Note 1 - Description of Business and Recent Developments Capital and Liquidity (Details) (USD $)	12 Months Ended			24 Months Ended	84 Months Ended	12 Months Ended				12 Months Ended		0 Months Ended	12 Months Ended					2 Months Ended	6 Months Ended	12 Months Ended			12 Months Ended		12 Months Ended						36 Months Ended			12 Months Ended		1 Months Ended	55 Months Ended				12 Months Ended		12 Months Ended							3 Months Ended	12 Months Ended			55 Months Ended	1 Months Ended		3 Months Ended	1 Months Ended		3 Months Ended	12 Months Ended					6 Months Ended	1 Months Ended			0 Months Ended		0 Months Ended		0 Months Ended					12 Months Ended
	Dec. 31, 2012 segment	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2007	Dec. 31, 2012	Dec. 31, 2012 Freddie Mac Approval [Member]	Dec. 31, 2012 Radian Guaranty [Member]	Dec. 31, 2011 Radian Guaranty [Member]	Dec. 31, 2012 Parent Company	Dec. 31, 2012 Five Point Three Seven Five Percent Senior Notes due 2015 [Member]	Jun. 01, 2005 Five Point Three Seven Five Percent Senior Notes due 2015 [Member]	Jan. 04, 2013 9.00% Senior Notes due 2017 [Member]	Dec. 31, 2012 9.00% Senior Notes due 2017 [Member]	Dec. 03, 2012 9.00% Senior Notes due 2017 [Member]	Dec. 31, 2012 Three Percent Convertible Senior Notes due 2017 [Member]	Dec. 31, 2011 Three Percent Convertible Senior Notes due 2017 [Member]	Nov. 15, 2010 Three Percent Convertible Senior Notes due 2017 [Member]	Feb. 23, 2012 Five Point Six Two Five Percent Senior Notes due 2013 [Member]	Sep. 30, 2012 Five Point Six Two Five Percent Senior Notes due 2013 [Member]	Dec. 31, 2012 Five Point Six Two Five Percent Senior Notes due 2013 [Member]	Feb. 01, 2003 Five Point Six Two Five Percent Senior Notes due 2013 [Member]	Dec. 31, 2010 Seven Point Seven Five Percent Debentures due 2011 [Member]	Dec. 31, 2013 Scenario, Forecast [Member]	Dec. 31, 2012 Scenario, Forecast [Member] Parent Company	Dec. 31, 2012 Scenario, Forecast [Member] Corporate Expenses [Member]	Dec. 31, 2012 Scenario, Forecast [Member] Corporate Expenses Due For The Next 12 Months [Member]	Dec. 31, 2012 Scenario, Forecast [Member] Performance Based Corporate Expenses [Member]	Dec. 31, 2012 Mortgage Insurance Segment customer	Dec. 31, 2011 Mortgage Insurance Segment	Dec. 31, 2010 Mortgage Insurance Segment	Dec. 31, 2012 Mortgage Insurance Segment	Dec. 31, 2012 Mortgage Insurance Segment State Insurance Regulations [Member] state	Sep. 30, 2012 Mortgage Insurance Segment State Insurance Regulations [Member] state	Dec. 31, 2013 Mortgage Insurance Segment Scenario, Forecast [Member]	Dec. 31, 2012 Radian Mortgage Assurance Inc. [Member] GSE Approval [Member]	Jul. 31, 2012 Radian Guaranty [Member]	Dec. 31, 2012 Radian Guaranty [Member] state	Dec. 31, 2011 Radian Guaranty [Member]	Dec. 31, 2012 Radian Guaranty [Member] Freddie Mac Approval [Member]	Dec. 31, 2012 Radian Guaranty [Member] State Insurance Regulations [Member] state	Dec. 31, 2012 Radian Guaranty [Member] Required Upon RBC Breach Per GSE Approval [Member] GSE Approval [Member]	Dec. 31, 2012 Radian Guaranty [Member] Mortgage Insurance Segment percentagepoint	Dec. 31, 2012 Parent Company		Dec. 31, 2011 Parent Company		Dec. 31, 2010 Parent Company		Dec. 31, 2010 Parent Company Seven Point Seven Five Percent Debentures due 2011 [Member]	Jun. 30, 2012 Radian Asset Assurance [Member]	Dec. 31, 2012 Radian Asset Assurance [Member]	Dec. 31, 2011 Radian Asset Assurance [Member]	Dec. 31, 2010 Radian Asset Assurance [Member]	Dec. 31, 2012 Radian Asset Assurance [Member]	Jan. 24, 2012 Radian Asset Assurance [Member] January 2012 Assured Guaranty Reinsurance Commutation [Member]	Jan. 24, 2012 Radian Asset Assurance [Member] January 2012 Assured Guaranty Ceded Public Finance Transaction [Member]	Jun. 30, 2012 Radian Asset Assurance [Member] April 2012 Commutation Transactions [Member] counterparty derivative	Jan. 24, 2012 Radian Asset Assurance [Member] January 2012 Assured Guaranty Transaction [Member]	Feb. 29, 2012 Radian Asset Assurance [Member] January 2012 Assured Guaranty Transaction [Member] state	Sep. 30, 2013 Radian Asset Assurance [Member] Scenario, Forecast [Member]	Dec. 31, 2012 Maximum [Member] Freddie Mac Approval [Member]	Dec. 31, 2012 Maximum [Member] Mortgage Insurance Segment State Insurance Regulations [Member]	Dec. 31, 2012 Maximum [Member] Radian Guaranty [Member] State Insurance Regulations [Member]	Dec. 31, 2012 Minimum [Member] Radian Guaranty [Member] Freddie Mac Approval [Member]	Dec. 31, 2012 Minimum [Member] Radian Guaranty [Member] State Insurance Regulations [Member]	Jun. 30, 2013 Legacy Portfolio Underwritten Between 2005 and 2008 [Member]	Feb. 28, 2013 State Insurance Regulations [Member] Radian Asset Assurance [Member]	Feb. 15, 2013 Repayment of Debt [Member] Five Point Six Two Five Percent Senior Notes due 2013 [Member]	Feb. 15, 2013 Repayment of Debt [Member] Parent Company Five Point Six Two Five Percent Senior Notes due 2013 [Member]	Jan. 09, 2013 2012 FGIC