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Leases - Additional Information (Detail) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Lessee Lease Description [Line Items] |  |
Operating and financing option to extend | true |
Operating and financing option to extend, description | Certain lease contracts contain options to extend the leases by up to 30 years, which the Company has included in the lease term when it is reasonably certain for the Company to exercise that option. |
Lease payments excluded from the capitalization | $ 5,000 |
Minimum [Member] |  |
Lessee Lease Description [Line Items] |  |
Operating and financing remaining lease term contract | 1 year |
Maximum [Member] |  |
Lessee Lease Description [Line Items] |  |
Operating and financing remaining lease term contract | 49 years |
Operating and financing option to extend, period | 30 years |
Finance lease right-of-use assets | $ 1,000,000 | $ 1,000,000

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- Definition Lessee operating and finance lease existence of option to extend. + References No definition available. + Details
Name: | stm_LesseeOperatingAndFinanceLeaseExistenceOfOptionToExtend
Namespace Prefix: | stm_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

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- Definition Lessee operating and finance lease option to extend. + References No definition available. + Details
Name: | stm_LesseeOperatingAndFinanceLeaseOptionToExtend
Namespace Prefix: | stm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Lessee operating and finance lease renewal term. + References No definition available. + Details
Name: | stm_LesseeOperatingAndFinanceLeaseRenewalTerm
Namespace Prefix: | stm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Lessee operating and finance lease term of contract. + References No definition available. + Details
Name: | stm_LesseeOperatingAndFinanceLeaseTermOfContract
Namespace Prefix: | stm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Operating and finance lease payments. + References No definition available. + Details
Name: | stm_OperatingAndFinanceLeasePayments
Namespace Prefix: | stm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Amount, after accumulated amortization, of right-of-use asset from finance lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977 + Details
Name: | us-gaap_FinanceLeaseRightOfUseAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LesseeLeaseDescriptionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |