Note 5 - Premises and Equipment, Net - Summary of Premises and Equipment (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Property, plant and equipment, gross	$ 76,623,000	$ 74,171,000
Less: accumulated depreciation	30,589,000	28,715,000
Total premises and equipment	46,034,000	45,456,000
Land and Land Improvements [Member]
Property, plant and equipment, gross	18,046,000	17,285,000
Building [Member]
Property, plant and equipment, gross	41,179,000	39,691,000
Furniture and Fixtures [Member]
Property, plant and equipment, gross	$ 17,398,000	$ 17,195,000