Wireless Licenses, Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2020	Mar. 31, 2020
Indefinite-lived Intangible Assets [Line Items]
Capitalized interest costs		$ 1,841,000	$ 555	$ 656
Loss on disposition of licenses, pre-tax		223	1,195	0
Wireless licenses		147,619	96,097
Media goodwill impairment	$ 186	0	0	$ 186
Goodwill impairment, after-tax	$ 176
Wireless Licenses
Indefinite-lived Intangible Assets [Line Items]
Wireless licenses under development		54,900	6,400
Capitalized interest costs		$ 1,600	$ 242
Assets held-for-sale						$ 2,800
Average remaining renewal period of wireless license portfolio (in years)		11 years	10 years
Spectrum Licenses, 39 GHz
Indefinite-lived Intangible Assets [Line Items]
Loss on disposition of licenses, pre-tax			$ 1,200
Loss on disposition of licenses			$ 914
Wireless licenses					$ 3,400
Disposal Group, Held-for-sale, Not Discontinued Operations | Loss on spectrum license transactions
Indefinite-lived Intangible Assets [Line Items]
Other intangible assets, net						$ 1,600