Note 8 - Loans - Non-accrual Troubled Debt Restructurings (Details) - Non-accruing Troubled Debt Restructuring [Member] - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Accruing TDRs	$ 19,787	$ 22,457	$ 24,189	$ 27,718	$ 30,347	$ 33,415
Payment Deferral [Member]
Accruing TDRs	19,686		19,194
Contractual Interest Rate Reduction [Member]
Accruing TDRs	0		0
Rate Reduction and Payment Deferral [Member]
Accruing TDRs	101		4,995
Commercial Portfolio Segment [Member]
Accruing TDRs	18,057		13,771
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	18,057		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	1,730		1,852
Residential Portfolio Segment [Member] | Payment Deferral [Member]
Accruing TDRs	1,629		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	$ 101		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