Name:	rdn_LossContingencyLegalActionsCommencementPeriod
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Name:	rdn_LossesAndLaeMortgageInsuranceAbstract
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This represents the maximum maturity duration when determining the investments in the portfolio which are grouped as short-term investments.

No definition available.

Name:	rdn_MaximumMaturityDurationForShortTermInvestmentGrouping
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This represents the number of groups states are placed in based on their foreclosure timing and other attributes used for reserve estimating.

No definition available.

Name:	rdn_NumberOfGroupsOfStatesUsedInReserveModeling
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The number of categories that captures the major groupings within the investment portfolio.

No definition available.

Name:	rdn_NumberOfInvestmentCategories
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The number of major categories used to define mortgage insurance products

No definition available.

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Number Of Payments Missed For Insured Loans

No definition available.

Name:	rdn_NumberOfPaymentsMissedForInsuredLoans
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Balance Type:	na
Period Type:	instant

The number of years used in determining held-for-sale classification for businesses that are for sale or have been sold.

No definition available.

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This represents the period of time insureds have after foreclosure to provide documents to perfect a claim.

No definition available.

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This represents the period of time given to an insured to rebut our decision to rescind coverage before considering a policy to be rescinded and removed from the default inventory.

No definition available.

Name:	rdn_PeriodOfTimeThatInsuredHasToRebutDecisionToRescindCoverage
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Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 4

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6812-107765

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Amount of expense related to deferred policy acquisition costs.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.7(a))

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 7

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 18

-Article 12

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35755530&loc=d3e11264-158415

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 30

-Section 35

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=28247317&loc=d3e10157-158409

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section 45

-Paragraph 2

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6480726&loc=d3e6691-158385

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Balance Type:	debit
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Name:	us-gaap_DeferredPolicyAcquisitionCostsDisclosuresAbstract
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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

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

Name:	us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
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Balance Type:	na
Period Type:	duration

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Period Type:	duration

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
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Namespace Prefix:
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Namespace Prefix:
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Name:	us-gaap_ProductOrServiceAxis=rdn_TotalPrimaryInsuranceMortgageInsuranceProductsMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=rdn_FurnitureFixturesAndOfficeEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerEquipmentMember
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Data Type:	na
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Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
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Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
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