Acquisitions and Dispositions (Narrative) (Details) (USD $)	12 Months Ended			0 Months Ended	12 Months Ended	0 Months Ended		12 Months Ended		0 Months Ended			0 Months Ended		12 Months Ended		0 Months Ended		12 Months Ended		0 Months Ended			12 Months Ended		0 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Parent Company [Member]	Sep. 26, 2013 West Delta 29 Acquisition [Member]	Dec. 31, 2013 West Delta 29 Acquisition [Member] MMBoe	Oct. 31, 2012 Hilcorp Acquisition [Member]	Oct. 31, 2012 Hilcorp Acquisition [Member]	Dec. 31, 2013 Hilcorp Acquisition [Member] MMBoe	Dec. 31, 2012 Hilcorp Acquisition [Member]	Oct. 31, 2012 Hilcorp Acquisition [Member] Senior Notes Due 2018 [Member]	Oct. 25, 2011 Hilcorp Acquisition [Member] Senior Notes Due 2018 [Member]	Oct. 25, 2012 Hilcorp Acquisition [Member] Senior Notes Due 2018 [Member]	May 15, 2012 South Timbalier Acquisition [Member]	Mar. 31, 2012 South Timbalier Acquisition [Member] MMBoe	Dec. 31, 2013 South Timbalier Acquisition [Member]	Dec. 31, 2012 South Timbalier Acquisition [Member]	Feb. 14, 2011 ASOP Acquisition [Member]	Dec. 31, 2010 ASOP Acquisition [Member] MMBoe	Dec. 31, 2012 ASOP Acquisition [Member]	Dec. 31, 2011 ASOP Acquisition [Member]	Feb. 14, 2011 ASOP Acquisition [Member] 2011 Senior Notes [Member]	Nov. 17, 2011 Main Pass Acquisition [Member]	Nov. 01, 2011 Main Pass Acquisition [Member] MMBoe	Dec. 31, 2012 Main Pass Acquisition [Member]	Dec. 31, 2011 Main Pass Acquisition [Member]	Apr. 02, 2013 Non-Operated Bay Marchand Field Disposition [Member]	Dec. 31, 2013 Non-Operated Bay Marchand Field Disposition [Member]	Jan. 15, 2014 Nexen Acquisition [Member]	Sep. 01, 2013 Nexen Acquisition [Member] MMBoe	Jan. 17, 2014 Revolving Credit Facility [Member]	Nov. 26, 2013 Revolving Credit Facility [Member]	Oct. 31, 2012 Revolving Credit Facility [Member]	May 01, 2012 Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Acquired certain interests in producing oil and natural gas assets				$ 21,800,000		$ 550,000,000	$ 550,000,000						$ 32,400,000				$ 200,700,000				$ 200,700,000	$ 38,600,000						$ 70,400,000
Proved Reserves BOE					0.7			37.2						1.0				8.1					1.3						2.6
Percentage of Oil Reserves					95.00%			49.00%						51.00%				84.00%					96.00%						91.00%
Percentage of proved developed reserves					58.00%			58.00%						84.00%				76.00%
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		300.0									210,000,000
Net proceeds from offering of Notes										289,500,000	289,500,000										202,000,000
Economic effective date					Jan. 01, 2013			Jul. 01, 2012							Apr. 01, 2012				Jan. 01, 2011					Nov. 01, 2011			Jan. 01, 2013
Purchase Price Adjustments					7,100,000			5,700,000							400,000				3,800,000					700,000			700,000
Incurred fees									500,000							100,000				500,000					100,000
Buyers Assumption of Certain Associated Liabilities																										11,300,000
Cash consideration from sale of proptery																										51,500,000
Total consideration from sale of property				16,500,000																						62,800,000
Pre-tax gain on sale of assets	28,681,000		28,219,000																								28,100,000
Line Of Credit Facility Increase To Current Borrowing Capacity																														50,000,000
Line of Credit Facility, Current Borrowing Capacity																														475,000,000	425,000,000	425,000,000	200,000,000
Asset Retirement Obligation, Revision of Estimate	$ 24,586,000	$ 22,308,000						$ 22,100,000