Supplementary Information for Certain Balance Sheet Accounts - Prepaid and Other Current Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Prepayments and accrued income	$ 133	$ 136
Deferred contract costs	72	102
Derivatives and investments	22	25
Deferred compensation plan assets	19	18
Retention incentives	7	5
Corporate income and other taxes	117	61
Other current assets	81	57
Total prepaid and other current assets	$ 451	$ 404