Oil and Gas Operations (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2013

Oil and Gas Exploration and Production Industries Disclosures [Abstract]

Schedule of capitalized costs

The following table sets forth capitalized costs:

(in thousands)	December 31, 2013		December 31, 2012
Proved	$	7,043,779	$	6,241,148
Unproved	168,975		197,979
Total capitalized costs	7,212,754		6,439,127
Accumulated depreciation, depletion and amortization	2,078,411		1,765,241
Capitalized costs, net	$	5,134,343	$	4,673,886

Schedule of cost incurred in property acquisition, exploration and development activities

The following table sets forth costs incurred in property acquisition, exploration and development activities and includes both capitalized costs and costs charged to expense during the year:

Years ended December 31, (in thousands)	2013		2012		2011
Property acquisition:
Proved	$	4,661	$	79,862	$	214,993
Unproved	26,820		58,634		91,888
Exploration	435,636		419,284		190,854
Development	655,353		749,256		623,775
Total costs incurred	$	1,122,470	$	1,307,036	$	1,121,510

Schedule of results of operations from producing activities

The following table sets forth results of the Company’s oil and gas operations from producing activities:

Years ended December 31, (in thousands)	2013		2012		2011
Gross revenues*	$	1,206,293	$	1,090,948	$	834,700
Production (lifting costs)	351,541		278,193		226,361
Exploration expense	27,942		19,356		12,967
Depreciation, depletion and amortization	449,700		339,569		210,532
Accretion expense	6,995		6,339		5,699
Income tax expense	128,773		160,551		134,564
Results of operations from producing activities	$	241,342	$	286,940	$	244,577

* The years ended December 31, 2013, 2012 and 2011 gross revenues include a pre-tax non-cash mark-to-market loss on derivatives of $47.8 million, a pre-tax non-cash mark-to-market gain on derivatives of $58.8 million and a pre-tax non-cash mark-to-market loss on derivatives of $37.6 million, respectively.

Schedule of proved developed and undeveloped oil and gas reserves

The independent reservoir engineers have issued reports covering approximately 98 percent of the Company’s ending proved reserves indicating that in their judgment the estimates are reasonable in the aggregate.

Year ended December 31, 2013	Gas MMcf		Oil MBbl		NGL MBbl		Total MMBOE
Proved reserves at beginning of period	809,128		155,348		56,155		346.4
Revisions of previous estimates	18,465		(680	)	2,211		4.6
Purchases	282		142		56		0.2
Extensions and discoveries	50,568		20,517		7,823		36.8
Production	(70,506	)	(10,378	)	(3,233	)	(25.4	)
Sales	(88,212	)	(79	)	(1	)	(14.8	)
Proved reserves at end of period	719,725		164,870		63,011		347.8
Proved developed reserves at end of period	623,305		113,795		42,087		259.8
Proved undeveloped reserves at end of period	96,420		51,075		20,924		88.0

Year ended December 31, 2012	Gas MMcf		Oil MBbl		NGL MBbl		Total MMBOE
Proved reserves at beginning of period	957,368		129,578		53,957		343.1
Revisions of previous estimates	(143,704	)	(8,546	)	(9,557	)	(42.1	)
Purchases	10,656		7,950		2,569		12.4
Extensions and discoveries	61,170		35,132		11,759		57.1
Production	(76,362	)	(8,766	)	(2,573	)	(24.1	)
Proved reserves at end of period	809,128		155,348		56,155		346.4
Proved developed reserves at end of period	708,657		105,976		36,440		260.5
Proved undeveloped reserves at end of period	100,471		49,372		19,715		85.9

Year ended December 31, 2011	Gas MMcf		Oil MBbl		NGL MBbl		Total MMBOE
Proved reserves at beginning of period	954,387		103,262		40,601		302.9
Revisions of previous estimates	(12,823	)	(4,513	)	841		(5.8	)
Purchases	19,362		12,583		5,055		20.8
Extensions and discoveries	68,160		24,564		9,637		45.6
Production	(71,718	)	(6,318	)	(2,177	)	(20.4	)
Proved reserves at end of period	957,368		129,578		53,957		343.1
Proved developed reserves at end of period	788,812		83,899		33,154		248.5
Proved undeveloped reserves at end of period	168,556		45,679		20,803		94.6

Schedule of standardized measure of discounted future net cash flows relating to proved oil and gas reserves

Years ended December 31, (in thousands)	2013		2012		2011
Future gross revenues	$	19,509,305	$	17,735,363	$	18,196,229
Future production costs	6,136,709		5,715,248		5,823,395
Future development costs	1,896,602		1,892,600		1,539,072
Future income tax expense	3,209,697		2,809,411		3,326,382
Future net cash flows	8,266,297		7,318,104		7,507,380
Discount at 10% per annum	4,248,456		3,618,785		3,878,217
Standardized measure of discounted future net cash flows relating to proved oil and gas reserves	$	4,017,841	$	3,699,319	$	3,629,163

Schedule of principal sources of changes in standardized measure of discounted future net cash flows

The following are the principal sources of changes in the standardized measure of discounted future net cash flows:

Years ended December 31, (in thousands)	2013			2012			2011
Balance at beginning of year	$	3,699,319		$	3,629,163		$	2,467,136
Revisions to reserves proved in prior years:
Net changes in prices, production costs and future development costs	566,838			(922,792		)	707,411
Net changes due to revisions in quantity estimates	(81,762		)	(383,755		)	(80,004		)
Development costs incurred, previously estimated	299,432			472,603			392,720
Accretion of discount	369,932			362,916			246,714
Changes in timing and other	(179,502		)	(317,244		)	(25,937		)
Total revisions	974,938			(788,272		)	1,240,904
New field discoveries and extensions, net of future production and development costs	376,326			1,025,419			755,977
Sales of oil and gas produced, net of production costs	(1,014,593		)	(812,781		)	(763,171		)
Purchases	4,690			189,755			232,768
Sales	(24,876		)	—			—
Net change in income taxes	2,037			456,035			(304,451		)
Net change in standardized measure of discounted future net cash flows	318,522			70,156			1,162,027
Balance at end of year	$	4,017,841		$	3,699,319		$	3,629,163