Note 4 -Investment Securities (Details Textual)	12 Months Ended
	Dec. 31, 2016 USD ($) security	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Investment Securities [Line Items]
Net (loss) gain on trading activities	$ (40,000)	$ 33,000	$ 156,000
Trading Securities, Change in Unrealized Holding Gain (Loss)	69,000	31,000
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	32,573,000	47,960,000	29,972,000
Income Tax Expense Benefit Related to Net Realized Gains Losses on Sales of Securities	229,000	266,000	378,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	0	0	0
Held-to-maturity	0	147,000
Proceeds from Sale of Held-to-maturity Securities	0	0	0
Available-for-sale Securities Pledged as Collateral	166,628,000	197,149,000
Available-for-sale, amortized cost	396,168,000	362,742,000
Fair value	$ 390,475,000	361,915,000
Fair Value Inputs, Prepayment Rate	1.00%
Threshold For Identifying Banks With Trust Preferred Securities	$ 15,000,000,000
Minimum Cost Saving for Refinance	2.00%
Bank Failure Rate	0.36%
Fair Value Inputs, Loss Severity	95.00%
Non-interest Income [Member]
Investment Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	$ 192,000
Collateralized Debt Obligations [Member]
Investment Securities [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	0	0	$ 0
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	0
Available-for-sale, amortized cost	2,909,000	3,291,000
Fair value	$ 2,281,000	$ 2,653,000
Number Of Trust Preferred Securities | security	6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security	5
Collateralized Debt Obligations [Member] | Minimum [Member]
Investment Securities [Line Items]
Fair Value Inputs, Probability of Default	0.23%
Fair Value Inputs, Loss Severity	0.00%
Collateralized Debt Obligations [Member] | Maximum [Member]
Investment Securities [Line Items]
Fair Value Inputs, Probability of Default	0.47%
Fair Value Inputs, Loss Severity	100.00%