Note 8 - Securities Sold Under Agreements to Repurchase - Securities Sold Under Agreements to Repurchase (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Average daily balance during the year	$ 11,485,000	$ 9,123,000
Average interest rate during the year	0.11%	0.09%
Maximum month-end balance during the year	$ 16,013,000	$ 13,706,000
Weighted average interest rate at year-end	0.12%	0.11%