Supplemental Oil And Gas Disclosures (Estimated Quantities Of Proved Oil And Gas Reserves) (Details)	12 Months Ended
	Dec. 31, 2012 bbl item	Dec. 31, 2011 bbl	Dec. 31, 2010 bbl	Dec. 31, 2009 bbl
Reserve Quantities [Line Items]
Total proved reserves, beginning balance	38,860,000	62,696,000	96,280,000
Revision of previous estimates	(1,508,000)	(14,683,000)	(25,714,000)
Production	(6,619,000)	(8,694,000)	(7,870,000)
Sales of reserves in place	(654,000)	(890,000)
Extensions and discoveries	2,105,000	431,000
Total proved reserves, ending balance	32,184,000	38,860,000	62,696,000
Total proved developed reserves	19,677,000	22,731,000	24,407,000	35,644,000
Percentage of dosmetic significant oil and gas fields analyzed	100.00%
Number of dosmetic significant oil and gas fields analyzed	40
Percentage benchmark discounted future net revenues	1.00%
Oil [Member]
Reserve Quantities [Line Items]
Total proved reserves, beginning balance	22,689,000	24,818,000	29,727,000
Revision of previous estimates	647,000	3,475,000	(1,555,000)
Production	(4,725,000)	(5,785,000)	(3,354,000)
Sales of reserves in place	(75,000)	(205,000)
Extensions and discoveries	1,434,000	386,000
Total proved reserves, ending balance	19,970,000	22,689,000	24,818,000
Total proved developed reserves	12,431,000	12,754,000	11,796,000	14,850,000
Natural Gas Liquids [Member]
Reserve Quantities [Line Items]
Total proved reserves, beginning balance	97,021,000,000	227,264,000,000	399,315,000,000
Revision of previous estimates	(12,926,000,000)	(108,947,000,000)	(144,954,000,000)
Production	(11,361,000,000)	(17,458,000,000)	(27,097,000,000)
Sales of reserves in place	(3,473,000,000)	(4,109,000,000)
Extensions and discoveries	4,026,000,000	271,000,000
Total proved reserves, ending balance	73,287,000,000	97,021,000,000	227,264,000,000
Total proved developed reserves	43,475,000,000	59,859,000,000	75,664,000,000	124,763,000,000
Camelot Field [Member]
Reserve Quantities [Line Items]
Total proved reserves, beginning balance				12,000,000,000
Total proved reserves, ending balance				12,000,000,000
Bushwood Field [Member] | Oil [Member]
Reserve Quantities [Line Items]
Revision of previous estimates			1,800,000
Bushwood Field [Member] | Natural Gas Liquids [Member]
Reserve Quantities [Line Items]
Revision of previous estimates		87,000,000,000	131,000,000,000