Equipment Installment Plans - Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Allowance for credit losses
Allowance for credit losses, beginning of year	$ 96
Allowance for credit losses, end of year	90	$ 96
Equipment Installment Plan Receivable
Allowance for credit losses
Write-offs, net of recoveries, originated in 2021	13
Write-offs, net of recoveries, originated in 2022	45
Write-offs, net of recoveries, originated in 2023	17
Write-offs, net of recoveries, Total	75	76
Allowance for credit losses, beginning of year	96	72
Bad debts expense	69	100
Write-offs, net of recoveries	(75)	(76)
Allowance for credit losses, end of year	$ 90	$ 96