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v3.20.4

Other Non-Current Assets - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Non-current assets sold without recourse | $ 96,000,000 | $ 131,000,000
Minimum [Member] |  |
Long-term receivables expected collection period | 1 year |
Maximum [Member] |  |
Non-current assets sold , cost | $ 1,000,000 | $ 1,000,000

X
- Definition Amount of non current assets sold without recourse. + References No definition available. + Details
Name: | stm_AmountOfNonCurrentAssetsSoldWithoutRecourse
Namespace Prefix: | stm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Cost of non current assets sold without recourse. + References No definition available. + Details
Name: | stm_CostOfNonCurrentAssetsSoldWithoutRecourse
Namespace Prefix: | stm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Long Term Receivables Collection Period + References No definition available. + Details
Name: | stm_LongTermReceivablesCollectionPeriod
Namespace Prefix: | stm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

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