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Description of Business - Additional Information (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Sep. 30, 2025 USD ($) | Sep. 30, 2025 USD ($) | Sep. 30, 2025 USD ($) Segment | Dec. 31, 2024 USD ($)
Business Overview [Abstract] |  |  |  |
Number of reportable business segments | Segment |  |  | 1 |
Expected proceeds from intercompany notes borrowings | $ 600 | $ 600 | $ 600 |
Debt instrument term |  | 10 years |  |
Inigo Limited |  |  |  |
Business Overview [Abstract] |  |  |  |
Business acquisition, agreement to acquire for purchase price in cash transaction | $ 1,700 |  |  |
Mortgage Insurance revenues |  |  |  |
Business Overview [Abstract] |  |  |  |
Down payment purchase price (percent) | 20.00% | 20.00% | 20.00% |
Equity in home (percent) | 20.00% | 20.00% | 20.00% |
Direct primary mortgage insurance in force | $ 280,600 | $ 280,600 | $ 280,600 | $ 275,100
Direct primary mortgage insurance risk in force | $ 74,000 | $ 74,000 | $ 74,000 | $ 72,100

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- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 47 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-47 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 54 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-54 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-18 + Details
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