Note 6 - Investments - Net Gains (Losses) on Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gain (Loss) on Securities [Line Items]
Net realized gains (losses) on investments	$ 14,246	$ 13,973	$ 18,330	$ 32,636
Impairment losses due to intent to sell	0	0	0	(1,401)
Net decrease (increase) in expected credit losses	0	186	918	(2,596)
Net unrealized gain (losses) on investments	(11,342)	2,813	(5,825)	916
Total net gains (losses) on investments	2,904	16,972	13,423	29,555
Fixed-maturities available for sale
Gain (Loss) on Securities [Line Items]
Fixed maturities available for sale, net realized gain (loss)	4,098	13,777	5,684	31,998
Gross investment gains from sales and redemptions	5,874	14,219	19,588	34,422
Gross investment losses from sales and redemptions	(1,776)	(442)	(13,904)	(2,424)
Trading Securities
Gain (Loss) on Securities [Line Items]
Trading securities, net realized gain (loss)	0	0	391	4
Equity securities
Gain (Loss) on Securities [Line Items]
Equity securities, net realized gain (loss)	8,632	0	8,405	361
Other investments
Gain (Loss) on Securities [Line Items]
Other investments, net realized gain (loss)	$ 1,516	$ 196	$ 3,850	$ 273