Foreign Exchange Risk Management (Details) € in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 EUR (€)
Foreign Exchange Risk Management
Terms of the foreign currency forward contracts and foreign currency option contracts	18 months
Net foreign currency transaction pre-tax loss in AOCI	$ 14
Foreign currency derivative contracts
Foreign Exchange Risk Management
Approximate effect of 10% adverse change in foreign currency rates on fair value loss	96
General and administrative | Foreign currency derivative contracts
Foreign Exchange Risk Management
Gain (loss) for contracts to purchase and sell foreign currency	$ (28)	$ (44)
Net Investment Hedging
Foreign Exchange Risk Management
Derivative Liability, Notional Amount | €			€ 1,650