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 $)											9 Months Ended
	Sep. 30, 2012 basispoint years		Dec. 31, 2011 basispoint		Sep. 30, 2011 basispoint	Dec. 31, 2010 basispoint	Sep. 30, 2012 Fair Value Liability before Consideration of Radian Non Performance Risk		Dec. 31, 2011 Fair Value Liability before Consideration of Radian Non Performance Risk		Sep. 30, 2012 Impact of Radian Non Performance Risk		Dec. 31, 2011 Impact of Radian Non Performance Risk
Fair Value Concentration of Risk Disclosure Items [Line Items]
Corporate CDOs	$ (1,100,000)		$ 5,100,000				$ 136,400,000		$ 463,100,000		$ (137,500,000)		$ (458,000,000)
Non Corporate CDO Related	170,300,000	[1]	114,900,000	[1]			803,300,000	[1]	1,520,200,000	[1]	(633,000,000)	[1]	(1,405,300,000)	[1]
NIMs related	7,700,000	[2]	7,800,000	[2]			13,000,000	[2]	17,400,000	[2]	(5,300,000)	[2]	(9,600,000)	[2]
Derivative liabilities, net	(176,900,000)		(127,800,000)				(952,700,000)		(2,000,700,000)		775,800,000		1,872,900,000
Market View Of The Probability That Registrant Will Default In The Next Five Years											54.30%		83.50%
Change in Impact of Non Performance Risk on Fair Value of Financial Instruments											$ 1,100,000,000
Five Year CDS Spread Details [Abstract]
Radian Group's five year CDS Spread (in basis points)	1,089		2,732		2,238	465
Number of Years for CDS Spread Related to Non Performance Risk In Fair Value Disclosure	5

[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.