Derivative Instruments (Schedule Of U.S. Crude Oil Derivative Positions) (Details) (U.S. Crude Oil Derivative Positions [Member])	Jun. 30, 2013 bbls
2013 [Member]
Derivative [Line Items]
Volumes (in Bbls)	1,766,400
Weighted Average Floor Price ($/Bbls)	90.17
Weighted Average Ceiling Price ($/Bbls)	100.87
2014 [Member]
Derivative [Line Items]
Volumes (in Bbls)	3,375,500
Weighted Average Floor Price ($/Bbls)	90.59
Weighted Average Ceiling Price ($/Bbls)	96.99
2015 [Member]
Derivative [Line Items]
Volumes (in Bbls)	1,806,750
Weighted Average Floor Price ($/Bbls)	89.41
Weighted Average Ceiling Price ($/Bbls)	94.96
2016 [Member]
Derivative [Line Items]
Volumes (in Bbls)	244,000
Weighted Average Floor Price ($/Bbls)	85.00
Weighted Average Ceiling Price ($/Bbls)	104.00