Note 15 - Fair Values of Financial Instruments - Changes in Level 3 Assets Measured on a Recurring Basis (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Balance at the beginning of the period	$ 3,500,000	$ 8,132,000
Included in earnings		1,000
Purchased into Level 3	750,000
Sold out of Level 3		(25,000)
Transfers in and/or out of Level 3		(4,608,000)
Balance at the end of the period	$ 4,250,000	$ 3,500,000