Note 5 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accruing TDRs	$ 24,189	$ 33,416	$ 29,722	$ 39,923
Payment Deferral [Member]
Accruing TDRs	19,194	20,472
Contractual Interest Rate Reduction [Member]
Accruing TDRs		1,677
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	4,995	11,267
Commercial Portfolio Segment [Member]
Accruing TDRs	13,771	12,944
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	13,771	12,944
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs
Commercial Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs
Commercial Real Estate Portfolio Segment [Member]
Accruing TDRs	8,566	19,021
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	3,682	6,231
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs		1,677
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	4,884	11,113
Residential Portfolio Segment [Member]
Accruing TDRs	1,852	1,451
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,741	1,297
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 111	$ 154