Reinsurance - QSR Program (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jul. 01, 2022	Jan. 01, 2020	Jan. 01, 2018	Jan. 01, 2016	Mar. 31, 2023	Dec. 31, 2022
2022 QSR Agreement | Radian Guaranty
Ceding commission %		20.00%
RIF ceded						$ 3,830	$ 3,307
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						1,936	1,993
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						826	876
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						1,124	$ 1,207
Maximum | 2022 QSR Agreement
RIF ceded						$ 8,500
Maximum | 2022 QSR Agreement | Radian Guaranty
Profit commission %		59.00%
Maximum | 2020 Single Premium QSR Agreement | Radian Guaranty
Profit commission %			56.00%
Maximum | 2018 Single Premium QSR Agreement | Radian Guaranty
Profit commission %				56.00%
Maximum | 2016 Single Premium QSR Agreement | Radian Guaranty
Profit commission %					55.00%
Maximum | 2016 Single Premium QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk
Quota share %	57.00%				65.00%
Minimum | 2016 Single Premium QSR Agreement | Radian Guaranty | Revenue Benchmark | Product Concentration Risk
Quota share %	18.00%				20.00%