| **Industry Segments Data (Reportable segment revenues) (Details) (USD $)In Thousands, unless otherwise specified** | 3 Months Ended | 9 Months Ended |
|--------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Segment Reporting Information [Line Items]**                                                                     |           |           |   |   |
| Intersegment                                                                                                       | $ 1,153        | $ 1,386        | $ 4,583 | $ 4,324 |
| External revenues                                                                                                  | 178,494        | 177,703        | 526,505 | 510,569 |
| Total Revenues                                                                                                     | 179,647        | 179,089        | 531,088 | 514,893 |
| Adjusted EBITDA                                                                                                    | 59,449         | 63,101         | 173,699 | 171,380 |
| Consumer [Member]                                                                                                  |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                     |           |           |   |   |
| Intersegment                                                                                                       | (356)          | 0              | 0 | 0 |
| External revenues                                                                                                  | 86,807         | 89,267         | 263,114 | 266,238 |
| Total Revenues                                                                                                     | 86,451         | 89,267         | 263,114 | 266,238 |
| Adjusted EBITDA                                                                                                    | 20,916         | 30,373         | 69,718 | 87,024 |
| Network Access [Member]                                                                                            |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                     |           |           |   |   |
| Intersegment                                                                                                       | 45             | 0              | 210 | 0 |
| External revenues                                                                                                  | 27,475         | 29,467         | 78,680 | 79,715 |
| Total Revenues                                                                                                     | 27,520         | 29,467         | 78,890 | 79,715 |
| Adjusted EBITDA                                                                                                    | 15,383         | 13,729         | 41,235 | 37,953 |
| Commercial [Member]                                                                                                |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                     |           |           |   |   |
| Intersegment                                                                                                       | 1,417          | 1,382          | 4,228 | 4,207 |
| External revenues                                                                                                  | 36,208         | 35,572         | 105,015 | 101,617 |
| Total Revenues                                                                                                     | 37,625         | 36,954         | 109,243 | 105,824 |
| Adjusted EBITDA                                                                                                    | 9,892          | 9,117          | 26,958 | 23,180 |
| Managed Broadband [Member]                                                                                         |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                     |           |           |   |   |
| Intersegment                                                                                                       | 0              | 0              | 0 | 0 |
| External revenues                                                                                                  | 22,685         | 17,407         | 63,431 | 46,041 |
| Total Revenues                                                                                                     | 22,685         | 17,407         | 63,431 | 46,041 |
| Adjusted EBITDA                                                                                                    | 12,249         | 8,844          | 32,561 | 20,264 |
| Regulated Operations [Member]                                                                                      |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                     |           |           |   |   |
| Intersegment                                                                                                       | 47             | 4              | 145 | 117 |
| External revenues                                                                                                  | 5,319          | 5,990          | 16,265 | 16,958 |
| Total Revenues                                                                                                     | 5,366          | 5,994          | 16,410 | 17,075 |
| Adjusted EBITDA                                                                                                    | $ 1,009        | $ 1,038        | $ 3,227 | $ 2,959 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents Company's specificly defined non-GAAP measure - the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, accretion expense, non-cash contribution expense and noncontrolling interest.
+ References
No definition available.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Revenues arising from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, such as pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's' management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of total revenue for the reportable segments, including revenue from external customers, transactions with other operating segments of the same entity, and (gross) interest revenue. All considered to be "operating revenue" for purposes of the taxonomy.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 131 -Paragraph 27 -Subparagraph a, b, c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (a),(b),(c) -URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8736-108599
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