Note 6 - Investments Investments In Any Person And Its Affiliates That Exceed 10% of Total Stockholders' Equity (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Securities
Investment Holdings [Line Items]
Assets Held by Insurance Regulators	$ 10.4	$ 12.1
Radian Guaranty Inc [Member] \| 2013 Freddie Mac Agreement [Member]
Investment Holdings [Line Items]
Restricted Investments Held as Collateral for Master Transaction Agreement, Net	$ 74.7	$ 209.3
Minimum [Member]
Investment Holdings [Line Items]
Investment as a Percentage of Total Stockholder's Equity	10.00%

This concept represents the threshold for reporting any investment holding in an individual or affiliate.

No definition available.

Name:	rdn_InvestmentasaPercentageofTotalStockholdersEquity
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Investments restricted as to use but included in the marketable securities categories of an unclassified balance sheet, net of final loss mitigation activity.

+ References

No definition available.

+ Details

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

- Definition

Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 320
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=28366721&loc=d3e22002-158495

+ Details

Name:	us-gaap_AssetsHeldByInsuranceRegulators
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

No definition available.

+ Details

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

- Details

Name:	us-gaap_DebtSecurityAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=rdn_RadianGuarantyIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	rdn_CapitalAndLiquidityAxis=rdn_A2013FreddieMacAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: