Note 2 - Accumulated Other Comprehensive Income - Amounts Reclassified Out of Accumulated Other Comprehensive Income by Component (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, 2014
Investment securities gains (losses), net   $ 3,800             $ 3,998 $ 171 $ (63)
Income tax benefit (expense) $ (931) (1,560) $ (1,235) $ (2,715) $ (1,080) $ (1,439) $ (1,369) $ (1,405) (6,441) (5,293) (6,099)
Net income 2,545 4,324 3,556 6,180 3,584 3,832 3,502 4,074 16,605 14,992 16,459
Salaries and employee benefits                 (32,296) (32,008) (29,763)
Total before tax                 23,046 20,285 22,558
Income tax expense $ 931 $ 1,560 $ 1,235 $ 2,715 $ 1,080 $ 1,439 $ 1,369 $ 1,405 6,441 5,293 6,099
Reclassification out of Accumulated Other Comprehensive Income [Member]                      
Net income                 2,563 51 (132)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]                      
Investment securities gains (losses), net                 3,998 171 (63)
Income tax benefit (expense)                 (1,399) (60) 22
Net income                 2,599 111 (41)
Total before tax                 (55) (93) (140)
Income tax expense                 1,399 60 (22)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]                      
Salaries and employee benefits                 (50) (51) (207)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]                      
Salaries and employee benefits                 (5) (42) 67
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]                      
Income tax benefit (expense)                 (19) (33) (49)
Net income                 (36) (60) (91)
Income tax expense                 $ 19 $ 33 $ 49