ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)

12 Months Ended

Dec. 31, 2024

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)

The following table sets forth the balance in accumulated other comprehensive loss for the periods indicated:

	Accumulated Other Comprehensive Loss
	(Thousands of dollars)
January 1, 2023	$	(704)
Pension plan obligation
Other comprehensive income (loss) before reclassification, net of tax of $140	(477)
Amounts reclassified from accumulated other comprehensive loss, net of tax of $—	(1)
Other comprehensive income (loss)	(478)
December 31, 2023	(1,182)
Pension plan obligation
Other comprehensive income (loss) before reclassification, net of tax of $(281)	961
Amounts reclassified from accumulated other comprehensive loss, net of tax of $—	(1)
Available-for-sale securities
Other comprehensive income (loss) before reclassification, net of tax of $(24)	94
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(1)	2
Other comprehensive income (loss)	1,056
December 31, 2024	$	(126)

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]

The following table sets forth the effect of reclassifications from accumulated other comprehensive loss in our consolidated statements of income for the periods indicated:

	Year Ended						Affected Line Item in the
Details About Accumulated Other	December 31,						Consolidated Statements
Comprehensive Loss Components	2024		2023		2022		of Income
	(Thousands of dollars)
Pension and other postemployment benefit plan obligations (a)
Amortization of net gain (loss)	$	(5,770)	$	(1,960)	$	(17,010)
Amortization of unrecognized prior service credit (cost)	(372)		(525)		(289)
	(6,142)		(2,485)		(17,299)
Regulatory adjustments (b)	6,143		2,486		17,141
Amounts reclassified from accumulated other comprehensive loss	1		1		(158)		Other income (expense), net
Available-for-sale securities
Amounts reclassified from accumulated other comprehensive loss	(3)		—		—		Other income (expense), net
Total available-for-sale securities	(3)		—		—
Total reclassifications before tax	(2)		1		(158)		Income before income taxes
Tax effect of reclassifications	1		—		36		Income tax expense
Net reclassifications for the period	$	(1)	$	1	$	(122)	Net income

(a) These components of accumulated other comprehensive loss are included in the computation of net periodic benefit credit. See Note 11 for additional detail of our net periodic benefit credit.

(b) Regulatory adjustments represent pension and other postemployment benefit credits or costs expected to be recovered through rates and are deferred as part of our regulatory assets. See Note 3 for additional disclosures of regulatory assets and liabilities.