Minimum policyholders surplus balance to be maintained.

No definition available.

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

- Definition

Proceeds from intercompany notes borrowings.

+ References

No definition available.

+ Details

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Namespace Prefix:	rdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

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).

+ References

No definition available.

+ Details

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- Definition

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.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Statutory Unassigned Positive (Negative) Surplus

+ References

No definition available.

+ Details

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

- Definition

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.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

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

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-5

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-3

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-1

Reference 6: 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

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Statutory Information - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Sep. 30, 2025 USD ($)	Jun. 30, 2026 USD ($)	Mar. 31, 2026 USD ($)	Jun. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Statutory Accounting Practices [Line Items]
Risk to capital ratio maximum		25		25
Restricted net assets held by consolidated subsidiaries		$ 5,500		$ 5,500
Debt instrument term	10 years			10 years
Proceeds from intercompany notes borrowings	$ 600				$ 600
Minimum policyholders surplus balance to be maintained		$ 500		$ 500
Radian Guaranty
Statutory Accounting Practices [Line Items]
Risk to capital ratio		10.4		10.4	10.3
Unassigned surplus		$ 282		$ 282	$ 346
Payments of ordinary dividends		$ 200	$ 140