Note 8 - Reinsurance - Single Premium QSR Program (Details) - USD ($) $ in Thousands	3 Months Ended		36 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2017	Dec. 31, 2020
Ceded premiums written	$ 8,835	$ 19,543
2016 Single Premium QSR | Radian Guaranty
Concentration Risk, Percentage			35.00%
Ceded Insurance Commission Percentage	25.00%
Risk In Force	$ 2,683,000			$ 3,071,000
2016 Single Premium QSR | Radian Guaranty | 2012-2014 Vintages
Concentration Risk, Percentage	20.00%
2018 Single Premium QSR | Radian Guaranty
Concentration Risk, Percentage	65.00%
Ceded Insurance Commission Percentage	25.00%
Risk In Force	$ 1,698,000			1,979,000
2020 Single Premium QSR | Radian Guaranty
Ceded premiums written	$ 250,000
Concentration Risk, Percentage	65.00%
Ceded Insurance Commission Percentage	25.00%
Risk In Force	$ 1,767,000			$ 1,597,000
Maximum | 2016 Single Premium QSR | Radian Guaranty
Concentration Risk, Percentage	65.00%
Loss Ratio	55.00%
Maximum | 2016 Single Premium QSR | Radian Guaranty | 2012-2014 Vintages
Concentration Risk, Percentage	35.00%
Maximum | 2018 Single Premium QSR | Radian Guaranty
Loss Ratio	56.00%
Maximum | 2020 Single Premium QSR | Radian Guaranty
Loss Ratio	56.00%