Reinsurance - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) reinsuranceArrangement	Dec. 31, 2022 USD ($)
Mortgage
Ceded Credit Risk [Line Items]
RIF ceded	$ 66,600.0	$ 66,100.0
Radian Guaranty
Ceded Credit Risk [Line Items]
Funds held under reinsurance agreements, asset	$ 176.2	174.5
Radian Guaranty | Mortgage
Ceded Credit Risk [Line Items]
Number of fully collateralized reinsurance arrangements with Eagle Re Issuers | reinsuranceArrangement	6
Number of active fully collateralized reinsurance arrangements with Eagle Re Issuers | reinsuranceArrangement	5
Radian Guaranty | Maximum | Mortgage
Ceded Credit Risk [Line Items]
Reinsurance retention policy, term of coverage, period	12 years 6 months
Radian Guaranty | Minimum | Mortgage
Ceded Credit Risk [Line Items]
Reinsurance retention policy, term of coverage, period	10 years
Excess-of-Loss Program | Radian Guaranty
Ceded Credit Risk [Line Items]
Percent of reinsurance coverage threshold (in percent)	0.10
Excess-of-Loss Program | Radian Guaranty | Maximum
Ceded Credit Risk [Line Items]
Right to termination on or after option call date, period after issuance of insurance-linked notes	7 years
Excess-of-Loss Program | Radian Guaranty | Minimum
Ceded Credit Risk [Line Items]
Right to termination on or after option call date, period after issuance of insurance-linked notes	5 years
2022 QSR Agreement | Maximum
Ceded Credit Risk [Line Items]
RIF ceded	$ 8,500.0
2022 QSR Agreement | Radian Guaranty
Ceded Credit Risk [Line Items]
RIF ceded	$ 3,830.0	$ 3,307.0