Wireless Licenses, Goodwill and Other Intangible Assets - Changes in Carrying Value of Goodwill (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Goodwill [Roll Forward]
Beginning balance	$ 22,841
Reclassifications, adjustments and other	1
Ending balance	22,842
Goodwill accumulated impairment charge		$ 5,800
Operating Segments | Consumer
Goodwill [Roll Forward]
Beginning balance	21,177
Reclassifications, adjustments and other	0
Ending balance	21,177
Operating Segments | Business
Goodwill [Roll Forward]
Beginning balance	1,664
Reclassifications, adjustments and other	1
Ending balance	$ 1,665