0.0078	0.0068
Tax effect of state income tax deduction	(393,000)	(209,000)	(443,000)
Tax effect of state income tax deduction, Percent	(0.0012)	(0.0008)	(0.0016)
Amortization of EDIT Regulatory Liability	(13,382,000)	(15,680,000)	(20,565,000)
Amortization of EDIT Regulatory Liability, Percent	(0.0416)	(0.0605)	(0.0757)
Amortization of EDIT Regulatory Liability - State Tax	(4,211,000)	(10,004,000)	(1,795,000)
Amortization of EDIT Regulatory Liability - State Tax, Percent	(0.0131)	(0.0386)	(0.0066)
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-Based Payment Arrangement, Amount	$ (116,000)	$ 1,063,000	$ 418,000
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-Based Payment Arrangement, Percent	(0.04%)	0.41%	0.15%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ (626,000)	$ 426,000	$ 123,000
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	(0.19%)	0.16%	0.05%
Income Tax Expense (Benefit)	$ 57,235,000	$ 36,386,000	$ 40,495,000
Effective Income Tax Rate Reconciliation, Percent	17.81%	14.03%	14.90%
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Regulatory adjustments	$ 95,721,000	$ 100,718,000
Deferred Tax Assets, Operating Loss Carryforwards	362,558,000	405,316,000
Deferred Tax Assets, Leasing Arrangements	2,773,000	3,669,000
Deferred Tax Assets, Regulatory Assets - purchased-gas cost adjustment	10,900,000	0
Deferred Tax Assets, Other	3,359,000	0
Deferred Tax Assets, Gross	475,311,000	509,703,000
Deferred Tax Liabilities, Property, Plant and Equipment	996,128,000	930,680,000
Deferred Tax Liabilities, Winter weather events	363,988,000	381,818,000
Deferred Tax Liabilities, Regulatory Liabilities - purchased-gas cost adjustment	0	8,654,000
Deferred Tax Liabilities, Regulatory Assets and Liabilities - other	69,962,000	73,904,000
Deferred Tax Liabilities, Tax Deferred Expense, Compensation and Benefits	6,165,000	934,000
Deferred Tax Liabilities, Leasing Arrangements	2,942,000	3,866,000
Deferred Tax Liabilities, Other	0	1,585,000
Deferred Tax Liabilities, Gross	1,439,185,000	1,401,441,000
Deferred income taxes	963,874,000	$ 891,738,000
Domestic Tax Jurisdiction
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	338,400,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 24,100,000