Note 1 - Condensed Consolidated Financial Statements - Basis of Presentation and Business Overview Capital and Liquidity (Details) (USD $)	3 Months Ended	0 Months Ended
Mar. 31, 2015 segment	Apr. 01, 2015
Business Overview [Abstract]
Number of Operating Segments	2us-gaap_NumberOfOperatingSegments
Mortgage Insurance Segment
Mortgage Insurance [Abstract]
Private Mortgage Insurance Protects Lenders For Loans Made With Less Than This Maximum Down Payment Percentage	20.00%
Percentage Of Primary Insurance On Domestic First-Lien Mortgages To Total Risk In Force	97.30%
First Lien Primary Mortgage Insurance Risk In Force	44,600,000,000
Percentage Of Pool Insurance On Domestic First-Lien Mortgages To Total Risk In Force	2.60%
Bank of America Settlement Agreement [Member] \| Mortgage Insurance Segment
BAC Settlement Agreement [Abstract]
Loss Contingency, Settlement Agreement, Percentage of Subject Loans Not Held by Insureds or Are Non-GSE Investors	12.00%
Minimum [Member]
Basis of Presentation and Business Overview [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Maximum [Member]
Basis of Presentation and Business Overview [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Subsequent Event [Member] \| Sale of Radian Asset Assurance [Member] \| Parent Company
Business Overview [Abstract]
Sale of Stock, Percentage of Ownership before Transaction		100.00%
Mortgage Insurance [Abstract]
Disposal Group, Including Discontinued Operation, Consideration		810,000,000
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds		$ 789,000,000

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- Details

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- Definition

This concept represents the percentage of total loans included in the settlement agreement that were either (1) not held in portfolio by the insureds, or (2) purchased by Non-GSE investors.

+ References

No definition available.

+ Details

Name:	rdn_LossContingencySettlementAgreementPercentageofSubjectLoansNotHeldbyInsuredsorAreNonGSEInvestors
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
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- Details

Name:	rdn_MortgageInsuranceAbstract
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- 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
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Period Type:	instant

- Definition

Risk In Force

+ References

No definition available.

+ Details

Name:	rdn_RiskInForce
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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

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
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

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

- Definition

The value of all consideration given or received by the Entity in the significant acquisition or disposal.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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- Details

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- Details

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- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=rdn_MortgageInsuranceSegmentMember
Namespace Prefix:
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- Details

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