Note 6 - Investment Securities (Details Textual)	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) security	Jun. 30, 2018 USD ($) security	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) security	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Investment Securities [Line Items]
Net realized gains					$ 27,000
Income tax expense benefit related to net realized gains losses on sales of securities		$ (14,000)	$ (48,000)	$ 38,000	350,000
Other than temporary impairment, credit losses recognized in earnings				0	0
(Gain) loss on sale of investments		(48,000)	(115,000)	(133,000)	(864,000)
Recorded OTTI credit loss		0	0	0	0
Debt Securities [Member]
Investment Securities [Line Items]
Proceeds from sale of investment securities		1,756,000	9,872,000	4,159,000	19,358,000
Available-for-sale securities pledged as collateral		187,915,000		187,915,000		$ 202,887,000
Other than temporary impairment, credit losses recognized in earnings				0	0
Recorded OTTI credit loss		0	0	0	0
Equity Securities [Member]
Investment Securities [Line Items]
Proceeds from sale of investment securities		678,000	752,000	1,390,000	5,262,000
Recorded OTTI credit loss		$ 0	0	$ 0	0
PreTSL [Member]
Investment Securities [Line Items]
Number of trust preferred securities | security		1		1
Available-for-sale, amortized cost		$ 123,000		$ 123,000
Fair value		118,000		118,000
Non-performing securities sold | security	5
Carrying value of securities	$ 2,235,000		2,235,000		2,235,000
Number of securities OTTI recorded | security	4
Recorded OTTI credit loss	$ 1,152,000
Amount of reduction in risk-based assets			19,000,000
PreTSL [Member] | Non-interest Income [Member]
Investment Securities [Line Items]
(Gain) loss on sale of investments			15,000
Collateralized Debt Obligations [Member]
Investment Securities [Line Items]
Other than temporary impairment, credit losses recognized in earnings		$ 0	$ 0	$ 0	$ 0