Accounting For Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense

	2014			2013		2012
Current income tax expense (benefit)	$	(67,059	)	$	37,743	$	18,710
Deferred income tax expense	139,299			20,271		21,054
Total income tax expense	$	72,240		$	58,014	$	39,764

Schedule of Effective Income Tax Rate Reconciliation

	2014			2013			2012
Federal income taxes at statutory rates	$	67,237		$	56,821		$	40,798
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility plant differences	4,008			3,532			2,432
State income tax expense	506			1,553			863
Settlement of prior year tax returns and adjustment of tax reserves	1,104			(1,104		)	(2,198		)
Manufacturing deduction	(169		)	(2,033		)	(1,100		)
Other	(446		)	(755		)	(1,031		)
Total income tax expense	$	72,240		$	58,014		$	39,764

Schedule of Deferred Income Tax Assets and Liabilities

	2014		2013
Deferred income tax assets:
Allowance for doubtful accounts	$	1,714	$	12,202
Reserves not currently deductible	2,889		6,322
Net operating loss from subsidiary acquisition	538		9,258
Deferred compensation	3,117		3,676
Unfunded benefit obligation	72,108		42,230
Utility energy commodity derivatives	19,493		13,303
Power and natural gas deferrals	3,811		9,226
Tax credits	16,662		11,365
Interest rate swaps	8,934		—
Other	1,776		29,133
Total deferred income tax assets	131,042		136,715
Deferred income tax liabilities:
Intangible assets from subsidiary acquisition	—		4,271
Differences between book and tax basis of utility plant	690,597		521,238
Regulatory asset for pensions and other postretirement benefits	82,515		54,945
Power exchange contract	—		5,484
Utility energy commodity derivatives	19,495		13,305
Loss on reacquired debt	5,128		5,732
Interest rate swaps	—		15,097
Settlement with Coeur d’Alene Tribe	12,751		13,190
Other	16,104		14,008
Total deferred income tax liabilities	826,590		647,270
Net deferred income tax liability	$	695,548	$	510,555
Consolidated balance sheet classification of net deferred income taxes:
Current deferred income tax asset	$	14,794	$	24,788
Long-term deferred income tax liability	710,342		535,343
Net deferred income tax liability	$	695,548	$	510,555

Schedule of Recovery of Deferred Income Tax Liabilities

	2014		2013
Regulatory assets for deferred income taxes	$	100,412	$	71,421
Regulatory liabilities for deferred income taxes	14,534		9,203