Note 5 - Investments Schedule of Contractual Maturities (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Available-for-sale Securities, Amortized Cost
Available-for-sale Debt Securities, Amortized Cost Basis		$ 3,218,614	$ 2,856,468
Available-for-sale Securities, Fair Value
Available-for-sale Securities, Debt Securities		3,256,581	2,838,512
Debt Securities
Available-for-sale Securities, Amortized Cost
Available-for-sale Debt Securities, Amortized Cost Basis	[1]	3,252,397
Available-for-sale Securities, Fair Value
Available-for-sale Securities, Debt Securities	[1]	3,290,207
Non Asset Backed Security Investments, Contractual Maturities
Available-for-sale Securities, Amortized Cost
Due in one year or less	[2]	41,767
Due after one year through five years	[2]	687,822
Due after five years through ten years	[2]	965,360
Due after ten years	[2]	330,056
Available-for-sale Securities, Fair Value
Due in one year or less	[2]	41,780
Due after one year through five years	[2]	694,932
Due after five years through ten years	[2]	974,600
Due after ten years	[2]	347,763
RMBS
Available-for-sale Securities, Amortized Cost
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	[3]	176,789
Available-for-sale Securities, Fair Value
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	[3]	175,408
CMBS
Available-for-sale Securities, Amortized Cost
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	[3]	433,916
Available-for-sale Securities, Fair Value
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	[3]	436,892
Other ABS
Available-for-sale Securities, Amortized Cost
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	[3]	616,687
Available-for-sale Securities, Fair Value
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	[3]	618,832
2013 Freddie Mac Agreement [Member] | Radian Guaranty Inc [Member]
Available-for-sale Securities, Fair Value
Marketable Securities, Restricted		$ 5,500	$ 63,900

[1] Includes securities loaned under securities lending agreements.

[2] Actual maturities may differ as a result of calls before scheduled maturity.

[3] RMBS, CMBS and Other ABS are shown separately, as they are not due at a single maturity date.