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Description of Business (Details) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2022 USD ($) segment | Dec. 31, 2021 USD ($)
Business Overview [Abstract] |  |
Number of reportable business segments | segment | 2 |
Mortgage |  |
Business Overview [Abstract] |  |
Down payment purchase price (percent) | 20.00% |
Equity in home (percent) | 20.00% |
Direct primary mortgage insurance in force | $ 254,200.0 | $ 246,000.0
Direct primary mortgage insurance risk in force | 63,800.0 | 60,900.0
Credit Risk Transfer Transactions | Mortgage |  |
Business Overview [Abstract] |  |
Direct primary mortgage insurance risk in force | $ 372.4 | $ 417.7

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- 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_
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- Definition This element represents the maximum equity-ownership percentage on a home's value that is used to measure the need for private mortgage insurance for refinancings. + References No definition available. + Details
Name: | rdn_PrivateMortgageInsuranceProtectsLendersForRefinancingsMadetoHomeBuyersWithLessThanThisMaximumEquityOwnershipPercentage
Namespace Prefix: | rdn_
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- Definition Risk In Force + References No definition available. + Details
Name: | rdn_RiskInForce
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Balance Type: | credit
Period Type: | instant

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- 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 Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 18 -URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8672-108599 + Details
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- Definition Amount of participating insurance in force. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 50 -Section 50 -Paragraph 1 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=6483535&loc=d3e16392-158451 + Details
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | rdn_RiskinForceAxis=rdn_CreditRiskTransferTransactionsMember
Namespace Prefix: |
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Balance Type: |
Period Type: |