Note 17 - Components of Accumulated Other Comprehensive Income (Loss) - Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Component of Accumulated Other Comprehensive Income (Loss)
Reclassification adjustment for gain included in net income, tax		$ (4)	$ (65)	$ (12)
Realized gain on available-for-sale securities, net of tax, reclassified out of accumulated other comprehensive income (loss)		(6)	(121)	(21)
Income tax benefit		38	38	38
Amortization of defined benefit pension items, net of tax, reclassified out of accumulated other comprehensive income (loss)		(71)	(72)	(72)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Component of Accumulated Other Comprehensive Income (Loss)
Realized securities gain, net		(10)	(186)	(33)
Reclassification adjustment for gain included in net income, tax		(4)	(65)	(12)
Realized gain on available-for-sale securities, net of tax, reclassified out of accumulated other comprehensive income (loss)		(6)	(121)	(21)
Prior service costs(1)	[1]	(109)	(110)	(110)
Income tax benefit		(38)	(38)	(38)
Amortization of defined benefit pension items, net of tax, reclassified out of accumulated other comprehensive income (loss)		$ (71)	$ (72)	$ (72)

[1] This accumulated other comprehensive income (loss) component is included in the computation of net periodic benefit cost. (For additional information, see Note 8, "Employee Benefit Plans.")