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

New Primary Defaults

No definition available.

Name:	rdn_NewPrimaryDefaults
Namespace Prefix:	rdn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number Of Payments Missed For Insured Loans

No definition available.

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

Amount of other increase (decrease) in accrued obligations to policyholders pertaining to insured events for the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b),(c)
-URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437

Name:	us-gaap_LiabilityForFuturePolicyBenefitsOtherIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Name:	us-gaap_StatementBusinessSegmentsAxis=rdn_MortgageInsuranceSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_ProductOrServiceAxis=rdn_TotalPrimaryInsuranceMortgageInsuranceProductsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	rdn_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseActivityInLiabilityAxis=rdn_IncurredButNotReportedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_ProductOrServiceAxis=rdn_PrimaryMortgageProductMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	rdn_DefaulttoClaimRateDefaultsNotinForeclosureStageAgeAxis=rdn_AgedLessThan2YearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	rdn_DefaulttoClaimRateDefaultsNotinForeclosureStageAgeAxis=rdn_Aged2To5YearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: