Note 8 - Reinsurance - Single Premium QSR Program (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		36 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2017	Dec. 31, 2014	Dec. 31, 2019
Ceded premiums written	$ 9,789	$ 15,455	$ 72,912	$ 39,900
2016 Single Premium QSR | Radian Guaranty
Ceded Insurance Commission Percentage			25.00%
2016 Single Premium QSR | Radian Guaranty | Reinsurer Concentration Risk
Concentration Risk, Percentage					35.00%
Risk In Force	3,676,000		$ 3,676,000				$ 5,351,000
2018 Single Premium QSR | Radian Guaranty
Ceded Insurance Commission Percentage			25.00%
2018 Single Premium QSR | Radian Guaranty | Reinsurer Concentration Risk
Concentration Risk, Percentage			65.00%
Risk In Force	2,352,000		$ 2,352,000				3,231,000
2020 Single Premium QSR | Radian Guaranty
Ceded premiums written			$ 250,000
Ceded Insurance Commission Percentage			25.00%
2020 Single Premium QSR | Radian Guaranty | Reinsurer Concentration Risk
Concentration Risk, Percentage			65.00%
Risk In Force	$ 1,331,000		$ 1,331,000				$ 0
Minimum | 2016 Single Premium QSR | Radian Guaranty | Reinsurer Concentration Risk
Concentration Risk, Percentage			20.00%
Maximum | 2016 Single Premium QSR | Radian Guaranty
Loss Ratio			55.00%
Maximum | 2016 Single Premium QSR | Radian Guaranty | Reinsurer Concentration Risk
Concentration Risk, Percentage			65.00%			35.00%
Maximum | 2018 Single Premium QSR | Radian Guaranty
Loss Ratio			56.00%
Maximum | 2020 Single Premium QSR | Radian Guaranty
Loss Ratio			56.00%