Note 16 - Share-Based and Other Compensation Plans (Phantom Stock) (Details) (2008 Equity Plan [Member], Phantom Stock [Member])	Dec. 31, 2011
2008 Equity Plan [Member] \| Phantom Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement, Dividend Equivalent Shares Accrued	6,030

Share-based Compensation Arrangement, Dividend Equivalent Shares Accrued

No definition available.

Name:	rdn_ShareBasedCompensationArrangementDividendEquivalentSharesAccrued
Namespace Prefix:	rdn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant