Device Payment Plan Agreement and Wireless Service Receivables - Balance and Aging of Receivables (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, at amortized cost	$ 17,079	$ 19,493
Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, at amortized cost	16,650
Device payment plan agreement | Unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	15,720
Device payment plan agreement | Billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	832
Past due	$ 98