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, 2025	Dec. 31, 2024
Mortgage Insurance revenues
Ceded Credit Risk [Line Items]
Direct primary mortgage insurance risk in force					$ 72,000	$ 72,100
Eagle Re 2023-1 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
RIF		$ 8,782			7,906	7,708
Coverage		353			327	312
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			286	285
Eagle Re 2021-2 Ltd. | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
RIF			$ 10,758		6,271	5,974
Coverage			484		247	224
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		241	241
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	[1]			$ 11,061	4,966	4,715
Coverage	[1]			498	155	136
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	[1]			$ 221	221	221
2023 XOL Agreement | Excess-of-Loss Program | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
Coverage		246			167	150
Direct primary mortgage insurance risk in force		8,002			6,815	6,576
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

[1] Radian Group purchased $45 million of Eagle Re 2021-1 Ltd. outstanding principal amounts of the respective mortgage insurance-linked notes issued in connection with that reinsurance transaction. On our condensed consolidated balance sheets at March 31, 2025, and December 31, 2024, these notes are included either in fixed-maturities available for sale or, if included in our securities lending program, in other assets. See Notes 5 and 6 for additional information.