Reinsurance - Excess-of-Loss Program (Details) - USD ($) $ in Millions	1 Months Ended				12 Months Ended
	Oct. 31, 2023	Nov. 30, 2021	Apr. 30, 2021	Feb. 29, 2020	Dec. 31, 2023	Dec. 31, 2022
Mortgage insurance
Ceded Credit Risk [Line Items]
Direct primary mortgage insurance risk in force					$ 69,700	$ 66,100
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 | Radian Guaranty | Eagle Re 2020-1 Ltd. | Radian Group Inc.
Ceded Credit Risk [Line Items]
Proceeds from issuance of debt					2
Excess-of-Loss Program | Mortgage insurance | Radian Guaranty | Eagle Re 2023-1 Ltd.
Ceded Credit Risk [Line Items]
RIF	$ 8,782				8,659	0
Coverage	353				353	0
Excess-of-Loss Program | Mortgage insurance | Radian Guaranty | Eagle Re 2021-2 Ltd.
Ceded Credit Risk [Line Items]
RIF		$ 10,758			7,651	9,150
Coverage		484			355	472
Excess-of-Loss Program | Mortgage insurance | Radian Guaranty | Eagle Re 2021-1 Ltd.
Ceded Credit Risk [Line Items]
RIF			$ 11,061		6,227	7,758
Coverage			498		250	366
Excess-of-Loss Program | Mortgage insurance | Radian Guaranty | Eagle Re 2020-1 Ltd.
Ceded Credit Risk [Line Items]
RIF				$ 9,866	2,031	2,401
Coverage				488	7	368
Excess-of-Loss Program | Mortgage insurance | Radian Guaranty | 2023 XOL Agreement
Ceded Credit Risk [Line Items]
Coverage	246				226	0
Direct primary mortgage insurance risk in force	8,002				7,814	0
Excess-of-Loss Program | XOL First Layer | Mortgage insurance | Radian Guaranty | Eagle Re 2023-1 Ltd.
Ceded Credit Risk [Line Items]
First layer retention	287				287	0
Excess-of-Loss Program | XOL First Layer | Mortgage insurance | Radian Guaranty | Eagle Re 2021-2 Ltd.
Ceded Credit Risk [Line Items]
First layer retention		$ 242			242	242
Excess-of-Loss Program | XOL First Layer | Mortgage insurance | 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 | Radian Guaranty | Eagle Re 2020-1 Ltd.
Ceded Credit Risk [Line Items]
First layer retention				$ 202	201	202
Excess-of-Loss Program | XOL First Layer | Mortgage insurance | Radian Guaranty | 2023 XOL Agreement
Ceded Credit Risk [Line Items]
First layer retention	$ 240				$ 240	$ 0