Marketable Securities (current and non-current) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Marketable Securities [Line Items]
Current marketable securities	$ 338	$ 1,076
Non-current marketable securities	27	27
Total marketable securities	365	1,103
Corporate debt securities
Marketable Securities [Line Items]
Current marketable securities		14
Commercial paper
Marketable Securities [Line Items]
Current marketable securities	304	899
Certificates of deposit/time deposits
Marketable Securities [Line Items]
Current marketable securities	31	76
U.S. municipal securities
Marketable Securities [Line Items]
Current marketable securities	3	3
Non-current marketable securities	$ 27	27
Asset-backed securities total
Marketable Securities [Line Items]
Current marketable securities		84
Asset-backed securities Automobile loan related
Marketable Securities [Line Items]
Current marketable securities		16
Asset-backed securities Credit card related
Marketable Securities [Line Items]
Current marketable securities		$ 68

Amount of investment in marketable security.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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