Device Payment Plan Agreement and Wireless Service Receivables - Allowance for Credit Losses (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 940
Adjusted opening balance, January 1, 2020	759
Ending balance	759
Device payment plan agreement
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	940
Adjusted opening balance, January 1, 2020	759
Current period provision for expected credit losses	434
Write-offs charged against the allowance	(653)
Recoveries collected	38
Ending balance	759
Wireless Service Plan Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	262
Adjusted opening balance, January 1, 2020	130
Current period provision for expected credit losses	185
Write-offs charged against the allowance	(383)
Recoveries collected	66
Ending balance	$ 130