Wireless Licenses, Goodwill and Other Intangible Assets - Changes in Carrying Value of Goodwill (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2026	Dec. 31, 2025
Goodwill [Roll Forward]
Beginning balance	$ 22,841
Acquisitions	7,888
Ending balance	30,729
Goodwill accumulated impairment charge	5,800	$ 5,800
Operating Segments \| Consumer
Goodwill [Roll Forward]
Beginning balance	21,177
Acquisitions	6,080
Ending balance	27,257
Operating Segments \| Business
Goodwill [Roll Forward]
Beginning balance	1,664
Acquisitions	1,808
Ending balance	$ 3,472

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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+ Details