v3.26.1
Fair Value Measurements - Narrative (Details)
$ / shares in Units, $ in Millions
 3 Months Ended
Mar. 31, 2026
USD ($)
pricingMethod
$ / shares
Mar. 31, 2025
USD ($)
Dec. 31, 2025
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Number of pricing methods | pricingMethod 3    
Fair value option, debt securities $ 3,351   $ 3,470
Debt securities 51,948   50,791
Transfers from Level 3 to Level 2 91 $ 58  
Transfers from Level 2 to Level 3 17 174  
Transfers from Level 3 to NAV $ 0 $ 0  
FHLBI capital stock, stock price (in usd per share) | $ / shares $ 100    
Unobservable Inputs | Level 3      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Debt securities $ 114   117
Funds withheld assets      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value option, assets carrying amount 3,758   3,867
Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value option, market risk benefit, debt securities 695   766
Debt securities 51,948   50,791
Variable Interest Entity, Primary Beneficiary      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value option, debt securities 2,650   2,698
Other Liabilities 323   258
Variable Interest Entity, Primary Beneficiary | Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Other Liabilities $ 2,543   $ 2,578