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Financial Instruments (Derivative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 4,556	$ 4,447
Restricted Cash and Cash Equivalents, Current	116	52
Restricted Cash and Cash Equivalents, Noncurrent	127	132
Total cash, cash equivalents, restricted cash and restricted cash equivalents presented in the consolidated statements of cash flows	4,799	4,631	$ 5,129	$ 4,403
Credit Derivative, Maximum Exposure, Undiscounted	49
Bank Time Deposits [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 2,400	$ 2,900