Disclosure About Oil and Gas Producing Activities (Unaudited) (Details 1)	Dec. 31, 2011 Bbl	Dec. 31, 2010 Bbl	Dec. 31, 2009 Bbl	Dec. 31, 2008 Bbl
Oil Reserves [Member]
Reserve Quantities [Line Items]
Developed	11,794,000	11,013,000	11,627,000	11,462,000
Undeveloped	21,287,000	20,671,000	17,558,000	15,546,000
Total Proved	33,081,000	31,684,000	29,185,000	27,007,000
Natural Gas Reserves [Member]
Reserve Quantities [Line Items]
Developed	1,973,391,000	1,678,697,000	1,541,813,000	1,412,562,000
Undeveloped	2,805,163,000	2,521,458,000	2,194,788,000	1,943,225,000
Total Proved	4,778,554,000	4,200,155,000	3,736,601,000	3,355,788,000