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

Estimated costs as of the balance sheet date of settling insured claims that have not yet been submitted to the insurer for reimbursement, as well as reserves for estimated reinstatements of previously rescinded policies and denied claims and other reserves for other potential payment of claims.

No definition available.

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

This concept represents the amount of reserve for losses excluding amounts for loss adjustment expenses.

No definition available.

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

The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

-Section 50

-Paragraph 3

-Subparagraph (a),(b),(c)

-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

Name:	us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

Amount after valuation allowance recoverable including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 6

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6824-158387

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),6)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_ReinsuranceRecoverables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_AltMortgageInsuranceProductMember
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Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_FirstLienMortgageInsuranceProductsMember
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Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_MinusAndBelowMortgageInsuranceProductMember
Namespace Prefix:
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Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_PoolInsuranceMortgageInsuranceProductMember
Namespace Prefix:
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Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_PrimaryMortgageProductMember
Namespace Prefix:
Data Type:	na
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Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_PrimeMortgageInsuranceProductMember
Namespace Prefix:
Data Type:	na
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Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_SecondLienMortgageInsuranceProductMember
Namespace Prefix:
Data Type:	na
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Name:	rdn_MortgageInsuranceDescriptionAxis=rdn_TotalPrimaryInsuranceMortgageInsuranceProductsMember
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