Restructuring Costs - Restructuring Plan Expenses Incurred (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Dec. 31, 2020	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 1,060	$ 1,060
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	178	178
Severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	385	385
Network decommissioning
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 497	$ 497

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration