Note 6 - Investments - Net Investment Income (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Investment Income [Line Items]
Gross investment income	$ 160,633	$ 179,932	$ 159,955
Investment expenses	(6,596)	(8,136)	(7,480)
Net investment income	154,037	171,796	152,475
Fixed-maturities available for sale
Net Investment Income [Line Items]
Gross investment income	148,127	155,104	141,552
Equity securities
Net Investment Income [Line Items]
Gross investment income	6,378	7,028	7,157
Short-term investments
Net Investment Income [Line Items]
Gross investment income	5,774	17,255	10,270
Other investments
Net Investment Income [Line Items]
Gross investment income	$ 354	$ 545	$ 976

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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