Summary of Significant Accounting Policies Foreign Currency - Devaluation (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) VEB / $
Impact of Foreign Currency Devaluation [Line Items]
Currency Devaluation and Related Charges	$ 41	$ 85	$ 245
Angola, Kwanza
Impact of Foreign Currency Devaluation [Line Items]
Currency Devaluation and Related Charges	31	39
Net Monetary Asset Position	116
Egypt, Pounds
Impact of Foreign Currency Devaluation [Line Items]
Currency Devaluation and Related Charges	$ 10
Venezuelan Bolivar
Impact of Foreign Currency Devaluation [Line Items]
Currency Devaluation and Related Charges		26	$ 245
Argentina, Pesos
Impact of Foreign Currency Devaluation [Line Items]
Currency Devaluation and Related Charges		11
Kazakhstan, Tenge
Impact of Foreign Currency Devaluation [Line Items]
Currency Devaluation and Related Charges		$ 9
SICAD II [Member] | Venezuelan Bolivar
Impact of Foreign Currency Devaluation [Line Items]
Foreign Currency Exchange Rate, Translation | VEB / $			50