Acquisitions and Divestitures (Details) customer in Thousands, $ in Millions	1 Months Ended								3 Months Ended
	Mar. 31, 2021 USD ($)	Feb. 28, 2021 USD ($) license	Nov. 30, 2020 USD ($)	Oct. 31, 2020 county customer	Sep. 30, 2020 USD ($) license shares	May 31, 2020 USD ($)	Mar. 31, 2020 USD ($) license	Dec. 31, 2019 USD ($)	Mar. 31, 2021 USD ($) Agreement	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
Number of licenses acquired | license							4,940
Payments for deposits									$ 44,783	$ 434
Loss on disposition of licenses, pre-tax									223	1,195
Goodwill	$ 24,837								24,837		$ 24,773
Huffington Post Business
Business Acquisition [Line Items]
Net gain from dispositions of assets and businesses			$ 126
Spectrum licenses
Business Acquisition [Line Items]
Payments for deposits							$ 1,600	$ 101
Spectrum licenses | Spectrum Licenses, C-Band
Business Acquisition [Line Items]
Number of licenses acquired | license		3,511
Payments for deposits		$ 45,500							44,600
Estimated clearing and incentive costs		$ 7,400
Spectrum licenses
Business Acquisition [Line Items]
Business acquisition consideration							3,400
Portion of price to be settled with 39 GHz licenses							$ 1,800
Loss on disposition of licenses, pre-tax										1,200
Loss on disposition of licenses										$ 914
Priority Access Licenses
Business Acquisition [Line Items]
Number of licenses acquired | license					557
Payments for deposits					$ 1,900
Average remaining renewal period of wireless license portfolio (in years)	10 years
Various Other Wireless Licenses | Spectrum licenses
Business Acquisition [Line Items]
Payments for deposits									90
Loss on disposition of licenses, pre-tax									223
Loss on disposition of licenses									$ 167
Number of agreements to sell licenses | Agreement									2
Blue Jeans Network
Business Acquisition [Line Items]
Business acquisition consideration						$ 397
Goodwill						246
Intangible assets other than goodwill						$ 190
TracFone Wireless, Inc.
Business Acquisition [Line Items]
Cash payment to acquire business					3,100
Common stock value consideration to acquire business					3,100
Future cash consideration related to achievement of certain performance measures					$ 650
TracFone Wireless, Inc. | Minimum
Business Acquisition [Line Items]
Number of shares issuable (in shares) | shares					47,124,445
TracFone Wireless, Inc. | Maximum
Business Acquisition [Line Items]
Number of shares issuable (in shares) | shares					57,596,544
Bluegrass Cellular, Certain Assets
Business Acquisition [Line Items]
Business acquisition consideration	$ 405
Goodwill	80								$ 80
Intangible assets other than goodwill	135								135
Number of customers | customer				210
Number of counties customers are serviced | county				34
Plant, property and equipment	$ 146								$ 146