v3.26.1
Bank Loans and Related Allowance for Credit Losses - Changes in Allowance for Credit Losses (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Beginning balance $ 36 $ 21 $ 21
Charge-offs 0 0  
Recoveries 0 0  
Provision for credit losses 0 0  
Ending balance 36 21 36
Residential real estate      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Beginning balance 29 15 15
Charge-offs 0 0  
Recoveries 0 0  
Provision for credit losses 1 0  
Ending balance 30 15 29
Residential real estate | First Mortgages      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Beginning balance 28 14 14
Charge-offs 0 0 0
Recoveries 0 0  
Provision for credit losses 1 0  
Ending balance 29 14 28
Residential real estate | HELOCs      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Beginning balance 1 1 1
Charge-offs 0 0 0
Recoveries 0 0  
Provision for credit losses 0 0  
Ending balance 1 1 1
Pledged asset lines      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Beginning balance 0 0 0
Charge-offs 0 0  
Recoveries 0 0  
Provision for credit losses 0 0  
Ending balance 0 0 0
Other      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Beginning balance 7 6 6
Charge-offs 0 0  
Recoveries 0 0  
Provision for credit losses (1) 0  
Ending balance $ 6 $ 6 $ 7