Receivables and Related Allowance for Credit Losses - Schedule of Equipment Installment Plan Receivables by Credit Category (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	$ 7,893	$ 8,060
Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	1,504
Originated in 2025	3,923
Originated prior to 2025	1,044
EIP receivables, net of unamortized imputed discount	6,471
Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	358
Originated in 2025	852
Originated prior to 2025	212
EIP receivables, net of unamortized imputed discount	1,422
Current - 30 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	7,710
Current - 30 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	1,489
Originated in 2025	3,864
Originated prior to 2025	1,026
EIP receivables, net of unamortized imputed discount	6,379
Current - 30 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	347
Originated in 2025	789
Originated prior to 2025	195
EIP receivables, net of unamortized imputed discount	1,331
31 - 60 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	81
31 - 60 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	13
Originated in 2025	24
Originated prior to 2025	6
EIP receivables, net of unamortized imputed discount	43
31 - 60 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	10
Originated in 2025	23
Originated prior to 2025	5
EIP receivables, net of unamortized imputed discount	38
61 - 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	52
61 - 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	2
Originated in 2025	19
Originated prior to 2025	5
EIP receivables, net of unamortized imputed discount	26
61 - 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	1
Originated in 2025	20
Originated prior to 2025	5
EIP receivables, net of unamortized imputed discount	26
More than 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	50
More than 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	0
Originated in 2025	16
Originated prior to 2025	7
EIP receivables, net of unamortized imputed discount	23
More than 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	0
Originated in 2025	20
Originated prior to 2025	7
EIP receivables, net of unamortized imputed discount	$ 27

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