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Fair Value Option - Components of Gain (Loss) on Instruments at Fair Value and Related Derivatives (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]      
Mark-to-market on the related derivatives $ 944us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet $ 391us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet  
Gain (loss) on instruments designated at fair value and related derivatives 75hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative (32)hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative (342)hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]      
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]      
Interest rate and other components (920)hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] (408)hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] (775)hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1]
Credit risk component, total 82hsbcusa_FairValueOptionCreditRiskGainsLossesNet
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] (19)hsbcusa_FairValueOptionCreditRiskGainsLossesNet
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] (387)hsbcusa_FairValueOptionCreditRiskGainsLossesNet
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3]
Total mark-to-market on financial instruments designated at fair value (838)us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (427)us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (1,162)us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Net realized loss on the financial instruments 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (8)hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (1)hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Mark-to-market on the related derivatives 845us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 337us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 758us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Net Realized Gain Losses On Related Long Term Debt Derivatives 68hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 66hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 63hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Gain (loss) on instruments designated at fair value and related derivatives 75hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (32)hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (342)hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Loans [Member]      
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]      
Interest rate and other components 0hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] 0hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] 3hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1]
Credit risk component, assets 0us-gaap_FairValueOptionCreditRiskGainsLossesOnAssets
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] 21us-gaap_FairValueOptionCreditRiskGainsLossesOnAssets
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] 49us-gaap_FairValueOptionCreditRiskGainsLossesOnAssets
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3]
Total mark-to-market on financial instruments designated at fair value 0us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 21us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 52us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Net realized loss on the financial instruments 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (8)hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (1)hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Mark-to-market on the related derivatives 0us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Net Realized Gain Losses On Related Long Term Debt Derivatives 0hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Gain (loss) on instruments designated at fair value and related derivatives 0hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 13hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 51hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_LoansReceivableMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Long-term debt [Member]      
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]      
Interest rate and other components (292)hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] 289hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] 13hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1]
Credit risk component, liabilities 6us-gaap_FairValueOptionCreditRiskGainsLossesOnLiabilities
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] (165)us-gaap_FairValueOptionCreditRiskGainsLossesOnLiabilities
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] (361)us-gaap_FairValueOptionCreditRiskGainsLossesOnLiabilities
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3]
Total mark-to-market on financial instruments designated at fair value (286)us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 124us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (348)us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Net realized loss on the financial instruments 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Mark-to-market on the related derivatives 239us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (294)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (38)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Net Realized Gain Losses On Related Long Term Debt Derivatives 68hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 66hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 63hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Gain (loss) on instruments designated at fair value and related derivatives 21hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (104)hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (323)hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_BorrowingsMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Hybrid Instrument [Member]      
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]      
Interest rate and other components (628)hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] (697)hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1] (791)hsbcusa_FairValueOptionInterestRateandOtherComponentsGainsLosses
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [1]
Credit risk component, liabilities 76us-gaap_FairValueOptionCreditRiskGainsLossesOnLiabilities
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] 125us-gaap_FairValueOptionCreditRiskGainsLossesOnLiabilities
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3] (75)us-gaap_FairValueOptionCreditRiskGainsLossesOnLiabilities
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 [2],[3]
Total mark-to-market on financial instruments designated at fair value (552)us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
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/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 (866)us-gaap_FairValueOptionChangesInFairValueGainLoss1
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/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Net realized loss on the financial instruments 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainsLossesOnFinancialInstrument
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Mark-to-market on the related derivatives 606us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 631us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 796us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
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Net Realized Gain Losses On Related Long Term Debt Derivatives 0hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 0hsbcusa_NetRealizedGainLossesOnRelatedLongTermDebtDerivatives
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/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
Gain (loss) on instruments designated at fair value and related derivatives $ 54hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 $ 59hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= us-gaap_HybridInstrumentMember
/ us-gaap_IncomeStatementLocationAxis
= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember		 $ (70)hsbcusa_GainLossOnInstrumentsDesignatedAtFairValueAndRelatedDerivative
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= hsbcusa_GainlossonInstrumentsDesignatedatFairValueandRelatedDerivativesMember
[1] As it relates to hybrid instruments, interest rate and other components includes interest rate, foreign exchange and equity contract risks.
[2] For 2012, the loss in the credit risk component for hybrid instruments was attributable primarily to the tightening of our own credit spreads related to structured deposits and structured notes.
[3] For 2014, the gain in the credit risk component for long-term debt is attributable to the widening of our own credit spreads while the losses in 2013 and 2012, were attributable to the tightening of our own credit spreads