Note 1 - Condensed Consolidated Financial Statements - Basis of Presentation Capital and Liquidity (Details) (USD $)	3 Months Ended				1 Months Ended		1 Months Ended			1 Months Ended			1 Months Ended		3 Months Ended	1 Months Ended		6 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended			1 Months Ended
	Mar. 31, 2013 segment	Mar. 31, 2012	Mar. 31, 2013 Mortgage Insurance Segment	Mar. 31, 2013 Less Than [Member] Mortgage Insurance Segment	Jan. 31, 2013 Five Point Three Seven Five Percent Senior Notes due 2015 [Member]	Mar. 31, 2013 Five Point Three Seven Five Percent Senior Notes due 2015 [Member]	Jan. 31, 2013 Nine Percent Notes Due 2017 [Member]	Mar. 31, 2013 Nine Percent Notes Due 2017 [Member]	Mar. 31, 2013 Two Point Two Five Percent Convertible Notes Due 2019 [Member]	Jan. 31, 2013 Debt Due 2015 Exchange [Member] Five Point Three Seven Five Percent Senior Notes due 2015 [Member]	Jan. 31, 2013 Debt Due 2015 Exchange [Member] Nine Percent Notes Due 2017 [Member]	Mar. 31, 2013 Radian Guaranty [Member]	Jan. 31, 2013 Radian Asset Assurance [Member] 2012 FGIC Commutation [Member]	Feb. 28, 2013 Radian Asset Assurance [Member] Strategic Capital and Liquidity Initiatives [Member]	Mar. 31, 2013 Radian Asset Assurance [Member] CDO Termination [Member] contract counterparty	Mar. 31, 2013 Common Stock	Mar. 31, 2013 Common Stock Stock Offering 2013 [Member]	Jun. 30, 2013 Legacy Portfolio Underwritten Between 2005 and 2008 [Member] Scenario, Forecast [Member] Less Than [Member] Mortgage Insurance Segment	Jan. 31, 2013 Reinsurance [Member] Radian Asset Assurance [Member] 2012 FGIC Commutation [Member]	Mar. 31, 2013 Primary Mortgage Product [Member] Mortgage Insurance Segment	Dec. 31, 2012 Primary Mortgage Product [Member] Mortgage Insurance Segment	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 Convertible Debt [Member] Two Point Two Five Percent Convertible Notes Due 2019 [Member]	Mar. 31, 2013 Convertible Debt [Member] Debt Offering 2013 [Member] Two Point Two Five Percent Convertible Notes Due 2019 [Member]
Risk to Capital Line Items [Line Items]
Equity Method Investment, Ownership Percentage																						20.00%	50.00%
Business Overview [Abstract]
Number of Operating Segments	2
Mortgage Insurance [Abstract]
Private Mortage Insurance Protects Lenders For Loans Made With This Maximum Downpayment Percentage			20.00%
Percentage Of Primary Insurance On Domestic First-Lien Mortgages To Total First Lien Insurance Risk In Force			94.80%
Total Risk In Force			$ 37,400,000,000
Percentage Of Pool Insurance On Domestic First-Lien Mortgages To Total First Lien Insurance Risk In Force			4.80%
NonTraditional Risk In Force			134,000,000
Percentage Of Non-Traditional RIF To Total RIF				1.00%
Business Conditions [Abstract]
Percentage Decrease In New Defaults																				20.00%	22.00%
Concentration Risk, Percentage																		50.00%
Maximum Loan To Value Percentage For G.S.E. Acquired Loans	80.00%
Minimum Percentage Of The Loans In Excess Of An 80% L.T.V. Which Must Be Retained By The Mortgage Originator Or Seller	10.00%
Capital Preservation and Liquidity Management Initiatives [Abstract]
Reduction In Net Par Outstanding															3,300,000,000				822,200,000
Contingency Reserve Release													6,700,000	61,100,000
Number Of Our Credit Derivative Counterparties That Excercised Their Termination Rights															4
Number of Corporate CDOs Terminated															9
Debt Instrument, Interest Rate, Stated Percentage						5.375%		9.00%	2.25%	5.375%	9.00%														2.25%
Debt Instrument, Increase, Additional Borrowings							195,200,000				195,200,000													400,000,000	400,000,000
Proceeds from Issuance of Long-term Debt																								389,800,000	389,800,000
Stock Issued During Period, Shares, New Issues																39,100,000	39,100,000.0
Sale of Stock, Price Per Share																$ 8.00	$ 8.00
Proceeds from Issuance of Common Stock	299,542,000	0														299,500,000	299,500,000
Unrestricted Cash and Liquid Investments	886,400,000
Extinguishment of Debt, Amount					195,200,000					195,200,000
Risk to Capital, Entity's Intended Maximum												0.20
Proceeds from Contributions from Affiliates	$ 71,000,000