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	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 934	$ 978	$ 776
Bad debt expense	1,192	898	1,026
Write-offs	(1,155)	(964)	(930)
Change in imputed discount on short-term and long-term EIP receivables	199	220	262
Impact on the imputed discount from sales of EIP receivables	(180)	(198)	(156)
Allowance for credit losses and imputed discount, end of period	990	934	978
Accounts Receivable Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	161	167	146
Bad debt expense	592	440	433
Write-offs	(577)	(446)	(412)
Allowance for credit losses and imputed discount, end of period	176	161	167
EIP Receivables Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	773	811	630
Bad debt expense	600	458	593
Write-offs	(578)	(518)	(518)
Change in imputed discount on short-term and long-term EIP receivables	199	220	262
Impact on the imputed discount from sales of EIP receivables	(180)	(198)	(156)
Allowance for credit losses and imputed discount, end of period	$ 814	$ 773	$ 811

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

12 Months Ended

Dec. 31, 2024

Dec. 31, 2023

Dec. 31, 2022

Financing Receivable, Allowance for Credit Loss [Roll Forward]

Allowance for credit losses and imputed discount, beginning of period

$ 934

$ 978

$ 776

Bad debt expense

1,192

898