Note 8 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Accruing TDRs	$ 8,284	$ 8,402	$ 8,985	$ 9,919	$ 12,670	$ 18,048
Payment Deferral [Member]
Accruing TDRs	8,284		8,985
Contractual Interest Rate Reduction [Member]
Accruing TDRs	0		0
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	0		0
Commercial Portfolio Segment [Member]
Accruing TDRs	7,784		8,462
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	7,784		8,462
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	0		0
Commercial Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	0		0
Commercial Real Estate Portfolio Segment [Member]
Accruing TDRs	0
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	0
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	0
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	0
Residential Portfolio Segment [Member]
Accruing TDRs	500		523
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	500		523
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	0		0
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 0		$ 0