Supplemental Crude Oil and Natural Gas Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013 MBoe	Dec. 31, 2012 MBoe	Dec. 31, 2011 MBoe
Reserve Quantities [Line Items]
Percentage of discounted future net cash flows	99.00%	99.00%	96.00%
Percent of proved crude oil reserve estimates prepared by external reserve engineers	99.00%
Percent of proved natural gas reserve estimates prepared by external reserve engineers	94.00%
Growth plan to drilling programs period	5 years
Revisions of previous estimates	(96,054)	4,149	2,237
Extensions, discoveries and other additions	444,654	233,652	161,981
Discount factor utilized as standardized measure for future net cash flows	10.00%
Crude Oil [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates	(55,783)	33,272	28,607
Extensions, discoveries and other additions	267,009	166,844	87,465
Weighted average price utilized in computation of future cash inflows	91.50	86.56	88.71
Natural Gas [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates	(241,623)	(174,736)	(158,219)
Extensions, discoveries and other additions	1,065,870	400,848	447,098
Weighted average price utilized in computation of future cash inflows	5.36	4.31	5.59
Bakken [Member]
Reserve Quantities [Line Items]
Revisions of previous estimates	42,000
Revisions of previous estimates	81,000
Extensions, discoveries and other additions	227,000
Extensions, discoveries and other additions	276,000
SCOOP [Member]
Reserve Quantities [Line Items]
Extensions, discoveries and other additions	36,000
Extensions, discoveries and other additions	158,000