Note 4 - Premises and Equipment, Net - Summary of Premises and Equipment (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Property, plant and equipment, gross	$ 77,547,000	$ 76,623,000
Less: accumulated depreciation	31,247,000	30,589,000
Premises and equipment, net	46,300,000	46,034,000
Land and Land Improvements [Member]
Property, plant and equipment, gross	17,938,000	18,046,000
Building [Member]
Property, plant and equipment, gross	41,751,000	41,179,000
Furniture and Fixtures [Member]
Property, plant and equipment, gross	$ 17,858,000	$ 17,398,000