Note 13 - Retirement Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year	$ 563
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	10,871
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	225	$ 615
Postretirement Health Coverage [Member]
Defined Benefit Plan, Funded (Unfunded) Status of Plan, Total	(356)
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	24
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	22	15
401K [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	209	212
Defined Benefit Plan, Plan Assets, Contributions by Employer	192	721
Defined Benefit Plan, Funded (Unfunded) Status of Plan, Total	(3,628)	(3,264)
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	10,871	12,534	$ 11,393
Defined Benefit ACS Retirement Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	192	721
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	117
Defined Benefit ACS Retirement Plan [Member] | Other Noncurrent Liabilities [Member]
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position, Total	$ 3,628	$ 3,264