Note 15 - Accumulated Other Comprehensive Income (Loss) Rollforward of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	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		78,023	$ (60,643)
Less: Reclassification adjustment for net gains (losses) included in net income (loss)		(391)	(3,132)
Unrealized foreign currency translation adjustments		0	3
Other comprehensive income (loss), net of tax		78,414	(57,508)
AOCI, Net of Tax, Balance at end of period		17,494
Other Comprehensive Income
Other Comprehensive Income, before Tax [Abstract]
AOCI before Tax, Balance at beginning of period		(77,114)	32,669
AOCI before Tax, Balance adjusted for cumulative effect of adopting accounting standard updates			32,953
Unrealized holding gains (losses) arising during the period		98,763	(76,763)
Less: Reclassification adjustment for net gains (losses) included in net income	[1]	(495)	(3,964)
Net unrealized gains (losses) on investments		99,258	(72,799)
Unrealized foreign currency translation adjustments			4
Other comprehensive income (loss)		99,258	(72,795)
AOCI before Tax, Balance at end of period		22,144	(39,842)
Other Comprehensive Income, Tax [Abstract]
AOCI, Tax, Balance at beginning of period		(16,194)	9,584
AOCI, Tax, Balance adjusted for Cumulative Effect of Adopting Accounting Standard Updates			6,920
Unrealized holding gains (losses) arising during the period		20,740	(16,120)
Less: Reclassification adjustment for net gains (losses) included in net income	[1]	(104)	(832)
Net unrealized gains (losses) on investments		20,844	(15,288)
Unrealized foreign currency translation adjustments			1
Other comprehensive income (loss)		20,844	(15,287)
AOCI Tax, Balance at end of period		4,650	(8,367)
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Balance at beginning of period		(60,920)	23,085
AOCI, Net of Tax, Balance adjusted for Cumulative Effect of Adopting Accounting Standard Updates			26,033
Unrealized holding gains (losses) arising during the period		78,023	(60,643)
Less: Reclassification adjustment for net gains (losses) included in net income (loss)	[1]	(391)	(3,132)
Net unrealized gains (losses) on investments		78,414	(57,511)
Net foreign currency translation adjustments			3
Other comprehensive income (loss), net of tax		78,414	(57,508)
AOCI, Net of Tax, Balance at end of period		$ 17,494	$ (31,475)
ASU 2016-01 | Other Comprehensive Income
Other Comprehensive Income, before Tax [Abstract]
AOCI before tax,Cumulative Effect of Adopting an Accounting Standard Update				$ 284
Other Comprehensive Income, Tax [Abstract]
AOCI, Tax, Cumulative Effect of Adopting an Accounting Standard Update				60
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Cumulative Effect of Adopting an Accounting Standard Update, Net of Tax				224
ASU 2018-02 | Other Comprehensive Income
Other Comprehensive Income, before Tax [Abstract]
AOCI before tax,Cumulative Effect of Adopting an Accounting Standard Update				0
Other Comprehensive Income, Tax [Abstract]
AOCI, Tax, Cumulative Effect of Adopting an Accounting Standard Update				(2,724)
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Cumulative Effect of Adopting an Accounting Standard Update, Net of Tax				$ 2,724

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