| **Benefit Plans (Components of net periodic cost (benefit)) (Details) - USD ($) $ in Millions** | 3 Months Ended | 6 Months Ended |
|-------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Non-service cost:**                                                                           |           |           |   |   |
| Insurance claims and policyholders’ benefits                                              | $ 1,327        | $ 1,280        | $ 2,666 | $ 2,573 |
| Other operating expenses                                                                        | 298            | 292            | 601 | 568 |
| Pension Plans, Defined Benefit                                                                  |           |           |   |   |
| **Net periodic pension cost (benefit)**                                                         |           |           |   |   |
| Service cost                                                                                    | 0              | 0              | 0 | 0 |
| **Non-service cost:**                                                                           |           |           |   |   |
| Interest cost on projected benefit obligation                                                   | 24             | 26             | 47 | 52 |
| Expected return on plan assets                                                                  | (40)           | (39)           | (80) | (78) |
| Amortization of net actuarial loss                                                              | 9              | 9              | 18 | 18 |
| Settlement loss                                                                                 | 1              | 0              | 5 | 2 |
| Total non-service cost                                                                          | (6)            | (4)            | (10) | (6) |
| Total net periodic pension cost (benefit)                                                       | (6)            | (4)            | (10) | (6) |
| Insurance claims and policyholders’ benefits                                              | 2              | 1              | 3 | 2 |
| Other operating expenses                                                                        | $ 4            | $ 3            | $ 7 | $ 4 |

| X                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Defined Benefit Plan, Net Periodic Benefit Expense (Reversal of Expense), Excluding Service Cost Component [Abstract]
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Defined Benefit Plan, Service Cost [Abstract]
+ References
No definition available.
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| - Definition
Insurance claims and policyholders' benefits, including policyholders' dividends
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cost recognized for passage of time related to defined benefit plan.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of net periodic benefit cost (credit) for defined benefit plan.
+ References
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| - Definition
Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense (reversal of expense) for net periodic benefit cost components, excluding service cost component, of defined benefit plan. Amount includes, but is not limited to, interest cost, expected (return) loss on plan asset, amortization of prior service cost (credit), amortization of (gain) loss, amortization of transition (asset) obligation, settlement (gain) loss, curtailment (gain) loss and certain termination benefits.
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| - Definition
The total amount of other operating cost and expense items that are associated with the entity's normal revenue producing operation.
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