Device Payment Plan Agreement and Wireless Service Receivables - Balance and Aging of Receivables (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	$ 21,303	$ 17,959
Device payment plan agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	20,945
Device payment plan agreement | Unbilled | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	19,777
Device payment plan agreement | Billed | Financial Asset, Not Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	963
Device payment plan agreement | Billed | Financial Asset, Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Device payment plan agreement receivables, gross	$ 205