Wireless Licenses, Goodwill and Other Intangible Assets - Composition of Other Intangible Assets, Net (Detail) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 35,977	$ 35,042
Accumulated Amortization	(25,342)	(23,913)
Net Amount	10,635	11,129
Customer Lists
Finite-Lived Intangible Assets [Line Items]
Gross Amount	4,245	4,242
Accumulated Amortization	(2,876)	(2,629)
Net Amount	$ 1,369	1,613
Customer Lists | Minimum
Finite-Lived Intangible Assets [Line Items]
Other intangible asset, useful life	6 years
Customer Lists | Maximum
Finite-Lived Intangible Assets [Line Items]
Other intangible asset, useful life	13 years
Non-Network Internal-Use Software
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 29,058	28,136
Accumulated Amortization	(20,787)	(19,743)
Net Amount	$ 8,271	8,393
Non-Network Internal-Use Software | Minimum
Finite-Lived Intangible Assets [Line Items]
Other intangible asset, useful life	3 years
Non-Network Internal-Use Software | Maximum
Finite-Lived Intangible Assets [Line Items]
Other intangible asset, useful life	7 years
Other
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 2,674	2,664
Accumulated Amortization	(1,679)	(1,541)
Net Amount	$ 995	$ 1,123
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Other intangible asset, useful life	4 years
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Other intangible asset, useful life	25 years