Reinsurance - Additional Information (Details) $ in Millions			3 Months Ended	6 Months Ended
	Jul. 01, 2024	Jul. 01, 2023	Jun. 30, 2025 USD ($) Agreement	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Radian Guaranty
Ceded Credit Risk [Line Items]
Funds held under reinsurance agreements, asset			$ 295	$ 295	$ 283
Number of quota share reinsurance arrangements | Agreement			3
Mortgage Insurance revenues
Ceded Credit Risk [Line Items]
Direct primary mortgage insurance risk in force			$ 72,800	$ 72,800	$ 72,100
2023 QSR Agreement | Radian Guaranty
Ceded Credit Risk [Line Items]
Ceding commission %		20.00%
Scheduled termination date		Jun. 30, 2034
2024 QSR Agreement | Radian Guaranty
Ceded Credit Risk [Line Items]
Ceding commission %	20.00%
Scheduled termination date	Jun. 30, 2035
2025 QSR Agreement | Radian Guaranty
Ceded Credit Risk [Line Items]
Percentage of policies ceded to reinsurer (in percent)			0.30	0.30
Policies issued period			1 year
Scheduled termination date			Jul. 01, 2029
2026 QSR Agreement | Radian Guaranty
Ceded Credit Risk [Line Items]
Percentage of policies ceded to reinsurer (in percent)			0.30	0.30
Policies issued period			1 year
Scheduled termination date			Jul. 01, 2030
2027 QSR Agreement | Radian Guaranty
Ceded Credit Risk [Line Items]
Percentage of policies ceded to reinsurer (in percent)			0.15	0.15
Policies issued period			1 year
Scheduled termination date			Jul. 01, 2031
Excess-of-Loss Program | Radian Guaranty
Ceded Credit Risk [Line Items]
Percent of reinsurance coverage threshold (in percent)				0.10
New QSR Agreement | Radian Guaranty
Ceded Credit Risk [Line Items]
Term of agreement			10 years
Maximum | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
Reinsurance retention policy, term of coverage, period				12 years 6 months
Maximum | 2024 QSR Agreement
Ceded Credit Risk [Line Items]
Direct primary mortgage insurance risk in force			$ 4,300	$ 4,300
Maximum | Excess-of-Loss Program | Radian Guaranty
Ceded Credit Risk [Line Items]
Right to termination on or after option call date, period after issuance of insurance-linked notes				7 years
Minimum | Mortgage Insurance revenues | Radian Guaranty
Ceded Credit Risk [Line Items]
Reinsurance retention policy, term of coverage, period				10 years
Minimum | Excess-of-Loss Program | Radian Guaranty
Ceded Credit Risk [Line Items]
Right to termination on or after option call date, period after issuance of insurance-linked notes				5 years