Supplementary Oil and Natural Gas Disclosures (Unaudited) (Costs Incurred Associated with Finding, Acquiring and Developing Proved Oil and Natural Gas Reserves) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Acquistions-Proved	$ 46,047,000	$ 706,322,000	$ 261,812,000
Acquisition - Unproved	2,200,000	7,496,000	14,000
Exploration	46,100,000	43,338,000	17,129,000
Development	303,245,000	180,938,000	83,577,000
Costs incurred	397,592,000	938,094,000	362,532,000
Liabilities assumed in acquisition	23,541,000	132,109,000
Asset retirement obligations incurred	1,200,000	1,200,000	200,000
Hilcorp Acquisition [Member]
Purchase Price Adjustments Associated with Acquiring Proved Reserves	29,700,000
West Delta 29 Acquisition [Member]
Purchase Price Adjustments Associated with Acquiring Proved Reserves	$ 16,700,000