Income Taxes, Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrecognized Tax Benefits
Unrecognized tax benefits	$ 970	$ 941	$ 936	$ 964
Tax refund claim not presented in our balance sheets	(277)	(274)
Other	88	77
Uncertain tax position liabilities presented in our balance sheets	$ 781	$ 744