13. Income Taxes

Components of the income tax provision applicable to federal, state and foreign income taxes for the years ended December 31, 2016, 2015 and 2014 are as follows (in thousands):

	2016			2015			2014
Federal income tax expense (benefit):
Current	$	(24,777	)	$	(42,020	)	$	39,438
Deferred		(134,592	)		(83,812	)		39,673
		(159,369	)		(125,832	)		79,111
State income tax expense (benefit):
Current		(257	)		(3,480	)		3,987
Deferred		(14,163	)		(12,433	)		5,292
		(14,420	)		(15,913	)		9,279
Foreign income tax expense (benefit):
Current		(368	)		(2,590	)		4,521
Deferred		(3,405	)		(3,628	)		(1,292	)
		(3,773	)		(6,218	)		3,229
Total income tax expense (benefit):
Current		(25,402	)		(48,090	)		47,946
Deferred		(152,160	)		(99,873	)		43,673
Total income tax expense (benefit):	$	(177,562	)	$	(147,963	)	$	91,619

The difference between the statutory federal income tax rate and the effective income tax rate for the years ended December 31, 2016, 2015 and 2014 is summarized as follows:

	2016			2015			2014
Statutory tax rate		35.0	%		35.0	%		35.0	%
State income taxes		2.0			2.1			2.5
Permanent differences		(0.1	)		(1.3	)		(1.4	)
Other differences, net		(1.1	)		(2.4	)		(0.1	)
Effective tax rate		35.8	%		33.4	%		36.0	%

The lower 2015 effective tax rate is primarily related to the impact of goodwill impairment charges in 2015, along with an adjustment to the Company’s deferred tax liability associated with the 2010 conversion of its Canadian operations to a controlled foreign corporation.

The tax effect of significant temporary differences representing deferred tax assets and liabilities at December 31, 2016 and 2015 are as follows (in thousands):

	2016			2015
Deferred tax assets:
Current:
Net operating loss carryforwards	$	4,702		$	27,887
Workers’ compensation allowance		25,736			28,734
Other		16,710			21,305
		47,148			77,926
Non-current:
Net operating loss carryforwards		198,783			77,514
AMT credit		7,907			—
Expense associated with employee stock options		14,443			14,591
Federal benefit of state deferred tax liabilities		23,026			24,485
Other		19,137			20,441
		263,296			137,031
Less:
Allowance to reduce deferred tax asset to expected realizable value		—			(603	)
Total deferred tax assets		310,444			214,354
Deferred tax liabilities:
Current:
Other		(10,709	)		(12,805	)
Non-current:
Property and equipment basis difference		(929,483	)		(986,922	)
Other		(16,789	)		(13,339	)
		(946,272	)		(1,000,261	)
Total deferred tax liabilities		(956,981	)		(1,013,066	)
Net deferred tax liability	$	(646,537	)	$	(798,712	)

In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized, and necessary allowances are provided. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. The Company expects the carrying value of its deferred tax assets at December 31, 2016 and 2015 to be realized as a result of the reversal of existing taxable temporary differences giving rise to deferred tax liabilities, as well as the generation of taxable income in future periods. As of December 31, 2016 the Company does not consider a valuation allowance necessary. The valuation allowance of $603,000 related to state net operating losses that expired in 2016.

Other deferred tax assets consist primarily of the tax effect of various allowance accounts and tax-deferred expenses expected to generate future tax benefits of approximately $35.8 million. Other deferred tax liabilities consist primarily of the tax effect of receivables from insurance companies and tax-deferred income not yet recognized for tax purposes.

For income tax purposes, the Company has approximately $484 million of federal net operating losses, approximately $16 million of Canadian net operating losses and approximately $389 million, of state net operating losses as of December 31, 2016. Of these amounts, approximately $16 million of Canadian and $5 million of state losses will be carried back to prior years and the remaining balance can be carried forward to future years. Net operating losses that can be carried forward, if unused, are scheduled to expire as follows: 2025—$2.8 million; 2026—$17.1 million; 2027—$102,000; 2029—$33.2 million; 2030—$28.6 million; 2031—$92.0 million; 2034—$30,000; 2035—$302.6 million, 2036 - $391.1 million.

As of December 31, 2016, the Company had no unrecognized tax benefits. The Company has established a policy to account for interest and penalties related to uncertain income tax positions as operating expenses. As of December 31, 2016, the tax years ended December 31, 2013 through December 31, 2015 are open for examination by U.S. taxing authorities. As of December 31, 2016, the tax years ended December 31, 2012 through December 31, 2015 are open for examination by Canadian taxing authorities.

On January 1, 2010, the Company converted its Canadian operations from a Canadian branch to a controlled foreign corporation for federal income tax purposes. This transaction triggered a $1.0 million increase in deferred tax liabilities, which is being amortized as an increase to deferred income tax expense over the weighted average remaining useful life of the Canadian assets. This amount was fully amortized as of December 31, 2016.

As a result of the above conversion, the Company’s Canadian assets are no longer directly subject to United States taxation, provided that the related unremitted earnings are permanently reinvested in Canada. Effective January 1, 2010, the Company has elected to permanently reinvest these unremitted earnings in Canada, and it intends to do so for the foreseeable future. As a result, no deferred United States federal or state income taxes have been provided on such unremitted foreign earnings, which totaled approximately $18.8 million as of December 31, 2016. The unrecognized deferred tax liability associated with these earnings was approximately $2.5 million, net of available foreign tax credits. This liability would be recognized if the Company received a dividend of the unremitted earnings.