Oil Gas Reserve Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2012 MMcf	Dec. 31, 2011 MMcf	Dec. 31, 2010 MMcf
Reserve Quantities [Line Items]
Adoption of assumption due to revision of oil and gas reporting requirements	Using a 12-month average pricing assumption
Average 12-month oil prices net of differentials	101.20	100.97	77.68
Average 12-month gas prices net of differentials	2.68	4.74	4.46
Annual discount rate for discounting future cash flows	10.00%
Pyrenees project
Reserve Quantities [Line Items]
Acquisition of additional working interested in pyrenees project		15.00%
Purchase of producing properties		6,000
Pompano and Mica fields
Reserve Quantities [Line Items]
Purchase of producing properties		102,000
Appalachia drilling program
Reserve Quantities [Line Items]
Extensions, discoveries and other additions	162,000	94,000	77,000
Deep gas development project at LaCantera
Reserve Quantities [Line Items]
Extensions, discoveries and other additions	17,000	11,000
GOM drilling program at Mississippi Canyon Block 109
Reserve Quantities [Line Items]
Extensions, discoveries and other additions		6,000	18,000
Sale of our non-operated interest in the Main Pass Block 296 and 311 fields
Reserve Quantities [Line Items]
Sale of reserves		13,000
Positive reserve report pricing changes
Reserve Quantities [Line Items]
Revisions of previous estimates			28,000
Well performance
Reserve Quantities [Line Items]
Revisions of previous estimates			5,000
Natural Gas Liquids (MBbls)
Reserve Quantities [Line Items]
Extensions, discoveries and other additions	4,856
Purchase of producing properties	619
Revisions of previous estimates	9,349	4,911	574
Average 12-month gas prices net of differentials	38.23	58.26