Note 11 - Losses and Loss Adjustment Expenses Mortgage Insurance Loss Reserves Rollforward (Details) $ in Thousands		3 Months Ended	12 Months Ended				24 Months Ended	36 Months Ended
		Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) incident percentagepoint		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) incident percentagepoint	Dec. 31, 2017 USD ($) incident percentagepoint	Dec. 31, 2014 USD ($)
Loss reserve [Roll Forward]
Balance at January 1			$ 760,269
Deduct paid claims and LAE related to [Abstract]
Balance at December 31			$ 507,588		$ 760,269		$ 507,588	$ 507,588
Number of Natural Disasters | incident			2				2	2
Mortgage Insurance Segment
Loss reserve [Roll Forward]
Balance at January 1			$ 760,269		976,399	$ 1,560,032	$ 976,399	$ 1,560,032
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	[1]		8,350		6,851	8,286	8,350	8,350	$ 26,665
Balance at beginning of period, net of reinsurance recoverables			753,418		968,113	1,533,367	968,113	1,533,367
Add losses and LAE incurred in respect of default notices reported and unreported in [Abstract]
Current year	[2]		185,486		206,383	229,061
Prior years			(49,286)		(3,516)	(29,647)
Total incurred losses and LAE			136,200		202,867	199,414
Deduct paid claims and LAE related to [Abstract]
Paid Losses and LAE Current year	[2]		25,011		11,410	10,837
Paid losses and LAE Prior years			365,369		406,152	753,831
Total paid losses and LAE			390,380	[3]	417,562	764,668
Balance at end of period, net of reinsurance recoverables			499,238		753,418	968,113	499,238	499,238
Balance at December 31			507,588		$ 760,269	$ 976,399	507,588	507,588
Risk In Force			$ 51,300,000				$ 51,300,000	$ 51,300,000
Default To Claim Rate Detail [Abstract]
Percentage Point Change In Severity Used In Assumption Shift Analysis | percentagepoint			1				1	1
Mortgage Insurance Segment | Primary Mortgage Product [Member]
Deduct paid claims and LAE related to [Abstract]
Default To Claim Rate Estimate, Gross, For New Defaults			10.00%		12.00%	13.00%	10.00%	10.00%	16.00%
Default To Claim Rate Estimate, Gross, For Pre-Foreclosure Stage Defaults			62.00%		62.00%		62.00%	62.00%
Default To Claim Rate Detail [Abstract]
Weighted Average Default To Claim Rate Assumption Net Of Denials Rescissions and Reinstatements			31.00%		42.00%
Weighted Average Default To Claim Rate Assumption Excluding Pending Claims Net Of Denials And Rescissions			29.00%		40.00%
Default To Claim Estimate, Gross, For Foreclosure Stage Defaults			81.00%		81.00%		81.00%	81.00%
Radian Guaranty Inc [Member] | 2013 Freddie Mac Agreement [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Marketable Securities, Restricted			$ 5,600		$ 63,900		$ 5,600	$ 5,600
Deduct paid claims and LAE related to [Abstract]
Paid losses and LAE Prior years		$ 54,800
Hurricanes Harvey and Irma [Member] | Mortgage Insurance Segment
Deduct paid claims and LAE related to [Abstract]
Risk In Force			4,600,000				4,600,000	4,600,000
Participating Policies, Amount in Force			$ 17,400,000				$ 17,400,000	$ 17,400,000
Concentration Risk, Percentage			9.00%
Hurricanes Harvey and Irma [Member] | Mortgage Insurance Segment | Primary Mortgage Product [Member]
Deduct paid claims and LAE related to [Abstract]
Default To Claim Rate Estimate, Gross, For New Defaults			3.00%				3.00%	3.00%

[1] Related to ceded losses recoverable, if any, on captive reinsurance transactions, the QSR Transactions and the 2016 Single Premium QSR Transaction. See Note 8 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. For 2017, includes payments made on pool commutations, in some cases for loans not previously in default.

[3] Includes the payment of $54.8 million made in connection with the scheduled settlement of the Freddie Mac Agreement in the third quarter of 2017.