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Expected Loss to be Paid (Recovered) - Additional Information (Details) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2023 USD ($) | Mar. 31, 2023 USD ($) | Jun. 30, 2022 USD ($) | Jun. 30, 2023 USD ($) Payment Curve scenario | Jun. 30, 2022 USD ($) | Dec. 31, 2022 USD ($) scenario | Mar. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Period of insured credit performance of guaranteed obligations (in some cases over) |  |  |  | 30 years |  |  |  |
Discount factor (as a percent) |  |  |  | 4.34% |  | 4.08% |  |
Net Expected Loss to be Paid (Recovered) | $ 560 | $ 517 | $ 442 | $ 560 | $ 442 | $ 522 | $ 432 | $ 411
Loss and LAE Reserve paid | 5 |  | 7 | 8 | 20 |  |  |
Expected LAE to be paid | 11 |  |  | 11 |  | 11 |  |
Net economic loss development (benefit) | 49 |  | (32) | $ 60 | (76) |  |  |
Additional loss recovery assumption, recovery period |  |  |  | 5 years |  |  |  |
First Lien |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Effect of recovery |  | 1 |  |  |  |  |  |
Second Lien |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Effect of recovery |  | 1 |  |  |  |  |  |
Public finance |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Net Expected Loss to be Paid (Recovered) | 443 | 393 | 217 | $ 443 | 217 | 412 | 191 | 209
Net economic loss development (benefit) | 54 |  | 6 | 59 | (44) |  |  |
Other structured finance |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Net Expected Loss to be Paid (Recovered) | 44 | 42 | 46 | 44 | 46 | $ 44 | 46 | 52
Net economic loss development (benefit) | 4 |  | 1 | $ 5 | 0 |  |  |
United States |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Net expected loss to be paid after recoveries for representations and warranties, percent |  |  |  | 98.30% |  | 98.50% |  |
United States | Public finance |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Net Expected Loss to be Paid (Recovered) | 433 | 380 | 210 | $ 433 | 210 | $ 403 | 181 | 197
Net economic loss development (benefit) | 57 |  | 8 | 58 | (40) |  |  |
United States | RMBS |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Net Expected Loss to be Paid (Recovered) | 73 | $ 82 | 179 | 73 | 179 | $ 66 | $ 195 | $ 150
Net economic loss development (benefit) | (9) |  | (39) | (4) | (32) |  |  |
United States | RMBS | First Lien |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Net economic loss development (benefit) | $ 0 |  | (14) | $ 0 | 4 |  |  |
Number of delinquent payments | Payment |  |  |  | 2 |  |  |  |
Projected loss assumptions, CDR, plateau rate, projection period |  |  |  | 36 months |  |  |  |
Projected loss assumptions, final CPR, period for voluntary prepayments to continue |  |  |  | 12 months |  |  |  |
Intermediate conditional default rate (as a percent) | 5.00% |  |  | 5.00% |  |  |  |
Number of scenarios weighted in estimating expected losses | scenario |  |  |  | 5 |  | 5 |  |
United States | RMBS | First Lien | Base Scenario |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Percent of deferred loan balances to be recovered |  |  |  | 20.00% |  | 20.00% |  |
United States | RMBS | First Lien | More Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Percent of deferred loan balances to be recovered |  | 10.00% |  |  |  |  |  |
United States | RMBS | First Lien | Least Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Percent of deferred loan balances to be recovered |  | 50.00% |  |  |  |  |  |
United States | RMBS | First Lien | Base Scenario |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Projected loss assumptions, CDR, plateau rate, projection period |  |  |  | 36 months |  |  |  |
Period from plateau to intermediate conditional default rate (in months) |  |  |  | 12 months |  |  |  |
Final conditional default rate as a percentage of plateau conditional default rate |  |  |  | 5.00% |  |  |  |
Projected loss assumptions, final CPR, period for voluntary prepayments to continue |  |  |  | 1 year |  |  |  |
Default from delinquentor rate, term |  |  |  | 36 months |  |  |  |
Performing or projected to reperform, projection period |  |  |  | 36 months |  |  |  |
Projected loss assumptions, loss severity, subsequent period |  |  |  | 18 months |  |  |  |
Estimated loss severity rate, one through six months (as a percent) |  |  |  | 18 months |  |  |  |
Loss severity (as a percent) | 40.00% |  |  | 40.00% |  |  |  |
Projected loss assumptions, period to reach final loss severity rate |  |  |  | 2 years 6 months |  |  |  |
Final CPR | 15.00% |  |  | 15.00% |  |  |  |
United States | RMBS | First Lien | More Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Period from plateau to intermediate conditional default rate (in months) |  |  |  | 16 months |  |  |  |
