Note 12 - Pension and Other Postretirement Benefit Plans - Amounts Recognized In Accumulated Other Comprehensive Income, On a Pre-tax Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Actuarial loss (gain)	$ 8,151	$ 9,323	$ 11,580
Prior Service cost (credit)	(401)	(447)	(492)
Total	7,750	8,876	11,088
Retirement Plan [Member]
Net Actuarial loss (gain)	8,055	8,589	9,938
Prior Service cost (credit)	0	0	0
Total	8,055	8,589	9,938
Other Postretirement Benefit Plan [Member]
Net Actuarial loss (gain)	636	1,296	2,130
Prior Service cost (credit)	(453)	(538)	(623)
Total	183	758	1,507
Directors' Plan [Member]
Net Actuarial loss (gain)	(540)	(562)	(488)
Prior Service cost (credit)	52	91	131
Total	$ (488)	$ (471)	$ (357)