Note 14 - Accumulated Other Comprehensive Income (Loss) Rollforward of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Balance at beginning of period				$ (60,920)
Unrealized holding gains (losses) arising during the period		$ 72,000	$ (27,804)	150,023	$ (88,447)
Less: Reclassification adjustment for net gains (losses) included in net income (loss)		1,029	(1,336)	638	(4,468)
Net foreign currency translation adjustments		(3)	0	(3)	3
Other comprehensive income (loss), net of tax		70,968	(26,468)	149,382	(83,976)
AOCI, Net of Tax, Balance at end of period		88,462		88,462
Other Comprehensive Income
Other Comprehensive Income, before Tax [Abstract]
AOCI before Tax, Balance at beginning of period		22,144	(39,842)	(77,114)	32,669
AOCI before tax,Cumulative Effect of Adopting an Accounting Standard Update						$ 0	$ 284
AOCI before Tax, Balance adjusted for cumulative effect of adopting accounting standard updates			(39,842)		32,953
Unrealized holding gains (losses) arising during the period		91,140	(35,194)	189,903	(111,957)
Less: Reclassification adjustment for net gains (losses) included in net income	[1]	1,303	(1,691)	808	(5,655)
Net unrealized gains (losses) on investments		89,837	(33,503)	189,095	(106,302)
Unrealized foreign currency translation adjustments					4
Unrealized foreign currency translation adjustments		(4)	0	(4)
Other comprehensive income (loss)		89,833	(33,503)	189,091	(106,298)
AOCI before Tax, Balance at end of period		111,977	(73,345)	111,977	(73,345)
Other Comprehensive Income, Tax [Abstract]
AOCI, Tax, Balance at beginning of period		4,650	(8,367)	(16,194)	9,584
AOCI, Tax, Cumulative Effect of Adopting an Accounting Standard Update						0	(2,664)
AOCI, Tax, Balance adjusted for Cumulative Effect of Adopting Accounting Standard Updates			(8,367)		6,920
Unrealized holding gains (losses) arising during the period		19,140	(7,390)	39,880	(23,510)
Less: Reclassification adjustment for net gains (losses) included in net income	[1]	274	(355)	170	(1,187)
Net unrealized gains (losses) on investments		18,866	(7,035)	39,710	(22,323)
Unrealized foreign currency translation adjustments					1
Unrealized foreign currency translation adjustments		(1)	0	(1)
Other comprehensive income (loss)		18,865	(7,035)	39,709	(22,322)
AOCI Tax, Balance at end of period		23,515	(15,402)	23,515	(15,402)
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Balance at beginning of period		17,494	(31,475)	(60,920)	23,085
AOCI, Net of Tax, Cumulative Effect of Adopting an Accounting Standard Update, Net of Tax						$ 0	$ 2,948
AOCI, Net of Tax, Balance adjusted for Cumulative Effect of Adopting Accounting Standard Updates			(31,475)		26,033
Unrealized holding gains (losses) arising during the period		72,000	(27,804)	150,023	(88,447)
Less: Reclassification adjustment for net gains (losses) included in net income (loss)	[1]	1,029	(1,336)	638	(4,468)
Net unrealized gains (losses) on investments		70,971	(26,468)	149,385	(83,979)
Net foreign currency translation adjustments		(3)	0	(3)	3
Other comprehensive income (loss), net of tax		70,968	(26,468)	149,382	(83,976)
AOCI, Net of Tax, Balance at end of period		$ 88,462	$ (57,943)	$ 88,462	$ (57,943)

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