Note 15 - Statutory Information Risk To Capital Calculation (Details) $ in Millions		3 Months Ended	9 Months Ended
		Mar. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) state	Dec. 31, 2016 USD ($)
Risk to Capital Line Items [Line Items]
Number Of States That Have A Statutory Or Regulatory Risk Based Capital Requirement | state			16
Risk To Capital Ratio, Regulatory Maximum			25
Radian Reinsurance [Member]
Risk to Capital Line Items [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Increase (Decrease)		$ 175.0
Statutory policyholders’ surplus			$ 332.1	$ 147.6
Radian Guaranty
Risk to Capital Line Items [Line Items]
Statutory Accounting Practices, Statutory Capital and Surplus, Increase (Decrease)		(175.0)	81.3
Statutory Accounting Practices, Dividends Paid with Approval of Regulatory Agency		$ 175.0
RIF, net (1)	[1]		38,712.8	35,357.8
Common stock and paid-in capital			1,866.2	2,041.0
Unassigned earnings (deficit)			(740.3)	(691.3)
Statutory policyholders’ surplus			1,125.9	1,349.7
Contingency reserve			1,565.7	1,260.6
Statutory capital			$ 2,691.6	$ 2,610.3
Risk-to-capital			14.4	13.5
Statutory Accounting Practices, Statutory Net Income Amount			$ 337.5
Non RBC States [Member] | Minimum [Member]
Risk to Capital Line Items [Line Items]
Capital Required for Capital Adequacy			1.0
Non RBC States [Member] | Maximum [Member]
Risk to Capital Line Items [Line Items]
Capital Required for Capital Adequacy			$ 5.0
Reportable Subsegments [Member]
Risk to Capital Line Items [Line Items]
Risk-to-capital			13.4	13.6

[1] Excludes risk ceded through reinsurance contracts (to third parties and affiliates) and RIF on defaulted loans.