Note 10 - Losses and LAE Rescissions And Denials (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Rescissions And Denials [Line Items]
Reserve for losses and loss adjustment expense (“LAE”) (Note 10)	$ 488,656	$ 507,588
Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Default To Claim Rate Estimate, Gross, For New Defaults		10.00%	11.50%
Decrease To Our Loss Reserves Due To Estimated Rescissions And Denials	19,000	$ 21,000
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	9,100	10,400
Reserve for losses and loss adjustment expense (“LAE”) (Note 10)	$ 485,192	$ 507,588	$ 726,169	$ 760,269
Primary Mortgage Product [Member] | Mortgage Insurance Segment
Rescissions And Denials [Line Items]
Weighted Average Default To Claim Rate Assumption Net Of Denials Rescissions and Reinstatements	33.00%	31.00%