Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015 and 2014 are presented below (in thousands):



	December 31,
	2015			2014
Deferred tax assets:
Benefit of tax loss carryforwards	$	35,153		$	—
Alternative minimum tax credit carryforward	16,620			17,701
Pensions and benefits	61,673			64,407
Asset retirement obligation	28,042			25,725
Deferred fuel	1,488			—
Other	15,421			15,768
Total gross deferred tax assets	158,397			123,601
Deferred tax liabilities:
Plant, principally due to depreciation and basis differences	(608,738		)	(536,264		)
Decommissioning	(41,100		)	(40,373		)
Deferred fuel	—			(3,531		)
Other	(3,796		)	(3,630		)
Total gross deferred tax liabilities	(653,634		)	(583,798		)
Net accumulated deferred income taxes	$	(495,237	)	$	(460,197	)

Schedule of Components of Income Tax Expense (Benefit)

The Company recognized income tax expense for 2015, 2014 and 2013 as follows (in thousands):



	Years Ended December 31,
	2015			2014			2013
Income tax expense:
Federal:
Current	$	2,319		$	(1,250	)	$	(2,877	)
Deferred	32,819			38,810			45,024
Total federal income tax	35,138			37,560			42,147
State:
Current	1,730			3,209			1,854
Deferred	(1,650		)	641			(414		)
Total state income tax	80			3,850			1,440
Generation (amortization) of accumulated investment tax credits	(323		)	(322		)	68
Total income tax expense	$	34,895		$	41,088		$	43,655

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,
	2015			2014			2013
Federal income tax expense computed on income at statutory rate	$	40,885		$	46,381		$	46,283
Difference due to:
State taxes, net of federal benefit	52			1,902			936
AEFUDC	(2,345		)	(3,757		)	(2,149		)
Permanent tax differences	(2,898		)	(2,921		)	(1,153		)
Other	(799		)	(517		)	(262		)
Total income tax expense	$	34,895		$	41,088		$	43,655
Effective income tax rate	29.9		%	31.0		%	33.0		%

Summary of Income Tax Contingencies

A reconciliation of the December 31, 2015, 2014 and 2013 amounts of unrecognized tax benefits are as follows (in thousands):



	2015		2014			2013
Balance at January 1	$	5,200	$	7,200		$	9,800
Additions for tax positions related to the current year	500		300			600
Reductions for tax positions related to the current year	—		—			—
Additions for tax positions of prior years	300		2,200			1,700
Reductions for tax positions of prior years	—		(4,500		)	(4,900		)
Balance at December 31	$	6,000	$	5,200		$	7,200