Equipment Installment Plans - Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Allowance for credit losses
Allowance for credit losses, beginning of period	$ 72
Allowance for credit losses, end of period	73
Equipment Installment Plan Receivable
Allowance for credit losses
Allowance for credit losses, beginning of period	72	$ 78
Bad debts expense	17	3
Write-offs, net of recoveries	(16)	(9)
Allowance for credit losses, end of period	$ 73	$ 72