Restructuring Costs - Restructuring Plan Expenses Incurred (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 48	$ 82
Incurred to Date	1,142	1,142
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3	9
Incurred to Date	187	187
Severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3	19
Incurred to Date	404	404
Network decommissioning
Restructuring Cost and Reserve [Line Items]
Restructuring charges	42	54
Incurred to Date	$ 551	$ 551

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109237686&loc=d3e17752-110868

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.P.3)
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140864-122747

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b)(1))
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

Name:	us-gaap_RestructuringCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration