Receivables and Related Allowance for Credit Losses - Schedule of Equipment Installment Plan Receivables by Credit Category (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	$ 7,579	$ 8,060
Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	2,649
Originated in 2025	2,996
Originated prior to 2025	569
EIP receivables, net of unamortized imputed discount	6,214
Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	606
Originated in 2025	648
Originated prior to 2025	111
EIP receivables, net of unamortized imputed discount	1,365
Current - 30 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	7,392
Current - 30 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	2,611
Originated in 2025	2,954
Originated prior to 2025	558
EIP receivables, net of unamortized imputed discount	6,123
Current - 30 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	569
Originated in 2025	599
Originated prior to 2025	101
EIP receivables, net of unamortized imputed discount	1,269
31 - 60 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	85
31 - 60 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	23
Originated in 2025	16
Originated prior to 2025	4
EIP receivables, net of unamortized imputed discount	43
31 - 60 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	21
Originated in 2025	18
Originated prior to 2025	3
EIP receivables, net of unamortized imputed discount	42
61 - 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	54
61 - 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	10
Originated in 2025	13
Originated prior to 2025	3
EIP receivables, net of unamortized imputed discount	26
61 - 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	11
Originated in 2025	15
Originated prior to 2025	2
EIP receivables, net of unamortized imputed discount	28
More than 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	48
More than 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	5
Originated in 2025	13
Originated prior to 2025	4
EIP receivables, net of unamortized imputed discount	22
More than 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2026	5
Originated in 2025	16
Originated prior to 2025	5
EIP receivables, net of unamortized imputed discount	$ 26

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