Financial Instruments (Details) (USD $)	9 Months Ended													9 Months Ended
	Sep. 30, 2012 item	Sep. 30, 2012 Natural gas liquids and crude oil contracts	Sep. 30, 2012 Natural Gas Calls 2013 MMBTUperday	Sep. 30, 2012 Natural Gas Liquids Swaps 2013 item	Sep. 30, 2012 Natural Gas Liquids Puts 2012 Bblperday	Dec. 31, 2011 Natural Gas Liquids Puts 2012 Bblperday	Sep. 30, 2012 Natural Gas Liquids Puts 2013 Bblperday	Dec. 31, 2011 Natural Gas Liquids Puts 2013 Bblperday	Sep. 30, 2012 Crude Oil Puts 2012 Bblperday	Dec. 31, 2011 Crude Oil Puts 2012 Bblperday	Sep. 30, 2012 Crude Oil Puts 2013 Bblperday	Dec. 31, 2011 Crude Oil Puts 2013 Bblperday	Sep. 30, 2012 Crude Oil Puts 2014 Bblperday	Sep. 30, 2012 Interest rate swaps
Derivative disclosures
Number of option counterparties that are not also lenders under revolving credit facility	2
Settlements expected to be reclassified as an increase to earnings in the next 12 months		$ 873,000												$ 28,000
Notional volumes of commodity positions (in Bbl per day)			2,787	1,000	4,625	5,400	2,650	1,650	1,500	1,500	1,400	750	500
Notional amount														$ 95,000,000
Average fixed interest rate (as a percent)														4.30%