Note 1 - Description of Business and Recent Developments Capital and Liquidity (Details) (USD $)	1 Months Ended	12 Months Ended						48 Months Ended	12 Months Ended		12 Months Ended				12 Months Ended							12 Months Ended				1 Months Ended			3 Months Ended		2 Months Ended	3 Months Ended		12 Months Ended			12 Months Ended					12 Months Ended			12 Months Ended
	Jan. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Radian Guaranty [Member]	Dec. 31, 2011 CMAC Of Texas [Member]	Dec. 31, 2011 Radian Asset Assurance [Member]	Dec. 31, 2011 Radian Asset Assurance [Member]	Dec. 31, 2011 Parent Company	Sep. 30, 2003 Parent Company	Dec. 31, 2011 Subsidiary of Common Parent [Member]	Dec. 31, 2011 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]	Feb. 15, 2013 Five Point Three Seven Five Percent Senior Notes due 2015 [Member] Parent Company	Dec. 31, 2010 Three Percent Convertible Senior Notes due 2017 [Member]	Dec. 31, 2011 Three Percent Convertible Senior Notes due 2017 [Member]	Nov. 01, 2010 Three Percent Convertible Senior Notes due 2017 [Member]	Dec. 31, 2011 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]	Feb. 15, 2013 Five Point Six Two Five Percent Senior Notes due 2013 [Member] Parent Company	Mar. 31, 2012 Five Point Six Two Five Percent Senior Notes due 2013 [Member] Parent Company	Dec. 31, 2010 Seven Point Seven Five Percent Debentures due 2011 [Member]	Dec. 31, 2009 Seven Point Seven Five Percent Debentures due 2011 [Member]	Dec. 31, 2011 Seven Point Seven Five Percent Debentures due 2011 [Member]	May 01, 2001 Seven Point Seven Five Percent Debentures due 2011 [Member]	Jan. 24, 2012 January 2012 Assured Guaranty Reinsurance Commutation [Member]	Jan. 24, 2012 January 2012 Assured Guaranty Ceded Public Finance Transaction [Member]	Jan. 24, 2012 January 2012 Assured Guaranty Transaction [Member]	Mar. 31, 2012 January 2012 Assured Guaranty Transaction [Member]	Feb. 29, 2012 January 2012 Assured Guaranty Transaction [Member]	Feb. 29, 2012 February 2012 CDO Termination [Member]	Dec. 31, 2011 CDO Of ABS Interest Shortfall [Member] Radian Asset Assurance [Member]	Dec. 31, 2011 Freddie Mac Approval [Member] Radian Guaranty [Member]	Dec. 31, 2011 Scenario, Forecast [Member]	Dec. 31, 2012 Scenario, Forecast [Member] Parent Company	Dec. 31, 2011 Scenario, Forecast [Member] Parent Company	Dec. 31, 2011 Scenario, Forecast [Member] Corporate Expenses [Member]	Dec. 31, 2011 Scenario, Forecast [Member] Corporate Expenses Due For The Next 12 Months [Member]	Dec. 31, 2011 Scenario, Forecast [Member] Performance Based Corporate Expenses [Member]	Mar. 31, 2012 Minimum [Member] February 2012 Quota Share Reinsurance Agreement [Member] Radian Guaranty [Member]	Dec. 31, 2011 Minimum [Member] Freddie Mac Approval [Member]	Dec. 31, 2011 Required Upon RBC Breach Per Freddie Mac Approval [Member] Freddie Mac Approval [Member]	Mar. 31, 2012 Maximum [Member] February 2012 Quota Share Reinsurance Agreement [Member] Radian Guaranty [Member]	Dec. 31, 2011 Maximum [Member] Freddie Mac Approval [Member]	Dec. 31, 2011 Requirement Per Fannie Mae Approval [Member] Fannie Mae Approval [Member]	Dec. 31, 2011 Required Upon RBC Breach Per Fannie Mae Approval [Member] Fannie Mae Approval [Member]
Risk to Capital Line Items [Line Items]
Unrestricted Cash And Liquid Investments Including Activity After The Balance Sheet Date									$ 482,800,000
Related Party Transaction, Due from (to) Related Party									(100,000,000)
Debt Instrument, Face Amount									950,000,000				250,000,000	250,000,000	450,000,000	450,000,000	450,000,000		250,000,000	250,000,000					250,000,000
Percentage of New Insurance Written Attributable To States With Statutory Or Regulatory Risk Based Capital Requirements					50.50%
