Summary of Significant Accounting Policies (Nature of Services and Products) (Details)	12 Months Ended
Dec. 31, 2018 payment
Certain Wireless Devices
Disaggregation of Revenue [Line Items]
Equipment installment plan period	24 months
Trade-In Equipment
Disaggregation of Revenue [Line Items]
Number of installment plan payments	12

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration