Note 5 - Fair Value Measurements - Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investment securities available for sale, at fair value	$ 98,114	$ 98,322
US Government Agencies Debt Securities [Member]
Investment securities available for sale, at fair value	7,182	7,471
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities available for sale, at fair value	20,197	17,758
Fair Value, Recurring [Member]
Investment securities available for sale, at fair value	98,788	98,938
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Investment securities available for sale, at fair value	7,182	7,471
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale, at fair value	70,735	73,093
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities available for sale, at fair value	20,197	17,758
Fair Value, Recurring [Member] | Debt Securities [Member]
Investment securities available for sale, at fair value	98,114	98,322
Fair Value, Recurring [Member] | Equity Securities [Member]
Investment securities available for sale, at fair value	674	616
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Investment securities available for sale, at fair value	674	616
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Debt Securities [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Investment securities available for sale, at fair value	674	616
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Investment securities available for sale, at fair value	98,114	98,322
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Investment securities available for sale, at fair value	7,182	7,471
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale, at fair value	70,735	73,093
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities available for sale, at fair value	20,197	17,758
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Debt Securities [Member]
Investment securities available for sale, at fair value	98,114	98,322
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Debt Securities [Member]
Investment securities available for sale, at fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Investment securities available for sale, at fair value