v3.25.1
Claim and Claim Adjustment Expense Reserves (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Dec. 31, 2024
Dec. 31, 2011
Dec. 31, 2010
Liability for Claims and Claims Adjustment Expense [Line Items]          
Unusual or infrequent item, or both, net of insurance proceeds $ 97 $ 88      
Pretax (favorable) unfavorable premium development, excluding Life & Group 83 (7)      
Retroactive reinsurance benefit recognized 17 12      
Cumulative amounts ceded under AEP Loss Portfolio Transfer 3,700   $ 3,700    
Asbestos and Environmental Reserves          
Liability for Claims and Claims Adjustment Expense [Line Items]          
Net A&EP claim and allocated claim adjustment expense reserves ceded to NICO         $ 1,600
Aggregate limit under A&EP Loss Portfolio Transfer         4,000
A&EP claim and allocated claim adjustment expense reserves ceded under existing third party reinsurance contracts transferred to NICO under A&EP Loss Portfolio Transfer         1,200
Reinsurance premium paid to NICO under A&EP Loss Portfolio Transfer         2,000
Net reinsurance receivables transferred to NICO under A&EP Loss Portfolio Transfer         215
Total consideration paid to NICO under AEP Loss Portfolio Transfer       $ 2,200 $ 2,200
Deferred reinsurance benefit yet to be recognized 408   $ 425    
Fair value of collateral trust account established by NICO under A&EP Loss Portfolio Transfer 2,300        
California Wildfires          
Liability for Claims and Claims Adjustment Expense [Line Items]          
Unusual or infrequent item, or both, net of insurance proceeds 53        
Corporate & Other          
Liability for Claims and Claims Adjustment Expense [Line Items]          
Pretax (favorable) unfavorable premium development, excluding Life & Group $ 22 $ 0