Note 8 - Reinsurance - Excess-of-Loss Program (Details) $ in Thousands	1 Months Ended				12 Months Ended
	Oct. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Apr. 30, 2019 USD ($)	Nov. 30, 2018 USD ($)	Dec. 31, 2020 USD ($) arrangements	Dec. 31, 2019 USD ($)
Total assets					$ 7,948,021	$ 6,808,313
Total liabilities					3,663,668	2,759,590
Variable Interest Entity, Primary Beneficiary
Total assets					1,539,029	865,454
Total liabilities					1,539,029	865,454
Mortgage segment
Risk In Force					$ 60,700,000	60,900,000
Mortgage segment | Radian Guaranty
Number of Fully Collateralized Reinsurance Arrangements with the Eagle Re Issuers | arrangements					4
Reinsurance Retention Policy, Term of Coverage, Period					10 years
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2020-2 (Primary)
Risk In Force	$ 13,011,000				$ 11,748,000	0
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	390,000				390,000	0
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2020-2 (Primary) | Variable Interest Entity, Primary Beneficiary
Total assets					390,324	0
Total liabilities					390,324	0
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2020-1 (Primary)
Risk In Force		$ 9,866,000			6,121,000	0
Reinsurance Retention Policy, Excess Retention, Amount Reinsured		488,000			488,000	0
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2020-1 (Primary) | Variable Interest Entity, Primary Beneficiary
Total assets					488,385	0
Total liabilities					488,385	0
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2019-1 (Primary)
Risk In Force			$ 10,705,000		4,657,000	8,409,000
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			562,000		385,000	487,000
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2019-1 (Primary) | Variable Interest Entity, Primary Beneficiary
Total assets					384,602	508,449
Total liabilities					384,602	508,449
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2018-1 (Primary)
Risk In Force				$ 9,109,000	3,986,000	7,026,000
Reinsurance Retention Policy, Excess Retention, Amount Reinsured				434,000	276,000	343,000
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Eagle Re 2018-1 (Primary) | Variable Interest Entity, Primary Beneficiary
Total assets					275,718	357,005
Total liabilities					275,718	357,005
Excess-of-Loss Program | Mortgage segment | Radian Guaranty | Separate Third-Party Reinsurer
Reinsurance Retention Policy, Excess Retention, Amount Reinsured				21,400
Excess-of-Loss Program | XOL First Layer | Mortgage segment | Radian Guaranty | Eagle Re 2020-2 (Primary)
Reinsurance Retention Policy, Amount Retained	$ 423,000				423,000	0
Excess-of-Loss Program | XOL First Layer | Mortgage segment | Radian Guaranty | Eagle Re 2020-1 (Primary)
Reinsurance Retention Policy, Amount Retained		$ 202,000			202,000	0
Excess-of-Loss Program | XOL First Layer | Mortgage segment | Radian Guaranty | Eagle Re 2019-1 (Primary)
Reinsurance Retention Policy, Amount Retained			$ 268,000		265,000	267,000
Excess-of-Loss Program | XOL First Layer | Mortgage segment | Radian Guaranty | Eagle Re 2018-1 (Primary)
Reinsurance Retention Policy, Amount Retained				$ 205,000	$ 201,000	$ 204,000