Note 8 - Loans (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018
Impaired Financing Receivable, Recorded Investment, Total	$ 88,847		$ 88,847		$ 88,847	$ 106,886
Percentage Of Charge Off To Contractual Balances For Impaired Loans	1.90%		1.90%		1.90%	9.30%
Financing Receivable, Troubled Debt Restructuring, Subsequent Default					$ 0
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	$ 0		$ 0		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Ending Balance	36,778		36,778		36,778	$ 0
Transfer of Portfolio Loans and Leases to Held-for-sale	75,300	$ 0	75,285	$ 0
Gain (Loss) on Sales of Loans, Net, Total	800		795	$ (0)
Increase (Decrease) in Loans Held-for-sale, Total	(120)		$ (120)
Minimum [Member]
Period Loan Is In Payment Default			60 days
Maximum [Member]
Period Loan Is In Payment Default			90 days
Nonaccrual Loans [Member]
Impaired Financing Receivable, Recorded Investment, Total	47,200		$ 47,200		47,200	41,800
Accruing Troubled Debt Restructuring [Member]
Impaired Financing Receivable, Recorded Investment, Total	41,600		41,600		41,600	65,100
Financing Receivable, Troubled Debt Restructuring	41,600		41,600		41,600	65,100
Troubled Debt Restructuring, Specific Reserves	1,200		1,200		1,200	1,500
Non-accruing Troubled Debt Restructuring [Member]
Financing Receivable, Troubled Debt Restructuring	19,800		19,800		19,800	24,200
Troubled Debt Restructuring, Specific Reserves	$ 141		$ 141		$ 141	$ 826