Note 2 - Revenue - Revenue Accounted for In Accordance With ASC 606, By Timing of Revenue Recognition (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Total revenue		$ 50,224	$ 49,042
Transferred over Time [Member]
Total revenue		44,119	43,046
Transferred at Point in Time [Member]
Total revenue		1,414	880
Regulatory Revenue, Access [Member]
Total revenue	[1]	$ 4,691	$ 5,116

[1] Includes customer ordered service and special access.