Device Payment Plan Agreement and Wireless Service Receivables - Balance and Aging of Receivables (Detail) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	$ 31,491	$ 31,308
Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	30,478
Unbilled | Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	28,980
Billed | Current | Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	1,189
Billed | Past due | Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	$ 309