| **Postretirement Benefits Expected Future Benefit Payments (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended |        | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------|-----------------|--------|-----------------|
||
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                        |            |   |            |   |   |  |   |
| Defined Contribution Plan, Cost Recognized                                                                            | $ 41            | $ 33   | $ 31            |   |   |  |   |
| Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months                                            |            |   |            | 326 | 135 | [1] |   |
| Defined Benefit Plan, Expected Future Benefit Payments, Year Two                                                      |            |   |            | 318 | 132 | [1] |   |
| Defined Benefit Plan, Expected Future Benefit Payments, Year Three                                                    |            |   |            | 308 | 134 | [1] |   |
| Defined Benefit Plan, Expected Future Benefit Payments, Year Four                                                     |            |   |            | 301 | 127 | [1] |   |
| Defined Benefit Plan, Expected Future Benefit Payments, Year Five                                                     |            |   |            | 294 | 121 | [1] |   |
| Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter                                  |            |   |            | $ 1,362 | $ 543 | [1] |   |
| Contribution To The Trust Shares                                                                                      |            |   |            |   |   |  | 25.5 |
|                                                                                                                       |
| [1](A)Payments are net of expected participant contributions and expected federal subsidy receipts.                   |

| X                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Contribution To The Trust Shares
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of benefits expected to be paid  in the five fiscal years after the fifth fiscal year following the latest fiscal year from a defined benefit plan.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of benefits expected to be paid in the next fiscal year following the latest fiscal year from a defined benefit plan.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of benefits expected to be paid in the fifth fiscal year following the latest fiscal year from a defined benefit plan.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
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| - Definition
Amount of benefits expected to be paid in the fourth fiscal year following the latest fiscal year from a defined benefit plan.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
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| - Definition
Amount of benefits expected to be paid in the third fiscal year following the latest fiscal year from a defined benefit plan.
+ References
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| - Definition
Amount of benefits expected to be paid in the second fiscal year following the latest fiscal year from a defined benefit plan.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of the cost recognized during the period for defined contribution plans.
+ References
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