Note 5 - Investments Schedule of Unrealized Losses (Details) $ in Thousands	Sep. 30, 2016 USD ($) security	Dec. 31, 2015 USD ($) security
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security	75	305
Fair value available-for-sale securities	$ 241,430	$ 1,462,577
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 948	$ 32,079
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	39	23
Fair value available-for-sale securities	$ 101,481	$ 54,203
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 1,184	$ 2,221
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	114	328
Fair value available-for-sale securities	$ 342,911	$ 1,516,780
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 2,132	$ 34,300
US government and agency securities
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security	4	1
Fair value available-for-sale securities	$ 3,536	$ 5,752
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 24	$ 21
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	0	0
Fair value available-for-sale securities	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0	$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	4	1
Fair value available-for-sale securities	$ 3,536	$ 5,752
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 24	$ 21
US States and Political Subdivisions Debt Securities [Member]
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security		2
Fair value available-for-sale securities		$ 11,674
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		$ 120
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security		0
Fair value available-for-sale securities		$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security		2
Fair value available-for-sale securities		$ 11,674
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 120
Corporate bonds and notes
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security	14	117
Fair value available-for-sale securities	$ 29,166	$ 510,807
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 115	$ 16,773
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	6	6
Fair value available-for-sale securities	$ 18,271	$ 8,700
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 276	$ 518
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	20	123
Fair value available-for-sale securities	$ 47,437	$ 519,507
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 391	$ 17,291
RMBS
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security	9	12
Fair value available-for-sale securities	$ 92,845	$ 168,415
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 220	$ 2,464
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	0	0
Fair value available-for-sale securities	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0	$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	9	12
Fair value available-for-sale securities	$ 92,845	$ 168,415
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 220	$ 2,464
CMBS
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security	19	58
Fair value available-for-sale securities	$ 54,676	$ 387,268
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 442	$ 8,939
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	0	0
Fair value available-for-sale securities	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0	$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	19	58
Fair value available-for-sale securities	$ 54,676	$ 387,268
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 442	$ 8,939
Other ABS
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security	28	96
Fair value available-for-sale securities	$ 60,953	$ 284,998
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 147	$ 2,559
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	30	14
Fair value available-for-sale securities	$ 79,609	$ 43,225
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 857	$ 1,415
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	58	110
Fair value available-for-sale securities	$ 140,562	$ 328,223
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,004	$ 3,974
Foreign government securities
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security	1	18
Fair value available-for-sale securities	$ 254	$ 18,733
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	$ 0	$ 1,095
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	3	3
Fair value available-for-sale securities	$ 3,601	$ 2,278
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 51	$ 288
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	4	21
Fair value available-for-sale securities	$ 3,855	$ 21,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 51	$ 1,383
Equity securities
Continuous Loss Position Less Than Twelve Months [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | security		1
Fair value available-for-sale securities		$ 74,930
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		$ 108
Continuous Unrealized Loss Position, Twelve Months Or Greater
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security		0
Fair value available-for-sale securities		$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security		1
Fair value available-for-sale securities		$ 74,930
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 108