Note 3 - Joint Venture - Certain Financial Information About the Joint Venture Included On the Company's Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, plant and equipment, net of accumulated depreciation of $211 and $112	$ 366,113	$ 366,849
ACS Cable Systems LLC and Quintillion Holdings, LLC Joint Venture [Member]
Cash	190	67
Property, plant and equipment, net of accumulated depreciation of $211 and $112	$ 1,930	$ 2,029