Subsequent Events (Notional Volumes Of Commodity Derivative Contracts) (Details) (Oil Positions [Member])	Feb. 28, 2013	Dec. 31, 2012
WTI [Member] | Mar-Dec 2013 [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day	469
Average price	96.55
WTI [Member] | 2014 [Member] | Swaps [Member]
Derivative [Line Items]
Hedged volume per day	464	6,661
Average price	93.50	96.35
WTS/WTI [Member] | Apr-Dec 2013 [Member] | Basis Swap [Member]
Derivative [Line Items]
Hedged volume per day	2,400
Average price	(1.90)
WTS/WTI [Member] | 2014 [Member] | Basis Swap [Member]
Derivative [Line Items]
Hedged volume per day	2,400
Average price	(2.10)