Note 1 - Condensed Consolidated Financial Statements - Basis of Presentation Capital and Liquidity (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		1 Months Ended				6 Months Ended		1 Months Ended	9 Months Ended		1 Months Ended	9 Months Ended				9 Months Ended			12 Months Ended					1 Months Ended	9 Months Ended		9 Months Ended	12 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended				3 Months Ended			3 Months Ended		12 Months Ended			9 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Mortgage Insurance Segment	Sep. 30, 2011 Mortgage Insurance Segment	Sep. 30, 2012 Mortgage Insurance Segment	Sep. 30, 2011 Mortgage Insurance Segment	Oct. 31, 2012 2012 CDS Termination Subsequent Event [Member] counterparty	Oct. 31, 2012 2012 CDO Termination Subsequent Event [Member] counterparty derivative	Sep. 30, 2012 3.00% Convertible Senior Notes due 2017 [Member]	Dec. 31, 2011 3.00% Convertible Senior Notes due 2017 [Member]	Sep. 30, 2012 5.625% Senior Notes due 2013 [Member]	Sep. 30, 2012 5.375% Senior Notes due 2015 [Member]	Jan. 24, 2012 January 2012 Assured Guaranty Ceded Public Finance Transaction [Member]	Sep. 30, 2012 January 2012 Assured Guaranty Transaction [Member]	Mar. 31, 2012 January 2012 Assured Guaranty Transaction [Member] state	Jan. 24, 2012 January 2012 Assured Guaranty Reinsurance Commutation [Member]	Sep. 30, 2012 2012 CDO Terminations [Member] derivative counterparty	Sep. 30, 2012 State Insurance Regulations [Member] Mortgage Insurance Segment state waiver	Sep. 30, 2012 State Insurance Regulations [Member] Minimum [Member] Mortgage Insurance Segment state	Sep. 30, 2012 State Insurance Regulations [Member] Maximum [Member] Mortgage Insurance Segment	Sep. 30, 2012 GSE Approval [Member] Required Upon RBC Breach Per GSE Approval [Member]	Sep. 30, 2012 Freddie Mac Approval [Member] Minimum [Member]	Sep. 30, 2012 Freddie Mac Approval [Member] Maximum [Member]	Sep. 30, 2013 Corporate Expenses [Member] Scenario, Forecast [Member]	Sep. 30, 2013 Interest Expense [Member] Scenario, Forecast [Member]	Sep. 30, 2012 Corporate Expenses and Interest Payments [Member] Scenario, Forecast [Member]	Sep. 30, 2012 Corporate Expenses Due For The Next 12 Months [Member] Scenario, Forecast [Member]	Sep. 30, 2012 Performance Based Corporate Expenses [Member] Scenario, Forecast [Member]	Jul. 31, 2012 Radian Guaranty [Member]	Sep. 30, 2012 Radian Guaranty [Member]	Dec. 31, 2011 Radian Guaranty [Member]	Sep. 30, 2012 Radian Guaranty [Member] Mortgage Insurance Segment percentagepoint	Dec. 31, 2011 Radian Guaranty [Member] Mortgage Insurance Segment	Sep. 30, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] state	Sep. 30, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Second Quota Share Reinsurance Transaction [Member] Minimum [Member]	Sep. 30, 2012 Radian Guaranty [Member] Scenario, Forecast [Member] Second Quota Share Reinsurance Transaction [Member] Maximum [Member]	Jun. 30, 2012 Radian Asset Assurance [Member]	Sep. 30, 2012 Radian Asset Assurance [Member] January 2012 Assured Guaranty Transaction [Member]	Jun. 30, 2012 Radian Asset Assurance [Member] CDO Of ABS Transaction [Member]	Sep. 30, 2012 Radian Asset Assurance [Member] Terminated TruPs Bonds [Member]	Jun. 30, 2012 Radian Asset Assurance [Member] Terminated TruPs Bonds [Member] derivative	Jun. 30, 2012 Radian Asset Assurance [Member] April 2012 Commutation Transactions [Member]	Sep. 30, 2012 Radian Asset Assurance [Member] April 2012 Commutation Transactions [Member] Internal Rating Of B Or Below [Member]	Jun. 30, 2012 Radian Asset Assurance [Member] April 2012 Commutation Transactions [Member] Internal Rating Of B Or Below [Member]	Sep. 30, 2012 Radian Asset Assurance [Member] Greece [Member]	Sep. 30, 2012 Parent Company	Sep. 30, 2013 Parent Company Scenario, Forecast [Member]	Sep. 30, 2012 Parent Company Scenario, Forecast [Member]	Sep. 30, 2012 Parent Company 3.00% Convertible Senior Notes due 2017 [Member]	Sep. 30, 2012 Parent Company 5.625% Senior Notes due 2013 [Member]	Sep. 30, 2012 Parent Company 5.375% Senior Notes due 2015 [Member]	Sep. 30, 2012 Initial Quota Share Reinsurance Transaction [Member] Radian Guaranty [Member]	Sep. 30, 2012 Initial Quota Share Reinsurance Transaction [Member] Radian Guaranty [Member] Scenario, Forecast [Member] Maximum [Member]
Capital Preservation and Liquidity Management Initiatives [Abstract]
Reduction In Net Par Outstanding										$ 4,400,000,000					$ 1,800,000,000			$ 13,800,000,000	$ 10,200,000,000
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																100,700,000																																							62,500,000
Number Of Our Credit Derivative Counterparties That Exercised Their Termination Rights									1	3									5
Number of Corporate CDOs Terminated										11									24
Number Of Our Credit Derivative Counterparties That Exercised Their Termination Rights With Respect to Credit Default Swaps																			1
Extinguishment of Debt, Amount													24,100,000																																							170,600,000
First Lien Primary Mortgage Insurance Risk In Force Ceded																																					750,000,000	2,000,000,000																1,400,000,000	1,600,000,000
Maximum exposure (1)																																									450,200,000
