Note 12 - Pension and Other Postretirement Benefit Plans - The Resulting Net Periodic Postretirement Expense Consisted of the Following Components for the Year (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest cost	$ 902	$ 889
Postretirement Plans [Member]
Service cost	359	382	$ 358
Interest cost	320	300	253
Amortization of unrecognized loss	47	119	0
Amortization of past service credit	(85)	(85)	(85)
Net pension expense	641	716	526
Current year actuarial (gain) loss	(613)	(715)	1,925
Amortization of actuarial loss	(47)	(119)	0
Amortization of prior service credit	85	85	85
Total recognized in other comprehensive income	(575)	(749)	2,010
Total recognized in net postretirement expense and other comprehensive income	$ 66	$ (33)	$ 2,536