| **Benefit Plans**                                     | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                          |
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| **Compensation and Retirement Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Benefit Plans                                         | Note G. Benefit PlansThe components of net periodic cost (benefit) are presented in the following table.Three months ended March 31   (In millions)2016 2015Pension cost (benefit)   Service cost$— $2Interest cost on projected benefit obligation28 28Expected return on plan assets(40) (43)Amortization of net actuarial loss9 9Net periodic pension cost (benefit)$(3) $(4) |

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| - References
No definition available.
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| - Definition
The entire disclosure for pension and other postretirement benefits.
+ References
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