Note 13 - Commitments and Contingencies Contract Underwriting (Details) $ in Millions	Dec. 31, 2017 USD ($) transaction
Contract Underwriting [Line Items]
Number of Guaranteed Structured Transactions For Radian Guaranty	2
Mortgage Insurance Segment
Contract Underwriting [Line Items]
Reserve For Contract Underwriting Obligations | $	$ 0.5
Indirect Guarantee of Indebtedness [Member]
Contract Underwriting [Line Items]
Number of Guaranteed Structured Transactions For Radian Guaranty	2