Note 4 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accruing TDRs	$ 18,048	$ 24,189	$ 33,416	$ 29,722
Payment Deferral [Member]
Accruing TDRs	17,912	19,194
Contractual Interest Rate Reduction [Member]
Accruing TDRs	0	0
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	136	4,995
Commercial Portfolio Segment [Member]
Accruing TDRs	16,692	13,771
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	16,692	13,771
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	1,356	1,852
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,220	1,741
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	$ 136	111
Commercial Real Estate Portfolio Segment [Member]
Accruing TDRs		8,566
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs		3,682
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		$ 4,884