Note 4 - Fair Value of Financial Instruments Impact of Non-Performance Risk on Fair Value Disclosure (Details) (Fair Value, Concentration of Risk, Market Risk Management, Additional Details [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 years		Dec. 31, 2011		Mar. 31, 2011	Dec. 31, 2010
Fair Value Concentration of Risk Disclosure Items [Line Items]
Corporate CDOs	$ (1.9)		$ 5.1
Non Corporate CDO Related	230.7	[1]	114.9	[1]
NIMs related	6.9	[2]	7.8	[2]
Derivative liabilities, net	(235.7)		(127.8)
Five Year CDS Spread Details [Abstract]
Radian Group's five year CDS Spread (in basis points)	1,521		2,732		642	465
Number of Years for CDS Spread Related to Non Performance Risk In Fair Value Disclosure	5
Fair Value Liability before Consideration of Radian Non Performance Risk
Fair Value Concentration of Risk Disclosure Items [Line Items]
Corporate CDOs	199.1		463.1
Non Corporate CDO Related	1,555.4	[1]	1,520.2	[1]
NIMs related	13.9	[2]	17.4	[2]
Derivative liabilities, net	(1,768.4)		(2,000.7)
Impact of Radian Non Performance Risk
Fair Value Concentration of Risk Disclosure Items [Line Items]
Corporate CDOs	(201.0)		(458.0)
Non Corporate CDO Related	(1,324.7)	[1]	(1,405.3)	[1]
NIMs related	(7.0)	[2]	(9.6)	[2]
Derivative liabilities, net	1,532.7		1,872.9
Market View Of The Probability That Radian Group Will Default In The Next Five Years	64.10%		83.50%
Change in Impact of Non Performance Risk on Fair Value of Financial Instruments	$ 340.2

[1] Includes the net fair value liability recorded within derivative assets and derivative liabilities, and the net fair value liabilities included in our consolidated VIEs.

[2] Includes NIMS VIE debt and NIMS derivative assets.