Note 4 - Revenues - Revenues by Product Line (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019	[1]	Sep. 30, 2019	[2]	Jun. 30, 2019	[2]	Mar. 31, 2019	[3]	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues	$ 318,751		$ 284,991		$ 285,650		$ 278,605		$ 269,852	$ 268,268	$ 268,414	$ 265,761	$ 1,167,997	$ 1,072,295	$ 959,956
Data [Member]
Revenues													547,240	492,816	416,355
Video [Member]
Revenues													335,190	343,384	332,536
Voice [Member]
Revenues													43,521	41,278	43,733
Business Services [Member]
Revenues													204,500	155,952	131,082
Product and Service, Other [Member]
Revenues													$ 37,546	$ 38,865	$ 36,250

[1] Includes Clearwave and Fidelity operations.

[2] Includes Clearwave operations.

[3] Includes Clearwave operations beginning January 8, 2019.