Derivative and Financial Instruments - FX Notional (Details 5) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Sell U.S. dollar, buy other currencies [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Net notional position of foreign currency exchange derivatives	[1]	$ 13	$ 347
Buy U.S. dollar, sell other currencies [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Net notional position of foreign currency exchange derivatives	[2]	25	20
Buy British pound, sell other currencies [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Net notional position of foreign currency exchange derivatives	[3]	1,069	567
Sell British pound, buy Norwegian krone [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Net notional position of foreign currency exchange derivatives		$ 51	$ 0

[1] *Primarily Canadian dollar, Norwegian krone and British pound.

[2] **Primarily Canadian dollar and British pound.

[3] ***Primarily Canadian dollar and Euro.