Note 1 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jan. 01, 2018
Income Tax Expense, Overstated Amount							$ 703
Net Income (Loss), Understated Amount							$ 703
Net Income (Loss) Per Share, Understated							$ 0.01
Income Tax Expense (Benefit), Total	$ 774	$ (112)	$ (422)		$ 2,080	$ (1,886)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	1,805	$ 2,069	284		7,276	(3,254)
Contract with Customer, Asset, Net, Current, Total								$ 6,898
Deferred Income Tax Liability from Contract Asset	1,960				1,960
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	(13)		$ 153		169	$ 461
Other Nonoperating Income (Expense) [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	(13)				169
Accounting Standards Update 2014-09 [Member]
Cumulative Effect on Retained Earnings, Net of Tax, Total					4,938
Reclassification of Net Periodic Pension Expense from Selling, General and Administrative to Other Income (Expense), Net [Member] | Three Months Ended September 30, 2018 [Member]
Prior Period Reclassification Adjustment					153
Reclassification of Net Periodic Pension Expense from Selling, General and Administrative to Other Income (Expense), Net [Member] | Nine Months Ended September 30, 2018 [Member]
Prior Period Reclassification Adjustment					461
Overstatement of Income Tax Benefit [Member]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 703				$ 703
Noncontrolling Interest [Member] | Quintillion Holdings, LLC [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage				50.00%
ACS Cable Systems LLC and Quintillion Holdings, LLC Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage				50.00%	50.00%