Note 15 - Accumulated Other Comprehensive Income Rollforward of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, beginning balance				$ 23,085
Unrealized holding gains (losses) arising during the period		$ (27,804)	$ 20,239	(88,447)	$ 27,606
Less: Reclassification adjustment for net gains (losses) included in net income (loss)		(1,336)	(1,167)	(4,468)	(2,798)
Unrealized foreign currency translation adjustments		0	74	3	108
Other comprehensive income (loss), net of tax		(26,468)	21,480	(83,976)	30,512
AOCI, Net of Tax, ending balance		(57,943)		(57,943)
Other Comprehensive Income
Accumulated Other Comprehensive Income [Line Items]
AOCI before Tax, Attributable to Parent, Adjusted for Cumulative Effect of Adopting Accounting Standard Updates						$ (39,842)	$ 32,953
Other Comprehensive Income, before Tax [Abstract]
AOCI before Tax, Attributable to Parent, beginning balance		(39,842)	(5,168)	32,669	(19,063)
Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax		(35,194)	31,137	(111,957)	42,471
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	[1]	(1,691)	(1,795)	(5,655)	(4,304)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax		(33,503)	32,932	(106,302)	46,775
Net foreign currency translation adjustments, before tax		0	114	4	166
Other comprehensive income, before tax		(33,503)	33,046	(106,298)	46,941
AOCI before Tax, Attributable to Parent, ending balance		(73,345)	27,878	(73,345)	27,878
Other Comprehensive Income, Tax [Abstract]
AOCI, Tax, beginning balance		(8,367)	(1,805)	9,584	(6,668)
Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax		(7,390)	10,898	(23,510)	14,865
Less: Reclassification adjustment for net (losses) gains included in net income, tax	[1]	(355)	(628)	(1,187)	(1,506)
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax		(7,035)	11,526	(22,323)	16,371
Net foreign currency translation adjustments, tax		0	40	1	58
Other Comprehensive Income, Tax		(7,035)	11,566	(22,322)	16,429
AOCI Tax, ending balance		(15,402)	9,761	(15,402)	9,761
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, beginning balance		(31,475)	(3,363)	23,085	(12,395)
Unrealized holding gains (losses) arising during the period		(27,804)	20,239	(88,447)	27,606
Less: Reclassification adjustment for net gains (losses) included in net income (loss)	[1]	(1,336)	(1,167)	(4,468)	(2,798)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent		(26,468)	21,406	(83,979)	30,404
Unrealized foreign currency translation adjustments		0	74	3	108
Other comprehensive income (loss), net of tax		(26,468)	21,480	(83,976)	30,512
AOCI, Net of Tax, ending balance		$ (57,943)	$ 18,117	$ (57,943)	$ 18,117
AOCI Tax, Attributable to Parent, Adjusted for Cumulative Effect of Adopting Accounting Standard Updates						(8,367)	6,920
Accumulated Other Comprehensive Income (Loss), Net of Tax, Adjusted for Cumulative Effect of Adopting Accounting Standard Updates						(31,475)	26,033
Accounting Standards Update 2016-01 [Member] | Other Comprehensive Income
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Cumulative Effect of Adopting an Accounting Standard Update, Before Tax						0	284
Other Comprehensive Income, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Cumulative Effect of Adopting an Accounting Standard Update						0	60
Other Comprehensive Income (Loss), Cumulative Effect of Adopting an Accounting Standard Update, Net of Tax						0	224
ASU 2018-02 [Member] | Other Comprehensive Income
Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Cumulative Effect of Adopting an Accounting Standard Update, Before Tax						0	0
Other Comprehensive Income, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Cumulative Effect of Adopting an Accounting Standard Update						0	(2,724)
Other Comprehensive Income (Loss), Cumulative Effect of Adopting an Accounting Standard Update, Net of Tax						$ 0	$ 2,724

[1] Included in net gains (losses) on investments and other financial instruments on our consolidated statements of operations.