Note 5 - Fair Value of Financial Instruments Impact of Non-Performance Risk on Fair Value Disclosure (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years		Dec. 31, 2010		Dec. 31, 2009	Dec. 31, 2008
Fair Value Liability before Consideration of Radian Non Performance Risk
Fair Value Concentration of Risk Disclosure Items [Line Items]
Corporate CDOs	463.1		387.1
Non Corporate CDO Related	1,520.2	[1]	1,696.2	[1]
NIMs related	17.4	[2]	134.1	[2]
Derivative Assets (Liabilities), at Fair Value, Net	2,000.7		2,217.4
Impact of Radian Non Performance Risk
Fair Value Concentration of Risk Disclosure Items [Line Items]
Corporate CDOs	(458.0)		(281.5)
Non Corporate CDO Related	(1,405.3)	[1]	(934.1)	[1]
NIMs related	(9.6)	[2]	(4.8)	[2]
Derivative Assets (Liabilities), at Fair Value, Net	(1,872.9)		(1,220.4)
Fair Value Liability Recorded Net of Radian Non Performance Risk
Fair Value Concentration of Risk Disclosure Items [Line Items]
Corporate CDOs	5.1		105.6
Non Corporate CDO Related	114.9	[1]	762.1	[1]
NIMs related	7.8	[2]	129.3	[2]
Derivative Assets (Liabilities), at Fair Value, Net	127.8		997.0
Fair Value, Concentration of Risk, Market Risk Management, Additional Details [Member]
Fair Value Concentration of Risk Disclosure Items [Line Items]
Number Of Years In Which The Market Believes Radian Group Will Default	5
Five Year CDS Spread Details [Abstract]
Radian Group's five year CDS Spread (in basis points)	2,732		465		1,530	2,466
Number of Years for CDS Spread Related to Non Performance Risk In Fair Value Disclosure	5
Fair Value, Concentration of Risk, Market Risk Management, Additional Details [Member] | Impact of Radian Non Performance Risk
Fair Value Concentration of Risk Disclosure Items [Line Items]
Market View Of The Probability That Radian Group Will Default In The Next Five Years	84.00%		32.00%
Change in Impact of Non Performance Risk on Fair Value of Financial Instruments	652.5

[1] Includes the net liability recorded within derivative assets and derivative liabilities, and the net liability recorded within VIE debt and other financial statement line items for consolidated VIEs.

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