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Reinsurance - Narrative (Details) $ in Thousands |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jul. 01, 2023 USD ($) | Jul. 01, 2022 | Oct. 31, 2023 USD ($) | Sep. 30, 2023 USD ($) | Jun. 30, 2023 USD ($) | Sep. 30, 2022 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2022 USD ($) | Jun. 30, 2024 USD ($) | Sep. 30, 2028 | Dec. 31, 2022 USD ($) | Feb. 29, 2020 USD ($) | Apr. 30, 2019 USD ($)
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage-linked insurance notes tendered |  |  |  | $ 5,116,509 |  |  | $ 5,116,509 |  |  |  |  |  |
Ceded premiums earned |  |  |  | 21,506 |  | $ 22,999 | 92,568 | $ 49,192 |  |  |  |  |
Mortgage insurance-linked notes | Fixed-maturities available for sale |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage-linked insurance notes tendered |  |  |  | 50,682 |  |  | 50,682 |  |  |  | $ 53,019 |  |
Mortgage |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
RIF ceded |  |  |  | 69,300,000 |  |  | 69,300,000 |  |  |  | 66,100,000 |  |
Ceded premiums earned |  |  |  | 21,406 |  | $ 22,859 | 92,268 | $ 48,772 |  |  |  |  |
Radian Guaranty |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Funds held under reinsurance agreements, asset |  |  |  | 200,000 |  |  | 200,000 |  |  |  | 175,000 |  |
Radian Guaranty | Eagle Re 2019-1 Ltd. | Mortgage insurance-linked notes | Fixed-maturities available for sale |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage-linked insurance notes tendered |  |  |  |  | $ 455,000 |  |  |  |  |  |  |  |
Mortgage-linked insurance notes tendered (as a percent) |  |  |  |  | 100.00% |  |  |  |  |  |  |  |
Radian Guaranty | Eagle Re 2020-1 Ltd. | Mortgage insurance-linked notes | Fixed-maturities available for sale |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage-linked insurance notes tendered |  |  |  |  | $ 332,000 |  |  |  |  |  |  |  |
Mortgage-linked insurance notes tendered (as a percent) |  |  |  |  | 82.00% |  |  |  |  |  |  |  |
Radian Guaranty | Eagle Re 2019-1 Ltd. and Eagle Re 2020-1 Ltd. |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded premiums earned |  |  |  |  |  |  | $ 21,000 |  |  |  |  |  |
One-time costs recovery period |  |  |  |  |  |  | 1 year |  |  |  |  |  |
Radian Guaranty | Eagle Re 2019-1 Ltd. and Eagle Re 2020-1 Ltd. | Forecast |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded premiums saved |  |  |  |  |  |  |  |  | $ 58,000 |  |  |  |
Radian Guaranty | Eagle Re 2019-1 Ltd. and Eagle Re 2020-1 Ltd. | Tender Premiums |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded premiums earned |  |  |  |  | $ 16,000 |  |  |  |  |  |  |  |
Radian Guaranty | Eagle Re 2019-1 Ltd. and Eagle Re 2020-1 Ltd. | Deferred Costs |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded premiums earned |  |  |  |  | $ 5,000 |  |  |  |  |  |  |  |
Radian Guaranty | Maximum | Mortgage |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Reinsurance retention policy, term of coverage, period |  |  |  |  |  |  | 12 years 6 months |  |  |  |  |  |
Radian Guaranty | Minimum | Mortgage |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Reinsurance retention policy, term of coverage, period |  |  |  |  |  |  | 10 years |  |  |  |  |  |
2023 QSR Agreement | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
RIF ceded | $ 3,000,000 |  |  |  |  |  |  |  |  |  |  |  |
2023 QSR Agreement | Radian Guaranty |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ceding commission % | 20.00% |  |  |  |  |  |  |  |  |  |  |  |
2023 QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Quota share % | 22.50% |  |  |  |  |  |  |  |  |  |  |  |
2023 QSR Agreement | Radian Guaranty | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Profit commission % | 55.00% |  |  |  |  |  |  |  |  |  |  |  |
Excess-of-Loss Program | Radian Guaranty |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Percent of reinsurance coverage threshold (in percent) |  |  |  |  |  |  | 0.10 |  |  |  |  |  |
Excess-of-Loss Program | Radian Guaranty | Mortgage | Eagle Re 2019-1 Ltd. |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
RIF ceded |  |  |  | 0 |  |  | $ 0 |  |  |  | 1,769,000 |  | $ 10,705,000
Excess-of-Loss Program | Radian Guaranty | Mortgage | Eagle Re 2020-1 Ltd. |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
RIF ceded |  |  |  | 2,113,000 |  |  | $ 2,113,000 |  |  |  | $ 2,401,000 | $ 9,866,000 |
Excess-of-Loss Program | Radian Guaranty | Mortgage | Eagle Re 2023-1 Ltd. | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
RIF ceded |  |  | $ 8,800,000 |  |  |  |  |  |  |  |  |  |
Aggregate excess-of-loss coverage (up to) |  |  | 353,000 |  |  |  |  |  |  |  |  |  |
Excess-of-Loss Program | Radian Guaranty | Mortgage | 2023 XOL Agreement | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
RIF ceded |  |  | 8,000,000 |  |  |  |  |  |  |  |  |  |
Aggregate excess-of-loss coverage (up to) |  |  | 246,000 |  |  |  |  |  |  |  |  |  |
Excess-of-Loss Program | Radian Guaranty | Mortgage | 2023 XOL Agreement | Forecast |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Increase to monthly premium if agreement is not terminated (as a percent) |  |  |  |  |  |  |  |  |  | 1.5 |  |  |
Excess-of-Loss Program | Radian Guaranty | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Right to termination on or after option call date, period after issuance of insurance-linked notes |  |  |  |  |  |  | 7 years |  |  |  |  |  |
Excess-of-Loss Program | Radian Guaranty | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Right to termination on or after option call date, period after issuance of insurance-linked notes |  |  |  |  |  |  | 5 years |  |  |  |  |  |
Excess-of-Loss Program | Eagle Re 2023-1 Ltd. | Mortgage | Eagle Re 2023-1 Ltd. | Subsequent Event | Mortgage insurance-linked notes |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of debt |  |  | $ 353,000 |  |  |  |  |  |  |  |  |  |
2022 QSR Agreement | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
RIF ceded |  |  |  | $ 8,500,000 |  |  | $ 8,500,000 |  |  |  |  |  |
2022 QSR Agreement | Radian Guaranty |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ceding commission % |  | 20.00% |  |  |  |  |  |  |  |  |  |  |
2022 QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Quota share % |  | 20.00% |  |  |  |  |  |  |  |  |  |  |
2022 QSR Agreement | Radian Guaranty | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Profit commission % |  | 59.00% |  |  |  |  |  |  |  |  |  |  |

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