Accounting For Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense

Income tax expense consisted of the following for the years ended December 31 (dollars in thousands):

	2022			2021		2020
Current income tax expense (benefit)	$	1,040		$	807	$	(37,913	)
Deferred income tax expense (benefit)		(18,231	)		11,224		44,964
Total income tax expense (benefit)	$	(17,191	)	$	12,031	$	7,051

Schedule of Effective Income Tax Rate Reconciliation

A reconciliation of federal income taxes derived from the statutory federal tax rate of 21 percent applied to income before income taxes is as follows for the years ended December 31 (dollars in thousands):

	2022					2021					2020
Federal income taxes at statutory rates	$	28,977		21.0	%	$	33,467		21.0	%	$	28,673		21.0	%
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility    plant differences (1)		(12,366	)	(9.0	)		(13,820	)	(8.7	)		(12,893	)	(9.4	)
State income tax expense		1,676		1.2			1,385		0.8			814		0.6
Flow through related to deduction of meters     and mixed service costs (2)		(34,454	)	(25.0	)		(8,678	)	(5.4	)		—		—
Non-plant excess deferred turnaround (3)		—		—			—		—			(8,476	)	(6.2	)
Customer refunds related to prior years at 35 percent		—		—			—		—			(1,189	)	(0.9	)
Other		(1,024	)	(0.7	)		(323	)	(0.2	)		122		0.1
Total income tax expense (benefit)	$	(17,191	)	(12.5	)%	$	12,031		7.5	%	$	7,051		5.2	%

(1)Prior to 2022, for the depreciation-related temporary differences under the normalization tax accounting method, the Company utilized the average rate assumption method to compute the amounts returned to customers. Beginning in 2022, the Company changed to the alternative method, to be in compliance with recently released revenue procedures and private letter rulings.

(2)During 2021 and 2022, new rates from the Company's Idaho, Oregon and Washington general rate cases went into effect with base rate increases offset by customer tax credits. As the customer tax credits are returned to customers, this results in a decrease to income tax expense as a result of flowing through the benefits related to meters and mixed service costs. This decrease in income tax expense offsets the increases in base rate granted to the Company in these general rate cases.

(3)As part of a settlement agreement in a Washington general rate case, the parties agreed to utilize $10.9 million ($8.4 million when tax-effected) of the electric benefits to offset costs associated with accelerating the depreciation of Colstrip, to reflect a remaining useful life through December 31, 2025.

Schedule of Deferred Income Tax Assets and Liabilities

The total net deferred income tax liability consisted of the following as of December 31 (dollars in thousands):

	2022			2021
Deferred income tax assets:
Regulatory liabilities	$	197,998		$	200,513
Tax credits and NOL carryforwards		74,782			64,994
Provisions for pensions		20,132			25,650
Other		54,903			38,181
Total gross deferred income tax assets		347,815			329,338
Valuation allowances for deferred tax assets		(3,874	)		(9,626	)
Total deferred income tax assets after valuation allowances		343,941			319,712
Deferred income tax liabilities:
Utility property, plant, and equipment		712,470			688,856
Regulatory assets		281,483			264,978
Other		24,983			8,587
Total deferred income tax liabilities		1,018,936			962,421
Net long-term deferred income tax liability	$	674,995		$	642,709