Reinsurance - Excess-of-Loss Program (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Oct. 31, 2023	Nov. 30, 2021	Apr. 30, 2021	Mar. 31, 2024	Dec. 31, 2023
Mortgage Insurance revenues
Ceded Credit Risk [Line Items]
Direct primary mortgage insurance risk in force				$ 70,300	$ 69,700
Eagle Re 2023-1 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
RIF	$ 8,782			8,525	8,659
Coverage	353			353	353
Eagle Re 2023-1 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | First layer retention
Ceded Credit Risk [Line Items]
First layer retention	287			287	287
Eagle Re 2021-2 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
RIF		$ 10,758		7,309	7,651
Coverage		484		328	355
Eagle Re 2021-2 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | First layer retention
Ceded Credit Risk [Line Items]
First layer retention		$ 242		242	242
Eagle Re 2021-1 Ltd. | Excess-of-Loss Program | Radian Guaranty | Radian Group Inc.
Ceded Credit Risk [Line Items]
Proceeds from issuance of debt				45
Eagle Re 2021-1 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
RIF			$ 11,061	5,922	6,227
Coverage			498	227	250
Eagle Re 2021-1 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | First layer retention
Ceded Credit Risk [Line Items]
First layer retention			$ 221	221	221
2023 XOL Agreement | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
Coverage	246			204	226
Direct primary mortgage insurance risk in force	8,002			7,581	7,814
2023 XOL Agreement | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty | First layer retention
Ceded Credit Risk [Line Items]
First layer retention	$ 240			$ 240	$ 240