Supplemental Oil And Gas Information (Schedule Of Net Proved Oil And Gas Reserves And The Changes In Net Proved Oil And Gas Reserves) (Details)	12 Months Ended
	Dec. 31, 2014 MBbls MBoe	Dec. 31, 2013 MBbls MBoe	Dec. 31, 2012 MBbls MBoe	Dec. 31, 2011 MBoe MBbls
Reserve Quantities [Line Items]
Proved reserves	2,040,000	2,217,000	2,592,000
Revisions of previous estimates	(253,000)	(151,000)	(327,000)
Extensions and discoveries	164,000	170,000	186,000
Production	(154,000)	(172,000)	(234,000)
Sales of reserves in place		(24,000)
Proved reserves	1,797,000	2,040,000	2,217,000	2,592,000
Proved developed reserves (equivalent)	1,438,000	1,575,000	1,826,000	1,940,000
Proved undeveloped reserves (equivalent)	359,000	465,000	391,000	652,000
Oil [Member]
Reserve Quantities [Line Items]
Proved reserves	2,040	2,213	2,591
Revisions of previous estimates	(253)	(153)	(337)
Extensions and discoveries	164	170	186
Production	(154)	(166)	(227)
Sales of reserves in place		(24)
Proved reserves	1,797	2,040	2,213
Proved developed reserves (volume)	1,438	1,575	1,822	1,939
Proved undeveloped reserves (volume)	359	465	391	652
Gas [Member]
Reserve Quantities [Line Items]
Proved reserves		22	4
Revisions of previous estimates		16	61
Production		(38)	(43)
Proved reserves			22
Proved developed reserves (volume)			22	4