Receivables and Related Allowance for Credit Losses - Schedule of Unamortized Imputed Discount and Allowance for Credit Losses for Equipment Installment Plan Receivables (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 1,172	$ 990
Bad debt expense	824	588
Write-offs	(809)	(592)
Change in imputed discount on short-term and long-term EIP receivables	80	50
Impact on the imputed discount from sales of EIP receivables	(94)	(88)
Allowance for credit losses and imputed discount, end of period	1,173	948
Accounts Receivable Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	226	176
Bad debt expense	374	290
Write-offs	(384)	(294)
Allowance for credit losses and imputed discount, end of period	216	172
EIP Receivables Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	946	814
Bad debt expense	450	298
Write-offs	(425)	(298)
Change in imputed discount on short-term and long-term EIP receivables	80	50
Impact on the imputed discount from sales of EIP receivables	(94)	(88)
Allowance for credit losses and imputed discount, end of period	$ 957	$ 776

Receivables and Related Allowance for Credit Losses - Schedule of Unamortized Imputed Discount and Allowance for Credit Losses for Equipment Installment Plan Receivables (Details) - USD ($)
$ in Millions

6 Months Ended

Jun. 30, 2026

Jun. 30, 2025

Financing Receivable, Allowance for Credit Loss [Roll Forward]

Allowance for credit losses and imputed discount, beginning of period

$ 1,172

$ 990

Bad debt expense

824

588

Write-offs

(809)