Other Financial Data (Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 1,030	$ 1,980	$ 3,954	$ 3,225
Restricted cash	$ 63	$ 63