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Accounts Receivable from Subscribers, Distributors, Recoverable Taxes Contractual Assets and Other, Net - Schedule of Changes in Allowance for Expected Credit Losses (Detail) - MXN ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Subclassifications of assets, liabilities and equities [abstract] |  |  |
Balance at beginning of year | $ (39,480,909) | $ (40,798,025) | $ (39,044,925)
Increases recorded in expenses | (19,112,635) | (16,346,395) | (19,535,707)
Adjustment on initial application of IFRS 9 |  |  | (2,400,783)
Write-offs | 11,953,227 | 17,839,957 | 15,497,254
Business combination | (2,066) | (3,265,490) |
Translation effect | 2,090,648 | 3,089,044 | 4,686,136
Balance at end of year | $ (44,551,735) | $ (39,480,909) | $ (40,798,025)

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- Definition Adjustment on initial application of IFRS 9. + References No definition available. + Details
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Namespace Prefix: | amx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Allowance for bad debts. + References No definition available. + Details
Name: | amx_AllowanceForBadDebts
Namespace Prefix: | amx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Bad debts from business combination. + References No definition available. + Details
Name: | amx_BadDebtsFromBusinessCombination
Namespace Prefix: | amx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Increases recorded in expenses. + References No definition available. + Details
Name: | amx_IncreasesRecordedInExpenses
Namespace Prefix: | amx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Translation effect on bad debts. + References No definition available. + Details
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Namespace Prefix: | amx_
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Balance Type: | credit
Period Type: | duration

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- Definition Write off bad debts. + References No definition available. + Details
Name: | amx_WriteOffBadDebts
Namespace Prefix: | amx_
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Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration