Wireless Licenses, Goodwill and Other Intangible Assets - Composition of Other Intangible Assets, Net (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 35,042	$ 32,515
Accumulated Amortization	(23,913)	(21,458)
Net Amount	11,129	11,057
Customer lists
Finite-Lived Intangible Assets [Line Items]
Gross Amount	4,242	4,335
Accumulated Amortization	(2,629)	(2,193)
Net Amount	$ 1,613	2,142
Customer lists | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life for finite-lived intangible assets, years	5 years
Customer lists | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life for finite-lived intangible assets, years	13 years
Non-Network Internal-Use Software
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 28,136	25,524
Accumulated Amortization	(19,743)	(17,949)
Net Amount	$ 8,393	7,575
Non-Network Internal-Use Software | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life for finite-lived intangible assets, years	3 years
Non-Network Internal-Use Software | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life for finite-lived intangible assets, years	7 years
Other
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 2,664	2,656
Accumulated Amortization	(1,541)	(1,316)
Net Amount	$ 1,123	$ 1,340
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life for finite-lived intangible assets, years	4 years
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life for finite-lived intangible assets, years	25 years