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Note 15 - Commitments and Contingencies Legal Proceedings (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
plaintiff
loan
Sep. 04, 2014
Loss Contingencies [Line Items]    
Minimum Number of Pending or Threatened Matters That Could Effect Our Results 1rdn_MinimumNumberofPendingorThreatenedMattersThatCouldEffectOurResults  
Minimum [Member]    
Loss Contingencies [Line Items]    
Number Of Home Mortgage Loans Involved In Pending Litigation 1rdn_NumberOfHomeMortgageLoansInvolvedInPendingLitigation
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		  
Loss Contingency, Number of Plaintiffs Whose Loans Were Insured 1us-gaap_LossContingencyNumberOfPlaintiffs
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		  
REMIC Residual [Member] | Internal Revenue Service (IRS) [Member]    
Loss Contingencies [Line Items]    
Income Tax Examination, Notice of Deficiency, Amounts Related to Unpaid Taxes and Penalties   $ 157rdn_IncomeTaxExaminationNoticeofDeficiencyAmountsRelatedtoUnpaidTaxesandPenalties
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_InternalRevenueServiceIRSMember
/ us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis
= rdn_REMICResidualMember