Number Of Trups CDOs Terminated																																											6
Net Par Outstanding																																											699,000,000			1,000,000,000
Net Cash Received (Paid) For Commutations, Terminations And Recaptures																																												(210,000,000)
Statutory Salvage Recovery																																										75,900,000
Gain (Loss) on Contract Termination																																												(108,000,000)
Percentage Of Net Par Outstanding																																													51.00%
Contingency Reserve Release																																							54,500,000
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries																															54,000,000	54,000,000				40,000,000
Impact to Statement of Operations [Abstract]
Decrease in Assumed Premiums Written																																								(119,800,000)
Decrease in Net Premiums Earned																																								(22,200,000)
Increase in Change in Fair Value of Derivatives	(41,056,000)	126,008,000	(146,937,000)	558,626,000	(1,000)	200,000	(32,000)	64,000																																1,400,000
Gain on sale of affiliate	0	0	7,708,000	0	0	0	0	0																																7,700,000
Increase in Policy Acquisition Costs	(12,927,000)	(11,449,000)	(51,778,000)	(39,967,000)	(10,126,000)	(7,834,000)	(26,662,000)	(26,651,000)																																(15,700,000)
Decrease in Pre-Tax Income	7,595,000	189,613,000	(287,346,000)	424,670,000	11,084,000	(78,224,000)	(79,157,000)	(402,962,000)																																(28,800,000)
Decrease in [Abstract]
Change in Cash Due to Commutation and Cession																																								93,600,000
Change in Deferred Policy Acquisition Costs Due to Commutation and Cession																																								26,200,000
Change in Accounts and Notes Receivable Net Due to Commutation and Cession																																								1,100,000
Change in Derivative Assets Due to Commutation and Cession																																								600,000
Change in Unearned Premium Due to Commutation and Cession																																								71,600,000
Change in Derivative Liabilities Due to Commutation and Cession																																								2,100,000
Change in Other Assets Due to Commutation and Cession																																								19,100,000
Regulatory Capital Requirements [Abstract]
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																				0.25	0.30	0.35
Percentage of New Insurance Written Attributable To States With Statutory Or Regulatory Risk Based Capital Requirements																																		54.70%
Risk To Capital Ratio																																0.201	0.215	0.201	0.215
Number of States Where the Minimum Policyholder Position is Exceeded																																				2
Weighted Average Default To Claim Rate Assumption Net Of Denials And Rescissions																																		46.00%	43.00%
Percentage Point Increase In Aggregate Weighted Average Default To Claim Rate Used In Assumption Shift Analysis																																		1
Impact To Incurred Losses Based On One Percentage Increase In Default To Claim Rate																																		56,000,000
Maximum Risk to Capital Ratio Requirement for Affiliated Reinsurance Entity From GSE Approval Documentation					0.20		0.20
Number Of States That Have Granted Waivers To Risk Based Capital Requirements																				10
Number Of States From Which We Are Pursuing Risk Based Capital Requirement Waivers																				1
Number Of States Where Statutory RBC Requirements Could Impact Ability To Write New Business																					1
Number Of Waivers To Risk Based Capital Requirements With Expirations in Current Year																				4
Capital Contributions																							50,000,000
Liquid Assets																								700,000,000								1,400,000,000
Statutory Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid																																															23,500,000
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%
Holding Company Liquidity [Abstract]
Unrestricted Cash And Liquid Investments																												38,700,000	22,200,000	20,400,000																		368,300,000
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months																																																				79,400,000
Debt Instrument, Interest Rate, Stated Percentage											3.00%		5.625%	5.375%																																						5.625%
Repayments of Long-term Debt			153,261,000	160,000,000
Payments for Operating Activities																										60,200,000
Interest Expense, Long-term Debt			24,531,000	34,660,000																							29,200,000
Debt Instrument, Face Amount											450,000,000	450,000,000																																							450,000,000		250,000,000
Common Stock, Dividends, Per Share																																																		$ 0.0025
Payments of Ordinary Dividends, Common Stock			1,001,000	1,001,000																																													1,300,000
Amount Available for Dividend Distribution without Prior Approval from Regulatory Agency																																																$ 914,100,000