Note 12 - Pension and Other Postretirement Benefit Plans - Assumptions Used to Determine Benefit Obligations and Periodic Pension Expense (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Weighted average discount rate	4.06%	3.76%	4.60%
Rate of increase in future compensation levels	0.00%	0.00%	0.00%
Directors' Plan [Member]
Weighted average discount rate for the benefit obligation	3.88%	4.06%	3.76%
Weighted average discount rate	4.06%	3.76%	4.60%
Rate of increase in future compensation levels	0.00%	0.00%	0.00%