Financial Guaranty and Discontinued Operations [Abstract]

No definition available.

Name:	rdn_FinancialGuarantyandDiscontinuedOperationsAbstract
Namespace Prefix:	rdn_
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Period Type:	duration

- Definition

Percentage Of Pool Insurance On Domestic First-Lien Mortgages To Total Risk In Force

+ References

No definition available.

+ Details

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

- Definition

Percentage Of Primary Insurance On Domestic First-Lien Mortgages To Total Risk In Force

+ References

No definition available.

+ Details

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

- Definition

This element represents the maximum down payment percentage on a home's purchase price that is used to measure the need for private mortgage insurance.

+ References

No definition available.

+ Details

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

- Definition

Risk In Force

+ References

No definition available.

+ Details

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

- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

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

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_RegulatoryCapitalRequirementsAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company before stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPercentageOfOwnershipBeforeTransaction
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsDisposedOfBySaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=rdn_RadianAssetAssuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 1 - Description of Business and Recent Developments Organization, Consolidation and Presentation of Financial Statements (Details) $ in Millions			12 Months Ended
	Apr. 02, 2015	Apr. 01, 2015 USD ($)	Dec. 31, 2016 USD ($) segment
Insurance Regulatory Capital Requirements [Abstract]
Number of Reportable Segments \| segment			2
Mortgage Insurance Segment
Insurance Regulatory Capital Requirements [Abstract]
Private Mortgage Insurance Protects Lenders For Loans Made With This Maximum Downpayment Percentage			20.00%
Percentage Of Primary Insurance On Domestic First-Lien Mortgages To Total Risk In Force			98.00%
Risk In Force			$ 47,700
Percentage Of Pool Insurance On Domestic First-Lien Mortgages To Total Risk In Force			2.00%
Discontinued Operations, Disposed of by Sale [Member] \| Radian Asset Assurance [Member]
Financial Guaranty and Discontinued Operations [Abstract]
Sale of Stock, Percentage of Ownership before Transaction	100.00%
Disposal Group, Including Discontinued Operation, Consideration		$ 810
Equity Method Investment, Net Sales Proceeds		$ 789