Note 14 - Accumulated Other Comprehensive Income (Loss) Rollforward of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 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		$ 40,654	$ (5,341)	190,677	$ (93,788)
Less: Reclassification adjustment for net gains (losses) included in net income (loss)		3,477	(4,044)	4,115	(8,512)
Net foreign currency translation adjustments		0	0	(3)	3
Other comprehensive income (loss), net of tax		37,177	(1,297)	186,559	(85,273)
AOCI, Net of Tax, Balance at end of period		125,639		125,639
Other Comprehensive Income
Other Comprehensive Income, before Tax [Abstract]
AOCI before Tax, Balance at beginning of period		111,977	(73,345)	(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			(73,345)		32,953
Unrealized holding gains (losses) arising during the period		51,460	(6,762)	241,363	(118,719)
Less: Reclassification adjustment for net gains (losses) included in net income	[1]	4,401	(5,120)	5,209	(10,775)
Net unrealized gains (losses) on investments		47,059	(1,642)	236,154	(107,944)
Unrealized foreign currency translation adjustments		0	0	(4)	4
Other comprehensive income (loss)		47,059	(1,642)	236,150	(107,940)
AOCI before Tax, Balance at end of period		159,036	(74,987)	159,036	(74,987)
Other Comprehensive Income, Tax [Abstract]
AOCI, Tax, Balance at beginning of period		23,515	(15,402)	(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			(15,402)		6,920
Unrealized holding gains (losses) arising during the period		10,806	(1,421)	50,686	(24,931)
Less: Reclassification adjustment for net gains (losses) included in net income	[1]	924	(1,076)	1,094	(2,263)
Net unrealized gains (losses) on investments		9,882	(345)	49,592	(22,668)
Unrealized foreign currency translation adjustments		0	0	(1)	1
Other comprehensive income (loss)		9,882	(345)	49,591	(22,667)
AOCI Tax, Balance at end of period		33,397	(15,747)	33,397	(15,747)
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Balance at beginning of period		88,462	(57,943)	(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			(57,943)		26,033
Unrealized holding gains (losses) arising during the period		40,654	(5,341)	190,677	(93,788)
Less: Reclassification adjustment for net gains (losses) included in net income (loss)	[1]	3,477	(4,044)	4,115	(8,512)
Net unrealized gains (losses) on investments		37,177	(1,297)	186,562	(85,276)
Net foreign currency translation adjustments		0	0	(3)	3
Other comprehensive income (loss), net of tax		37,177	(1,297)	186,559	(85,273)
AOCI, Net of Tax, Balance at end of period		$ 125,639	$ (59,240)	$ 125,639	$ (59,240)

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