Equipment Installment Plans - EIP Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, gross	$ 1,151	$ 1,211
Allowance for credit losses	(90)	(96)
Equipment installment plan receivables, net	1,061	1,115
Accounts receivable — Customers and agents (Current portion)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, net	577	646
Other assets and deferred charges (Non-current portion)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, net	$ 484	$ 469