Note 2 - Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
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 2 [Member] | US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value	15,303	13,473
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	90,154	87,652
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	822
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
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
Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
Assets, fair value