Note 5 - Investments Schedule of Unrealized Losses (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) security	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments	$ 1,000	$ 0	$ 1,000	$ 0
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	311		311		362
Fair value available-for-sale securities	$ 1,139,971		$ 1,139,971		$ 1,566,440
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 13,490		$ 13,490		$ 37,941
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	5		5		21
Fair value available-for-sale securities	$ 11,303		$ 11,303		$ 58,451
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 180		$ 180		$ 842
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	316		316		383
Fair value available-for-sale securities	$ 1,151,274		$ 1,151,274		$ 1,624,891
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 13,670		$ 13,670		$ 38,783
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	7		7		7
Fair value available-for-sale securities	$ 36,682		$ 36,682		$ 73,160
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 564		$ 564		$ 3,459
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		0
Fair value available-for-sale securities	$ 0		$ 0		$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0		$ 0		$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	7		7		7
Fair value available-for-sale securities	$ 36,682		$ 36,682		$ 73,160
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 564		$ 564		$ 3,459
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	10		10		7
Fair value available-for-sale securities	$ 47,282		$ 47,282		$ 30,901
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 340		$ 340		$ 821
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		0
Fair value available-for-sale securities	$ 0		$ 0		$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0		$ 0		$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	10		10		7
Fair value available-for-sale securities	$ 47,282		$ 47,282		$ 30,901
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 340		$ 340		$ 821
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	132		132		185
Fair value available-for-sale securities	$ 530,077		$ 530,077		$ 788,876
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 7,718		$ 7,718		$ 22,135
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	1		1		2
Fair value available-for-sale securities	$ 3,736		$ 3,736		$ 4,582
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 102		$ 102		$ 277
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	133		133		187
Fair value available-for-sale securities	$ 533,813		$ 533,813		$ 793,458
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 7,820		$ 7,820		$ 22,412
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	32		32		56
Fair value available-for-sale securities	$ 128,589		$ 128,589		$ 311,031
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 2,733		$ 2,733		$ 7,822
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		1
Fair value available-for-sale securities	$ 6,529		$ 6,529		$ 1,398
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 75		$ 75		$ 9
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	35		35		57
Fair value available-for-sale securities	$ 135,118		$ 135,118		$ 312,429
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 2,808		$ 2,808		$ 7,831
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	31		31		37
Fair value available-for-sale securities	$ 113,103		$ 113,103		$ 218,170
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 1,095		$ 1,095		$ 2,909
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	1		1		2
Fair value available-for-sale securities	$ 1,038		$ 1,038		$ 6,585
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 3		$ 3		$ 114
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	32		32		39
Fair value available-for-sale securities	$ 114,141		$ 114,141		$ 224,755
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,098		$ 1,098		$ 3,023
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	83		83		58
Fair value available-for-sale securities	$ 205,378		$ 205,378		$ 131,268
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 575		$ 575		$ 470
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		16
Fair value available-for-sale securities	$ 0		$ 0		$ 45,886
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0		$ 0		$ 442
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	83		83		74
Fair value available-for-sale securities	$ 205,378		$ 205,378		$ 177,154
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 575		$ 575		$ 912
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	5		5		12
Fair value available-for-sale securities	$ 5,419		$ 5,419		$ 13,034
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 27		$ 27		$ 325
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		0
Fair value available-for-sale securities	$ 0		$ 0		$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0		$ 0		$ 0
Continuous Loss Position, Total
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	5		5		12
Fair value available-for-sale securities	$ 5,419		$ 5,419		$ 13,034
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	27		$ 27		$ 325
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments	500
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments	$ 500
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	11		11
Fair value available-for-sale securities	$ 73,441		$ 73,441
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 438		$ 438
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	11		11
Fair value available-for-sale securities	$ 73,441		$ 73,441
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 438		$ 438