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| **Accounting Policies [Abstract]**                                             |                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Schedule of New Accounting Pronouncements and Changes in Accounting Principles | Adoption of the updated guidance resulted in the following changes to the Condensed Consolidated Balance Sheet on January 1, 2019:(In millions)Balance as of December 31, 2018 Adjustments Due to Adoption of Topic 842 Balance as of January 1, 2019Property and equipment at cost (less accumulated depreciation)$324 $2 $326Other assets1,208 237 1,445Other liabilities3,089 239 3,328 |

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| - Definition
Tabular disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.
+ References
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