Note 7 - Reinsurance Reinsurance Transactions (Details) - Reinsurer Concentration Risk [Member] - Radian Guaranty $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended	15 Months Ended	24 Months Ended	33 Months Ended
		Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015	Mar. 31, 2013	Dec. 31, 2017 USD ($)	Dec. 31, 2015	Dec. 31, 2012 transaction
Quota Share Reinsurance Transactions [Member]
Ceded Credit Risk [Line Items]
Number of Quota Share Reinsurance Agreements | transaction										2
Ceded Insurance Commission Percentage				30.00%		35.00%
Ceded Premiums Written	[1]	$ 6,730	$ 8,466	$ 22,048	$ 23,279
Ceded Premiums Earned	[1]	10,597	12,203	33,094	36,452
Accrued Liabilities for Commissions, Expense and Taxes		1,922	2,743	6,291	8,890
Fees and Commissions	[2]	$ 3,974	2,463	12,199	10,987
Single Premium QSR Transaction [Member]
Ceded Credit Risk [Line Items]
Ceded Insurance Commission Percentage		25.00%
Concentration Risk, Percentage							20.00%		35.00%
Ceded Premiums Written	[1]	$ 13,004		222,085
Ceded Premiums Earned	[1]	8,608		21,748
Accrued Liabilities for Commissions, Expense and Taxes		5,482		61,258
Fees and Commissions	[2]	$ 4,382		11,173
Scenario, Forecast [Member] | Single Premium QSR Transaction [Member]
Ceded Credit Risk [Line Items]
Concentration Risk, Percentage								35.00%
Maximum [Member] | Single Premium QSR Transaction [Member]
Ceded Credit Risk [Line Items]
Loss Ratio		55.00%
Maximum [Member] | Scenario, Forecast [Member] | Single Premium QSR Transaction [Member]
Ceded Credit Risk [Line Items]
Ceded Premiums Written								$ 195,000
First Lien Mortgage Insurance Products [Member] | Quota Share Reinsurance Transactions [Member]
Ceded Credit Risk [Line Items]
Risk In Force		$ 1,700,000	$ 2,300,000	1,700,000	$ 2,300,000
First Lien Mortgage Insurance Products [Member] | Single Premium QSR Transaction [Member]
Ceded Credit Risk [Line Items]
Risk In Force		$ 3,600,000		$ 3,600,000

[1] Net of profit commission.

[2] Includes amounts reported in policy acquisition costs and other operating expenses.