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

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).

No definition available.

Name:	rdn_RiskToCapitalRatio
Namespace Prefix:	rdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

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.

No definition available.

Name:	rdn_RiskToCapitalRatioRegulatoryMaximum
Namespace Prefix:	rdn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Statutory surplus balance.

No definition available.

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

Statutory Unassigned Positive (Negative) Surplus

No definition available.

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

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

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

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

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.

Reference 1: 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