Note 2 - Revenue Recognition - Disaggregation of Revenue (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
Revenue Accounted for Under ASC 606										$ 199,210
Revenue Accounted for Under Other Guidance										33,258
Operating revenues		$ 58,689	$ 58,229	$ 59,578	$ 55,972	$ 54,935	$ 56,703	$ 58,536	$ 56,731	232,468	$ 226,905
Business and Wholesale Revenue, Business Broadband [Member]
Revenue Accounted for Under ASC 606										60,697
Revenue Accounted for Under Other Guidance
Operating revenues										60,697
Business and Wholesale Revenue, Business Voice and Other [Member]
Revenue Accounted for Under ASC 606										28,429
Revenue Accounted for Under Other Guidance
Operating revenues										28,429
Business and Wholesale Revenue, Managed IT Services [Member]
Revenue Accounted for Under ASC 606										5,742
Revenue Accounted for Under Other Guidance
Operating revenues										5,742
Business and Wholesale Revenue, Equipment Sales and Installations [Member]
Revenue Accounted for Under ASC 606										5,127
Revenue Accounted for Under Other Guidance
Operating revenues										5,127
Business and Wholesale Revenue, Wholesale Broadband [Member]
Revenue Accounted for Under ASC 606										31,931
Revenue Accounted for Under Other Guidance
Operating revenues										31,931
Business and Wholesale Revenue, Wholesale Voice and Other [Member]
Revenue Accounted for Under ASC 606										6,000
Revenue Accounted for Under Other Guidance
Operating revenues										6,000
Business and Wholesale Revenue, Operating Leases and Other Deferred Revenue [Member]
Revenue Accounted for Under ASC 606
Revenue Accounted for Under Other Guidance										6,668
Operating revenues										6,668
Business and Wholesale Revenue [Member]
Revenue Accounted for Under ASC 606										137,926
Revenue Accounted for Under Other Guidance										6,668
Operating revenues										144,594
Consumer Revenue, Broadband [Member]
Revenue Accounted for Under ASC 606										26,144
Revenue Accounted for Under Other Guidance
Operating revenues										26,144
Consumer Revenue, Voice and Other [Member]
Revenue Accounted for Under ASC 606										11,158
Revenue Accounted for Under Other Guidance
Operating revenues										11,158
Consumer Revenue [Member]
Revenue Accounted for Under ASC 606										37,302
Revenue Accounted for Under Other Guidance
Operating revenues										37,302
Regulatory Revenue, Access, Including Customer Ordered Service and Special Access [Member]
Revenue Accounted for Under ASC 606	[1]									23,982
Revenue Accounted for Under Other Guidance	[1]
Operating revenues	[1]									23,982
Regulatory Revenue, Access, Including Carrier of Last Resort and Carrier Common Line [Member]
Revenue Accounted for Under ASC 606	[2]
Revenue Accounted for Under Other Guidance	[2]									6,896
Operating revenues	[2]									6,896
Regulatory, High-cost Support [Member]
Revenue Accounted for Under ASC 606
Revenue Accounted for Under Other Guidance										19,694
Operating revenues										19,694
Regulatory Revenue [Member]
Revenue Accounted for Under ASC 606										23,982
Revenue Accounted for Under Other Guidance										26,590
Operating revenues										$ 50,572

[1] Includes customer ordered service and special access.

[2] Includes carrier of last resort and carrier common line.