Income Taxes

The following table summarizes our provision for income taxes for the periods presented:



	Year Ended December 31,
	2013			2012			2011
Current income taxes (benefit)
Federal	$	—		$	—		$	1,279
State	—			(26		)	(3,933		)
	—			(26		)	(2,654		)
Deferred income tax benefit
Federal	(77,046		)	(60,676		)	(80,529		)
State	(650		)	(8,000		)	(4,972		)
	(77,696		)	(68,676		)	(85,501		)
	$	(77,696	)	$	(68,702	)	$	(88,155	)

The following table reconciles the difference between the income taxes computed by applying the statutory tax rate to income from continuing operations before income taxes and our reported income tax expense for the periods presented:



	Year Ended December 31,
	2013					2012					2011
Computed at federal statutory rate	$	(77,268	)	(35.0	)%	$	(60,652	)	(35.0	)%	$	(77,374	)	(35.0	)%
State income taxes, net of federal income tax benefit	(650		)	(0.3	)%	(8,026		)	(4.6	)%	(4,825		)	(2.2	)%
Other, net	222			0.1	%	(24		)	—	%	(5,956		)	(2.7	)%
	$	(77,696	)	(35.2	)%	$	(68,702	)	(39.6	)%	$	(88,155	)	(39.9	)%

The following table summarizes the principal components of our net deferred income tax liability as of the dates presented:



	As of December 31,
	2013			2012
Deferred tax liabilities:
Property and equipment	$	248,164		$	311,002
Fair value of derivative instruments	—			5,268
Total deferred tax liabilities	248,164			316,270
Deferred tax assets:
Fair value of derivative instruments	1,665			—
Pension and postretirement benefits	2,248			2,864
Share-based compensation	6,907			10,760
Net operating loss (“NOL”) carryforwards	115,355			102,407
Other	18,029			15,788
	144,204			131,819
Less: Valuation allowance	(35,727		)	(26,686		)
Total deferred tax assets	108,477			105,133
Net deferred tax liability	$	139,687		$	211,137

As of December 31, 2013, we had federal NOL carryforwards of approximately $225.3 million, which expire starting in 2031, and state NOL carryforwards of approximately $56.2 million, which expire between 2024 and 2033. As of December 31, 2013 and 2012, valuation allowances of $55.0 million and $41.0 million, respectively, had been recorded for deferred tax assets associated with state NOL carryforwards that were not more-likely-than-not to be realized.

As of December 31, 2011, we classified $31.2 million of deferred tax assets as a current income tax receivable attributable to the federal NOL expected to be utilized. In 2012, we received a federal tax refund of approximately $32 million from the carryback of the 2011 federal NOL, and the remainder of the NOL is available for carryforward.

We have no liability for unrecognized tax benefits as of December 31, 2013 and 2012. There were no interest and penalty charges recognized during the years ended December 31, 2013, 2012 and 2011. Tax years from 2010 forward remain open for examination by the Internal Revenue Service and various state jurisdictions.