Note 16 - Statutory Information Risk to Capital (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Second Quota Share Reinsurance Transaction [Member]
Capital and Liquidity Line Items
First Lien Primary Mortgage Insurance Risk In Force Ceded	$ 368.4
Second Quota Share Reinsurance Transaction [Member] | Maximum [Member] | Scenario, Forecast [Member]
Capital and Liquidity Line Items
First Lien Primary Mortgage Insurance Risk In Force Ceded	2,000.0
Second Quota Share Reinsurance Transaction [Member] | Maximum [Member] | Scenario, Forecast [Member] | Radian Guaranty [Member]
Capital and Liquidity Line Items
First Lien Primary Mortgage Insurance Risk In Force Ceded	2,000.0
Second Quota Share Reinsurance Transaction [Member] | Minimum [Member] | Scenario, Forecast [Member]
Capital and Liquidity Line Items
First Lien Primary Mortgage Insurance Risk In Force Ceded	750.0
Second Quota Share Reinsurance Transaction [Member] | Minimum [Member] | Scenario, Forecast [Member] | Radian Guaranty [Member]
Capital and Liquidity Line Items
First Lien Primary Mortgage Insurance Risk In Force Ceded	750.0
Initial Quota Share Reinsurance Transaction [Member]
Capital and Liquidity Line Items
First Lien Primary Mortgage Insurance Risk In Force Ceded	1,500.0
Initial Quota Share Reinsurance Transaction [Member] | Radian Guaranty [Member]
Capital and Liquidity Line Items
First Lien Primary Mortgage Insurance Risk In Force Ceded	$ 1,500.0