Note 10 - Losses and LAE Mortgage Insurance Loss Reserves Rollforward (Details) $ in Thousands	3 Months Ended				12 Months Ended
	Mar. 31, 2018 USD ($) incident		Mar. 31, 2017 USD ($)		Dec. 31, 2017 USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
Number of Natural Disasters | incident	2
Loss reserve [Roll Forward]
Balance at January 1	$ 507,588
Deduct paid claims and LAE related to [Abstract]
Balance at September 30	$ 488,656				$ 507,588
Mortgage Insurance Segment
Liability for Claims and Claims Adjustment Expense [Line Items]
Average Default To Claim Rate Estimate, Gross, For New Defaults	9.00%
Loss reserve [Roll Forward]
Balance at January 1	$ 507,588		$ 760,269		760,269
Less reinsurance recoverables	8,350	[1]	6,851	[1]	6,851	[1]
Balance at beginning of period, net of reinsurance recoverables	499,238		753,418		753,418
Add losses and LAE incurred in respect of default notices reported and unreported in [Abstract]
Current year	36,516	[2]	51,447	[2]
Prior years	391		(4,316)
Total incurred losses and LAE	36,907		47,131
Deduct paid claims and LAE related to [Abstract]
Paid Losses and LAE Current year	226	[2]	42	[2]
Paid losses and LAE Prior years	59,700		82,046
Total paid losses and LAE	59,926		82,088
Balance at end of period, net of reinsurance recoverables	476,219		718,461		499,238
Add reinsurance recoverables	8,973	[1]	7,708	[1]	8,350	[1]
Balance at September 30	485,192		$ 726,169		$ 507,588
Default To Claim Rate Detail [Abstract]
Default To Claim Rate Estimate, Gross, For New Defaults			11.50%		10.00%
Mortgage Insurance Segment | Pool Insurance Mortgage Insurance Product [Member]
Loss reserve [Roll Forward]
Balance at January 1	13,463
Less reinsurance recoverables	35	[3]
Deduct paid claims and LAE related to [Abstract]
Add reinsurance recoverables	20	[3]			$ 35	[3]
Balance at September 30	11,952				13,463
Mortgage Insurance Segment | Primary Mortgage Product [Member]
Loss reserve [Roll Forward]
Less reinsurance recoverables	8,315	[3]
Deduct paid claims and LAE related to [Abstract]
Add reinsurance recoverables	$ 8,953	[3]			$ 8,315	[3]
Default To Claim Rate Detail [Abstract]
Weighted Average Default To Claim Rate Assumption Net Of Denials Rescissions and Reinstatements	33.00%				31.00%
Default To Claim Rate Estimate, Gross, For Pre-Foreclosure Stage Defaults	68.00%
Gross Default To Claim Rate Estimate	75.00%
Hurricanes Harvey and Irma [Member] | Mortgage Insurance Segment
Liability for Claims and Claims Adjustment Expense [Line Items]
Concentration Risk, Percentage	9.00%				9.00%
Default To Claim Rate Detail [Abstract]
Risk In Force	$ 4,700,000				$ 4,600,000
Participating Policies, Amount in Force	$ 17,900,000				$ 17,400,000
Hurricanes Harvey and Irma [Member] | Mortgage Insurance Segment | Primary Mortgage Product [Member]
Default To Claim Rate Detail [Abstract]
Default To Claim Rate Estimate, Gross, For New Defaults	3.00%

[1] Related to ceded losses recoverable, if any, on captive reinsurance transactions, the QSR Transactions and the Single Premium QSR Transactions. See Note 7 for additional information.

[2] Related to underlying defaulted loans with a most recent default notice dated in the year indicated. For example, if a loan had defaulted in a prior year, but then subsequently cured and later re-defaulted in the current year, that default would be considered a current year default.

[3] Represents ceded losses on captive reinsurance transactions, the QSR Transactions and the Single Premium QSR Transactions.