Note 4 - Premises and Equipment, Net - Summary of Premises and Equipment (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Property, plant and equipment, gross	$ 96,887,000	$ 92,598,000
Less: accumulated depreciation	36,441,000	35,271,000
Premises and equipment, net	60,446,000	57,327,000
Land and Land Improvements [Member]
Property, plant and equipment, gross	17,032,000	17,039,000
Building [Member]
Property, plant and equipment, gross	57,275,000	52,847,000
Furniture and Fixtures [Member]
Property, plant and equipment, gross	$ 22,580,000	$ 22,712,000