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Financial Instruments and Risk Management - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 Securities Customer | Dec. 31, 2013 Securities Customer | Dec. 31, 2012 Customer | Dec. 31, 2009
Derivative [Line Items] |  |  |  |
Maximum percentage for Research and Development and Corporate costs of the total forecasted transactions | 80.00%stm_MaximumPercentageForResearchAndDevelopmentAndCorporateCostsOfForecastedTransactions |  |  |
Maximum percentage for manufacturing costs of forecasted transactions | 70.00%stm_MaximumPercentageForManufacturingCostsOfForecastedTransactions |  |  |
Maximum percentage for designated hedged item of forecasted transactions | 100.00%stm_MaximumPercentageForDesignatedHedgedItemOfForecastedTransactions |  |  |
Hedge exposure to the variability of cash flows for forecasted transactions | 24 months |  |  |
Realized gain (loss) on reduction in cost of sales | $ (4,906)us-gaap_CostOfGoodsAndServicesSold | $ (5,468)us-gaap_CostOfGoodsAndServicesSold | $ (5,710)us-gaap_CostOfGoodsAndServicesSold |
Realized gain (loss) on reduction in operating expenses | (1)stm_RealizedGainLossOnReductionInOperatingExpenses | 17stm_RealizedGainLossOnReductionInOperatingExpenses | (32)stm_RealizedGainLossOnReductionInOperatingExpenses |
Ineffective portion of hedge was recorded on Other income and expenses, net | 0us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet | 0us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet | 0us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet |
Deferred losses on derivative instrument, net of tax | 76us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months |  |  |
Period of Accumulated other comprehensive income (loss) | 12 months |  |  |
Amount reclassified as Other Income and Expenses, net | 0us-gaap_OtherCostAndExpenseOperating |  |  |
Fair value of liabilities | 73us-gaap_DerivativeFairValueOfDerivativeLiability | 4us-gaap_DerivativeFairValueOfDerivativeLiability |  |
Fair value of assets | 1us-gaap_DerivativeFairValueOfDerivativeAsset | 43us-gaap_DerivativeFairValueOfDerivativeAsset |  |
Maximum outstanding amount per instrument with each Bank , as percentage of total |  |  |  | 20.00%stm_MaximumPercentageOfOutstandingAmountPerInstrumentWithBank
Maximum outstanding percentage of counterparty risk |  |  |  | 15.00%stm_ReducedMaximumOutstandingAmountPerInstrumentWithBank
Number of customer represented more than 10% of trade accounts receivable |  | 0stm_NumberOfCustomerAccountedMoreThanTenPercentAccountsReceivable | 0stm_NumberOfCustomerAccountedMoreThanTenPercentAccountsReceivable |
Impairment loss of intangible assets | 24us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill |  |  |
Aggregate carrying amount of cost-method investments | 3us-gaap_CostMethodInvestmentsOriginalCost |  |  |
Cost-method investments, Other-than-temporary impairment charge | 3us-gaap_CostmethodInvestmentsOtherThanTemporaryImpairment |  |  |
Securities in unrealized loss position | 0stm_NumberOfSecuritiesInUnrealizedLossPosition | 0stm_NumberOfSecuritiesInUnrealizedLossPosition |  |
Zero Coupon due 2019 (Tranche A) [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Debt discount rate | 2.40%us-gaap_FairValueInputsDiscountRate / us-gaap_DebtInstrumentAxis = stm_ZeroCouponDueTwoThousandNineteenTrancheAMember |  |  |
Interest rate | 1.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = stm_ZeroCouponDueTwoThousandNineteenTrancheAMember |  |  |
Expected life of the instrument | 5 years |  |  |
1.0% due 2021 (Tranche B) [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Debt discount rate | 3.22%us-gaap_FairValueInputsDiscountRate / us-gaap_DebtInstrumentAxis = stm_OnePointZeroPercentageDueTwoThousandTwentyOneTrancheBMember |  |  |
Interest rate | 1.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = stm_OnePointZeroPercentageDueTwoThousandTwentyOneTrancheBMember |  |  |
Expected life of the instrument | 7 years |  |  |
Fair Value, Inputs, Level 3 [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Fair value of liability component | 878us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |  |
Minimum [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Major customer percentage of trade accounts receivable |  | 10.00%stm_MajorCustomerPercentageOfTradeAccountsReceivables / us-gaap_RangeAxis = us-gaap_MinimumMember | 10.00%stm_MajorCustomerPercentageOfTradeAccountsReceivables / us-gaap_RangeAxis = us-gaap_MinimumMember |
Foreign Exchange Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Realized gain (loss) on reduction in cost of sales | (1)us-gaap_CostOfGoodsAndServicesSold / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember | 16us-gaap_CostOfGoodsAndServicesSold / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember | (39)us-gaap_CostOfGoodsAndServicesSold / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember |
Collars [Member] | Option One [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Fair value of net assets (liabilities) | (28)us-gaap_DerivativeFairValueOfDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = stm_CurrencyCollarsMember / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = stm_OptionOneMember |  |  |
Fair value of liabilities | 28us-gaap_DerivativeFairValueOfDerivativeLiability / us-gaap_DerivativeInstrumentRiskAxis = stm_CurrencyCollarsMember / us-gaap_EligibleItemOrGroupForFairValueOptionAxis = stm_OptionOneMember |  |  |
Forward Contracts [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Fair value of liabilities | 45us-gaap_DerivativeFairValueOfDerivativeLiability / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  |  |
Fair value of assets | 1us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  |  |
Not Designated as Hedging Instrument [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Notional amount of Derivative Instruments | 286invest_DerivativeNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | 319invest_DerivativeNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | 817invest_DerivativeNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |
Foreign currency forward contracts maturity term | 37 days |  |  |
Fair value of liabilities | 2us-gaap_DerivativeFairValueOfDerivativeLiability / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | 1us-gaap_DerivativeFairValueOfDerivativeLiability / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |  |
Fair value of assets | 1us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | 2us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |  |
Not Designated as Hedging Instrument [Member] | Minimum [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Foreign currency forward contracts remaining terms | 2 days |  |  |
Not Designated as Hedging Instrument [Member] | Maximum [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Foreign currency forward contracts remaining terms | 11 months |  |  |
Designated as Hedging Instrument [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Notional amount of Derivative Instruments | 1,386invest_DerivativeNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | 1,702invest_DerivativeNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | 1,552invest_DerivativeNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember |
Foreign currency forward contracts maturity term | 115 days |  |  |
Fair value of liabilities | 71us-gaap_DerivativeFairValueOfDerivativeLiability / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember | 3us-gaap_DerivativeFairValueOfDerivativeLiability / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember |  |
Fair value of assets |  | $ 41us-gaap_DerivativeFairValueOfDerivativeAsset / us-gaap_HedgingDesignationAxis = us-gaap_DesignatedAsHedgingInstrumentMember |  |
Designated as Hedging Instrument [Member] | Minimum [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Foreign currency forward contracts remaining terms | 5 days |  |  |
Designated as Hedging Instrument [Member] | Maximum [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Foreign currency forward contracts remaining terms | 12 months |  |  |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the cost method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6872867&loc=d3e40691-111596 + Details
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- Definition The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 2 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(a),(d)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
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- Definition The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -Subparagraph (a)(1),(2) -URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986 + Details
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- Definition The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994 + Details
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- Definition The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16373-109275 + Details
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