| **Benefit Plans (Summary of non-service cost (benefit) in the condensed consolidated statements of operations (Details) - Pension Plan - USD ($) $ in Millions** | 3 Months Ended | 9 Months Ended |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                                   |           |           |   |   |
| Total net periodic pension cost (benefit)                                                                                                                        | $ (13)         | $ (11)         | $ (41) | $ (33) |
| Insurance claims and policyholders' benefits                                                                                                                     |           |           |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                                   |           |           |   |   |
| Non-Service Cost (Benefit)                                                                                                                                       | (3)            | (3)            | (11) | (9) |
| Other operating expenses                                                                                                                                         |           |           |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                                   |           |           |   |   |
| Non-Service Cost (Benefit)                                                                                                                                       | $ (10)         | $ (8)          | $ (30) | $ (24) |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of net periodic benefit cost (credit) for defined benefit plan.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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.
+ References
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| X                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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