Note 9 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities	2,000	1,977
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities
US Government-sponsored Enterprises Debt Securities [Member]
Investment securities	2,000	1,977
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities	73,300	72,370
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities	73,300	72,370
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities	25,318	22,357
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities
US States and Political Subdivisions Debt Securities [Member]
Investment securities	25,318	22,357
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities	100,618
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities
Corporate Debt Securities [Member]
Investment securities	$ 100,618
Fair Value, Inputs, Level 1 [Member]
Investment securities
Fair Value, Inputs, Level 2 [Member]
Investment securities		96,704
Fair Value, Inputs, Level 3 [Member]
Investment securities
Investment securities		$ 96,704