Supplemental Information On Oil And Natural Gas Producing Activities (Proved Reserves) (Details) - MMBoe MMBoe in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Changes in proved developed and undeveloped reserves
Balance	16,627	15,209
Extensions and discoveries	3	509
Purchase of reserves in place	5,124	72
Revisions of previous estimates	(9,038)	2,361
Production	(1,074)	(1,524)
Balance	11,642	16,627
Proved developed reserves	11,523	12,439
Proved undeveloped reserves	119	4,188
Oil [Member]
Changes in proved developed and undeveloped reserves
Balance	1,662	2,072
Extensions and discoveries	3	416
Purchase of reserves in place	3,516	72
Revisions of previous estimates	(1,754)	(590)
Production	(268)	(308)
Balance	3,159	1,662
Proved developed reserves	3,071	1,523
Proved undeveloped reserves	88	139
Natural Gas [Member]
Changes in proved developed and undeveloped reserves
Balance	14,907	12,994
Extensions and discoveries		93
Purchase of reserves in place	799
Revisions of previous estimates	(7,175)	3,008
Production	(795)	(1,188)
Balance	7,736	14,907
Proved developed reserves	7,705	10,858
Proved undeveloped reserves	31	4,049
Natural Gas Liquids [Member]
Changes in proved developed and undeveloped reserves
Balance	58	143
Purchase of reserves in place	809
Revisions of previous estimates	(109)	(57)
Production	(11)	(28)
Balance	747	58
Proved developed reserves	747	58