Note 1 - Condensed Consolidated Financial Statements - Basis of Presentation Capital and Liquidity (Details) (USD $)	3 Months Ended					3 Months Ended				3 Months Ended				3 Months Ended				3 Months Ended				1 Months Ended			3 Months Ended		2 Months Ended	0 Months Ended		12 Months Ended		3 Months Ended	12 Months Ended			12 Months Ended	3 Months Ended	0 Months Ended	3 Months Ended		0 Months Ended	3 Months Ended		3 Months Ended		3 Months Ended				3 Months Ended			3 Months Ended			12 Months Ended					12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2012 Mortgage Insurance Segment	Mar. 31, 2011 Mortgage Insurance Segment	Mar. 31, 2012 Mortgage Insurance Segment	Mar. 31, 2011 Mortgage Insurance Segment	Mar. 31, 2012 Minimum [Member]	Mar. 31, 2012 3.00% Convertible Senior Notes due 2017 [Member]	Mar. 31, 2012 5.625% Senior Notes due 2013 [Member]	Mar. 31, 2012 5.375% Senior Notes due 2015 [Member]	Mar. 31, 2012 Parent Company	Dec. 31, 2011 Parent Company	Mar. 31, 2012 Parent Company Scenario, Forecast [Member]	Mar. 31, 2012 Parent Company 3.00% Convertible Senior Notes due 2017 [Member]	Mar. 31, 2012 Parent Company 5.625% Senior Notes due 2013 [Member]	Dec. 31, 2011 Parent Company 5.625% Senior Notes due 2013 [Member]	Mar. 31, 2012 Parent Company Long Term Debt Due Between 2015 and 2017 [Member]	Mar. 31, 2012 Parent Company 5.375% Senior Notes due 2015 [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]	Mar. 31, 2012 January 2012 Assured Guaranty Transaction [Member]	Feb. 29, 2012 February 2012 CDO Termination [Member]	May 02, 2012 May 2012 CDO Termination [Member]	Mar. 31, 2012 State Insurance Regulations [Member] Mortgage Insurance Segment	Dec. 31, 2011 Radian Guaranty [Member]	Mar. 31, 2012 Radian Guaranty [Member]	Mar. 31, 2012 Radian Guaranty [Member] Mortgage Insurance Segment	Dec. 31, 2011 Radian Guaranty [Member] Mortgage Insurance Segment	Apr. 02, 2012 Radian Guaranty [Member] Quota Share Reinsurance Agreement [Member]	Mar. 31, 2012 Radian Guaranty [Member] Quota Share Reinsurance Agreement [Member] Maximum [Member]	Dec. 31, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Mortgage Insurance Segment	Mar. 31, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Quota Share Reinsurance Agreement [Member]	Mar. 31, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Quota Share Reinsurance Agreement [Member] Minimum [Member]	Mar. 31, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Quota Share Reinsurance Agreement [Member] Minimum [Member]	Apr. 02, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Quota Share Reinsurance Agreement [Member] Minimum [Member]	Mar. 31, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Quota Share Reinsurance Agreement [Member] Maximum [Member]	Mar. 31, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Quota Share Reinsurance Agreement [Member] Maximum [Member]	Apr. 02, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Quota Share Reinsurance Agreement [Member] Maximum [Member]	Jun. 30, 2012 Radian Asset Assurance	Mar. 31, 2012 Radian Asset Assurance CDO Of ABS Transaction [Member]	Mar. 31, 2012 Radian Asset Assurance Terminated TruPs Bonds [Member]	Jun. 30, 2012 Radian Asset Assurance April 2012 Commutation Transactions [Member]	Mar. 31, 2012 Radian Asset Assurance April 2012 Commutation Transactions [Member] Internal Rating Of B Or Below [Member]	Mar. 31, 2012 Radian Mortgage Assurance [Member] Mortgage Insurance Segment	Mar. 31, 2012 Fannie Mae Approval [Member] Requirement Per Fannie Mae Approval [Member]	Mar. 31, 2012 Fannie Mae Approval [Member] Required Upon RBC Breach Per Fannie Mae Approval [Member]	Mar. 31, 2012 Freddie Mac Approval [Member] Minimum [Member]	Mar. 31, 2012 Freddie Mac Approval [Member] Maximum [Member]	Mar. 31, 2012 Freddie Mac Approval [Member] Requirement Per Fannie Mae Approval [Member]	Mar. 31, 2012 Freddie Mac Approval [Member] Required Upon RBC Breach Per Freddie Mac Approval [Member]	Mar. 31, 2013 Corporate Expenses [Member] Scenario, Forecast [Member]	Mar. 31, 2013 Interest Expense [Member] Scenario, Forecast [Member]	Mar. 31, 2012 Corporate Expenses and Interest Payments [Member] Scenario, Forecast [Member]	Mar. 31, 2012 Corporate Expenses Due For The Next 12 Months [Member] Scenario, Forecast [Member]	Mar. 31, 2012 Performance Based Corporate Expenses [Member] Scenario, Forecast [Member]	Dec. 31, 2011 Subsidiary of Common Parent [Member]
Capital Preservation and Liquidity Management Initiatives [Abstract]
Reduction In Net Par Outstanding																						$ 13,800,000,000	$ 1,800,000,000				$ 8,300,000,000
Number Of States In Which The Financial Guaranty Insurance Shell Is Licensed To Conduct Business																									37
Percentage Reduction On Net Par Outstanding																								22.50%
Impact To Statutory Capital And Surplus																									93,500,000													50,000,000	50,000,000		62,500,000	62,500,000
Impact of Commutation and Cession of Financial Guaranty Net Par Outstanding [Abstract]
Impact of Commutation and Cession on Assumed Premiums Written																									119,800,000
Impact of Commutation and Cession on Net Premiums Earned																									(22,200,000)
Impact of Commutation and Cession on Change in Fair Value of Derivatives	(72,757,000)	243,892,000				21,000	(394,000)																		1,400,000
Impact of Commutation and Cession on Policy Acquisition Costs	28,046,000	14,131,000				8,646,000	10,216,000																		15,700,000
Impact of Commutation and Cession on Pre-Tax Income	(178,125,000)	99,990,000				(57,046,000)	(232,531,000)																		(36,500,000)
