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Debt (Estimated Fair Value of Significant Financial Instruments) (Details) - USD ($) $ in Millions | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Carrying Amount |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term debt | $ 1,562 | $ 314
Long-term debt | 11,472 | 5,510
Fair Value |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term debt | 1,561 | 313
Long-term debt | $ 11,943 | $ 5,437

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- Definition Long Term Debt and Capital Lease Obligation, Noncurrent, Fair Value + References No definition available. + Details
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