Receivables and Allowance for Credit Losses - EIP Receivables (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) class segment	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio segments \| segment	2
Customer classes \| class	2
EIP receivables, gross	$ 4,582	$ 4,534
Unamortized imputed discount	(299)	(330)
EIP receivables, net of unamortized imputed discount	4,283	4,204
Allowance for credit losses	(100)	(119)
Equipment installment plan receivables, net	4,183	4,085
Equipment installment plan receivables, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, net	2,600	2,538
Equipment installment plan receivables due after one year, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, net	$ 1,583	$ 1,547

Number of Customer Classes

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Number of Portfolio Segments

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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.

+ References

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- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References

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- Definition

Amount, before allowance for credit loss, of financing receivable.

+ References

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Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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- Definition

Disclosure of the unamortized amount of the discount on the note or receivable which is deducted from the face amount of the receivable or loan. The discount or premium is the difference between the present value and the face amount.

+ References

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- Definition

The receivable or note face amount less the unamortized discount or premium.

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