| **Industry Segments Data (Reconciliation of Reportable Segment Adjusted EBITDA) (Details) - USD ($) $ in Thousands** | 3 Months Ended | 12 Months Ended |
|----------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
||
| **Segment Reporting [Abstract]**                                                                                     |           |            |   |   |   |   |   |   |   |   |   |
| Income (loss) before income taxes                                                                                    |           |            |   |   |   |   |   |   | $ 1,069 | $ (27,713) | $ 69,273 |
| Plus other expense, net                                                                                              |           |            |   |   |   |   |   |   | 78,034 | 133,924 | 74,289 |
| Consolidated operating income                                                                                        | $ 13,185       | $ 26,368        | $ 19,531 | $ 20,019 | $ 20,794 | $ 45,473 | $ 39,203 | $ 741 | 79,103 | 106,211 | 143,562 |
| Plus depreciation and amortization expense                                                                           |           |            |   |   |   |   |   |   | 193,775 | 181,767 | 170,285 |
| Plus share-based compensation expense                                                                                |           |            |   |   |   |   |   |   | 11,043 | 10,902 | 8,392 |
| Plus imputed interest on financed devices                                                                            |           |            |   |   |   |   |   |   | 2,557 | 751 | 0 |
| Plus accretion expense                                                                                               |           |            |   |   |   |   |   |   | 1,229 | 1,121 | 1,249 |
| Plus software impairment charge                                                                                      |           |            |   |   |   |   |   |   | 0 | 29,839 | 0 |
| Other                                                                                                                |           |            |   |   |   |   |   |   | 337 | (240) | (372) |
| Adjusted EBITDA                                                                                                      |           |            |   |   |   |   |   |   | $ 288,044 | $ 330,351 | $ 323,116 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Earnings plus imputed interest on financed devices before:Net interest expense,Income taxes,Depreciation and amortization expense,Loss on extinguishment of debt,Software impairment charge,Derivative instrument unrealized income (loss),Share-based compensation expense,Accretion expense,Loss attributable to non-controlling interest resulting from NMTC transactions,Gains and impairment losses on equity and cost method investments,Gain recorded for adjusting to fair value assets that were included as consideration paid to acquire a fiber system, andOther non-cash adjustments.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Imputed interest income from receivables with financing component.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The expense charged against earnings to eliminate the capitalized costs of projects that have been terminated during the reporting period, which is added back to net income when calculating cash provided by (used in) operations using the indirect method.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The net result for the period of deducting operating expenses from operating revenues.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The net amount of other operating income and expenses, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operations.
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No definition available.
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| - References
No definition available.
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| - Definition
The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.
+ References
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