ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)

12 Months Ended

Dec. 31, 2021

Accumulated Other Comprehensive Income (Loss) [Line Items]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

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, 2020	$	(6,739)
Pension and other postemployment benefit plans obligations
Other comprehensive income before reclassification, net of tax of $587	(1,932)
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(298)	894
Other comprehensive loss	(1,038)
December 31, 2020	(7,777)
Pension and other postemployment benefit plans obligations
Other comprehensive loss before reclassification, net of tax of $11	78
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(390)	1,172
Other comprehensive income	1,250
December 31, 2021	(6,527)

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

The following table sets forth the effect of reclassifications from accumulated other comprehensive loss on our Consolidated Statements of Income for the periods indicated:

							Affected Line Item in the
Details about Accumulated Other Comprehensive	Years Ended December 31,						Consolidated Statements of
Loss Components	2021		2020		2019		Income
	(Thousands of dollars)
Pension and other postemployment benefit plan obligations (a)
Amortization of net loss	$	45,896	$	42,492	$	35,283
Amortization of unrecognized prior service cost	(279)		(117)		(673)
	45,617		42,375		34,610
Regulatory adjustments (b)	(44,055)		(41,183)		(33,758)
	1,562		1,192		852		Income before income taxes
	(390)		(298)		(213)		Income tax expense
Total reclassifications for the period	$	1,172	$	894	$	639	Net income

(a) These components of accumulated other comprehensive loss are included in the computation of net periodic benefit cost. See Note 13 for additional information regarding our net periodic benefit cost.

(b) Regulatory adjustments represent pension and other postemployment benefit costs expected to be recovered through rates and are deferred as part of our regulatory assets. See Note 10 for additional information regarding our regulatory assets and liabilities.