Commutation [Member] Radian Asset Assurance [Member]	Dec. 31, 2012 2012 FGIC Commutation [Member] Reinsurance [Member] Radian Asset Assurance [Member]	Jan. 04, 2013 Debt Due 2015 Exchange [Member] Five Point Three Seven Five Percent Senior Notes due 2015 [Member]	Jan. 04, 2013 Debt Due 2015 Exchange [Member] Five Point Three Seven Five Percent Senior Notes due 2015 [Member] Parent Company	Jan. 04, 2013 Debt Due 2015 Exchange [Member] 9.00% Senior Notes due 2017 [Member]	Jan. 04, 2013 Debt Due 2015 Exchange [Member] 9.00% Senior Notes due 2017 [Member] Parent Company	Dec. 31, 2012 Internal Revenue Service (IRS) [Member]	May 03, 2010 Internal Revenue Service (IRS) [Member]	Jun. 30, 2008 Internal Revenue Service (IRS) [Member]	Dec. 31, 2012 Internal Revenue Service (IRS) [Member] Maximum [Member]	Dec. 31, 2012 Internal Revenue Service (IRS) [Member] Minimum [Member]	Dec. 31, 2012 Less Than [Member] Mortgage Insurance Segment
Risk to Capital Line Items [Line Items]
Number of Operating Segments	2
Radian Group [Abstract]
Unrestricted Cash And Liquid Investments Including Activity After The Balance Sheet Date									$ 375,600,000
Extinguishment of Debt, Amount																		146,500,000	24,100,000	170,600,000																													31,900,000																			79,449,000	79,400,000			195,176,000
Debt Instrument, Interest Rate, Stated Percentage											5.375%			9.00%			3.00%			5.625%	5.625%	7.75%
Debt Instrument, Maturity Date										Jun. 15, 2015			Jun. 15, 2017
Debt Instrument, Face Amount											250,000,000				450,000,000	450,000,000	450,000,000				250,000,000																																																				54,800,000		195,200,000
Mortgage Insurance [Abstract]
Private Mortage Insurance Protects Lenders For Loans Made With This Maximum Downpayment Percentage																												20.00%			20.00%
Percentage Of Primary Insurance On Domestic First-Lien Mortgages To Total Risk In Force																												94.50%			94.50%
First Lien Primary Mortgage Insurance Risk In Force																												36,400,000,000			36,400,000,000
Percentage Of Pool Insurance On Domestic First-Lien Mortgages To Total Risk In Force																												5.00%			5.00%
NonTraditional Risk In Force																												148,000,000			148,000,000
Percentage Of Non-Traditional RIF To Total RIF																																																																																	1.00%
Capital Preservation and Liquidity Management Initiatives [Abstract]
New Insurance Written																												37,061,000,000	15,510,000	11,558,000
Percent of Total Primary Risk In Force That Has Successfully Completed a HARP Refinance																												9.00%			9.00%
Number of New Customers																												300
Percent of New Insurance Written Attributable to New Customers																															32.00%
Risk To Capital Ratio							0.208	0.215																				0.208			0.208						20.8	21.5
Percentage Reduction On Net Par Outstanding																																																						70.70%				22.50%
Net Par Outstanding																																																			33,700,000,000			33,700,000,000			699,000,000														822,200,000
Contingency Reserve Release																																																		54,500,000				357,000,000													61,100,000			6,700,000
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries																																				54,000,000	383,800,000														54,000,000	53,400,000	69,200,000							35,000,000
Reduction In Net Par Outstanding																																																							13,800,000,000	1,800,000,000
Number Of States In Which New York Is Licensed To Conduct Business																																																											37
(Increase) Decrease To Statutory Capital And Surplus																																																										(100,700,000)
Number of Derivative Counterparties Involved in Commutation																																																									1
Net par outstanding on CDO of ABS transaction																																																									450,200,000
Number Of Trups CDOs Terminated																																																									6
Net Cash (Paid) Received For Commutations, Terminations And Recaptures	240,110,000	92,599,000	(85,657,000)		835,700,000																																																				(210,000,000)
Commutation Payment																																																																							52,400,000
Debt Conversion, Converted Instrument, Expiration or Due Date												Jan. 04, 2013																																																														Jan. 04, 2013
Insurance Regulatory Capital Requirements [Abstract]
Number Of States That Have A Statutory Or Regulatory Risk Based Capital Requirement																																16	16
Risk To Capital Ratio, Regulatory Maximum																																																														0.25
