Note 11 - Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
US Government Agencies Debt Securities [Member] | Available-for-sale Securities [Member] | Fair Value, Inputs, Level 2 [Member]
State, County and Municipal	$ 303,810	$ 291,050
Assets, fair value, recurring	303,810	291,050
Nonrecurring
State, County and Municipal	303,810	291,050
US Government Agencies Debt Securities [Member] | Available-for-sale Securities [Member]
State, County and Municipal	303,810	291,050
Assets, fair value, recurring	303,810	291,050
Nonrecurring
State, County and Municipal	303,810	291,050
US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member] | Fair Value, Inputs, Level 2 [Member]
State, County and Municipal	4,101	4,169
Assets, fair value, recurring	4,101	4,169
Nonrecurring
State, County and Municipal	4,101	4,169
US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member] | Fair Value, Inputs, Level 3 [Member]
State, County and Municipal	929	930
Assets, fair value, recurring	929	930
Nonrecurring
State, County and Municipal	929	930
US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
State, County and Municipal	5,030	5,099
Assets, fair value, recurring	5,030	5,099
Nonrecurring
State, County and Municipal	5,030	5,099
Available-for-sale Securities [Member] | Fair Value, Inputs, Level 2 [Member]
State, County and Municipal	307,911	295,219
Assets, fair value, recurring	307,911	295,219
Nonrecurring
State, County and Municipal	307,911	295,219
Available-for-sale Securities [Member] | Fair Value, Inputs, Level 3 [Member]
State, County and Municipal	929	930
Assets, fair value, recurring	929	930
Nonrecurring
State, County and Municipal	929	930
Available-for-sale Securities [Member]
State, County and Municipal	308,840	296,149
Assets, fair value, recurring	308,840	296,149
Nonrecurring
State, County and Municipal	308,840	296,149
Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member]
Nonrecurring
Assets, fair value, nonrecurring	6,187	8,545
Fair Value, Inputs, Level 3 [Member] | Other Real Estate [Member]
Nonrecurring
Assets, fair value, nonrecurring	2,941	2,536
Impaired Loans [Member]
Nonrecurring
Assets, fair value, nonrecurring	6,187	8,545
Other Real Estate [Member]
Nonrecurring
Assets, fair value, nonrecurring	$ 2,941	$ 2,536