Note 6 - Investments - Net Gains (Losses) on Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Gain (Loss) on Securities [Line Items]
Net realized gains (losses) on investments	$ 13,973	$ 4,597	$ 32,636	$ 4,631
Impairment losses due to intent to sell	0	0	(1,401)	0
Net decrease (increase) in expected credit losses	186	0	(2,596)	0
Net unrealized gain (losses) on investments	2,813	4,419	916	33,005
Total net gains (losses) on investments	16,972	9,016	29,555	37,636
Fixed-maturities available for sale
Gain (Loss) on Securities [Line Items]
Fixed maturities available for sale, net realized gain (loss)	13,777	4,401	31,998	5,209
Gross investment gains from sales and redemptions	14,219	4,697	34,422	10,926
Gross investment losses from sales and redemptions	(442)	(296)	(2,424)	(5,717)
Trading Securities
Gain (Loss) on Securities [Line Items]
Trading securities, net realized gain (loss)	0	19	4	(391)
Equity securities
Gain (Loss) on Securities [Line Items]
Equity securities, net realized gain (loss)	0	(28)	361	(708)
Other investments
Gain (Loss) on Securities [Line Items]
Other investments, net realized gain (loss)	$ 196	$ 205	$ 273	$ 521