Supplemental Information on Oil and Natural Gas Operations (Unaudited) - Oil and Natural Gas Reserves (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 bbl	Dec. 31, 2013 bbl	Dec. 31, 2012 bbl	Dec. 31, 2011 bbl
Proved Developed and Undeveloped Reserves (Volume)
Number of major acquisitions	2
Number of existing vertical wells	280
Number of existing horizontal wells	6
Number of horizontal PUDs included in the acquired reserves	0
Number of vertical wells developed, working interest	18
Number of horizontal wells developed, working interest	103
Number of vertical wells developed, mineral interest	1
Number of horizontal wells developed, mineral interest	14
Number of vertical wells developed	19
Number of horizontal wells developed	117
Number of vertical wells developed, proved undeveloped category	5
Number of horizontal wells developed, proved undeveloped category	66
Number of vertical locations downgraded	73	92
Proved undeveloped reserves, increase (Energy)	12,763,000
Proved Undeveloped Reserves (Energy)
Beginning proved undeveloped reserves at December 31, 2013	33,584,908
Undeveloped reserves transferred to developed	(10,537,000)
Revisions	(6,607,000)
Extensions and discoveries	29,907,000
Ending proved undeveloped reserves at December 31, 2014	46,347,908	33,584,908
Percent of proved undeveloped reserve extensions that are more than one offset away from existing producing wells	16.00%
Distance from producing wells	2,000
Downward revisions	7,592
Proved undeveloped reserves, planned development period	5 years
Capital expenditures towards development of proved undeveloped reserves	86,097	88,460	106,261
Oil [Member]
Proved Developed and Undeveloped Reserves (Volume)
Beginning of the period	42,600,852	26,196,859	18,100,473
Extensions and discoveries	37,068,820	17,041,744	3,106,433
Revisions of previous estimates	(6,784,560)	(5,943,164)	(1,464,243)
Purchase of reserves in place	8,186,053	7,328,162	7,210,482
Production	(5,381,576)	(2,022,749)	(756,286)
End of the period	75,689,589	42,600,852	26,196,859
Proved Developed Reserves (Volume)	43,885,835	19,789,965	7,189,367	3,949,099
Proved Undeveloped Reserves (Volume)	31,803,754	22,810,887	19,007,492	14,151,375
Natural Gas Liquids [Member]
Proved Developed and Undeveloped Reserves (Volume)
Beginning of the period	10,705,724	8,251,429	5,049,560
Extensions and discoveries	7,828,094	4,597,856	869,741
Revisions of previous estimates	649,476	(3,455,306)	(5,811)
Purchase of reserves in place	360,536	1,672,824	2,521,053
Production	(1,001,898)	(361,079)	(183,114)
End of the period	18,541,932	10,705,724	8,251,429
Proved Developed Reserves (Volume)	11,221,428	4,973,493	2,999,440	1,263,711
Proved Undeveloped Reserves (Volume)	7,320,504	5,732,231	5,251,989	3,785,850
Natural Gas [Member]
Proved Developed and Undeveloped Reserves (Volume)
Beginning of the period	61,679,496	34,570,148	20,551,465
Extensions and discoveries	52,099,252	24,184,540	3,759,684
Revisions of previous estimates	(17,726,552)	(5,786,180)	383,335
Purchase of reserves in place	19,898,649	10,441,485	10,709,180
Production	(4,345,585)	(1,730,497)	(833,516)
End of the period	111,605,260	61,679,496	34,570,148
Proved Developed Reserves (Volume)	68,264,113	31,428,756	12,864,941	5,285,945
Proved Undeveloped Reserves (Volume)	43,341,147	30,250,740	21,705,207	15,265,520
Martin County, Texas [Member]
Proved Developed and Undeveloped Reserves (Volume)
Number of major acquisitions	1