Note 2 - Revenue - Revenue Accounted for In Accordance With ASC 606, By Timing of Revenue Recognition (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Total revenue		$ 52,623	$ 50,925	$ 154,350	$ 148,898
Transferred over Time [Member]
Total revenue		45,859	44,978	135,717	131,028
Transferred at Point in Time [Member]
Total revenue		2,102	942	4,708	2,830
Regulatory Revenue, Access [Member]
Total revenue	[1]	$ 4,662	$ 5,005	$ 13,925	$ 15,040

[1] Includes customer ordered service and special access.