Equipment Installment Plan Receivables, Gross Receivables by Credit Category (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables, gross	$ 628	$ 381
Unbilled
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables	591	354
Billed
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables	25	18
Equipment installment plan receivables, past due	12	9
Lower Risk
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables, gross	586	368
Lower Risk \| Unbilled
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables	553	343
Lower Risk \| Billed
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables	23	17
Equipment installment plan receivables, past due	10	8
Higher Risk
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables, gross	42	13
Higher Risk \| Unbilled
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables	38	11
Higher Risk \| Billed
Financing Receivable, Recorded Investment [Line Items]
Equipment installment plan receivables	2	1
Equipment installment plan receivables, past due	$ 2	$ 1

Financing receivables that are current.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

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+ References

No definition available.

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- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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