Reinsurance - Single Premium QSR Program (Details) - Radian Guaranty - USD ($) $ in Millions	Jul. 01, 2024	Jul. 01, 2023	Jul. 01, 2022	Jan. 01, 2020	Jan. 01, 2018	Jan. 01, 2016	Dec. 31, 2024	Dec. 31, 2023
2024 QSR Agreement
Ceded Credit Risk [Line Items]
Ceding commission %	20.00%
RIF ceded							$ 1,621	$ 0
NIW policy dates	Jul 1, 2024-Jun 30, 2025
Effective date	Jul. 01, 2024
Scheduled termination date	Jun. 30, 2035
Optional termination date	Jul. 01, 2028
2024 QSR Agreement | Product Concentration Risk | Revenue Benchmark
Ceded Credit Risk [Line Items]
Quota share %	25.00%
2024 QSR Agreement | Maximum
Ceded Credit Risk [Line Items]
Profit commission %	59.00%
2023 QSR Agreement
Ceded Credit Risk [Line Items]
Ceding commission %		20.00%
RIF ceded							2,518	1,366
NIW policy dates		Jul 1, 2023-Jun 30, 2024
Effective date		Jul. 01, 2023
Scheduled termination date		Jun. 30, 2034
Optional termination date		Jul. 01, 2027
2023 QSR Agreement | Product Concentration Risk | Revenue Benchmark
Ceded Credit Risk [Line Items]
Quota share %		22.50%
2023 QSR Agreement | Maximum
Ceded Credit Risk [Line Items]
Profit commission %		55.00%
2022 QSR Agreement
Ceded Credit Risk [Line Items]
Ceding commission %			20.00%
RIF ceded							4,059	4,454
NIW policy dates			Jan 1, 2022-Jun 30, 2023
Effective date			Jul. 01, 2022
Scheduled termination date			Jun. 30, 2033
Optional termination date			Jul. 01, 2026
2022 QSR Agreement | Product Concentration Risk | Revenue Benchmark
Ceded Credit Risk [Line Items]
Quota share %			20.00%
2022 QSR Agreement | Maximum
Ceded Credit Risk [Line Items]
Profit commission %			59.00%
2020 Single Premium QSR Agreement
Ceded Credit Risk [Line Items]
Ceding commission %				25.00%
RIF ceded							1,525	1,783
NIW policy dates				Jan 1, 2020-Dec 31, 2021
Effective date				Jan. 01, 2020
Scheduled termination date				Dec. 31, 2031
Optional termination date				Jan. 01, 2024
2020 Single Premium QSR Agreement | Product Concentration Risk | Revenue Benchmark
Ceded Credit Risk [Line Items]
Quota share %				65.00%
2020 Single Premium QSR Agreement | Maximum
Ceded Credit Risk [Line Items]
Profit commission %				56.00%
2018 Single Premium QSR Agreement
Ceded Credit Risk [Line Items]
Ceding commission %					25.00%
RIF ceded							661	739
NIW policy dates					Jan 1, 2018-Dec 31, 2019
Effective date					Jan. 01, 2018
Scheduled termination date					Dec. 31, 2029
Optional termination date					Jan. 01, 2022
2018 Single Premium QSR Agreement | Product Concentration Risk | Revenue Benchmark
Ceded Credit Risk [Line Items]
Quota share %					65.00%
2018 Single Premium QSR Agreement | Maximum
Ceded Credit Risk [Line Items]
Profit commission %					56.00%
2016 Single Premium QSR Agreement
Ceded Credit Risk [Line Items]
Ceding commission %						25.00%
RIF ceded							$ 873	$ 982
NIW policy dates						Jan 1, 2012-Dec 31, 2017
Effective date						Jan. 01, 2016
Scheduled termination date						Dec. 31, 2027
Optional termination date						Jan. 01, 2020
2016 Single Premium QSR Agreement | Minimum | Product Concentration Risk | Revenue Benchmark
Ceded Credit Risk [Line Items]
Quota share %						18.00%
2016 Single Premium QSR Agreement | Maximum
Ceded Credit Risk [Line Items]
Profit commission %						55.00%
2016 Single Premium QSR Agreement | Maximum | Product Concentration Risk | Revenue Benchmark
Ceded Credit Risk [Line Items]
Quota share %						57.00%