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