Accounting For Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Schedule of Components of Income Tax Expense



	2018		2017		2016
Current income tax expense (benefit)	$	17,490	$	13,101	$	(46,457	)
Deferred income tax expense	8,570		69,657		124,543
Total income tax expense	$	26,060	$	82,758	$	78,086

Schedule of Effective Income Tax Rate Reconciliation



	2018					2017					2016
Federal income taxes at statutory rates	$	34,158		21.0	%	$	69,542		35.0	%	$	75,391		35.0	%
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility plant differences	(8,153		)	(5.0	)	3,482			1.7		3,297			1.5
State income tax expense	1,191			0.7		1,110			0.6		1,316			0.6
Settlement of prior year tax returns and adjustment of tax reserves	(140		)	(0.1	)	(384		)	(0.2	)	13			—
Manufacturing deduction	—			—		(1,119		)	(0.6	)	—			—
Settlement of equity awards	(990		)	(0.6	)	(1,439		)	(0.7	)	(1,597		)	(0.7	)
Acquisition costs	329			0.2		2,491			1.3		—			—
Federal income tax rate change	—			—		10,169			5.1		—			—
Other	(335		)	(0.2	)	(1,094		)	(0.5	)	(334		)	(0.1	)
Total income tax expense	$	26,060		16.0	%	$	82,758		41.7	%	$	78,086		36.3	%

Schedule of Deferred Income Tax Assets and Liabilities



	2018			2017
Deferred income tax assets:
Unfunded benefit obligation	$	45,842		$	41,944
Utility energy commodity and interest rate swap derivatives	11,724			23,364
Regulatory deferred tax credits	6,244			6,359
Tax credits	21,008			23,042
Power and natural gas deferrals	17,618			14,379
Deferred compensation	5,536			7,080
Deferred taxes on regulatory liabilities	106,909			105,508
Other	16,793			15,892
Total gross deferred income tax assets	231,674			237,568
Valuation allowances for deferred tax assets	(13,651		)	(10,982		)
Total deferred income tax assets after valuation allowances	218,023			226,586
Deferred income tax liabilities:
Differences between book and tax basis of utility plant	509,789			494,783
Regulatory asset on utility, property plant and equipment	83,141			81,860
Regulatory asset for pensions and other postretirement benefits	47,893			43,914
Utility energy commodity and interest rate swap derivatives	11,724			23,364
Long-term debt and borrowing costs	24,609			19,992
Settlement with Coeur d’Alene Tribe	6,400			6,802
Other regulatory assets	15,318			16,695
Other	6,751			5,806
Total deferred income tax liabilities	705,625			693,216
Net long-term deferred income tax liability	$	487,602		$	466,630

Schedule of Recovery of Deferred Income Tax Liabilities

The Company had regulatory assets and liabilities related to the probable recovery/refund of certain deferred income tax assets and liabilities through future customer rates as of December 31 (dollars in thousands):



	2018		2017
Regulatory assets for deferred income taxes	$	91,188	$	90,315
Regulatory liabilities for deferred income taxes	453,610		460,542