Name:	rdn_DecreaseToOurLossReservesDueToEstimatedRescissionsAndDenials
Namespace Prefix:	rdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This concept represents the rate at which defaulted loans that have reached the stage where the foreclosure sale has been scheduled or held are expected to result in a claim.

No definition available.

Name:	rdn_DefaultToClaimEstimateGrossForForeclosureStageDefaults
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

This concept represents the rate at which newly reported defaulted loans are expected to result in a claim.

No definition available.

Name:	rdn_DefaultToClaimRateEstimateGrossForNewDefaults
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

This concept represents the rate at which defaulted loans that have not yet reached the foreclosure stage are expected to result in a claim.

No definition available.

Name:	rdn_DefaultToClaimRateEstimateGrossForPreForeclosureStageDefaults
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

This concept represents the calculated amount of claim paid by the original loan amount which represents the severity of the claim. The main determinants of the severity of a claim are the size of the loan, the amount of insurance coverage placed on the loan and the impact of loss mitigation activities.

No definition available.

Name:	rdn_FirstLienPrimaryClaimSeverity
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Impact To Loss Reserves Based On One Percentage Change in Default To Claim Rate

No definition available.

Name:	rdn_ImpactToLossReservesBasedOnOnePercentageChangeInDefaultToClaimRate
Namespace Prefix:	rdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Impact To Loss Reserves Based On One Percentage Change In Primary Claim Severity

No definition available.

Name:	rdn_ImpactToLossReservesBasedOnOnePercentageChangeInPrimaryClaimSeverity
Namespace Prefix:	rdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Number of natural disasters

No definition available.

Name:	rdn_NumberofNaturalDisasters
Namespace Prefix:	rdn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Percentage Point Change In Severity Used In Assumption Shift Analysis

No definition available.

Name:	rdn_PercentagePointChangeInSeverityUsedInAssumptionShiftAnalysis
Namespace Prefix:	rdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

The number of percentage point shift in our default to claim rate used in our assumption shift analysis.

No definition available.

Name:	rdn_PercentagePointDefaulttoClaimRateUsedInAssumptionShiftAnalysis
Namespace Prefix:	rdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Weighted Average Default To Claim Rate Assumption Excluding Pending Claims Net Of Denials And Rescissions

No definition available.

Name:	rdn_WeightedAverageDefaultToClaimRateAssumptionExcludingPendingClaimsNetOfDenialsAndRescissions
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The concept represents the rate at which defaulted loans are expected to result in claim net of denials, rescissions and reinstatements.

No definition available.

Name:	rdn_WeightedAverageDefaultToClaimRateAssumptionNetOfDenialsRescissionsAndReinstatements
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Weighted Average Default To Claim Rate Assumption Net Of Denials Rescissions and Reinstatements Excluding Defaults in FEMA Designated Areas

No definition available.

Name:	rdn_WeightedAverageDefaultToClaimRateAssumptionNetOfDenialsRescissionsandReinstatementsExcludingDefaultsinFEMADesignatedAreas
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_CausesOfIncreaseDecreaseInLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Estimated costs as of the balance sheet date of settling insured claims and costs incurred in the claims settlement process for claims that have not yet been submitted to the insurance company for reimbursement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.W)
-URI http://asc.fasb.org/extlink&oid=27015833&loc=d3e570705-122907