v3.25.1
Shareholders' Equity - Accumulated Other Comprehensive Income (Loss) Rollforward (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Balance, beginning of period $ 6,097 $ 5,648
Other comprehensive loss 66 (28)
Balance, end of period 6,213 5,746
AOCI    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Balance, beginning of period (341) (336)
Other comprehensive loss 66 (28)
Balance, end of period (275) (364)
Unrealized (losses) gains on available-for-sale investments    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Balance, beginning of period (361) (368)
Before reclassifications 64 (33)
Other comprehensive loss 66 (27)
Balance, end of period (295) (395)
Unrealized (losses) gains on available-for-sale investments, with allowance for credit loss    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Reclassification from AOCI   1
Unrealized (losses) gains on available-for-sale investments, without allowance for credit loss    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Reclassification from AOCI 2 5
Cumulative currency translation adjustment    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Balance, beginning of period 10 12
Before reclassifications   (1)
Other comprehensive loss 0 (1)
Balance, end of period 10 11
Insurance contracts - net liability for losses and LAE at fair value - Instrument-specific credit risk    
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]    
Balance, beginning of period 10 20
Other comprehensive loss 0 0
Balance, end of period $ 10 $ 20