Note 9 - Short-term Borrowings - Overnight Repurchase Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Repurchase Agreements with Customers [Member]
Average daily balance	$ 1,495	$ 4,231
Average daily interest rate	0.40%	0.73%
Maximum month-end balance	$ 2,377	$ 4,177
Weighted average rate as of December 31		1.00%
Federal Funds Purchased [Member]
Average daily balance	$ 19,573	$ 12,594
Average daily interest rate	0.36%	2.56%
Maximum month-end balance	$ 30,430	$ 17,010
Weighted average rate as of December 31	0.06%	1.50%