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Expected Loss to be Paid (Recovered) - Net Economic Loss Development (Benefit) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |
RMBS losses | $ (38) | $ (34) | $ (17) | $ (20)
RMBS | United States |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |
RMBS losses | (31) | (56) | (40) | (69)
RMBS | United States | First Lien |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |
RMBS losses | (2) | (21) | (4) | (24)
RMBS | United States | Second Lien |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |
RMBS losses | $ (29) | $ (35) | $ (36) | $ (45)

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