Note 13 - Income Taxes Summary of Income Tax Examinations (Details) (REMIC Residual [Member], Internal Revenue Service (IRS) [Member], USD $) In Millions, unless otherwise specified	May 03, 2010	Jun. 30, 2008
REMIC Residual [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Qualified Deposit With The U.S. Department Of Treasury Relating to Tax Years 2000 Through 2004		$ 85
Qualified Deposit With The U.S. Department Of Treasury Relating To Tax Years 2005 Through 2007	$ 4

This concept represents qualified deposits made with the United States Department of Treasury relating to proposed adjustments to the entity's tax losses and deductions based on examinations by the Internal Revenue Department.

No definition available.

Name:	rdn_QualifiedDepositWithUSDepartmentOfTreasuryRelatingToTaxYears2000Through2004
Namespace Prefix:	rdn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant