Note 8 - Reinsurance - Excess-of-Loss Program (Details) $ in Thousands	1 Months Ended				9 Months Ended
	Oct. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Apr. 30, 2019 USD ($)	Nov. 30, 2018 USD ($)	Sep. 30, 2020 USD ($) arrangements	Dec. 31, 2019 USD ($)
Mortgage segment
Risk In Force					$ 61,000,000	$ 60,900,000
Radian Guaranty | Mortgage segment
Reinsurance Retention Policy, Term of Coverage, Period					10 years
Excess-of-Loss Program | Radian Guaranty | Mortgage segment
VIE, Non-consolidated, Carrying Amount, Assets					$ 1,148,705	865,454
VIE, Non-consolidated, Carrying Amount, Liabilities					1,148,705	865,454
Excess-of-Loss Program | Radian Guaranty | Mortgage segment | Eagle Re 2020-1 (Primary)
VIE, Non-consolidated, Carrying Amount, Assets					488,385	0
VIE, Non-consolidated, Carrying Amount, Liabilities					488,385	0
Excess-of-Loss Program | Radian Guaranty | Mortgage segment | Eagle Re 2019-1 (Primary)
VIE, Non-consolidated, Carrying Amount, Assets					384,602	508,449
VIE, Non-consolidated, Carrying Amount, Liabilities					384,602	508,449
Excess-of-Loss Program | Radian Guaranty | Mortgage segment | Eagle Re 2018-1 (Primary)
VIE, Non-consolidated, Carrying Amount, Assets					275,718	357,005
VIE, Non-consolidated, Carrying Amount, Liabilities					$ 275,718	$ 357,005
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk
Number of Fully Collateralized Reinsurance Arrangements with the Eagle Re Issuers | arrangements					3
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Eagle Re 2020-1 (Primary)
Risk In Force		$ 9,866,000			$ 7,155,000
Reinsurance Retention Policy, Excess Retention, Amount Reinsured		488,000			488,000
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Eagle Re 2020-1 (Primary) | XOL First Layer
Reinsurance Retention Policy, Amount Retained		$ 202,000			202,000
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Eagle Re 2019-1 (Primary)
Risk In Force			$ 10,705,000		5,514,000
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			562,000		385,000
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Eagle Re 2019-1 (Primary) | XOL First Layer
Reinsurance Retention Policy, Amount Retained			$ 268,000		266,000
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Eagle Re 2018-1 (Primary)
Risk In Force				$ 9,109,000	4,742,000
Reinsurance Retention Policy, Excess Retention, Amount Reinsured				434,000	276,000
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Eagle Re 2018-1 (Primary) | XOL First Layer
Reinsurance Retention Policy, Amount Retained				205,000	$ 202,000
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Separate Third-Party Reinsurer
Reinsurance Retention Policy, Excess Retention, Amount Reinsured				$ 21,400
Excess-of-Loss Program | Radian Guaranty | Reinsurer Concentration Risk | Mortgage segment | Eagle Re 2020-2 (Primary) | Subsequent Event
Risk In Force	$ 13,000,000
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	390,300
Proceeds from Issuance of Debt	$ 390,300