Receivables and Related Allowance for Credit Losses - Schedule of Equipment Installment Plan Receivables by Credit Category (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	$ 6,878	$ 6,766
Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	4,244
Originated in 2023	1,133
Originated prior to 2023	19
EIP receivables, net of unamortized imputed discount	5,396
Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	1,172
Originated in 2023	303
Originated prior to 2023	7
EIP receivables, net of unamortized imputed discount	1,482
Current - 30 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	6,747
Current - 30 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	4,213
Originated in 2023	1,118
Originated prior to 2023	18
EIP receivables, net of unamortized imputed discount	5,349
Current - 30 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	1,109
Originated in 2023	283
Originated prior to 2023	6
EIP receivables, net of unamortized imputed discount	1,398
31 - 60 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	55
31 - 60 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	15
Originated in 2023	6
Originated prior to 2023	0
EIP receivables, net of unamortized imputed discount	21
31 - 60 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	27
Originated in 2023	7
Originated prior to 2023	0
EIP receivables, net of unamortized imputed discount	34
61 - 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	38
61 - 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	9
Originated in 2023	4
Originated prior to 2023	0
EIP receivables, net of unamortized imputed discount	13
61 - 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	19
Originated in 2023	6
Originated prior to 2023	0
EIP receivables, net of unamortized imputed discount	25
More than 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	38
More than 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2024	7
Originated in 2023	5
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	17
Originated in 2023	7
Originated prior to 2023	1
EIP receivables, net of unamortized imputed discount	$ 25

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