Percentage of New Insurance Written Attributable To States With Statutory Or Regulatory Risk Based Capital Requirements							54.30%	50.50%
Risk To Capital Ratio							0.208	0.215																				0.208			0.208						20.8	21.5
Number of States Where the Minimum Policyholder Position Has Been Exceeded																																					2
Percentage Decrease In New Defaults																												22.00%	18.00%					24.00%
Weighted Average Default To Claim Rate Assumption Net Of Denials And Rescissions																												47.00%	43.00%	40.00%
Percentage Point Increase In Aggregate Weighted Average Default To Claim Rate Used In Assumption Shift Analysis																																										1
Increase To Provison For Losses Based On One Percentage Change in Default To Claim Rate																												55,000,000			55,000,000
Proceeds from Contributions from Affiliates																									39,400,000	15,300,000	29,400,000																0		0		268,530,000
Debt Instrument, Face Amount											250,000,000				450,000,000	450,000,000	450,000,000				250,000,000																																																				54,800,000		195,200,000
Risk To Capital Ratio Revised Range for Waivers																																																															0.35		0.30
Number Of States From Which We Are Pursuing Risk Based Capital Requirement Waivers																																								2
Maximum Risk to Capital Ratio Requirement for Affiliated Reinsurance Entity From GSE Approval Documentation																																			0.20
Capital Contributions																																									50,000,000		100,384,000	[1]	50,587,000	[1]	423,146,000	[1]
Liquid Assets																																							868,900,000																									700,000,000
Concentration Risk, Percentage																																																																		50.00%
Holding Company Liquidity [Abstract]
Unrestricted Cash And Liquid Investments Including Activity After The Balance Sheet Date									375,600,000
Extinguishment of Debt, Amount																		146,500,000	24,100,000	170,600,000																													31,900,000																			79,449,000	79,400,000			195,176,000
Debt Instrument, Face Amount											250,000,000				450,000,000	450,000,000	450,000,000				250,000,000																																																				54,800,000		195,200,000
Other Cost and Expense, Operating	196,672,000	175,810,000	191,942,000																				63,200,000					152,448,000	132,225,000	141,172,000
Interest Expense, Long-term Debt																							35,900,000
Proceeds from Contributions from Affiliates																									39,400,000	15,300,000	29,400,000																0		0		268,530,000
Dividends Payable, Amount Per Share									$ 0.0025
Common Stock, Shares, Outstanding	133,647,216	133,199,159			133,647,216				133,647,216																																		133,647,216		133,199,159
Dividends Payable, Amount																								1,300,000
Amount Available for Dividend Distribution without Prior Approval from Regulatory Agency																																											734,800,000
Maturity Of Securities Rated Single A Or Higher By The Rating Agencies																																																													5 years
U.S. Treasury Securities Maturity																																																													10 years
Maturity of U.S. Treasury Securities Comprising Ten Percent Of Liquid Assets																																																													5 years
Percentage of U.S. Treasury Securities With Maturities Greater Than Five Years To Liquid Assets																																																																10.00%
Maximum Loan To Value Percentage For G.S.E. Acquired Loans	80.00%				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%				10.00%
Proposed Increase To Tax Liability Resulting From I.R.S. Examination Of Tax Years 2000 Through 2007																																																																												128,000,000
Income Tax Examination, Proposed Penalties																																																																												42,000,000
Qualified Deposit With The U.S. Department Of Treasury Relating to Tax Years 2000 Through 2004																																																																														85,000,000
Qualified Deposit With The U.S. Department Of Treasury Relating To Tax Years 2005 Through 2007																																																																													4,000,000
Amount of Claimed Income Tax Refund for Tax Years 2006 and 2007				$ 105,000,000
Number of Years Extension of Approval from GSE						1 year
Number of Months Until IRS Office of Appeals Issues Deficiency Notice																																																																															6 months	3 months
Number of Days Company Has to Respond to IRS Office of Appeals Deficiency Notice																																																																															90 days

[1] See Note A.