Device Payment Plan Agreement and Wireless Service Receivables - Allowance for Credit Losses (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2025 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,315
Ending balance	1,431
Device payment plan agreement
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,315
Current period provision for expected credit losses	765
Write-offs charged against the allowance	(672)
Recoveries collected	23
Ending balance	1,431
Wireless Service Plan Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	240
Current period provision for expected credit losses	250
Write-offs charged against the allowance	(277)
Recoveries collected	27
Ending balance	$ 240