Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of Deferred Tax Assets and Liabilities

The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities at December 31, 2016 and 2015 are presented below (in thousands):



	December 31,
	2016			2015
Deferred tax assets:
Benefit of tax loss carryforwards	$	60,749		$	35,153
Alternative minimum tax credit carryforward	16,620			16,620
Pensions and benefits	57,756			61,673
Asset retirement obligation	26,929			28,042
Deferred fuel	—			1,488
Other	(200		)	15,421
Total gross deferred tax assets	161,854			158,397
Deferred tax liabilities:
Plant, principally due to depreciation and basis differences	(668,303		)	(608,738		)
Decommissioning	(43,463		)	(41,100		)
Deferred fuel	(3,962		)	—
Other	(1,192		)	(3,796		)
Total gross deferred tax liabilities	(716,920		)	(653,634		)
Net accumulated deferred income taxes	$	(555,066	)	$	(495,237	)

Schedule of Components of Income Tax Expense (Benefit)

The Company recognized income tax expense for 2016, 2015 and 2014 as follows (in thousands):



	Years Ended December 31,
	2016			2015			2014
Income tax expense:
Federal:
Current	$	2,642		$	2,319		$	(1,250	)
Deferred	47,909			32,819			38,810
Total federal income tax	50,551			35,138			37,560
State:
Current	766			1,730			3,209
Deferred	3,285			(1,650		)	641
Total state income tax	4,051			80			3,850
Generation (amortization) of accumulated investment tax credits	(684		)	(323		)	(322		)
Total income tax expense	$	53,918		$	34,895		$	41,088

Schedule of Effective Income Tax Rate Reconciliation

Income tax provisions differ from amounts computed by applying the statutory federal income tax rate of 35% to book income before federal income tax as follows (in thousands):



	Years Ended December 31,
	2016			2015			2014
Federal income tax expense computed on income at statutory rate	$	52,740		$	40,885		$	46,381
Difference due to:
State taxes, net of federal benefit	2,633			52			1,902
AEFUDC	(475		)	(2,345		)	(3,757		)
Permanent tax differences	(2,369		)	(2,898		)	(2,921		)
Other	1,389			(799		)	(517		)
Total income tax expense	$	53,918		$	34,895		$	41,088
Effective income tax rate	35.8		%	29.9		%	31.0		%

Summary of Income Tax Contingencies

A reconciliation of the December 31, 2016, 2015 and 2014 amounts of unrecognized tax benefits are as follows (in thousands):



	2016			2015		2014
Balance at January 1	$	6,000		$	5,200	$	7,200
Additions for tax positions related to the current year	400			500		300
Reductions for tax positions related to the current year	—			—		—
Additions for tax positions of prior years	100			300		2,200
Reductions for tax positions of prior years	(1,200		)	—		(4,500		)
Balance at December 31	$	5,300		$	6,000	$	5,200