Derivative Instruments And Hedging Activities (Volumes Under Derivative Contracts Related To Oil And Gas Producing Activities) (Details)	9 Months Ended
	Sep. 30, 2012 bbl
Minimum [Member] | Crude Oil [Member] | Brent [Member] | Collar [Member]
Weighted Average Price	98.44	[1]
Current Remaining Year [Member] | Crude Oil [Member] | Collar [Member]
Average Monthly Volumes	75,000
Current Remaining Year [Member] | Crude Oil [Member] | Brent [Member] | Swap [Member]
Average Monthly Volumes	103,700
Weighted Average Price	92.15	[1]
Current Remaining Year [Member] | Crude Oil [Member] | Brent [Member] | Collar [Member]
Average Monthly Volumes	80,300
Current Remaining Year [Member] | Natural Gas [Member] | Swap [Member]
Average Monthly Volumes	776,700,000
Weighted Average Price	4.31	[1]
Current Remaining Year [Member] | Natural Gas [Member] | Collar [Member]
Average Monthly Volumes	130,000,000
Current Remaining Year [Member] | Maximum [Member] | Crude Oil [Member] | Collar [Member]
Weighted Average Price	118.57	[2]
Current Remaining Year [Member] | Maximum [Member] | Crude Oil [Member] | Brent [Member] | Collar [Member]
Weighted Average Price	118.71	[1]
Current Remaining Year [Member] | Maximum [Member] | Natural Gas [Member] | Collar [Member]
Weighted Average Price	5.13	[1]
Current Remaining Year [Member] | Minimum [Member] | Crude Oil [Member] | Collar [Member]
Weighted Average Price	96.67	[2]
Current Remaining Year [Member] | Minimum [Member] | Crude Oil [Member] | Brent [Member] | Collar [Member]
Weighted Average Price	99.77	[1]
Current Remaining Year [Member] | Minimum [Member] | Natural Gas [Member] | Collar [Member]
Weighted Average Price	4.75	[1]
Next Year [Member] | Crude Oil [Member] | Brent [Member] | Swap [Member]
Average Monthly Volumes	88,900
Weighted Average Price	95.28	[1]
Next Year [Member] | Crude Oil [Member] | Brent [Member] | Collar [Member]
Average Monthly Volumes	133,300
Next Year [Member] | Natural Gas [Member] | Swap [Member]
Average Monthly Volumes	500,000,000
Weighted Average Price	4.09	[1]
Next Year [Member] | Maximum [Member] | Crude Oil [Member] | Brent [Member] | Collar [Member]
Weighted Average Price	115.85	[1]

[1] The prices quoted in the table above are NYMEX Henry Hub for natural gas. Our oil contracts are indexed to the Brent crude oil price unless otherwise indicated.

[2] This contract is priced using NYMEX West Texas Intermediate for crude oil.