Derivatives (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Oil (in million barrels) MillionBarrels	Dec. 31, 2011 Oil (in million barrels) MillionBarrels	Sep. 30, 2012 Natural Gas (in billion cubic feet) BillionCubicFeet	Dec. 31, 2011 Natural Gas (in billion cubic feet) BillionCubicFeet	Sep. 30, 2012 Precious metals (in million troy ounces) MillionTroyOunces	Dec. 31, 2011 Precious metals (in million troy ounces) MillionTroyOunces
Outstanding commodity derivatives contracts not designated as hedging instruments
Net Outstanding Position Long/(Short)					(4)	(9)	(178)	(242)	1	3
Net Gains (Losses) from derivatives not designated as hedging instruments. (in dollars)	$ 78	$ 20	$ 42	$ 124