Outstanding Oil Contracts That Are Not Designated For Hedge Accounting (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Oil contracts [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Total	$ (25)
Natural gas contracts [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Total	(11)
Fixed Price Swaps With Sold Puts [Member] | Oil contracts [Member] | January 2014 - March 2014 [Member]
Derivative [Line Items]
Volume in MBbls	1,440,000
Derivative, Swap Type, Average Fixed Price	95.16
Derivative Weighted Average Additional Put Price	75
Derivative Liability, Fair Value, Total	(4)
Fixed Price Swaps With Sold Puts [Member] | Oil contracts [Member] | April 2014 - June 2014 [Member]
Derivative [Line Items]
Volume in MBbls	1,456,000
Derivative, Swap Type, Average Fixed Price	95.16
Derivative Weighted Average Additional Put Price	75
Derivative Liability, Fair Value, Total	(3)
Fixed Price Swaps With Sold Puts [Member] | Oil contracts [Member] | July 2014 - September 2014 [Member]
Derivative [Line Items]
Volume in MBbls	1,472,000
Derivative, Swap Type, Average Fixed Price	95.16
Derivative Weighted Average Additional Put Price	75
Derivative Liability, Fair Value, Total	0
Fixed Price Swaps With Sold Puts [Member] | Oil contracts [Member] | October 2014 - December 2014 [Member]
Derivative [Line Items]
Volume in MBbls	1,472,000
Derivative, Swap Type, Average Fixed Price	95.16
Derivative Weighted Average Additional Put Price	75
Derivative Asset, Fair Value, Total	2
Fixed Price Swaps With Sold Puts [Member] | Oil contracts [Member] | January 2015 - December 2015 [Member]
Derivative [Line Items]
Volume in MBbls	4,567,000
Derivative, Swap Type, Average Fixed Price	90.03
Derivative Weighted Average Additional Put Price	68.2
Derivative Asset, Fair Value, Total	3
Collars With Sold Puts [Member] | Oil contracts [Member] | January 2014 - March 2014 [Member]
Derivative [Line Items]
Volume in MBbls	540,000
Derivative Weighted Average Additional Put Price	75.83
Derivative, Weighted Average Floor Price	90.83
Derivative, Weighted Average Ceiling Price	103
Derivative Liability, Fair Value, Total	(1)
Collars With Sold Puts [Member] | Oil contracts [Member] | April 2014 - June 2014 [Member]
Derivative [Line Items]
Volume in MBbls	546,000
Derivative Weighted Average Additional Put Price	75.83
Derivative, Weighted Average Floor Price	90.83
Derivative, Weighted Average Ceiling Price	103
Derivative Liability, Fair Value, Total	0
Collars With Sold Puts [Member] | Oil contracts [Member] | July 2014 - September 2014 [Member]
Derivative [Line Items]
Volume in MBbls	552,000
Derivative Weighted Average Additional Put Price	75.83
Derivative, Weighted Average Floor Price	90.83
Derivative, Weighted Average Ceiling Price	103
Derivative Asset, Fair Value, Total	1
Collars With Sold Puts [Member] | Oil contracts [Member] | October 2014 - December 2014 [Member]
Derivative [Line Items]
Volume in MBbls	552,000
Derivative Weighted Average Additional Put Price	75.83
Derivative, Weighted Average Floor Price	90.83
Derivative, Weighted Average Ceiling Price	103
Derivative Asset, Fair Value, Total	1
Fixed-price swaps | Oil contracts [Member] | January 2014 - March 2014 [Member]
Derivative [Line Items]
Volume in MBbls	1,350,000
Derivative, Swap Type, Average Fixed Price	89.60
Derivative Liability, Fair Value, Total	(12)
Fixed-price swaps | Oil contracts [Member] | April 2014 - June 2014 [Member]
Derivative [Line Items]
Volume in MBbls	1,729,000
Derivative, Swap Type, Average Fixed Price	90.07
Derivative Liability, Fair Value, Total	(12)
Fixed-price swaps | Oil contracts [Member] | July 2014 - September 2014 [Member]
Derivative [Line Items]
Volume in MBbls	1,932,000
Derivative, Swap Type, Average Fixed Price	89.86
Derivative Liability, Fair Value, Total	(9)
Fixed-price swaps | Oil contracts [Member] | October 2014 - December 2014 [Member]
Derivative [Line Items]
Volume in MBbls	2,116,000
Derivative, Swap Type, Average Fixed Price	89.95
Derivative Liability, Fair Value, Total	(5)
Fixed-price swaps | Oil contracts [Member] | January 2015 - December 2015 [Member]
Derivative [Line Items]
Volume in MBbls	6,567,000
Derivative, Swap Type, Average Fixed Price	90.39
Derivative Asset, Fair Value, Total	14
Fixed-price swaps | Natural gas contracts [Member] | January 2014 - March 2014 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price	3.98
Derivative Liability, Fair Value, Total	(6)
Fixed-price swaps | Natural gas contracts [Member] | April 2014 - June 2014 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price	3.98
Derivative Liability, Fair Value, Total	(3)
Fixed-price swaps | Natural gas contracts [Member] | July 2014 - September 2014 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price	3.98
Derivative Liability, Fair Value, Total	(4)
Fixed-price swaps | Natural gas contracts [Member] | October 2014 - December 2014 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price	3.98
Derivative Liability, Fair Value, Total	(5)
Fixed-price swaps | Natural gas contracts [Member] | January 2015 - December 2015 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price	4.28
Derivative Asset, Fair Value, Total	$ 7