Note 2 - Accumulated Other Comprehensive Income (Tables)
 12 Months Ended
Dec. 31, 2016
Notes Tables  
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
Year Ended December 31,
 
2016
   
2015
 
(In thousands)
  
Unrealized
Gains and
Losses on
Available
for Sale
Investment
Securities
    
Postretirement
Benefit
Obligation
    
Total
    
Unrealized
Gains and
Losses on
Available
for Sale
Investment
Securities
    
Postretirement
Benefit
Obligation
    
Total
  
Beginning balance
   $
3,219
     $
(437
 )   $
2,782
     $
5,174
     $
(299
 )   $
4,875
  
Other comprehensive (loss) income before reclassifications
    
(3,983
 )    
356
      
(3,627
 )    
(1,844
 )    
(198
 )    
(2,042
 )
Amounts reclassified from accumulated other comprehensive income
    
(2,599
 )    
36
      
(2,563
 )    
(111
 )    
60
      
(51
 )
Net current-period other comprehensive (loss) income
    
(6,582
 )    
392
      
(6,190
 )    
(1,955
 )    
(138
 )    
(2,093
 )
Ending balance
   $
(3,363
 )   $
(45
 )   $
(3,408
 )   $
3,219
     $
(437
 )   $
2,782
  
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]
(In thousands)
  
Amount Reclassified from Accumulated
Other Comprehensive Income
  
Affected Line Item in the Statement
Where Net Income is Presented
Year Ended December 31,
 
2016
    
2015
    
2014
    
Unrealized gains and losses on available for sale investment securities
   $
3,998
     $
171
     $
(63
 )
Investment securities gains (losses), net
     
(1,399
 )    
(60
 )    
22
  
Income tax (expense) benefit
    $
2,599
     $
111
     $
(41
 )
Net of tax
                           
Amortization related to postretirement benefits
                         
Prior service costs
   $
(50
 )   $
(51
 )   $
(207
 )
Salaries and employee benefits
Actuarial losses
    
(5
 )    
(42
 )    
67
  
Salaries and employee benefits
     
(55
 )    
(93
 )    
(140
 )
Total before tax
     
19
      
33
      
49
  
Income tax expense
    $
(36
 )   $
(60
 )   $
(91
 )
Net of tax
                           
Total reclassifications for the period
   $
2,563
     $
51
     $
(132
 )
Net of tax