Reinsurance - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) reinsuranceArrangement	Dec. 31, 2020 USD ($)
Ceded Credit Risk [Line Items]
Funds held under reinsurance agreements, off-balance sheet, asset	$ 167.9	$ 228.6
Radian Guaranty | Mortgage
Ceded Credit Risk [Line Items]
Number of fully collateralized reinsurance arrangements with the eagle re-issuers | reinsuranceArrangement	6
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	$ 207.1	$ 381.8