Receivables and Expected Credit Losses - Gross EIP Receivables by Credit Category (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	$ 6,603	$ 5,888
Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	2,193
Originated in 2020	1,630
Originated prior to 2020	226
Total EIP Receivables, net of unamortized imputed discounts	4,049
Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	1,461
Originated in 2020	985
Originated prior to 2020	108
Total EIP Receivables, net of unamortized imputed discounts	2,554
Current - 30 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	6,501
Current - 30 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	2,177
Originated in 2020	1,613
Originated prior to 2020	221
Total EIP Receivables, net of unamortized imputed discounts	4,011
Current - 30 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	1,436
Originated in 2020	954
Originated prior to 2020	100
Total EIP Receivables, net of unamortized imputed discounts	2,490
31 - 60 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	63
31 - 60 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	12
Originated in 2020	11
Originated prior to 2020	2
Total EIP Receivables, net of unamortized imputed discounts	25
31 - 60 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	18
Originated in 2020	17
Originated prior to 2020	3
Total EIP Receivables, net of unamortized imputed discounts	38
61 - 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	19
61 - 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	2
Originated in 2020	3
Originated prior to 2020	1
Total EIP Receivables, net of unamortized imputed discounts	6
61 - 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	5
Originated in 2020	7
Originated prior to 2020	1
Total EIP Receivables, net of unamortized imputed discounts	13
More than 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	20
More than 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	2
Originated in 2020	3
Originated prior to 2020	2
Total EIP Receivables, net of unamortized imputed discounts	7
More than 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2021	2
Originated in 2020	7
Originated prior to 2020	4
Total EIP Receivables, net of unamortized imputed discounts	$ 13

Financing Receivable, Originated, More than Two Years before Current Fiscal Year

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- Definition

Amount of financing receivable originated in current fiscal year.

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+ References

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- Definition

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

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