v3.26.1
Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]        
Pretax total accumulated other comprehensive income (loss), beginning balance $ 130 $ (1,809)    
Pretax total accumulated other comprehensive income (loss), Investment securities (628) 1,108    
Pretax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities 98 (30)    
Total reclassification adjustment for amounts realized in net income, pre tax 98 (30)    
Total other comprehensive income (loss), pre tax (726) 1,138    
Pretax total accumulated other comprehensive income (loss), ending balance (596) (671)    
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]        
Total tax (provision) benefit, beginning balance (27) 386    
Total tax (provision) benefit, Investment securities 132 (233)    
Total tax (provision) benefit, Net realized gains (losses) on securities (20) 6    
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit (20) 6    
Total other comprehensive income (loss), tax (provision) benefit 152 (239)    
Total tax (provision) benefit, ending balance 125 147    
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
After tax total accumulated other comprehensive income (loss), beginning balance 103 (1,423)    
Stockholders' Equity Attributable to Parent 32,039 28,954 $ 30,323  
After tax total accumulated other comprehensive income (loss), Investment securities (496) 875    
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities 78 (24)    
Total reclassification adjustment for amounts realized in net income, after tax 78 (24)    
Total other comprehensive income (loss), after tax (574) 899    
After tax total accumulated other comprehensive income (loss), ending balance (471) (524)    
Total net unrealized gains (losses) on securities        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Stockholders' Equity Attributable to Parent (457) (509) 117 $ (1,408)
After tax total accumulated other comprehensive income (loss), Investment securities (496) 875    
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities 78 (24)    
Total reclassification adjustment for amounts realized in net income, after tax 78 (24)    
Total other comprehensive income (loss), after tax (574) 899    
Net unrealized losses on forecasted transactions        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Stockholders' Equity Attributable to Parent (13) (14) (13) (14)
After tax total accumulated other comprehensive income (loss), Investment securities 0 0    
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities 0 0    
Total reclassification adjustment for amounts realized in net income, after tax 0 0    
Total other comprehensive income (loss), after tax 0 0    
Foreign currency translation adjustment        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Stockholders' Equity Attributable to Parent (1) (1) $ (1) $ (1)
After tax total accumulated other comprehensive income (loss), Investment securities 0 0    
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities 0 0    
Total reclassification adjustment for amounts realized in net income, after tax 0 0    
Total other comprehensive income (loss), after tax $ 0 $ 0