Note 5 - Loans - Newly Restructured Loans and Types of Modifications (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing receivable modifications	$ 60,000	$ 2,447,000	$ 1,505,000
Contractual Interest Rate Reduction [Member]
Financing receivable modifications		1,049,000	115,000
Interest Rate Reduction and Extension of Maturity [Member]
Financing receivable modifications		81,000	39,000
Principal Forgiveness [Member]
Financing receivable modifications
Rate Reduction and Payment Deferral [Member]
Financing receivable modifications	60,000		264,000
Extended Maturity [Member]
Financing receivable modifications		1,120,000
Payment Deferral [Member]
Financing receivable modifications		197,000	1,087,000
Commercial Portfolio Segment [Member]
Financing receivable modifications		2,025,000	747,000
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Financing receivable modifications		905,000
Commercial Portfolio Segment [Member] | Interest Rate Reduction and Extension of Maturity [Member]
Financing receivable modifications			39,000
Commercial Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member]
Financing receivable modifications
Commercial Portfolio Segment [Member] | Extended Maturity [Member]
Financing receivable modifications		1,120,000
Commercial Portfolio Segment [Member] | Payment Deferral [Member]
Financing receivable modifications			708,000
Residential Portfolio Segment [Member] | Individual Tax Identification Number Loan [Member] | Real Estate Loan [Member]
Financing receivable modifications	60,000	278,000	758,000
Residential Portfolio Segment [Member] | Mortgage Receivable [Member] | Real Estate Loan [Member]
Financing receivable modifications		144
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member] | Individual Tax Identification Number Loan [Member] | Real Estate Loan [Member]
Financing receivable modifications			115,000
Residential Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member] | Mortgage Receivable [Member] | Real Estate Loan [Member]
Financing receivable modifications		144
Residential Portfolio Segment [Member] | Interest Rate Reduction and Extension of Maturity [Member] | Individual Tax Identification Number Loan [Member] | Real Estate Loan [Member]
Financing receivable modifications		81,000
Residential Portfolio Segment [Member] | Interest Rate Reduction and Extension of Maturity [Member] | Mortgage Receivable [Member] | Real Estate Loan [Member]
Financing receivable modifications
Residential Portfolio Segment [Member] | Principal Forgiveness [Member] | Individual Tax Identification Number Loan [Member] | Real Estate Loan [Member]
Financing receivable modifications
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member] | Individual Tax Identification Number Loan [Member] | Real Estate Loan [Member]
Financing receivable modifications	60,000		264,000
Residential Portfolio Segment [Member] | Rate Reduction and Payment Deferral [Member] | Mortgage Receivable [Member] | Real Estate Loan [Member]
Financing receivable modifications
Residential Portfolio Segment [Member] | Extended Maturity [Member] | Individual Tax Identification Number Loan [Member] | Real Estate Loan [Member]
Financing receivable modifications
Residential Portfolio Segment [Member] | Extended Maturity [Member] | Mortgage Receivable [Member] | Real Estate Loan [Member]
Financing receivable modifications
Residential Portfolio Segment [Member] | Payment Deferral [Member] | Individual Tax Identification Number Loan [Member] | Real Estate Loan [Member]
Financing receivable modifications		197,000	$ 379,000
Residential Portfolio Segment [Member] | Payment Deferral [Member] | Mortgage Receivable [Member] | Real Estate Loan [Member]
Financing receivable modifications