Supplemental Oil and Gas Reserve Information - Unaudited (Tables)

12 Months Ended

Dec. 31, 2016

Oil and Gas Exploration and Production Industries Disclosures [Abstract]

Net Proved, Proved Developed and Proved Undeveloped Reserves

The following table sets forth the Company’s estimated net proved, proved developed and proved undeveloped reserves at December 31, 2016, 2015 and 2014:

	Oil (MBbl)		Gas (MMcf)		MBoe
2014
Proved reserves
Beginning balance	198,590		175,979		227,920
Revisions of previous estimates	(23,069	)	(12,290	)	(25,117	)
Extensions, discoveries and other additions	80,855		70,449		92,596
Sales of reserves in place	(7,640	)	(4,850	)	(8,448	)
Purchases of reserves in place	1,546		1,523		1,799
Production	(14,883	)	(10,691	)	(16,664	)
Net proved reserves at December 31, 2014	235,399		220,120		272,086
Proved developed reserves, December 31, 2014	127,340		114,016		146,343
Proved undeveloped reserves, December 31, 2014	108,059		106,104		125,743
2015
Proved reserves
Beginning balance	235,399		220,120		272,086
Revisions of previous estimates	(75,458	)	(55,065	)	(84,635	)
Extensions, discoveries and other additions	38,962		46,072		46,640
Sales of reserves in place	—		—		—
Purchases of reserves in place	2,115		2,702		2,565
Production	(16,090	)	(14,001	)	(18,423	)
Net proved reserves at December 31, 2015	184,928		199,828		218,233
Proved developed reserves, December 31, 2015	127,445		120,789		147,577
Proved undeveloped reserves, December 31, 2015	57,483		79,039		70,656
2016
Proved reserves
Beginning balance	184,928		199,828		218,233
Revisions of previous estimates	11,713		116,539		31,136
Extensions, discoveries and other additions	10,790		24,520		14,876
Sales of reserves in place	(5,828	)	(10,839	)	(7,635	)
Purchases of reserves in place	50,164		100,629		66,936
Production	(15,174	)	(19,573	)	(18,436	)
Net proved reserves at December 31, 2016	236,593		411,104		305,110
Proved developed reserves, December 31, 2016	152,337		229,568		190,598
Proved undeveloped reserves, December 31, 2016	84,256		181,536		114,512

Standardized Measure of Discounted Future Cash Flows

The following table sets forth the Standardized Measure of discounted future net cash flows from projected production of the Company’s estimated net proved reserves at December 31, 2016, 2015 and 2014:

	At December 31,
	2016			2015			2014
	(In thousands)
Future cash inflows	$	9,426,963		$	8,582,831		$	21,656,832
Future production costs	(3,996,657		)	(3,842,517		)	(7,094,426		)
Future development costs	(784,727		)	(909,562		)	(2,563,062		)
Future income tax expense	(279,345		)	(225,662		)	(3,188,389		)
Future net cash flows	4,366,234			3,605,090			8,810,955
10% annual discount for estimated timing of cash flows	(1,883,169		)	(1,690,760		)	(4,829,294		)
Standardized measure of discounted future net cash flows	$	2,483,065		$	1,914,330		$	3,981,661

Changes in Standardized Measure of Discounted Future Net Cash Flows Applicable to Proved Oil and Natural Gas Reserves

The following table sets forth the changes in the Standardized Measure of discounted future net cash flows applicable to estimated net proved reserves for the periods presented:

	2016			2015			2014
	(In thousands)
January 1	$	1,914,330		$	3,981,661		$	3,727,559
Net changes in prices and production costs	(367,527		)	(3,201,195		)	(588,212		)
Net changes in future development costs	69,992			150,333			(61,760		)
Sales of oil and natural gas, net	(403,739		)	(477,755		)	(979,938		)
Extensions	165,926			409,838			1,751,007
Discoveries	—			—			—
Purchases of reserves in place	533,505			14,378			38,035
Sales of reserves in place	(57,770		)	—			(251,002		)
Revisions of previous quantity estimates	333,398			(946,729		)	(604,651		)
Previously estimated development costs incurred	91,518			216,981			249,926
Accretion of discount	(36,303		)	548,141			548,690
Net change in income taxes	202,272			1,391,358			259,592
Changes in timing and other	37,463			(172,681		)	(107,585		)
December 31	$	2,483,065		$	1,914,330		$	3,981,661