Acquisitions (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended	0 Months Ended	9 Months Ended	12 Months Ended	0 Months Ended		9 Months Ended	0 Months Ended		9 Months Ended	0 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013 2012 Notes [Member]	Sep. 30, 2013 Parent Company [Member]	Sep. 30, 2013 Parent Company [Member]	Oct. 31, 2012 Hilcorp Acquisition [Member]	Sep. 30, 2013 Hilcorp Acquisition [Member]	Dec. 31, 2012 Hilcorp Acquisition [Member] MMBoe	Oct. 25, 2012 Hilcorp Acquisition [Member] 2012 Notes [Member]	Sep. 26, 2013 West Delta 29 Acquisition [Member]	Sep. 30, 2013 West Delta 29 Acquisition [Member] MMBoe	May 15, 2012 South Timbalier Acquisition [Member]	Mar. 31, 2012 South Timbalier Acquisition [Member] MMBoe	Sep. 30, 2013 South Timbalier Acquisition [Member]	Feb. 14, 2011 ASOP Acquisition [Member] 2011 Notes [Member]	Apr. 02, 2013 Non-Operated Bay Marchand Field Disposition [Member]	Sep. 30, 2013 Non-Operated Bay Marchand Field Disposition [Member]
Business Acquisition [Line Items]
Acquired certain interests in producing oil and natural gas assets						$ 550,000,000				$ 16,500,000		$ 32,400,000			$ 200,700,000
Proved Reserves Mmboe								37.2			600,000		1.0
Percentage of Oil Reserves								49.00%			90.00%		51.00%
Percentage of proved developed reserves								58.00%			94.00%		84.00%
Working interest by acquirer prior to acquisition												60.00%
Working interest by acquiree prior to acquisition												40.00%
Senior Notes, face amount			300,000,000						300,000,000						210,000,000
Interest Rate, Debt Instrument	8.25%	8.25%
Net proceeds from offering of Notes									289,500,000						202,000,000
Economic effective date							Jul. 01, 2012				Jan. 01, 2013			Apr. 01, 2012			Jan. 01, 2013
Purchase Price Adjustments							6,200,000				4,700,000			400,000			700,000
Buyers Assumption of Certain Associated Liabilities																11,300,000
Cash consideration from sale of proptery																51,500,000
Total consideration from sale of property										21,800,000						62,800,000
Pre-tax gain on sale of assets	$ 1,745,000	$ 28,601,000		$ 1,745,000	$ 28,139,000												$ 28,100,000