Note 4 - Premises and Equipment, Net - Summary of Premises and Equipment (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Property, plant and equipment, gross	$ 80,571,000	$ 76,623,000
Less: accumulated depreciation	32,467,000	30,589,000
Premises and equipment, net	48,104,000	46,034,000
Land and Land Improvements [Member]
Property, plant and equipment, gross	18,178,000	18,046,000
Building [Member]
Property, plant and equipment, gross	44,416,000	41,179,000
Furniture and Fixtures [Member]
Property, plant and equipment, gross	$ 17,977,000	$ 17,398,000