Quarterly report pursuant to Section 13 or 15(d)

Note 10 - Fair Value Measurement - Financial Assets and Financial Liabilities Carried at Fair Value on a Recurring Basis (Details)

v3.7.0.1
Note 10 - Fair Value Measurement - Financial Assets and Financial Liabilities Carried at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Thousands
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Available-for-sale securities $ 438,808   $ 422,375
US Treasury and Government [Member]      
Available-for-sale securities 57,125   46,254
Collateralized Mortgage Backed Securities [Member]      
Available-for-sale securities 241,271   227,190
US States and Political Subdivisions Debt Securities [Member]      
Available-for-sale securities 140,412   139,930
Corporate Debt Securities [Member]      
Available-for-sale securities   $ 9,001  
Fair Value, Measurements, Recurring [Member]      
Available-for-sale securities 438,808   422,375
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]      
Available-for-sale securities 57,125   46,254
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member]      
Available-for-sale securities 241,271   227,190
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]      
Available-for-sale securities 140,412   139,930
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]      
Available-for-sale securities     9,001
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury and Government [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Backed Securities [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]      
Available-for-sale securities    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]      
Available-for-sale securities 438,808   422,375
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury and Government [Member]      
Available-for-sale securities 57,125   46,254
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member]      
Available-for-sale securities 241,271   227,190
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]      
Available-for-sale securities 140,412   139,930
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]      
Available-for-sale securities     9,001
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury and Government [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Backed Securities [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]      
Available-for-sale securities  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]      
Available-for-sale securities