Reinsurance - Single Premium QSR Program (Details) - Radian Guaranty - USD ($) $ in Millions		1 Months Ended		12 Months Ended	15 Months Ended	33 Months Ended	36 Months Ended
	Dec. 31, 2017	Jan. 31, 2020	Oct. 31, 2017	Dec. 31, 2020	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2017	Mar. 31, 2022	Dec. 31, 2021
2020 Single Premium QSR Agreement
Ceding commission %		25.00%
RIF ceded								$ 2,137	$ 2,198
2020 Single Premium QSR Agreement | Revenue Benchmark | Product Concentration Risk
Quota share %		65.00%
2018 Single Premium QSR Agreement
Ceding commission %			25.00%
RIF ceded								1,021	1,117
2018 Single Premium QSR Agreement | Revenue Benchmark | Product Concentration Risk
Quota share %			65.00%
2016 Single Premium QSR Agreement
Ceding commission %				25.00%
RIF ceded								$ 1,698	$ 1,913
2016 Single Premium QSR Agreement | Revenue Benchmark | Product Concentration Risk
Quota share %	65.00%				20.00%	35.00%	35.00%
Maximum | 2020 Single Premium QSR Agreement
Profit commission %				56.00%
Maximum | 2018 Single Premium QSR Agreement
Profit commission %			56.00%
Maximum | 2016 Single Premium QSR Agreement
Profit commission %				55.00%