| **Business and Summary of Significant Accounting Principles (Narratives) (Details) $ in Millions** | 9 Months Ended |        |        |
|----------------------------------------------------------------------------------------------------|----------------|--------|--------|
||
| **Business**                                                                                       |           |   |   |
| Year founded                                                                                       | 1979           |   |   |
| **Principles of Consolidation**                                                                    |           |   |   |
| Voting interests acquired                                                                          |           |   | 66.67% |
| Interests acquired from noncontrolling interest                                                    |           |   | 33.33% |
| Number of VIEs | entity                                                                            | 4              |   |   |
| **Accounts Receivable and Allowance for Doubtful Receivables**                                     |           |   |   |
| Period past due for write-off of trade accounts receivable                                         | 120 days       |   |   |
| Number of Installment Plan Payments                                                                | 12             |   |   |
| Accounting Standards Update 2015-03 [Member]                                                       |           |   |   |
| **New Accounting Pronouncements and Changes in Accounting Principles [Abstract]**                  |           |   |   |
| Deferred debt issuance costs | $                                                                   |           | $ 15.4 |   |
| Maximum [Member]                                                                                   |           |   |   |
| **Accounts Receivable and Allowance for Doubtful Receivables**                                     |           |   |   |
| Equipment Installment Plan Payment Term                                                            | 24 months      |   |   |

| X                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Business Acquisition, Percentage of Voting Interests Acquired from Noncontrolling Interest
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Equipment Installment Plan Payment Term
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General Business Information [Abstract]
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Number of Installment Plan Payments required for right to trade-in handset.
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Principles of Consolidation [Abstract]
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| - Definition
Number of consolidated variable interest entities
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of voting equity interests acquired at the acquisition date in the business combination.
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| - Definition
Amount, after accumulated amortization, of debt issuance costs classified as noncurrent. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.
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| - Definition
Threshold period past due for trade accounts receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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Year the entity was founded, in CCYY format.
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