Receivables and Related Allowance for Credit Losses - Schedule of Equipment Installment Plan Receivables by Credit Category (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	$ 5,615	$ 6,766
Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	2,830
Originated in 2023	1,434
Originated prior to 2023	98
EIP receivables, net of unamortized imputed discount	4,362
Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	820
Originated in 2023	397
Originated prior to 2023	36
EIP receivables, net of unamortized imputed discount	1,253
Current - 30 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	5,499
Current - 30 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	2,809
Originated in 2023	1,417
Originated prior to 2023	95
EIP receivables, net of unamortized imputed discount	4,321
Current - 30 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	776
Originated in 2023	369
Originated prior to 2023	33
EIP receivables, net of unamortized imputed discount	1,178
31 - 60 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	45
31 - 60 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	9
Originated in 2023	6
Originated prior to 2023	1
EIP receivables, net of unamortized imputed discount	16
31 - 60 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	19
Originated in 2023	9
Originated prior to 2023	1
EIP receivables, net of unamortized imputed discount	29
61 - 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	35
61 - 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	6
Originated in 2023	5
Originated prior to 2023	1
EIP receivables, net of unamortized imputed discount	12
61 - 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	14
Originated in 2023	8
Originated prior to 2023	1
EIP receivables, net of unamortized imputed discount	23
More than 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	36
More than 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	6
Originated in 2023	6
Originated prior to 2023	1
EIP receivables, net of unamortized imputed discount	13
More than 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	11
Originated in 2023	11
Originated prior to 2023	1
EIP receivables, net of unamortized imputed discount	$ 23

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