Note 7 - Loans (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Impaired Financing Receivable, Recorded Investment	$ 143,863,000		$ 143,863,000		$ 115,074,000
Percentage Of Charge Off To Contractual Balances For Impaired Loans	10.00%		10.00%		8.40%
Allowance for Credit Losses, Change in Method of Calculating Impairment		$ 171,000		$ 171,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down
Loans and Leases Receivable, Impaired, Commitment to Lend	0		0
Commercial Portfolio Segment [Member]
Allowance for Credit Losses, Change in Method of Calculating Impairment		148,000		148,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment			50,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down			$ 2,100,000
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	64,000,000		$ 64,000,000		$ 49,700,000
Accruing Troubled Debt Restructuring [Member]
Impaired Financing Receivable, Recorded Investment	79,800,000		79,800,000		65,400,000
Financing Receivable, Modifications, Recorded Investment	79,800,000		79,800,000		65,400,000
Allowance for Credit Losses, Change in Method of Calculating Impairment	523,000		523,000		1,300,000
Non-accruing Troubled Debt Restructuring [Member]
Financing Receivable, Modifications, Recorded Investment	30,000,000		30,000,000		29,700,000
Allowance for Credit Losses, Change in Method of Calculating Impairment	$ 681,000		$ 681,000		$ 1,100,000