Litigation And Other Contingencies (Narrative) (Details) (USD $)	Oct. 24, 2011	Oct. 09, 2014	Jun. 27, 2007	May 01, 2007
Production Sharing Contract (PSC) [Member]
Litigation And Other Contingencies [Line Items]
Percent interest in Erha block PSC	56.25%
Pending Or Threatened Litigation [Member]
Litigation And Other Contingencies [Line Items]
Amount of award relating to excess lifting of crude oil	1,800,000,000
Accrued interest relating to award for excess lifting of crude oil	234,000,000
Expropriation Of Assets [Member] | Mobil Cerro Negro, Ltd. (MCN) [Member]
Litigation And Other Contingencies [Line Items]
Percentage ownership interest in Cerro Negro Project			41.67%	41.67%
Final award related to Cerro Negro Project arbitration		1,600,000,000
Interest rate on award for Cerro Negro Project		3.25%
Earlier Cerro Negro award for breach of contractual obligations		$ 908,000,000