Derivative and Financial Instruments - FX Notional (Details 5) In Millions, unless otherwise specified	Dec. 31, 2014 Sell U.S. dollar, buy British pound [Member] USD ($)	Dec. 31, 2014 Buy U.S. dollar, sell other currencies [Member] USD ($)	Dec. 31, 2013 Buy U.S. dollar, sell other currencies [Member] USD ($)	Dec. 31, 2014 Buy British pound, sell euro [Member] GBP (£)	Dec. 31, 2013 Buy British pound, sell euro [Member] GBP (£)
Trading Activity, Gains and Losses, Net [Line Items]
Net notional position of foreign currency exchange derivatives	$ 7	$ 44	$ 6	£ 20	£ 17