Note 18 - Business Segments - Service and Product Revenues From External Customers (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Revenues	$ 58,689	$ 58,229	$ 59,578	$ 55,972	$ 54,935	$ 56,703	$ 58,536	$ 56,731	$ 232,468	$ 226,905
Wireline Revenue [Member] | Business and Wholesale Revenue [Member]
Revenues									144,594	139,120
Wireline Revenue [Member] | Business and Wholesale Revenue [Member] | Business Broadband [Member]
Revenues									60,934	61,559
Wireline Revenue [Member] | Business and Wholesale Revenue [Member] | Business Voice and Other [Member]
Revenues									28,429	26,508
Wireline Revenue [Member] | Business and Wholesale Revenue [Member] | Managed IT Services [Member]
Revenues									5,742	4,293
Wireline Revenue [Member] | Business and Wholesale Revenue [Member] | Equipment Sales and Installations [Member]
Revenues									5,127	4,412
Wireline Revenue [Member] | Business and Wholesale Revenue [Member] | Wholesale Broadband [Member]
Revenues									38,362	36,081
Wireline Revenue [Member] | Business and Wholesale Revenue [Member] | Wholesale Voice and Other [Member]
Revenues									6,000	6,267
Wireline Revenue [Member] | Consumer Revenue [Member]
Revenues									37,302	37,117
Wireline Revenue [Member] | Consumer Revenue [Member] | Broadband [Member]
Revenues									26,144	25,441
Wireline Revenue [Member] | Consumer Revenue [Member] | Voice and Other [Member]
Revenues									11,158	11,676
Wireline Revenue [Member] | Business, Wholesale and Consumer Revenue [Member]
Revenues									181,896	176,237
Wireline Revenue [Member] | Regulatory Revenue [Member]
Revenues									50,572	50,668
Wireline Revenue [Member] | Regulatory Revenue [Member] | Access [Member]
Revenues									30,878	30,974
Wireline Revenue [Member] | Regulatory Revenue [Member] | High Cost Support [Member]
Revenues									$ 19,694	$ 19,694