Note 4 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accruing TDRs	$ 8,985	$ 18,048	$ 24,189	$ 33,416
Payment Deferral [Member]
Accruing TDRs	8,985	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	8,462	16,692
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	8,462	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	523
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	523
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
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Accruing TDRs		1,356
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs		1,220
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs		0
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs		$ 136