Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified						6 Months Ended														6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2011 Oil [Member]	Jun. 30, 2012 Open costless collar contracts [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 1 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 2 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 3 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 4 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 5 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 6 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 7 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 8 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 9 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 10 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 11 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 12 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Oil [Member] Oil contract 13 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Natural Gas [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Natural Gas [Member] Natural Gas contract 1 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Natural Gas [Member] Natural Gas contract 2 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Natural Gas [Member] Natural Gas contract 3 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Natural Gas [Member] Natural Gas Contract 4 [Member]	Jun. 30, 2012 Open costless collar contracts [Member] Natural Gas [Member] Natural Gas Contract 5 [Member]
Summary of contracts for oil and natural gas
Calculation Period						07/01/2012 – 12/31/2012	07/01/2012 – 12/31/2012	07/01/2012 – 12/31/2012	07/01/2012 – 12/31/2012	07/01/2012 – 12/31/2012	07/01/2012 – 12/31/2012	07/01/2012 – 03/31/2013	01/01/2013 – 12/31/2013	01/01/2013 – 12/31/2013	01/01/2013 – 12/31/2013	01/01/2013 – 12/31/2013	01/01/2013 – 06/30/2014	01/01/2013 – 06/30/2014		07/01/2012 – 12/31/2012	07/01/2012 – 12/31/2012	07/01/2012 – 12/31/2012	07/01/2012 – 07/31/2013	07/01/2012 – 12/31/2013
Notional Quantity						20,000	10,000	10,000	20,000	20,000	20,000	20,000	20,000	20,000	20,000	20,000	8,000	12,000		300,000	150,000	70,000	150,000	100,000
Price Floor						90.00	90.00	90.00	90.00	90.00	95.00	90.00	85.00	90.00	85.00	85.00	90.00	90.00		4.50	4.25	2.50	4.50	3.00
Price Ceiling						104.20	108.00	109.50	111.00	111.90	116.00	110.00	102.25	115.00	110.40	108.80	114.00	115.50		5.60	6.17	3.34	5.75	3.83
Fair Value of Asset (Liability)	$ 21,126	$ 9,282	$ (554)	$ 21,126	$ 14,670	$ 784	$ 407	$ 411	$ 829	$ 832	$ 1,274	$ 1,294	$ 938	$ 2,065	$ 1,356	$ 1,292	$ 1,258	$ 1,930	$ 6,456	$ 2,801	$ 1,187	$ (26)	$ 2,557	$ (63)