Note 15 - Fair Values of Financial Instruments - Changes in Level 3 Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Balance at the beginning of the period	$ 4,022	$ 3,500
Included in other comprehensive income	234	(228)
Purchased into Level 3		1,250
Transfers in and/or out of Level 3	(2,250)	(500)
Balance at the end of the period	$ 2,006	$ 4,022