Device Payment Plan Agreement and Wireless Service Receivables - Allowance for Credit Losses (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2025 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,315
Ending balance	1,348
Device payment plan agreement
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,315
Current period provision for expected credit losses	393
Write-offs charged against the allowance	(371)
Recoveries collected	11
Ending balance	1,348
Wireless Service Plan Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	240
Current period provision for expected credit losses	136
Write-offs charged against the allowance	(144)
Recoveries collected	13
Ending balance	$ 245