Note 8 - Reinsurance - Single Premium QSR Program (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		36 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2017	Dec. 31, 2020
Ceded premiums written	$ 14,555	$ 9,789	$ 35,157	$ 72,912
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	2,046,000		$ 2,046,000			$ 1,597,000
2018 Single Premium QSR | Radian Guaranty
Concentration Risk, Percentage			65.00%
Ceded Insurance Commission Percentage			25.00%
Risk In Force	1,279,000		$ 1,279,000			1,979,000
2016 Single Premium QSR | Radian Guaranty
Concentration Risk, Percentage					35.00%
Ceded Insurance Commission Percentage			25.00%
Risk In Force	$ 2,115,000		$ 2,115,000			$ 3,071,000
2016 Single Premium QSR | Radian Guaranty | 2012-2014 Vintages
Concentration Risk, Percentage			20.00%
Maximum | 2020 Single Premium QSR | Radian Guaranty
Loss Ratio			56.00%
Maximum | 2018 Single Premium QSR | Radian Guaranty
Loss Ratio			56.00%
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%