Receivables and Related Allowance for Credit Losses - Unamortized Imputed Discount and Allowance for Credit Losses for Equipment Installment Plan Receivables (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 776	$ 799
Bad debt expense	760	259
Write-offs, net of recoveries	(665)	(356)
Change in imputed discount on short-term and long-term EIP receivables	146	109
Impact on the imputed discount from sales of EIP receivables	(107)	(104)
Allowance for credit losses and imputed discount, end of period	910	707
Accounts Receivable Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	146	194
Bad debt expense	305	127
Write-offs, net of recoveries	(290)	(192)
Allowance for credit losses and imputed discount, end of period	161	129
EIP Receivables Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	630	605
Bad debt expense	455	132
Write-offs, net of recoveries	(375)	(164)
Change in imputed discount on short-term and long-term EIP receivables	146	109
Impact on the imputed discount from sales of EIP receivables	(107)	(104)
Allowance for credit losses and imputed discount, end of period	$ 749	$ 578