Accounting For Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of Components of Income Tax Expense



	2016			2015		2014
Current income tax expense (benefit)	$	(46,457	)	$	12,212	$	(67,059	)
Deferred income tax expense	124,543			55,237		139,299
Total income tax expense	$	78,086		$	67,449	$	72,240

Schedule of Effective Income Tax Rate Reconciliation



	2016					2015					2014
Federal income taxes at statutory rates	$	75,391		35.0	%	$	64,967		35.0	%	$	67,237		35.0	%
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility plant differences	3,297			1.5		4,358			2.3		4,008			2.1
State income tax expense	1,316			0.6		1,012			0.5		506			0.2
Settlement of prior year tax returns and adjustment of tax reserves	13			—		(992		)	(0.5	)	1,104			0.6
Manufacturing deduction	—			—		(1,198		)	(0.6	)	(169		)	(0.1	)
Settlement of equity awards	(1,597		)	(0.7	)	—			—		—			—
Other	(334		)	(0.1	)	(698		)	(0.4	)	(446		)	(0.2	)
Total income tax expense	$	78,086		36.3	%	$	67,449		36.3	%	$	72,240		37.6	%

Schedule of Deferred Income Tax Assets and Liabilities



	2016			2015
Deferred income tax assets:
Unfunded benefit obligation	$	80,230		$	75,716
Derivatives	31,872			47,009
Regulatory deferred tax credits	15,192			—
Tax credits	27,931			15,011
Power and natural gas deferrals	19,415			12,866
Deferred compensation	11,141			10,354
Other	29,512			29,471
Total gross deferred income tax assets	215,293			190,427
Valuation allowances for deferred tax assets	(7,946		)	(2,862		)
Total deferred income tax assets after valuation allowances	207,347			187,565
Deferred income tax liabilities:
Differences between book and tax basis of utility plant	812,916			723,661
Regulatory asset on utility, property plant and equipment	37,301			36,917
Regulatory asset for pensions and other postretirement benefits	84,040			82,253
Utility energy commodity derivatives	31,871			47,010
Long-term debt and borrowing costs	31,955			14,027
Settlement with Coeur d’Alene Tribe	11,711			12,084
Other regulatory assets	30,183			11,691
Other	8,298			7,399
Total deferred income tax liabilities	1,048,275			935,042
Net long-term deferred income tax liability	$	840,928		$	747,477

Schedule of Recovery of Deferred Income Tax Liabilities

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



	2016		2015
Regulatory assets for deferred income taxes	$	109,853	$	101,240
Regulatory liabilities for deferred income taxes	28,966		17,609