Note 4 - Investments - Fair Value of Financial Instruments (Details) - US Government Agencies Debt Securities [Member] - Fair Value, Recurring [Member] - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Estimate of Fair Value Measurement [Member]
U.S. government and agency securities, held-to-maturity		$ 3,086	$ 4,242
Reported Value Measurement [Member]
U.S. government and agency securities, held-to-maturity	[1]	3,122	4,314
Fair Value, Inputs, Level 1 [Member]
U.S. government and agency securities, held-to-maturity		0	0
Fair Value, Inputs, Level 2 [Member]
U.S. government and agency securities, held-to-maturity		3,086	4,242
Fair Value, Inputs, Level 3 [Member]
U.S. government and agency securities, held-to-maturity		$ 0	$ 0

[1] The carrying value measurements in the tables above do not equal Investments on our Consolidated Balance Sheets as they exclude investment in limited partnership carried at NAV (as defined below) as a practical expedient.