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	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 934	$ 978
Bad debt expense	836	663
Write-offs	(835)	(704)
Change in imputed discount on short-term and long-term EIP receivables	87	120
Impact on the imputed discount from sales of EIP receivables	(155)	(151)
Allowance for credit losses and imputed discount, end of period	867	906
Accounts Receivable Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	161	167
Bad debt expense	409	322
Write-offs	(408)	(323)
Allowance for credit losses and imputed discount, end of period	162	166
EIP Receivables Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	773	811
Bad debt expense	427	341
Write-offs	(427)	(381)
Change in imputed discount on short-term and long-term EIP receivables	87	120
Impact on the imputed discount from sales of EIP receivables	(155)	(151)
Allowance for credit losses and imputed discount, end of period	$ 705	$ 740

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

9 Months Ended

Sep. 30, 2024

Sep. 30, 2023

Financing Receivable, Allowance for Credit Loss [Roll Forward]

Allowance for credit losses and imputed discount, beginning of period

$ 934

$ 978

Bad debt expense

836

663

Write-offs

(835)