Wireless Licenses, Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Indefinite-lived Intangible Assets [Line Items]
Gain (loss) on disposition of licenses, pre-tax		$ 0	$ 0	$ (1,195)	$ 0
Wireless licenses		95,767		95,767		$ 95,059
Wireless Licenses
Indefinite-lived Intangible Assets [Line Items]
Wireless licenses under development		3,500	$ 6,600	3,500	6,600
Interest costs capitalized				$ 101	$ 168
Assets held-for-sale	$ 2,800
Average remaining renewal period of wireless license portfolio (in years)				10 years
Spectrum Licenses, 39 GHz
Indefinite-lived Intangible Assets [Line Items]
Gain (loss) on disposition of licenses, pre-tax	(1,200)			$ (1,200)
Gain (loss) on disposition of licenses	(914)			(914)
Wireless licenses		$ 3,400		$ 3,400
Disposal Group, Held-for-sale, Not Discontinued Operations | Spectrum licenses
Indefinite-lived Intangible Assets [Line Items]
Intangible assets held-for-sale	$ 1,600