Note 11 - Fair Value of Financial Instruments and Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Recurring Securities Available for Sale	$ 409,839	$ 353,066
Fair Value, Inputs, Level 1 [Member]
Recurring Securities Available for Sale
Fair Value, Inputs, Level 2 [Member]
Recurring Securities Available for Sale		348,789
Fair Value, Inputs, Level 3 [Member]
Recurring Securities Available for Sale		4,277
Fair Value, Recurring [Member]
Recurring Securities Available for Sale	409,839
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Recurring Securities Available for Sale
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Recurring Securities Available for Sale	406,405
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Recurring Securities Available for Sale	3,434
Fair Value, Nonrecurring [Member]
Impaired Loans	2,679	3,352
Other Real Estate	714	1,183
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Impaired Loans
Other Real Estate
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Impaired Loans
Other Real Estate
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired Loans	2,679	3,352
Other Real Estate	714	1,183
US Government Agencies Debt Securities [Member]
Recurring Securities Available for Sale	403,408	346,205
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member]
Recurring Securities Available for Sale	403,408	346,205
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Recurring Securities Available for Sale
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Recurring Securities Available for Sale	400,189	342,142
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Recurring Securities Available for Sale	3,219	4,063
US States and Political Subdivisions Debt Securities [Member]
Recurring Securities Available for Sale	3,574	3,989
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member]
Recurring Securities Available for Sale	3,574	3,989
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Recurring Securities Available for Sale
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Recurring Securities Available for Sale	3,359	3,775
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Recurring Securities Available for Sale	215	214
Corporate Debt Securities [Member]
Recurring Securities Available for Sale	2,857	2,872
Corporate Debt Securities [Member] | Fair Value, Recurring [Member]
Recurring Securities Available for Sale	2,857	2,872
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Recurring Securities Available for Sale
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Recurring Securities Available for Sale	2,857	2,872
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Recurring Securities Available for Sale