Reinsurance - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) reinsuranceArrangement	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Ceded Credit Risk [Line Items]
Funds held under reinsurance agreements, off-balance sheet, asset	$ 174.5		$ 167.9
Mortgage
Ceded Credit Risk [Line Items]
RIF	$ 66,100.0		60,900.0
QSR Program | Maximum
Ceded Credit Risk [Line Items]
RIF		$ 8,500.0
Radian Guaranty | Mortgage
Ceded Credit Risk [Line Items]
Number of fully collateralized reinsurance arrangements with the eagle re-issuers | reinsuranceArrangement	6
Number of Active Fully Collateralized Reinsurance Arrangements With the Eagle Re Issuers | reinsuranceArrangement	5
Radian Guaranty | Mortgage | Minimum
Ceded Credit Risk [Line Items]
Reinsurance retention policy, term of coverage, period	10 years
Radian Guaranty | Mortgage | Maximum
Ceded Credit Risk [Line Items]
Reinsurance retention policy, term of coverage, period	12 years 6 months
Radian Guaranty | QSR Program
Ceded Credit Risk [Line Items]
RIF ceded	$ 142.4		$ 207.1
Radian Guaranty | Excess-of-Loss Program
Ceded Credit Risk [Line Items]
Reinsurance optional clean-up call, outstanding principal balance percentage threshold	0.10
Radian Guaranty | Excess-of-Loss Program | Minimum
Ceded Credit Risk [Line Items]
Reinsurance right to terminate, optional call date, years after issuance	5 years
Radian Guaranty | Excess-of-Loss Program | Maximum
Ceded Credit Risk [Line Items]
Reinsurance right to terminate, optional call date, years after issuance	7 years