Note 8 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accruing TDRs	$ 9,919	$ 12,670	$ 18,048	$ 19,787	$ 22,457	$ 24,189
Payment Deferral [Member]
Accruing TDRs	9,919		17,912
Contractual Interest Rate Reduction [Member]
Accruing TDRs	0		0
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	0		136
Commercial Portfolio Segment [Member]
Accruing TDRs	8,902		16,692
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	8,902		16,692
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
Residential Portfolio Segment [Member]
Accruing TDRs	1,017
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,017
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	0
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 0
Commercial Real Estate Portfolio Segment [Member]
Accruing TDRs			1,356
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs			1,220
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			$ 136