Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2013

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Capitalized Exploratory Wells

The following table sets forth capitalized exploratory well costs and includes additions pending determination of proved reserves, reclassifications to proved reserves and costs charged to expense during the year:

Years ended December 31, (in thousands)	2013			2012			2011
Capitalized exploratory well costs at beginning of period	$	79,791		$	70,437		$	21,438
Additions pending determination of proved reserves	421,599			406,226			178,005
Reclassifications due to determination of proved reserves	(442,909		)	(396,872		)	(129,006		)
Exploratory well costs charged to expense	(881		)	—			—
Capitalized exploratory well costs at end of period	$	57,600		$	79,791		$	70,437

The following table sets forth capitalized exploratory wells costs at year end and includes amounts capitalized for a period greater than one year:

Years ended December 31, (in thousands)	2013		2012		2011
Exploratory wells in progress	$	14,794	$	77,693	$	70,437
Capitalized exploratory well costs for a period of one year or less	42,481		—		—
Capitalized exploratory well costs for a period greater than one year	1,206		2,098		—
Total capitalized exploratory well costs	$	58,481	$	79,791	$	70,437

Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance

Open mark-to-market gains (losses) on derivatives included in operating revenues were as follows:

Years ended December 31, (in thousands)	2013			2012		2011
Mark-to-market gain (loss) on derivatives	$	(47,832	)	$	58,750	$	(37,587	)

Schedule of taxes other than income taxes

The collection and payment of revenue taxes such as utility license taxes and fees, franchise fees and taxes imposed by other governmental authorities are reported on a gross basis. These amounts are included in taxes, other than income taxes on the consolidated statements of income as follows:

Years ended December 31, (in thousands)	2013		2012		2011
Taxes on revenues	$	25,870	$	21,479	$	25,268