v3.25.2
Outstanding Exposure - Components of BIG Net Par Outstanding (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Schedule of Insured Financial Obligations [Line Items]    
Net $ 272,778 $ 261,552
Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 261,848 250,375
Other structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 9,494 9,670
Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 10,930 11,177
BIG    
Schedule of Insured Financial Obligations [Line Items]    
Net 10,508 10,182
BIG | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 9,642 9,286
BIG | Other structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 75 77
BIG | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 866 896
BIG | BIG 1    
Schedule of Insured Financial Obligations [Line Items]    
Net 5,554 8,102
BIG | BIG 1 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 5,471 7,998
BIG | BIG 1 | Other structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 0 0
BIG | BIG 1 | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 83 104
BIG | BIG 2    
Schedule of Insured Financial Obligations [Line Items]    
Net 3,550 706
BIG | BIG 2 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 3,502 656
BIG | BIG 2 | Other structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 19 21
BIG | BIG 2 | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 48 50
BIG | BIG 3    
Schedule of Insured Financial Obligations [Line Items]    
Net 1,404 1,374
BIG | BIG 3 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 669 632
BIG | BIG 3 | Other structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 56 56
BIG | BIG 3 | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 735 742
United States | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 208,716 201,175
United States | RMBS    
Schedule of Insured Financial Obligations [Line Items]    
Net 1,436 1,507
United States | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 8,166 8,453
United States | BIG | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 2,550 2,888
United States | BIG | RMBS    
Schedule of Insured Financial Obligations [Line Items]    
Net 791 819
United States | BIG | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 866 896
United States | BIG | BIG 1 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 1,410 2,119
United States | BIG | BIG 1 | RMBS    
Schedule of Insured Financial Obligations [Line Items]    
Net 83 104
United States | BIG | BIG 2 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 471 137
United States | BIG | BIG 2 | RMBS    
Schedule of Insured Financial Obligations [Line Items]    
Net 29 29
United States | BIG | BIG 3 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 669 632
United States | BIG | BIG 3 | RMBS    
Schedule of Insured Financial Obligations [Line Items]    
Net 679 686
Non-U.S. public finance | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 53,132 49,200
Non-U.S. public finance | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 2,764 2,724
Non-U.S. public finance | BIG | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 7,092 6,398
Non-U.S. public finance | BIG | Structured finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 0 0
Non-U.S. public finance | BIG | BIG 1 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 4,061 5,879
Non-U.S. public finance | BIG | BIG 2 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net 3,031 519
Non-U.S. public finance | BIG | BIG 3 | Public finance    
Schedule of Insured Financial Obligations [Line Items]    
Net $ 0 $ 0