Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Nature of Services and Products) (Details)

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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