Impact of Commutation and Cession on Cash	31,784,000	19,209,000		35,589,000	20,334,000																				(108,300,000)
Impact of Commutation and Cession on Deferred Policy Acquisition Costs	107,941,000			139,906,000		49,786,000	42,322,000																		(26,200,000)
Impact of Commutation and Cession on Accounts and Notes Receivable																									(1,100,000)
Impact of Commutation and Cession on Derivative Assets	17,212,000		16,202,000																							(600,000)
Impact of Commutation and Cession on Unearned Premiums	572,565,000			637,372,000		256,809,000	191,910,000																		(71,600,000)
Impact of Commutation and Cession on Derivative Liabilities	126,006,000		202,100,000					0	0																	(2,100,000)
Impact of Commutation and Cession on Other Assets	339,018,000			314,864,000																					26,000,000
Number Of Our Credit Derivative Counterparties That Excercised Their Termination Rights																											3
Number of Corporate CDOs Terminated																											20	2
Percentage of New Insurance Written To Be Ceded Pursuant To The April 2012 Quota Share Reinsurance Agreement																																					20.00%
First Lien Primary Mortgage Insurance Risk In Force						33,000,000,000																												532,000,000						1,250,000,000			1,600,000,000
Maximum exposure (1)																																													450,200,000
Number Of Trups CDOs Terminated																																														6
Net Par Outstanding																												900,000,000																		699,000,000		1,000,000,000
Statutory Salvage Recovery																																															75,000,000
Net Cash Received (Paid) For Commutations, Terminations And Recaptures																																															210,000,000
Statutory Gain (Loss) on Contract Termination																																															7,000,000
Gain (Loss) on Contract Termination																																															108,000,000
Percentage Of Net Par Outstanding																																																51.00%
Contingency Reserve Release																																												55,000,000
Percentage of Reinsurance Able To Be Commuted																																			66.66%
Regulatory Capital Requirements [Abstract]
Number Of States That Have A Statutory Or Regulatory Risk Based Capital Requirement																													16
Number Of States Which Have A Risk To Capital Ratio Limit of 25 To 1																													11
Risk To Capital Ratio, Regulatory Maximum																													0.25
Percentage of New Insurance Written Attributable To States With Statutory Or Regulatory Risk Based Capital Requirements																																55.10%
Risk To Capital Ratio																																0.206	0.215																				0.20
Percentage Decrease In New Defaults																																20.00%	18.00%			15.00%
Weighted Average Default To Claim Rate Assumption Net Of Denials And Rescissions																																46.00%	43.00%
Percentage Point Change In Severity Used In Assumption Shift Analysis																																1.00%
Impact To Loss Reserves Based On One Percentage Change in Default To Claim Rate																																61,000,000
Number Of States That Have Granted Waivers To Risk Based Capital Requirements																													7
Number Of States From Which We Are Pursuing Risk Based Capital Requirement Waivers																													4
Maximum Risk to Capital Ratio Requirement for Affiliated Reinsurance Entity From GSE Approval Documentation																																																	0.20
Capital Contributions														(100,000,000)																																				100,000,000	50,000,000			100,000,000	50,000,000
Number Of States Where Statutory RBC Requirements Could Impact Ability To Write New Business										1
Liquid Assets																															1,400,000,000																					700,000,000
Holding Company Liquidity [Abstract]
Unrestricted Cash And Liquid Investments														363,700,000	482,800,000																																											37,800,000	15,000,000	20,900,000
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months																		103,500,000	250,000,000
Debt Instrument, Interest Rate, Stated Percentage											3.00%	5.625%	5.375%					5.625%
Debt Instrument, Face Amount											450,000,000						450,000,000			700,000,000	250,000,000
Payments for Operating Activities																																																								61,200,000
Interest Expense, Long-term Debt	8,061,000	7,283,000																																																							32,800,000
Aggregate Principal Amount of Long Term Debt Tendered Through Modifiied Dutch Auction Tender Offer																		146,500,000
Price Per Principal Amount Tendered Through Modified Dutch Auction Tender Offer																		900
Principal Amount of Note Used as Basis for Determining Tender Cap Range of Purchase																		1,000
Percent of Principal Amount of Notes Purchased in Modified Dutch Auction Tender Offer for Long Term Debt																		59.00%
Gains (Losses) on Extinguishment of Debt																		15,200,000
Common Stock, Dividends, Per Share																$ 0.0025
Common Stock, Shares, Outstanding	133,290,984			133,199,159
Dividends Payable, Amount																1,300,000
Maturity Of Securities Rated Single A Or Higher By he 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%
Income Taxes, Parent Refund To Subsidiary																														$ 77,000,000																															$ 7,000,000