Sales of Certain Receivables - Sales of Receivables and Continuing Involvement (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Other current assets	$ 1,711		$ 1,711		$ 2,005
Other long-term assets	3,433		3,433		3,232
Other current liabilities	1,120		1,120		1,070
Of which:
Gain (loss) on sale of receivables	(62)	$ 12	(108)	$ 30
Factoring and EIP Securitization Arrangement | Variable Interest Entity, Primary Beneficiary
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Derecognized net service receivables and EIP receivables	2,315		2,315		2,492
Other current assets	596		596		655
Carrying amounts of deferred purchase price assets	704		704		779
Other long-term assets	110		110		125
Other current liabilities	494		494		348
Net cash proceeds since inception			1,741		1,754
Of which:
Change in net cash proceeds during the year-to-date period			(13)		39
Net cash proceeds funded by reinvested collections			1,754		1,715
Gain (loss) on sale of receivables	(61)	$ 12	(108)	$ 30
Factoring and EIP Securitization Arrangement | Variable Interest Entity, Primary Beneficiary | Other current assets - of which, deferred purchase price
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Carrying amounts of deferred purchase price assets	594		594		654
Factoring and EIP Securitization Arrangement | Variable Interest Entity, Primary Beneficiary | Other long-term assets - of which, deferred purchase price
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Carrying amounts of deferred purchase price assets	$ 110		$ 110		$ 125