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Financial Instruments and Risk Management - Notional Amounts of Outstanding Derivative Instruments (Detail) - Dec. 31, 2019 - Designated as Hedging Instrument [Member]	EUR (€)	SGD ($)
Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional amount of Derivative Instruments	€ 203,000,000
Notional amount of Derivative Instruments	333,000,000	$ 143,000,000
Currency Collars [Member]
Derivative [Line Items]
Notional amount of Derivative Instruments	243,000,000
Notional amount of Derivative Instruments	€ 309,000,000

X

- Definition

Derivative notional Amount for hedge on forecasted manufacturing costs.

+ References

No definition available.

+ Details

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X

- Definition

Derivative notional amount for hedge on forecasted research and development and other operating expenses.

+ References

No definition available.

+ Details

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X

- 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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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X

- Details

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Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=stm_CurrencyCollarsMember
Namespace Prefix:
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Period Type: