Note 4 - Loans - Accruing Troubled Debt Restructurings (Details) - Accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accruing TDRs	$ 27,721	$ 35,336	$ 65,071	$ 68,565
Payment Deferral [Member]
Accruing TDRs	6,222	8,355
Contractual Interest Rate Reduction [Member]
Accruing TDRs	5,910	6,059
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	15,589	20,922
Commercial Portfolio Segment [Member]
Accruing TDRs	3,983	5,215
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	3,983	5,215
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	19,575	25,142
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	515	615
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	5,635	5,748
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	13,425	18,779
Residential Portfolio Segment [Member]
Accruing TDRs	4,163	4,979
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,724	2,525
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	275	311
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 2,164	$ 2,143