Income Taxes

Deferred tax assets and liabilities as of December 31 are as follows:



	2015			2014
	(in thousands)
Deferred income tax assets:
Allowance for doubtful accounts	$	562		$	478
Accrued expenses	9,212			8,969
Stock-based compensation	529			677
Insurance accruals	28,159			25,395
State net operating loss carryforward	1,688			3,241
Indirect tax benefits of unrecognized tax benefits	4,262			4,595
Other	387			772
Total gross deferred tax assets	44,799			44,127
Less valuation allowance	—			—
Net deferred tax assets	44,799			44,127
Deferred income tax liabilities:
Property and equipment	(133,720		)	(125,611		)
Goodwill	(3,725		)	(2,385		)
Prepaid expenses	(2,810		)	(2,969		)
	(140,255		)	(130,965		)
Net deferred tax liability	$	(95,456	)	$	(86,838	)

The deferred tax amounts above have been classified in the accompanying consolidated balance sheets at December 31, 2015 and 2014 as follows:



	2015			2014
	(in thousands)
Current assets, net	$	16,662		$	14,767
Long-term liabilities, net	(112,118		)	(101,605		)
	$	(95,456	)	$	(86,838	)

We have not recorded a valuation allowance against any deferred tax assets at December 31, 2015 and 2014. In management’s opinion, it is more likely than not that we will be able to utilize these deferred tax assets in future periods as a result of our history of profitability, taxable income, and reversal of deferred tax liabilities.

Income tax expense consists of the following:



	2015		2014		2013
	(in thousands)
Current income taxes:
Federal	$	33,364	$	6,860	$	30,560
State	2,703		855		1,152
	36,067		7,715		31,712
Deferred income taxes:
Federal	5,170		36,706		7,192
State	2,478		2,362		3,070
	7,648		39,068		10,262
Total	$	43,715	$	46,783	$	41,974

The income tax provision differs from the amount determined by applying the U.S. federal tax rate as follows:



	2015			2014			2013
	(in thousands)
Federal tax at statutory rate (35%)	$	40,870		$	46,066		$	39,395
State taxes, net of federal benefit	4,022			2,737			3,242
Non-taxable interest income	(6		)	(7		)	(20		)
Uncertain income tax penalties and interest, net	(1,006		)	(993		)	(766		)
Other	(165		)	(1,020		)	123
	$	43,715		$	46,783		$	41,974

At December 31, 2015 and December 31, 2014, we had a total of $11.6 million and $12.6 million in gross unrecognized tax benefits, respectively. Of this amount, $7.3 million and $8.0 million represents the amount of unrecognized tax benefits that, if recognized, would impact our effective tax rate as of December 31, 2015 and December 31, 2014, respectively. Unrecognized tax benefits were a net decrease of $1.1 million and $0.8 million during the years ended December 31, 2015 and 2014, respectively, due mainly to the expiration of certain statutes of limitation net of additions and settlements with respective states. This had the effect of reducing the effective state tax rate during these respective periods. The total net amount of accrued interest and penalties for such unrecognized tax benefits was $4.7 million and $5.7 million at December 31, 2015 and December 31, 2014, respectively, and is included in income taxes payable in the consolidated balance sheets. Net interest and penalties included in income tax expense for the years ended December 31, 2015, 2014 and 2013 was a benefit of approximately $1.0 million, $1.0 million, and $0.8 million respectively. Income tax expense is increased each period for the accrual of interest on outstanding positions and penalties when the uncertain tax position is initially recorded. Income tax expense is reduced in periods by the amount of accrued interest and penalties associated with reversed uncertain tax positions due to lapse of applicable statute of limitations, when applicable or when a position is settled. Income tax expense was reduced during the years ended December 31, 2015, 2014 and 2013 due to reversals of interest and penalties due to lapse of applicable statute of limitations and settlements, net of additions for interest and penalty accruals during the same period. These unrecognized tax benefits relate to risks associated with state income tax filing positions for our corporate subsidiaries.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:



	2015			2014
	(in thousands)
Balance at January 1,	$	12,632		$	13,432
Additions based on tax positions related to current year	954			983
Additions for tax positions of prior years	—			277
Reductions for tax positions of prior years	(90		)	—
Reductions due to lapse of applicable statute of limitations	(1,927		)	(2,060		)
Settlements	—			—
Balance at December 31,	$	11,569		$	12,632

A number of years may elapse before an uncertain tax position is audited and ultimately settled. It is difficult to predict the ultimate outcome or the timing of resolution for uncertain tax positions. It is reasonably possible that the amount of unrecognized tax benefits could significantly increase or decrease within the next twelve months. These changes could result from the expiration of the statute of limitations, examinations or other unforeseen circumstances. We do not have any outstanding litigation related to tax matters. At this time, management’s best estimate of the reasonably possible change in the amount of gross unrecognized tax benefits is a decrease of approximately $1.8 million to a decrease of $2.8 million during the next twelve months, mainly due to the expiration of certain statute of limitations, net of additions. The federal statute of limitations remains open for the years 2012 and forward. Tax years 2005 and forward are subject to audit by state tax authorities depending on the tax code and administrative practice of each state.