Note 7 - Reinsurance Excess-of-Loss Program (Details) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended		12 Months Ended
		Apr. 30, 2019	Nov. 30, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Mortgage Insurance Segment
Risk In Force				$ 57,400,000
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid				34,589	$ 59,926
Subsequent Event | Mortgage Insurance Segment | Radian Guaranty | Eagle Re 2019-1 (Primary)
Reinsurance Retention Policy, Excess Retention, Amount Reinsured		$ 562,000
Proceeds from Issuance of Debt		562,000
Risk In Force		$ 10,700,000
Excess-of-Loss Program | Eagle Re 2018-1 (Primary)
Derivative Asset							$ 1,700
Excess-of-Loss Program | Mortgage Insurance Segment | Radian Guaranty
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	[1]			434,034			434,034
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				435,717			435,148
Excess-of-Loss Program | Mortgage Insurance Segment | Radian Guaranty | Eagle Re 2018-1 (Primary)
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			$ 434,000
Proceeds from Issuance of Debt							434,000
Risk In Force			9,100,000
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	[1]			434,034			434,034
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				435,717			435,148
Excess-of-Loss Program | Mortgage Insurance Segment | Radian Guaranty | Separate Third-Party Reinsurer
Reinsurance Retention Policy, Excess Retention, Amount Reinsured			$ 21,400
Excess-of-Loss Program | Mortgage Insurance Segment | Radian Guaranty | On-Balance Sheet
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				1,683			1,114
Excess-of-Loss Program | Mortgage Insurance Segment | Radian Guaranty | On-Balance Sheet | Eagle Re 2018-1 (Primary)
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	[2]			1,683			1,114
Excess-of-Loss Program | Mortgage Insurance Segment | Radian Guaranty | Off-Balance Sheet
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	[3]			434,034			434,034
Excess-of-Loss Program | Mortgage Insurance Segment | Radian Guaranty | Off-Balance Sheet | Eagle Re 2018-1 (Primary)
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	[3]			434,034			$ 434,034
Excess-of-Loss Program | Scenario, Forecast | Mortgage Insurance Segment | Radian Guaranty | Eagle Re 2018-1 (Primary)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid						$ 660,400
Excess-of-Loss Program | Reinsurer Concentration Risk | Mortgage Insurance Segment | Radian Guaranty
Ceding Commissions Earned				0
Ceded losses				$ 0

[1] Assets of Eagle Re 2018-1 are required to be invested in U.S. government money market funds, cash or U.S. Treasury securities. Liabilities of Eagle Re 2018-1 consist of its mortgage insurance-linked notes of $434.0 million, as described above.

[2] Represents the fair value of the related embedded derivative, included in other assets in our condensed consolidated balance sheets.

[3] Represents the maximum amount that would be payable in the future by Radian Guaranty to its policyholders on claims, without the benefit of any corresponding reinsurance recoverables, in the event of the combination of two events: (i) all of the assets in the reinsurance trust (consisting of U.S. government money market funds, cash or U.S. Treasury securities) have become worthless and (ii) $660.4 million of claims have been paid on the reinsured RIF.