Note 5 - Investments Contractual Maturities (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Available-for-sale Securities, Amortized Cost
Fixed-maturities available for sale—at amortized cost		$ 4,003,367	$ 4,098,962
Available-for-sale Securities, Fair Value
Fixed-maturity investments available for sale, Total, Fair Value		4,113,650	4,021,575
Non Asset Backed Security Investments, Contractual Maturities [Member]
Available-for-sale Securities, Amortized Cost
Due in one year or less	[1]	102,282
Due after one year through five years	[1]	863,246
Due after five years through ten years	[1]	1,041,249
Due after ten years	[1]	375,451
Available-for-sale Securities, Fair Value
Due in one year or less	[1]	102,313
Due after one year through five years	[1]	878,955
Due after five years through ten years	[1]	1,087,023
Due after ten years	[1]	403,030
RMBS
Available-for-sale Securities, Amortized Cost
Fixed-maturity investments available for sale, Maturity, without Single Maturity Date, Amortized Cost	[2]	425,138
Available-for-sale Securities, Fair Value
Fixed-maturity investments available for sale, Maturity, without Single Maturity Date, Fair Value	[2]	433,773
CMBS
Available-for-sale Securities, Amortized Cost
Fixed-maturity investments available for sale, Maturity, without Single Maturity Date, Amortized Cost	[2]	557,353
Available-for-sale Securities, Fair Value
Fixed-maturity investments available for sale, Maturity, without Single Maturity Date, Fair Value	[2]	571,923
Other ABS
Available-for-sale Securities, Amortized Cost
Fixed-maturity investments available for sale, Maturity, without Single Maturity Date, Amortized Cost	[2]	661,898
Available-for-sale Securities, Fair Value
Fixed-maturity investments available for sale, Maturity, without Single Maturity Date, Fair Value	[2]	661,089
Total fixed-maturities available for sale
Available-for-sale Securities, Amortized Cost
Fixed-maturities available for sale—at amortized cost		4,026,617
Available-for-sale Securities, Fair Value
Fixed-maturity investments available for sale, Total, Fair Value		4,138,106
Fixed maturities | RMBS
Available-for-sale Securities, Amortized Cost
Available-for-sale Securities, Amortized Cost Basis		425,138	334,843
Available-for-sale Securities, Fair Value
Available-for-sale Securities		433,773	332,142
Fixed maturities | CMBS
Available-for-sale Securities, Amortized Cost
Available-for-sale Securities, Amortized Cost Basis		557,353	546,729
Available-for-sale Securities, Fair Value
Available-for-sale Securities		571,923	539,915
Fixed maturities | Other ABS
Available-for-sale Securities, Amortized Cost
Available-for-sale Securities, Amortized Cost Basis		661,898	712,748
Available-for-sale Securities, Fair Value
Available-for-sale Securities		661,089	704,662
Fixed maturities | Total fixed-maturities available for sale
Available-for-sale Securities, Amortized Cost
Fixed-maturities available for sale—at amortized cost		4,003,367	4,098,962
Available-for-sale Securities, Amortized Cost Basis		4,026,617	4,106,594
Available-for-sale Securities, Fair Value
Fixed-maturity investments available for sale, Total, Fair Value		4,113,650	4,021,575
Available-for-sale Securities		4,138,106	4,028,987
Fixed maturities | Securities Financing Transaction, Cost | Total fixed-maturities available for sale
Available-for-sale Securities, Amortized Cost
Available-for-sale Securities, Amortized Cost Basis		23,250	7,632
Fixed maturities | Securities Financing Transaction, Fair Value | Total fixed-maturities available for sale
Available-for-sale Securities, Fair Value
Available-for-sale Securities		$ 24,456	$ 7,412

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

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