Device Payment Plan Agreement and Wireless Service Receivables - Balance and Aging of Receivables (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	$ 30,805	$ 31,308
Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	29,829
Unbilled | Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	28,405
Billed | Current | Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	1,136
Billed | Past due | Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	$ 288