Projected loss assumptions, period to reach final loss severity rate |  |  |  | 9 years |  |  |  |
Percent of deferred loan balances to be recovered |  |  |  | 10.00% |  |  |  |
Projected loss assumptions, increase (decrease) in expected loss to be paid, net |  |  |  | $ 22 |  |  |  |
United States | RMBS | First Lien | Least Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Projected loss assumptions, CDR, plateau rate, projection period |  |  |  | 30 months |  |  |  |
Period from plateau to intermediate conditional default rate (in months) |  |  |  | 8 months |  |  |  |
Percent of deferred loan balances to be recovered |  |  |  | 50.00% |  |  |  |
Projected loss assumptions, increase (decrease) in expected loss to be paid, net |  |  |  | $ (31) |  |  |  |
Decrease in the plateau period used to calculate potential change in loss estimate (in months) |  |  |  | 6 months |  |  |  |
United States | RMBS | Second Lien |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Net economic loss development (benefit) | $ (9) |  | $ (25) | $ (4) | $ (36) |  |  |
Projected loss assumptions, period of consistent conditional default rate |  |  |  | 36 months |  |  |  |
Period of conditional default rate downward trend |  |  |  | 1 year |  |  |  |
Percent of original period of consistent conditional default rate |  |  |  | 5.00% |  |  |  |
Loss recovery assumption (as a percent) | 2.00% |  |  | 2.00% |  | 2.00% |  |
Number of conditional default rate curves modeled in estimating losses | Curve |  |  |  | 5 |  |  |  |
Liquidation rate | 30.00% |  |  | 30.00% |  |  |  |
United States | RMBS | Second Lien | More Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Percent of deferred loan balances to be recovered |  |  |  | 10.00% |  |  |  |
United States | RMBS | Second Lien | Least Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Percent of deferred loan balances to be recovered |  |  |  | 50.00% |  |  |  |
United States | RMBS | Second Lien | Home Equity Line of Credit and Closed-end Mortgage |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Final CPR | 15.00% |  |  | 15.00% |  |  |  |
United States | RMBS | Second Lien | More Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Projected loss assumptions, CDR, plateau rate, projection period |  |  |  | 42 months |  |  |  |
Period from plateau to intermediate conditional default rate (in months) |  |  |  | 16 months |  |  |  |
Stress period (in months) |  |  |  | 58 months |  |  |  |
Increase in conditional default rate ramp down period |  |  |  | 4 months |  |  |  |
United States | RMBS | Second Lien | More Stressful Environment | Home Equity Line of Credit |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Change in estimate for increased conditional default rate plateau period |  |  |  | $ (62) |  |  |  |
United States | RMBS | Second Lien | Least Stressful Environment |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Stress period (in months) |  |  |  | 38 months |  |  |  |
Period of constant conditional default rate (in months) |  |  |  | 30 months |  |  |  |
Decreased conditional default rate ramp down period |  |  |  | 8 months |  |  |  |
Change in estimate for decreased prepayment rate, Percent |  |  |  | 10.00% |  |  |  |
United States | RMBS | Second Lien | Least Stressful Environment | Home Equity Line of Credit |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Change in estimate for decreased conditional default rate ramp down period |  |  |  | $ 63 |  |  |  |
United States | Home Equity Line of Credit |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Initial period for which borrower can pay only interest payments |  |  |  | 10 years |  |  |  |
United States | Home Equity Line of Credit Insured |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Initial period for which borrower can pay only interest payments |  |  |  | 15 years |  |  |  |
Minimum |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Risk free discount rate |  |  |  | 3.73% |  | 3.82% |  |
Maximum |  |  |  |  |  |  |  |
Schedule of Expected Losses to be Paid [Line Items] |  |  |  |  |  |  |  |
Risk free discount rate |  |  |  | 5.37% |  | 4.69% |  |

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- Definition Represents the initial period over which defaults projected to occur on a pool of insured obligations represent defaults that can be attributed to obligations that are currently delinquent or in foreclosure. + References No definition available. + Details
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- Definition Represents the period over which the conditional prepayment rate assumed for a pool of insured obligations trends from the initial to the final rate. + References No definition available. + Details
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