Note 8 - Securities Sold Under Agreements to Repurchase - Securities Sold Under Agreements to Repurchase (Details) - Securities Sold under Agreements to Repurchase [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Outstanding balance at end of period	$ 40,430		$ 40,430		$ 31,895
Weighted average interest rate at end of period	0.07%		0.07%		0.22%
Average outstanding balance during the period	$ 40,832	$ 37,705	$ 38,595	$ 38,402
Average interest rate during the period	0.07%	0.27%	0.11%	0.28%
Maximum outstanding at any month end during the period	$ 40,655	$ 38,362	$ 42,722	$ 43,160