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	3 Months Ended
Mar. 31, 2026	Mar. 31, 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	426	323
Write-offs	(410)	(324)
Change in imputed discount on short-term and long-term EIP receivables	42	36
Impact on the imputed discount from sales of EIP receivables	(48)	(42)
Allowance for credit losses and imputed discount, end of period	1,182	983
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	184	165
Write-offs	(193)	(166)
Allowance for credit losses and imputed discount, end of period	217	175
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	242	158
Write-offs	(217)	(158)
Change in imputed discount on short-term and long-term EIP receivables	42	36
Impact on the imputed discount from sales of EIP receivables	(48)	(42)
Allowance for credit losses and imputed discount, end of period	$ 965	$ 808

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

3 Months Ended

Mar. 31, 2026

Mar. 31, 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

426

323

Write-offs

(410)