Note 7 - Loans (Details Textual)	3 Months Ended
	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Impaired Financing Receivable, Recorded Investment	$ 128,376,000	$ 115,074,000	$ 115,100,000
Percentage Of Charge Off To Contractual Balances For Impaired Loans	10.30%		8.40%
Allowance for Credit Losses, Change in Method of Calculating Impairment
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down
Financing Receivable, Modifications, Number of Contracts	2	0
Loans and Leases Receivable, Impaired, Commitment to Lend	$ 0
Commercial Portfolio Segment [Member]
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	547,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 1,600,000
Minimum [Member]
Period Loan Is In Payment Default	60 days
Maximum [Member]
Period Loan Is In Payment Default	90 days
Rate Reduction [Member] | Minimum [Member]
Troubled Debt Restructurings Length Of Modifications	90 days
Rate Reduction [Member] | Maximum [Member]
Troubled Debt Restructurings Length Of Modifications	300 days
Nonaccrual Loans [Member]
Impaired Financing Receivable, Recorded Investment	$ 48,000,000		$ 49,700,000
Accruing Troubled Debt Restructuring [Member]
Impaired Financing Receivable, Recorded Investment	80,400,000		65,400,000
Financing Receivable, Modifications, Recorded Investment	80,400,000		65,400,000
Allowance for Credit Losses, Change in Method of Calculating Impairment	586,000		1,300,000
Non-accruing Troubled Debt Restructuring [Member]
Financing Receivable, Modifications, Recorded Investment	32,800,000		29,700,000
Allowance for Credit Losses, Change in Method of Calculating Impairment	$ 1,300,000		$ 1,100,000