Note 16 - Statutory Information - Statutory Capital Requirements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) state payment	Dec. 31, 2019
Risk to Capital Line Items [Line Items]
Risk To Capital Ratio, Regulatory Maximum	25
PMIERS Disaster Related Capital Charge	30.00%
Reduction in Capital Charges	70.00%
Radian Guaranty
Risk to Capital Line Items [Line Items]
Risk-to-capital	12.7	13.6
Minimum | Mortgage segment
Risk to Capital Line Items [Line Items]
Number of missed payments | payment	2
Maximum
Risk to Capital Line Items [Line Items]
Number of Months that Disaster Related Capital Charge is Applied.	3 months
State Insurance Regulations
Risk to Capital Line Items [Line Items]
Number Of States That Have A Statutory Or Regulatory Risk Based Capital Requirement | state	16
Non RBC States | Minimum
Risk to Capital Line Items [Line Items]
Capital Required for Capital Adequacy	$ 1
Non RBC States | Maximum
Risk to Capital Line Items [Line Items]
Capital Required for Capital Adequacy	$ 5