Note 2 - Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, fair value
Fair Value, Inputs, Level 1 [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value
Fair Value, Inputs, Level 1 [Member] | Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Assets, fair value
Fair Value, Inputs, Level 1 [Member] | Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Assets, fair value
Fair Value, Inputs, Level 1 [Member] | Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Nonowner Occupied [Member]
Assets, fair value
Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value
Fair Value, Inputs, Level 1 [Member] | Derivative Financial Instruments, Assets [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Assets, fair value
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, fair value	(74)	(59)
Fair Value, Inputs, Level 2 [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value	14,588,000	13,473,000
Fair Value, Inputs, Level 2 [Member] | Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Assets, fair value
Fair Value, Inputs, Level 2 [Member] | Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Assets, fair value
Fair Value, Inputs, Level 2 [Member] | Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Nonowner Occupied [Member]
Assets, fair value
Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value	85,577,000	87,652,000
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Assets [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Assets, fair value	74	59
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, fair value
Fair Value, Inputs, Level 3 [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value
Fair Value, Inputs, Level 3 [Member] | Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Assets, fair value	822,000	822,000
Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Assets, fair value		756,000
Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Nonowner Occupied [Member]
Assets, fair value		216,000
Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Assets [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Assets, fair value