Note 4 - Investment Securities (Tables)
 12 Months Ended
Dec. 31, 2016
Notes Tables  
Available-for-sale Securities [Table Text Block]
(dollars in thousands)
 
Amortized
Cost
 
 
Gross
Unrealized
Gains
 
 
Gross
Unrealized
Losses
 
 
Fair Value
 
U.S. Treasury securities
  $
200,094
     $
3
     $
—
     $
200,097
  
Obligations of the U.S. government and agencies
   
83,111
      
167
      
(1,080
)
    
82,198
  
Obligations of state and political subdivisions
   
33,625
      
26
      
(121
)
    
33,530
  
Mortgage-backed securities
   
185,997
      
1,260
      
(1,306
)
    
185,951
  
Collateralized mortgage obligations
   
49,488
      
108
      
(902
)
    
48,694
  
Other investments
   
16,575
      
105
      
(154
)
    
16,526
  
Total
  $
568,890
     $
1,669
     $
(3,563
)
   $
566,996
  
(dollars in thousands)
 
Amortized
Cost
 
 
Gross
Unrealized
Gains
 
 
Gross
Unrealized
Losses
 
 
Fair Value
 
U.S. Treasury securities
  $
101
     $
—
     $
(1
)
   $
100
  
Obligations of the U.S. government and agencies
   
101,342
      
470
      
(317
)
    
101,495
  
Obligations of state and political subdivisions
   
41,892
      
123
      
(49
)
    
41,966
  
Mortgage-backed securities
   
157,422
      
1,482
      
(215
)
    
158,689
  
Collateralized mortgage obligations
   
29,756
      
166
      
(123
)
    
29,799
  
Other investments
   
17,263
      
38
      
(384
)
    
16,917
  
Total
  $
347,776
     $
2,279
     $
(1,089
)
   $
348,966
  
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block]
 
 
Less than 12
Months
 
 
12 Months
or Longer
 
 
Total
 
(dollars in thousands)
 
Fair
Value
 
 
Unrealized
Losses
 
 
Fair
Value
 
 
Unrealized
Losses
 
 
Fair
Value
 
 
Unrealized
Losses
 
Obligations of the U.S. government and agencies
   $
62,211
     $
(1,080
)
   $
—
     $
—
     $
62,211
     $
(1,080
)
Obligations of state and political subdivisions
   
24,482
      
(121
)
    
—
      
—
      
24,482
      
(121
)
Mortgage-backed securities
   
101,433
      
(1,306
)
    
—
      
—
      
101,433
      
(1,306
)
Collateralized mortgage obligations
    
35,959
      
(902
)
    
—
      
—
      
35,959
      
(902
)
Other investments
   
2,203
      
(93
)
    
11,895
      
(61
)
    
14,098
      
(154
)
Total
  $
226,288
     $
(3,502
)
   $
11,895
     $
(61
)
   $
238,183
     $
(3,563
)
 
 
Less than 12
Months
 
 
12 Months
or Longer
 
 
Total
 
(dollars in thousands)
 
Fair
Value
 
 
Unrealized Losses
 
 
Fair
Value
 
 
Unrealized Losses
 
 
Fair
Value
 
 
Unrealized Losses
 
U.S. Treasury securities
  $
100
     $
(1
)
   $
—
     $
—
     $
100
     $
(1
)
Obligations of the U.S. government and agencies
   
49,759
      
(317
)
    
—
      
—
      
49,759
      
(317
)
Obligations of state and political subdivisions
   
18,725
      
(46
)
    
2,016
      
(3
)
    
20,741
      
(49
)
Mortgage-backed securities
   
55,763
      
(215
)
    
—
      
—
      
55,763
      
(215
)
Collateralized mortgage obligations
    
6,407
      
(85
)
    
2,436
      
(38
)
    
8,843
      
(123
)
Other investments
   
3,945
      
(238
)
    
11,810
      
(146
)
    
15,755
      
(384
)
Total
  $
134,699
     $
(902
)
   $
16,262
     $
(187
)
   $
150,961
     $
(1,089
)
Held-to-maturity Securities [Table Text Block]
(dollars in thousands)
 
Amortized
Cost
 
 
Gross
Unrealized
Gains
 
 
Gross
Unrealized
Losses
 
 
Fair Value
 
Mortgage-backed securities
   $
2,879
     $
—
     $
(61
)
   $
2,818
  
Total
  $
2,879
     $
—
     $
(61
)
   $
2,818
  
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block]
 
 
Less than 12
Months
 
 
12 Months
or Longer
 
 
Total
 
(dollars in thousands)
 
Fair
Value
 
 
Unrealized
Losses
 
 
Fair
Value
 
 
Unrealized
Losses
 
 
Fair
Value
 
 
Unrealized
Losses
 
Mortgage-backed securities
   $
2,818
     $
(61
)
   $
—
     $
—
     $
2,818
     $
(61
)
Total
  $
2,818
     $
(61
)
   $
—
     $
—
     $
2,818
     $
(61
)
Held-to-maturity Securities [Member]  
Notes Tables  
Investments Classified by Contractual Maturity Date [Table Text Block]
 
 
Dec
ember 3
1
, 2016
 
(dollars in thousands)
 
Amortized
Cost
 
 
Fair
Value
 
Mortgage-related securities
1
    
2,879
      
2,818
  
Total
  $
2,879
     $
2,818
  
Available-for-sale Securities [Member]  
Notes Tables  
Investments Classified by Contractual Maturity Date [Table Text Block]
 
 
December 31, 201
6
 
(dollars in thousands)
 
Amortized
Cost
 
 
Fair
Value
 
Investment securities*:
                
Due in one year or less
  $
213,876
     $
213,885
  
Due after one year through five years...
    
40,335
      
40,270
  
Due after five years through ten years
   
45,840
      
44,914
  
Due after ten years
   
18,079
      
18,055
  
Subtotal
   
318,130
      
317,124
  
Mortgage-related securities
   
235,485
      
234,644
  
Total
  $
553,615
     $
551,768
  
 
 
December 31, 2015
 
(dollars in thousands)
 
Amortized
Cost
 
 
Fair
Value
 
Investment securities*:
                
Due in one year or less
   $
9,570
     $
9,574
  
Due after one year through five years
    
61,368
      
61,467
  
Due after five years through ten years
    
53,193
      
53,070
  
Due after ten years
    
20,904
      
21,141
  
Subtotal
    
145,035
      
145,252
  
Mortgage-related securities
    
187,178
      
188,488
  
Total
   $
332,213
     $
333,740