Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents as presented in our Consolidated Balance Sheets	$ 1,498	$ 1,196	$ 1,085
Restricted cash included in prepaid and other current assets	40	48	45
Restricted cash included in other noncurrent assets	0	49	110
Cash, cash equivalents and restricted cash as presented in our Consolidated Statements of Cash Flows	1,538	1,293	$ 1,240	$ 963
Foreign currency translation adjustment	$ 3	$ (8)