Receivables and Related Allowance for Credit Losses - Schedule of Equipment Installment Plan Receivables by Credit Category (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	$ 8,060	$ 6,878
Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	4,998
Originated in 2024	1,522
Originated prior to 2024	105
EIP receivables, net of unamortized imputed discount	6,625
Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	1,078
Originated in 2024	347
Originated prior to 2024	10
EIP receivables, net of unamortized imputed discount	1,435
Current - 30 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	7,875
Current - 30 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	4,936
Originated in 2024	1,499
Originated prior to 2024	102
EIP receivables, net of unamortized imputed discount	6,537
Current - 30 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	1,011
Originated in 2024	319
Originated prior to 2024	8
EIP receivables, net of unamortized imputed discount	1,338
31 - 60 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	86
31 - 60 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	35
Originated in 2024	9
Originated prior to 2024	1
EIP receivables, net of unamortized imputed discount	45
31 - 60 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	31
Originated in 2024	10
Originated prior to 2024	0
EIP receivables, net of unamortized imputed discount	41
61 - 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
EIP receivables, net of unamortized imputed discount	53
61 - 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	17
Originated in 2024	7
Originated prior to 2024	1
EIP receivables, net of unamortized imputed discount	25
61 - 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	19
Originated in 2024	8
Originated prior to 2024	1
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	46
More than 90 days past due \| Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	10
Originated in 2024	7
Originated prior to 2024	1
EIP receivables, net of unamortized imputed discount	18
More than 90 days past due \| Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2025	17
Originated in 2024	10
Originated prior to 2024	1
EIP receivables, net of unamortized imputed discount	$ 28

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