|**Benefit Plans**                             | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|--------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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|**Retirement Benefits [Abstract]**            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Benefit Plans                                 | Benefit PlansThe components of net periodic pension cost (benefit) are presented in the following table.Three months ended March 31(In millions)20242023Net periodic pension cost (benefit)Interest cost on projected benefit obligation$22$25Expected return on plan assets(29)(30)Amortization of net actuarial loss78Total net periodic pension cost (benefit)$—$3The following table indicates the line items in which the non-service cost (benefit) is presented in the Condensed Consolidated Statements of Operations.Three months ended March 31(In millions)20242023Non-Service Cost (Benefit):Insurance claims and policyholder's benefits$—$1Other operating expenses—2Total net periodic pension cost (benefit)$—$3
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|Three months ended March 31                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|(In millions)                                 | 2024                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Net periodic pension cost (benefit)           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Interest cost on projected benefit obligation | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Expected return on plan assets                | (29)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Amortization of net actuarial loss            | 7                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Total net periodic pension cost (benefit)     | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Three months ended March 31                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|(In millions)                                 | 2024                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Non-Service Cost (Benefit):                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|Insurance claims and policyholder's benefits  | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Other operating expenses                      | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Total net periodic pension cost (benefit)     | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

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