Reinsurance - QSR Programs (Details) - USD ($) $ in Millions						33 Months Ended	36 Months Ended
	Sep. 30, 2022	Jul. 01, 2022	Jan. 01, 2020	Jan. 01, 2018	Jan. 01, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2021
2022 QSR Agreement | Radian Guaranty
Ceding commission %		20.00%
RIF ceded	$ 2,710							$ 0
2022 QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk
Quota share %		20.00%
2020 Single Premium QSR Agreement | Radian Guaranty
Ceding commission %			25.00%
RIF ceded	2,038							2,137
2020 Single Premium QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk
Quota share %			65.00%
2018 Single Premium QSR Agreement | Radian Guaranty
Ceding commission %				25.00%
RIF ceded	917							1,021
2018 Single Premium QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk
Quota share %				65.00%
2016 Single Premium QSR Agreement | Radian Guaranty
Ceding commission %					25.00%
RIF ceded	1,319							$ 1,698
Maximum | 2022 QSR Agreement
RIF ceded	$ 8,500
Maximum | 2022 QSR Agreement | Radian Guaranty
Loss Ratio		59.00%
Maximum | 2020 Single Premium QSR Agreement | Radian Guaranty
Loss Ratio			56.00%
Maximum | 2018 Single Premium QSR Agreement | Radian Guaranty
Loss Ratio				56.00%
Maximum | 2016 Single Premium QSR Agreement | Radian Guaranty
Loss Ratio					55.00%
Maximum | 2016 Single Premium QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk
Quota share %	57.00%				65.00%	35.00%
Minimum | 2016 Single Premium QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk
Quota share %	18.00%				20.00%		35.00%