|**Benefit Plans (Tables)**                    | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|--------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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|**Retirement Benefits [Abstract]**            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Components of net periodic cost (benefit)     | The 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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
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|Total net periodic pension cost (benefit)     | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
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|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)     | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  

X- ReferencesNo definition available.
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duration X- DefinitionTabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments.
+ ReferencesReference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (h) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1
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