Reinsurance - Excess-of-Loss Program (Details) - USD ($) $ in Millions	1 Months Ended			12 Months Ended
	Oct. 31, 2023	Nov. 30, 2021	Apr. 30, 2021	Dec. 31, 2024	Dec. 31, 2023
Mortgage Insurance revenues
Ceded Credit Risk [Line Items]
Direct primary mortgage insurance risk in force				$ 72,100	$ 69,700
Excess-of-Loss Program | Radian Guaranty | Eagle Re 2021-1 Ltd. | Radian Group Inc.
Ceded Credit Risk [Line Items]
Proceeds from issuance of debt				45
Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | Eagle Re 2023-1 Ltd.
Ceded Credit Risk [Line Items]
RIF	$ 8,782			7,906	8,659
Coverage	353			327	353
Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | Eagle Re 2021-2 Ltd.
Ceded Credit Risk [Line Items]
RIF		$ 10,758		6,271	7,651
Coverage		484		247	355
Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | Eagle Re 2021-1 Ltd.
Ceded Credit Risk [Line Items]
RIF			$ 11,061	4,966	6,227
Coverage			498	155	250
Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | 2023 XOL Agreement
Ceded Credit Risk [Line Items]
Coverage	246			167	226
Direct primary mortgage insurance risk in force	8,002			6,815	7,814
Excess-of-Loss Program | XOL First Layer | Mortgage Insurance revenues | Radian Guaranty | Eagle Re 2023-1 Ltd.
Ceded Credit Risk [Line Items]
First layer retention	287			286	287
Excess-of-Loss Program | XOL First Layer | Mortgage Insurance revenues | Radian Guaranty | Eagle Re 2021-2 Ltd.
Ceded Credit Risk [Line Items]
First layer retention		$ 242		241	242
Excess-of-Loss Program | XOL First Layer | Mortgage Insurance revenues | Radian Guaranty | Eagle Re 2021-1 Ltd.
Ceded Credit Risk [Line Items]
First layer retention			$ 221	221	221
Excess-of-Loss Program | XOL First Layer | Mortgage Insurance revenues | Radian Guaranty | 2023 XOL Agreement
Ceded Credit Risk [Line Items]
First layer retention	$ 240			$ 240	$ 240