Name:	rdn_MortgageGuarantyInsuranceCompaniesAreRequiredEachYearToEstablishContingencyReserveEqualToThisPercentageOfPremiumsEarnedInSuchYear
Namespace Prefix:	rdn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Number Of Subsidiaries

No definition available.

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

Number Of Years That A Contingency Reserve Must Be Maintained Under SAPP

No definition available.

Name:	rdn_NumberOfYearsThatAContingencyReserveMustBeMaintainedUnderSAPP
Namespace Prefix:	rdn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The amount of the entity's restricted net assets which are held by consolidated subsidiaries (entity's investment in subsidiaries).

No definition available.

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

This concept represents an entity's ratio of net risk in force (excludes risk ceded through reinsurance contracts and risk in force on defaulted loans) to the amount of statutory capital (defined as the sum of statutory policyholders' surplus plus statutory contingency reserves).

No definition available.

Name:	rdn_RiskToCapitalRatio
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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

This concept represents the maximum ratio of net risk in force (net of risk ceded through reinsurance contracts and risk in force on defaulted loans) to statutory capital (defined as the sum of statutory policyholders' surplus plus statutory contingency reserves) allowed in those states which have statutory risk-based capital requirements.

No definition available.

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

Funds separated from retained earnings and held to cover any unforeseen future business losses.

No definition available.

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

Statutory Accounting Practices, Release Of Contingency Reserve

No definition available.

Name:	rdn_StatutoryAccountingPracticesReleaseOfContingencyReserve
Namespace Prefix:	rdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Statutory Unassigned Positive (Negative) Surplus

No definition available.

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

Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

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

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Ratio of non-life losses and loss expenses to non-life net premiums earned.

No definition available.

Name:	us-gaap_LossRatio
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The number of states the entity operates in as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Cash outflow in the form of ordinary dividends to common shareholders, preferred shareholders and noncontrolling interests, generally out of earnings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

Name:	us-gaap_PaymentsOfOrdinaryDividends
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of asset related to consideration paid in advance for income and other taxes that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (g)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483467/210-10-45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 340
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483032/340-10-45-1

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 340
-SubTopic 10
-Name Accounting Standards Codification
-Section 05
-Paragraph 5
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482955/340-10-05-5

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

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

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

Name:	dei_LegalEntityAxis=rdn_RadianGuarantyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_LegalEntityAxis=rdn_RadianTitleInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatutoryAccountingPracticesByJurisdictionAxis=stpr_PA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatutoryAccountingPracticesByJurisdictionAxis=rdn_DifferencesBetweenGaapBasisAndStatBasisMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatutoryAccountingPracticesByJurisdictionAxis=rdn_NonRBCStatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
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