Receivables and Related Allowance for Credit Losses - Unamortized Imputed Discount and Allowance for Credit Losses for Equipment Installment Plan Receivables (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 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	521	154
Write-offs, net of recoveries	(410)	(251)
Change in imputed discount on short-term and long-term EIP receivables	75	91
Impact on the imputed discount from sales of EIP receivables	(63)	(73)
Allowance for credit losses and imputed discount, end of period	899	720
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	201	76
Write-offs, net of recoveries	(170)	(147)
Allowance for credit losses and imputed discount, end of period	177	123
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	320	78
Write-offs, net of recoveries	(240)	(104)
Change in imputed discount on short-term and long-term EIP receivables	75	91
Impact on the imputed discount from sales of EIP receivables	(63)	(73)
Allowance for credit losses and imputed discount, end of period	$ 722	$ 597