Device Payment Plan Agreement and Wireless Service Receivables - Allowance for Credit Losses (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,151
Ending balance	1,315
Device payment plan agreement
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,151
Current period provision for expected credit losses	1,585
Write-offs charged against the allowance	(1,458)
Recoveries collected	37
Ending balance	1,315
Wireless service
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	213
Current period provision for expected credit losses	538
Write-offs charged against the allowance	(557)
Recoveries collected	46
Ending balance	$ 240