Acquisitions and Divestitures - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended			3 Months Ended	1 Months Ended			6 Months Ended
	Dec. 31, 2012	Jun. 18, 2012	Dec. 28, 2011	Dec. 31, 2011 Main Pass Block 296 and 311	Jan. 31, 2011 Pyrenees Project	Dec. 31, 2011 Wideberth Development Project	Jan. 31, 2011 Wideberth Development Project	Dec. 31, 2011 West Virginia Leasehold acre	Jun. 18, 2012 Block Deep Water Pompano Field Mississippi Canyon	Jun. 18, 2012 Mississippi Canyon Block 29	Jun. 18, 2012 Mississippi Canyon Block 72	Dec. 28, 2011 BP Exploration and Production Inc	Dec. 28, 2011 Adjacent Mississippi Canyon Block 29	Dec. 28, 2011 Mica Field	Dec. 28, 2011 Pompano Field
Business Acquisition [Line Items]
Fair value of Land and Building at the time of Acquisition	$ 8,539
Purchase Consideration	8,539
Percentage of working interest acquired									25.00%	14.00%	10.00%
Cash consideration transferred		26,398	167,631
Percentage of operated working capital acquired												75.00%	51.00%
Percentage of non-operated working capital acquired														50.00%	75.00%
Percentage Of additional operated working capital acquired					15.00%
Ownership working interested					30.00%
Cost of additional non operated working capital acquired					14,974	31,000
Percentage of operated working capital acquired during period							25.00%
Estimates asset retirement obligation				10,900		1,078
Leasehold positions Net								10,000
Leasehold positions acquired								6,700
Cost of leasehold positions acquired								19,000
Sale of interest cash consideration				$ 80,381