Note 5 - Allowance For Loan Losses and Credit Quality of Loans - Activity in the Allowance for Loan Losses (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Balance       $ 10,896       $ 13,208 $ 10,896 $ 13,208    
Charge-offs                 (1,463) (2,112)    
Recoveries                 1,225 2,800    
Provision $ (1,000) $ (700) $ (200) (300) $ (2,000) $ (200) (800) (2,200) (3,000)    
Balance 8,458       10,896       8,458 10,896    
Ending balance individually evaluated for impairment                     $ 1,141 $ 2,552
Ending balance collectively evaluated for impairment                     7,317 8,344
Ending balance 8,458     10,896 10,896     13,208 10,896 10,896 8,458 10,896
Ending balance individually evaluated for impairment                     17,711 24,886
Ending balance collectively evaluated for impairment                     634,626 592,422
Ending balance                     652,337 617,308
Agriculture and Agricultural Real Estate Loans Portfolio Segment [Member]                        
Balance       389       216 389 216    
Charge-offs                 (221) (188)    
Recoveries                 6 325    
Provision                 27 36    
Balance 201       389       201 389    
Ending balance individually evaluated for impairment                     5 240
Ending balance collectively evaluated for impairment                     196 149
Ending balance 201     389 389     216 389 389 201 389
Ending balance individually evaluated for impairment                     1,212 882
Ending balance collectively evaluated for impairment                     20,306 18,361
Ending balance                     21,518 19,243
Commercial Portfolio Segment [Member]                        
Balance       2,279       1,361 2,279 1,361    
Charge-offs                 (26) (352)    
Recoveries                 150 311    
Provision                 (771) 959    
Balance 1,632       2,279       1,632 2,279    
Ending balance individually evaluated for impairment                     199 672
Ending balance collectively evaluated for impairment                     1,433 1,607
Ending balance 1,632     2,279 2,279     1,361 2,279 2,279 1,632 2,279
Ending balance individually evaluated for impairment                     355 958
Ending balance collectively evaluated for impairment                     96,406 83,480
Ending balance                     96,761 84,438
Commercial Real Estate Portfolio Segment [Member]                        
Balance       4,350       6,179 4,350 6,179    
Charge-offs                 (742) (559)    
Recoveries                 194 502    
Provision                 (466) (1,772)    
Balance 3,336       4,350       3,336 4,350    
Ending balance individually evaluated for impairment                     129 634
Ending balance collectively evaluated for impairment                     3,207 3,716
Ending balance 3,336     4,350 4,350     6,179 4,350 4,350 3,336 4,350
Ending balance individually evaluated for impairment                     6,853 13,398
Ending balance collectively evaluated for impairment                     245,316 229,822
Ending balance                     252,169 243,220
Construction Real Estate Portfolio Segment [Member]                        
Balance       420       803 420 803    
Charge-offs                 (2)    
Recoveries                 151 648    
Provision                 (46) (1,029)    
Balance 525       420       525 420    
Ending balance individually evaluated for impairment                     388 277
Ending balance collectively evaluated for impairment                     137 143
Ending balance 525     420 420     803 420 420 525 420
Ending balance individually evaluated for impairment                     1,717 1,809
Ending balance collectively evaluated for impairment                     17,737 14,110
Ending balance                     19,454 15,919
Residential Portfolio Segment [Member]                        
Balance       2,235       3,226 2,235 3,226    
Charge-offs                 (319) (893)    
Recoveries                 588 863    
Provision                 (905) (961)    
Balance 1,599       2,235       1,599 2,235    
Ending balance individually evaluated for impairment                     236 506
Ending balance collectively evaluated for impairment                     1,363 1,729
Ending balance 1,599     2,235 2,235     3,226 2,235 2,235 1,599 2,235
Ending balance individually evaluated for impairment                     7,098 7,343
Ending balance collectively evaluated for impairment                     209,338 206,646
Ending balance                     216,436 213,989
Consumer and Other Portfolio Segment [Member]                        
Balance       1,223       1,423 1,223 1,423    
Charge-offs                 (155) (118)    
Recoveries                 136 151    
Provision                 (39) (233)    
Balance 1,165       1,223       1,165 1,223    
Ending balance individually evaluated for impairment                     184 223
Ending balance collectively evaluated for impairment                     981 1,000
Ending balance $ 1,165     $ 1,223 $ 1,223     $ 1,423 $ 1,223 $ 1,223 1,165 1,223
Ending balance individually evaluated for impairment                     476 496
Ending balance collectively evaluated for impairment                     45,523 40,003
Ending balance                     $ 45,999 $ 40,499