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, 2020	Jun. 30, 2019		Jun. 30, 2020	Jun. 30, 2019
Other Comprehensive Income, before Tax [Abstract]
Unrealized foreign currency translation adjustments			$ (4)			$ (4)
Other Comprehensive Income, Tax [Abstract]
Unrealized foreign currency translation adjustments			(1)			(1)
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Balance at beginning of period					$ 110,488
Unrealized holding gains (losses) arising during the period for which an allowance for expected credit losses has not been recognized		$ 185,056	72,000		112,763	150,023
Net realized gains (losses) on disposals and non-credit related impairment losses		4,894	1,029		13,288	638
Net decrease (increase) in expected credit losses		(2,198)	0		(2,198)	0
Unrealized foreign currency translation adjustments		0	(3)		0	(3)
Other comprehensive income (loss), net of tax		182,360	70,968		101,673	149,382
AOCI, Net of Tax, Balance at end of period		212,161			212,161
Other Comprehensive Income
Other Comprehensive Income, before Tax [Abstract]
AOCI before Tax, Balance at beginning of period		37,722	22,144		139,858	(77,114)
Unrealized holding gains (losses) arising during the period for which an allowance for expected credit losses has not been recognized		234,249	91,140		142,738	189,903
Net realized gains (losses) on disposals and non-credit related impairment losses	[1]	6,195			16,820
Net decrease (increase) in expected credit losses	[1]	(2,782)	1,303		(2,782)	808
Net unrealized gains (losses) on investments		230,836	89,837	[1]	128,700	189,095	[1]
Other comprehensive income (loss)		230,836	89,833		128,700	189,091
AOCI before Tax, Balance at end of period		268,558	111,977		268,558	111,977
Other Comprehensive Income, Tax [Abstract]
AOCI, Tax, Balance at beginning of period		7,921	4,650		29,370	(16,194)
Unrealized holding gains (losses) arising during the period for which an allowance for expected credit losses has not been recognized		49,193	19,140		29,975	39,880
Net realized gains (losses) on disposals and non-credit related impairment losses	[1]	1,301			3,532
Net decrease (increase) in expected credit losses	[1]	(584)	274		(584)	170
Net unrealized gains (losses) on investments		48,476	18,866	[1]	27,027	39,710	[1]
Other comprehensive income (loss)		48,476	18,865		27,027	39,709
AOCI Tax, Balance at end of period		56,397	23,515		56,397	23,515
Other Comprehensive Income, Net of Tax [Abstract]
AOCI, Net of Tax, Balance at beginning of period		29,801	17,494		110,488	(60,920)
Unrealized holding gains (losses) arising during the period for which an allowance for expected credit losses has not been recognized		185,056	72,000		112,763	150,023
Net realized gains (losses) on disposals and non-credit related impairment losses	[1]	4,894			13,288
Net decrease (increase) in expected credit losses	[1]	(2,198)	1,029		(2,198)	638
Net unrealized gains (losses) on investments		182,360	70,971	[1]	101,673	149,385	[1]
Other comprehensive income (loss), net of tax		182,360	70,968		101,673	149,382
AOCI, Net of Tax, Balance at end of period		$ 212,161	$ 88,462		$ 212,161	$ 88,462

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