v2.4.0.6
Subsequent Event (Details) (Cline And Midland-Wolfcamp Shale Plays [Member], USD $)
In Millions, unless otherwise specified
1 Months Ended
Aug. 31, 2012
Subsequent Event [Line Items]  
Subsequent Event, Date August 2012
Subsequent Event, Percentage of Interest Sold 30.00%
Sold Interest And Future Drilling Costs [Member]
 
Subsequent Event [Line Items]  
Subsequent Event, Cash Received 1,365
Sold Interest [Member]
 
Subsequent Event [Line Items]  
Subsequent Event, Cash Received 340
Future Drilling Costs [Member]
 
Subsequent Event [Line Items]  
Subsequent Event, Cash Received 1,025