Derivative Instruments (Details) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended															6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 2012 Oil	Jun. 30, 2012 2012 Natural Gas	Jun. 30, 2012 2013 Oil	Jun. 30, 2012 2013 Natural Gas	Jun. 30, 2012 Full 2014 Term Oil	Jun. 30, 2012 Full 2014 Term Natural Gas	Jun. 30, 2012 Three-way collars - Derivative 1 Full 2014 Term Oil	Jun. 30, 2012 Three-way collars - Derivative 2 Full 2014 Term Oil	Jun. 30, 2012 Call Options - Derivative 1 2013 Natural Gas	Jun. 30, 2012 Call Options - Derivative 2 2013 Natural Gas	Jun. 30, 2012 Call Options - Derivative 3 2013 Natural Gas	Jun. 30, 2012 Call Options - Derivative 4 2013 Natural Gas	Jun. 30, 2012 Termination of Natural Gas Derivatives Natural Gas	Mar. 31, 2011 Termination of Natural Gas Derivatives Natural Gas	Jun. 30, 2012 Sold Put Three-way collars - Derivative 1 Full 2014 Term Oil	Jun. 30, 2012 Sold Put Three-way collars - Derivative 2 Full 2014 Term Oil	Jun. 30, 2012 Purchased Put Three-way collars - Derivative 1 Full 2014 Term Oil	Jun. 30, 2012 Purchased Put Three-way collars - Derivative 2 Full 2014 Term Oil	Jun. 30, 2012 Sold Call Three-way collars - Derivative 1 Full 2014 Term Oil	Jun. 30, 2012 Sold Call Three-way collars - Derivative 2 Full 2014 Term Oil
Derivative instruments
Notional amount of derivatives (Bbl/MMBtu per day)							21,000	0	15,000	8,000	4,000	0	1,000	1,000	1,000	1,000	1,000	2,000		15,000
Put (in dollars per barrel)																					70.00	70.00	90.00	90.00
Call (in dollars per barrel)																									120.00	121.80
Derivative, Price Risk Option Strike Price															3.50	3.50	3.50	3.50
Deferred Premium per MMBtu															0.43	0.46	0.4975	0.5325
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Losses) Before Tax	$ (5,200,000)	$ (5,200,000)		$ (5,200,000)		$ (8,900,000)
Accumulated other comprehensive loss	(3,241,000)	(3,241,000)		(3,241,000)		(5,517,000)
Reclassified unrealized losses, before tax from AOCL into earnings		(1,600,000)		(3,700,000)
Reclassified unrealized losses, after tax from AOCL into earnings		(1,009,000)	(9,522,000)	(2,276,000)	(19,045,000)
Net losses after-tax expected to be reclassified into earnings from AOCL during the remainder of 2012	(3,200,000)
Termination of Natural Gas Derivatives
Net loss resulting from termination of natural gas derivatives																			$ (1,900,000)