Note 9 - Quantitative Information about Assets Measured at Fair Value (Details) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements		$ 1,341	$ 1,101
Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements		1,336	1,067
Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements		5	34
Fair Value, Inputs, Level 3 [Member] | Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements		1,341	1,101
Fair Value, Inputs, Level 3 [Member] | Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements		1,336	1,067
Fair Value, Inputs, Level 3 [Member] | Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements		$ 5	$ 34
Fair Value, Inputs, Level 3 [Member] | Appraisal Valuation Technique [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value liquidation inputs	[1],[2]	(10.00%)	(10.00%)
Fair Value, Inputs, Level 3 [Member] | Appraisal Valuation Technique [Member] | Measurement Input, Comparability Adjustment [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value range of value inputs	[2],[3]	0.00	(0.15)
Fair Value, Inputs, Level 3 [Member] | Appraisal Valuation Technique [Member] | Measurement Input, Comparability Adjustment [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value range of value inputs	[2],[3]	(0.90)	(0.90)
Fair Value, Inputs, Level 3 [Member] | Appraisal Valuation Technique [Member] | Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements	[2]	$ 1,269	$ 943
Fair Value, Inputs, Level 3 [Member] | Market Approach Valuation Technique [Member] | Minimum [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value range of value inputs	[4]	(25.00%)	(25.00%)
Fair Value, Inputs, Level 3 [Member] | Market Approach Valuation Technique [Member] | Maximum [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value range of value inputs	[4]	(80.00%)	(50.00%)
Fair Value, Inputs, Level 3 [Member] | Market Approach Valuation Technique [Member] | Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements	[4]	$ 58	$ 124
Fair Value, Inputs, Level 3 [Member] | Used Commercial Vehicle Guides Valuation Technique [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value range of value inputs	[5]	0.00%
Fair Value, Inputs, Level 3 [Member] | Used Commercial Vehicle Guides Valuation Technique [Member] | Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements	[5]	$ 9
Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow Valuation Technique [Member] | Measurement Input, Expected Term [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value expected term		2 years	2 years
Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow Valuation Technique [Member] | Measurement Input, Expected Term [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value expected term		26 years	26 years
Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow Valuation Technique [Member] | Measurement Input, Discount Rate [Member] | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value range of value inputs		12.00%	13.00%
Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow Valuation Technique [Member] | Measurement Input, Discount Rate [Member] | Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Nonrecurring fair value range of value inputs		12.50%	15.00%
Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow Valuation Technique [Member] | Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Asset fair value measurements		$ 5	$ 34

[1] Appraisals and pending agreements of sale are adjusted by management for estimated liquidation expenses. The range is presented as a percent of the initial appraised value.

[2] Fair value is primarily determined through appraisals of the underlying collateral by independent parties, which generally includes various level 3 inputs which are not always identifiable.

[3] Appraisals may be adjusted by management for qualitative factors such as economic conditions and the age of the appraisal. The range is presented as a percent of the initial appraised value.

[4] Values obtained from financial statements for UCC collateral (fixed assets and inventory) are discounted to estimated realizable liquidation value.

[5] If lendable (lower than wholesale) value is utilized, then no additional discounts are taken. If lendable value is not provided, then additional discounts are applied.