Note 11 - Securities Sold Under Agreements to Repurchase - Securities Sold Under Agreements to Repurchase (Details) - Securities Sold under Agreements to Repurchase [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Outstanding balance at end of period	$ 31,895	$ 36,094
Weighted average interest rate at end of period	0.22%	0.27%
Average outstanding balance during the period	$ 38,555	$ 62,580	$ 70,187
Average interest rate during the period	0.26%	0.25%	0.19%
Maximum outstanding at any month end during the period	$ 52,599	$ 74,725	$ 75,365