Number Of States That Have A Statutory Or Regulatory Risk Based Capital Requirement		16
States Which Have A Risk To Capital Ratio Limit of 25 To 1		11
Risk To Capital Ratio, Regulatory Maximum		25.0
Risk To Capital Ratio					21.5																																							20.00
Number Of States That Have Granted Waivers To Risk Based Capital Requirements		6
Number Of States From Which We Are Pursuing Risk Based Capital Requirement Waivers		5
Consolidation, Wholly Owned Subsidiary, Parent Ownershi Interest Changes, Transfer of Interest by Parent					17,000,000
Payments for (Proceeds from) Businesses and Interest in Affiliates					6,000,000
Common Stock, Dividends, Per Share																																				$ 0.0025
Common Stock, Shares, Outstanding		133,199,159	133,049,213																																133,199,159
Dividends Payable, Amount																																			1,300,000
Contingency Reserve Release								215,500,000
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries								329,800,000
Statutory Incurred Losses							99,200,000
Gain on sale of affiliate		0	34,815,000	0																									9,000,000
Number Of Our Credit Derivative Counterparties That Excercised Their Termination Rights																															3
Number of Corporate CDOs Terminated																															14
Reduction In Net Par Outstanding																										13,800,000,000	1,800,000,000				5,800,000,000
Number Of States In Which New York Is Licensed To Conduct Business																														37
New Insurance Written	2,000,000,000
First Lien Primary Mortgage Insurance Risk In Force		32,800,000,000																																						1,200,000,000			1,500,000,000
Percentage Reduction On Net Par Outstanding																												22.50%
(Increase) Decrease To Statutory Capital And Surplus																												(100,000,000)				91,800,000
Net par outstanding on CDO of ABS transaction																																450,600,000
Interest Shortfall On CDO Of ABS																																36,000
Net Cash Received (Paid) For Commutations, Terminations And Recaptures		92,599,000	(85,657,000)	369,926,000
Debt Instrument, Interest Rate, Stated Percentage												5.375%	5.375%			3.00%	3.00%	5.625%	5.625%	5.625%				7.75%	7.75%
Amount Approved For Repurchase Of Long Term Debt																					100,000,000
Principal Amount of Note Used as Basis for Determining Tender Cap Range of Purchase																					1,000
Income Taxes, Parent Refund To Subsidiary					77,000,000						7,000,000
Committed Preferred Custodial Trust Securities										150,000,000
Extinguishment of Debt, Amount																						31,900,000	57,700,000
Amount Per Dollar of Principal of Debt Repurchased																						$ 0.92	$ 0.79
Gains (Losses) on Extinguishment of Debt																						2,500,000	12,000,000
Proceeds from Issuance of Common Stock		0	525,887,000	0
Proceeds from Issuance of Debt		0	391,310,000	0											391,300,000
Capital Contributions					30,000,000	20,600,000			50,600,000																																	50,000,000			100,000,000	50,000,000
Capital Contribution Receivable					100,000,000
Other Cost and Expense, Operating		175,810,000	191,942,000	203,770,000																														59,600,000
Interest Expense, Long-term Debt																																		41,000,000
Proceeds from Contributions from Affiliates																																					30,700,000	16,700,000	15,800,000
Liquid Assets Minimum Threshold Per Freddie Mac Provision																																									700,000,000
Unrestricted Cash and Liquid Investments																																	$ 1,200,000,000