Note 4 - Loans - Accruing Troubled Debt Restructurings (Details) - Accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accruing TDRs	$ 35,336	$ 65,071	$ 68,565	$ 65,393
Payment Deferral [Member]
Accruing TDRs	8,355	35,510
Contractual Interest Rate Reduction [Member]
Accruing TDRs	6,059	7,747
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	20,922	21,814
Commercial Portfolio Segment [Member]
Accruing TDRs	5,215	18,135
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	5,215	18,135
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	25,142	40,860
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	615	14,022
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	5,748	7,420
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	18,779	19,418
Residential Portfolio Segment [Member]
Accruing TDRs	4,979	6,076
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	2,525	3,353
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	311	327
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 2,143	$ 2,396