Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 20,341	$ 19,272	$ 17,671	$ 11,113	$ 11,878	$ 11,061	$ 10,979	$ 11,080	$ 68,397	$ 44,998	$ 43,310
Postpaid phone revenues
Disaggregation of Revenue [Line Items]
Revenues									33,939	21,329	19,745
Postpaid other revenues
Disaggregation of Revenue [Line Items]
Revenues									2,367	1,344	1,117
Postpaid service revenues
Disaggregation of Revenue [Line Items]
Revenues									36,306	22,673	20,862
Wireless service revenues \| Sprint
Disaggregation of Revenue [Line Items]
Revenues									626
Equipment revenues from the lease of mobile communication devices
Disaggregation of Revenue [Line Items]
Revenues									$ 4,181	$ 599	$ 692