Schedule II Financial Information of Registrant - Parent Company Only Supplemental Notes (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) transaction	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Condensed Financial Statements, Captions [Line Items]
Total Operating Expenses Allocated to Subsidiaries From Parent Company	$ 129,870	$ 124,412	$ 94,815
Total Interest Expense Allocated to Subsidiaries From Parent Company	68,938	53,692	42,195
Supplemental Notes [Abstract]
Deferred Income Tax Liabilities, Net	213,897	71,084
Parent Company
Supplemental Notes [Abstract]
Total Operating Expenses and Interest Expense Allocated to Subsidiaries From Parent Company	198,808	178,104	137,010
Deferred Income Tax Liabilities, Net	272,868	253,739
Investments in and Advances to Affiliates, at Fair Value, Period Increase (Decrease)	116,800
Radian Mortgage Assurance
Supplemental Notes [Abstract]
Statutory Accounting Practices, Statutory Capital and Surplus Required	5,000
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	8,700
Risk In Force	0
Radian Guaranty
Supplemental Notes [Abstract]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 481,500	$ 637,700	$ 814,100
Indirect Guarantee of Indebtedness | Radian Guaranty
Supplemental Notes [Abstract]
Number of Guaranteed Structured Transactions For Radian Guaranty | transaction	2
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 73,200