Note 3 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Impaired Loans, Average Investment and Interest Income (Details) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Average recorded investment in impaired loans(1)	[1]	$ 6,108	$ 5,227	$ 5,093
Interest income recognized on impaired loans, after designation as impaired		175	$ 49	54
Investor Owned Residential Real Estate [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[2]	193		196
Interest income recognized on impaired loans, after designation as impaired	[2]	9		13
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[2]	2,866		3,217
Interest income recognized on impaired loans, after designation as impaired	[2]	72		19
Commercial Real Estate Other [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[2]	2,724		790
Interest income recognized on impaired loans, after designation as impaired	[2]	83		0
Commercial and Industrial [Member] | Commercial Non Real Estate Segment [Member]
Average recorded investment in impaired loans(1)	[1],[2]	324		887
Interest income recognized on impaired loans, after designation as impaired	[2]	11		22
Automobile Loan [Member] | Consumer Non Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[2]	$ 1		$ 3

[1] Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.

[2] Only classes with impaired loans are shown.