Note 4 - Securities - Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale securities, less than 12 months, fair value	$ 36,107	$ 120,812
Available-for-sale securities, less than 12 months, unrealized losses	(269)	(1,363)
Available-for-sale securities, 12 months or more, fair value	144,730	54,495
Available-for-sale securities, 12 months or more, unrealized losses	(5,432)	(1,310)
Available-for-sale securities, fair value	180,837	175,307
Available-for-sale securities, unrealized losses	(5,701)	(2,673)
US Government Agencies Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value	7,223	18,140
Available-for-sale securities, less than 12 months, unrealized losses	(39)	(102)
Available-for-sale securities, 12 months or more, fair value	12,274	2,131
Available-for-sale securities, 12 months or more, unrealized losses	(291)	(44)
Available-for-sale securities, fair value	19,497	20,271
Available-for-sale securities, unrealized losses	(330)	(146)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value	5,545	15,030
Available-for-sale securities, less than 12 months, unrealized losses	(40)	(255)
Available-for-sale securities, 12 months or more, fair value	16,320	8,368
Available-for-sale securities, 12 months or more, unrealized losses	(549)	(223)
Available-for-sale securities, fair value	21,865	23,398
Available-for-sale securities, unrealized losses	(589)	(478)
Residential Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]
Available-for-sale securities, less than 12 months, fair value	21,791	75,323
Available-for-sale securities, less than 12 months, unrealized losses	(183)	(827)
Available-for-sale securities, 12 months or more, fair value	93,038	31,036
Available-for-sale securities, 12 months or more, unrealized losses	(3,798)	(711)
Available-for-sale securities, fair value	114,829	106,359
Available-for-sale securities, unrealized losses	(3,981)	(1,538)
Corporate Debt Securities [Member]
Available-for-sale securities, less than 12 months, fair value
Available-for-sale securities, less than 12 months, unrealized losses
Available-for-sale securities, 12 months or more, fair value	2,922	2,934
Available-for-sale securities, 12 months or more, unrealized losses	(100)	(105)
Available-for-sale securities, fair value	2,922	2,934
Available-for-sale securities, unrealized losses	(100)	(105)
Commercial Mortgage Backed Securities [Member]
Available-for-sale securities, less than 12 months, fair value	1,548	11,162
Available-for-sale securities, less than 12 months, unrealized losses	(7)	(151)
Available-for-sale securities, 12 months or more, fair value	20,176	10,026
Available-for-sale securities, 12 months or more, unrealized losses	(694)	(227)
Available-for-sale securities, fair value	21,724	21,188
Available-for-sale securities, unrealized losses	$ (701)	(378)
Asset-backed Securities [Member]
Available-for-sale securities, less than 12 months, fair value		1,157
Available-for-sale securities, less than 12 months, unrealized losses		(28)
Available-for-sale securities, 12 months or more, fair value
Available-for-sale securities, 12 months or more, unrealized losses
Available-for-sale securities, fair value		1,157
Available-for-sale securities, unrealized losses		$ (28)