Financial Instruments (Foreign Exchange Risk) (Details) - USD ($) $ in Billions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Cross-currency interest rate swap contracts
Derivative [Line Items]
Types of Foreign Currency Derivatives Used	400
Derivatives Not Designated as Hedging Instruments \| Foreign Exchange Forward
Derivative [Line Items]
Aggregate notional amount	$ 1.3	$ 1.4

Description of the types of foreign currency exchange rate derivative instruments used. For example, forward contracts, options, and so forth.

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