Marketable Securities (current and non-current) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Marketable securities
Current marketable securities	$ 139	$ 380
Non-current marketable securities	46	37
Total marketable securities	185	417
Commercial paper
Marketable securities
Current marketable securities	102	366
Certificates of deposit/time deposits
Marketable securities
Current marketable securities	34	10
U.S. municipal securities
Marketable securities
Current marketable securities	3	3
Non-current marketable securities	$ 46	37
Asset-backed securities
Marketable securities
Current marketable securities		$ 1

Amount of investment in marketable security.

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