Note 8 - Loans - Accruing Troubled Debt Restructurings (Details) - Accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accruing TDRs	$ 28,587	$ 31,671	$ 35,336	$ 41,647	$ 64,898	$ 65,071
Payment Deferral [Member]
Accruing TDRs	6,928		8,355
Contractual Interest Rate Reduction [Member]
Accruing TDRs	5,946		6,059
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	15,713		20,922
Commercial Portfolio Segment [Member]
Accruing TDRs	4,406		5,215
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	4,406		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	19,770		25,142
Commercial Real Estate Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	582		615
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	5,662		5,748
Commercial Real Estate Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	13,526		18,779
Residential Portfolio Segment [Member]
Accruing TDRs	4,411		4,979
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,940		2,525
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Accruing TDRs	284		311
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Accruing TDRs	$ 2,187		$ 2,143