Note 10 - Losses and Loss Adjustment Expenses Rescissions And Denials (Details) $ in Millions		1 Months Ended	4 Months Ended	12 Months Ended		24 Months Ended	48 Months Ended
	Aug. 30, 2017 USD ($)	Oct. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) percentagepoint	Dec. 31, 2015 USD ($) percentagepoint	Dec. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) percentagepoint	Aug. 29, 2017 USD ($)
Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Claim Rescissions And Denials, Net of Reinstatements				$ 64.5	$ 144.7
Decrease To Our Loss Reserves Due To Estimated Rescissions And Denials			$ 69.0	69.0	125.0	$ 125.0	$ 69.0
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount			26.6	26.6	163.6	163.6	26.6
Accrued Liability For Premiums Expected To Be Refunded From Rescissions			$ 2.3	$ 2.3	9.0	9.0	$ 2.3
Percentage Point Change In Severity Used In Assumption Shift Analysis | percentagepoint			1	1			1
First Lien Primary Claim Severity				101.40%
Impact To Loss Reserves Based On One Percentage Change In Primary Claim Severity			$ 8.2	$ 8.2			$ 8.2
Impact To Loss Reserves Based On One Percentage Change in Default To Claim Rate			17.4	17.4			17.4
Mortgage Insurance Segment | Denials [Member]
Rescissions And Denials [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount			13.3	13.3			13.3
Mortgage Insurance Segment | Rescissions [Member]
Rescissions And Denials [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount			0.6	0.6			0.6
Mortgage Insurance Segment | Claim Curtailments [Member]
Rescissions And Denials [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount			2.1	2.1			2.1
Mortgage Insurance Segment | Claims Denied in the Last Twelve Months [Member]
Rescissions And Denials [Line Items]
Gross Exposure Related to Denied Claims From Previous Twelve Months				41.9
Mortgage Insurance Segment | Policies Rescinded in the Last Twenty Four Months [Member]
Rescissions And Denials [Line Items]
Gross Exposure Related to Rescinded Policies Within Twenty Four Months						42.8
Mortgage Insurance Segment | Claim Curtailments [Member]
Rescissions And Denials [Line Items]
Claim Curtailments, Gross						22.7
Bank of America Settlement Agreement [Member] | Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount			$ 3.0	$ 3.0	$ 133.0	133.0	$ 3.0
Loss Contingency, Settlement Agreement, Percentage of Subject Loans Not Held by Insureds or Are Non-GSE Investors			12.00%	12.00%			12.00%
Primary Mortgage Product [Member] | Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Weighted Average Default To Claim Rate Assumption Net Of Denials And Rescissions				46.00%	52.00%
Maximum [Member] | Bank of America Settlement Agreement [Member] | Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Number of Days Delinquent for a Loan to be Considered for Curtailment				90 days
2013 Freddie Mac Agreement [Member] | Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Final Loss Mitigation Activity		$ 135.9	$ 4.4
Not Final Loss Mitigation Activity							$ 8.9
2013 Freddie Mac Agreement [Member] | Scenario, Forecast [Member] | Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Loss Mitigation Shortfall	$ 57.5
2013 Freddie Mac Agreement [Member] | Maximum [Member] | Scenario, Forecast [Member] | Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Restricted Investments Held as Collateral for Master Transaction Agreement, Net								$ 74.0
Radian Guaranty Inc [Member] | 2013 Freddie Mac Agreement [Member]
Rescissions And Denials [Line Items]
Restricted Investments Held as Collateral for Master Transaction Agreement, Net			$ 74.7	$ 74.7	$ 209.3	$ 209.3	$ 74.7