Fair Value Option - Summary of Fair Value and Unpaid Principal Balance (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Option, Quantitative Disclosures [Line Items]
Client share repurchase asset, Fair Value	$ 10	$ 325
Client shares repurchase liability, Fair Value	10	325
Student loans held for investment
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, designated under fair value option	15	20
Loans held for investment, Unpaid Principal Balance	17	22
Fair Value Over (Under) Unpaid Principal Balance	(2)	(2)
Commercial loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Commercial loans held for sale, Fair Value	250	237
Commercial loans held for sale, Unpaid Principal Balance	256	291
Fair Value Over (Under) Unpaid Principal Balance	(6)	(54)
Client share repurchase asset
Fair Value, Option, Quantitative Disclosures [Line Items]
Client share repurchase asset, Fair Value	10	325
Client share repurchase asset, Unpaid Principal Balance	10	325
Fair Value Over (Under) Unpaid Principal Balance	0	0
Fixed rate long-term debt
Fair Value, Option, Quantitative Disclosures [Line Items]
Fixed rate long-term debt, Fair Value	749	706
Fixed rate long-term debt, Unpaid Principal Balance	741	741
Fair Value Over (Under) Unpaid Principal Balance	8	(35)
Fixed rate long-term debt \| Structured notes
Fair Value, Option, Quantitative Disclosures [Line Items]
Hybrid instruments, structured notes, Fair Value	6,790	7,672
Hybrid instruments, Unpaid Principal Balance	6,418	8,051
Fair Value Over (Under) Unpaid Principal Balance	372	(379)
Structured deposits
Fair Value, Option, Quantitative Disclosures [Line Items]
Hybrid instruments, structured deposits, Fair Value	1,821	1,554
Hybrid instruments, Unpaid Principal Balance	1,816	1,520
Fair Value Over (Under) Unpaid Principal Balance	5	34
Client share repurchase liability
Fair Value, Option, Quantitative Disclosures [Line Items]
Client shares repurchase liability, Fair Value	10	325
Unpaid Principal Balance, Other Liabilities, Fair Value Disclosure	10	325
Fair Value Over (Under) Unpaid Principal Balance	$ 0	$ 0

Fair Value, Option, Loans Held As Assets

No definition available.

Name:	hsbcusa_FairValueOptionLoansHeldAsAssets
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair Value Over (Under) Unpaid Principal Balance

+ References

No definition available.

+ Details

Name:	hsbcusa_FairValueOverUnderUnpaidPrincipalBalance
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fixed-rate debt accounted for under fair value option.

+ References

No definition available.

+ Details

Name:	hsbcusa_FixedRateDebtAccountedForUnderFairValueOption
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unpaid Principal Balance Commercial Syndicated Loans Held For Sale Carried At Fair Value

+ References

No definition available.

+ Details

Name:	hsbcusa_UnpaidPrincipalBalanceCommercialSyndicatedLoansHeldForSaleCarriedAtFairValue
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unpaid Principal Balance, Loans Receivable

+ References

No definition available.

+ Details

Name:	hsbcusa_UnpaidPrincipalBalanceLoansReceivable
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unpaid principal balance on fixed-rate debt accounted for under FVO.

+ References

No definition available.

+ Details

Name:	hsbcusa_UnpaidPrincipalBalanceOnFixedRateDebtAccountedForUnderFairValueOption
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unpaid Principal Balance On Hybrid Instruments At Fair Value Option

+ References

No definition available.

+ Details

Name:	hsbcusa_UnpaidPrincipalBalanceOnHybridInstrumentsAtFairValueOption
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unpaid Principal Balance, Other Assets, Fair Value Disclosure

+ References

No definition available.

+ Details

Name:	hsbcusa_UnpaidPrincipalBalanceOtherAssetsFairValueDisclosure
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unpaid Principal Balance, Other Liabilities, Fair Value Disclosure

+ References

No definition available.

+ Details

Name:	hsbcusa_UnpaidPrincipalBalanceOtherLiabilitiesFairValueDisclosure
Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

+ Details

Name:	us-gaap_DepositsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-30

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-31

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-32

+ Details

Name:	us-gaap_FairValueOptionQuantitativeDisclosuresLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

+ Details

Name:	us-gaap_LoansHeldForSaleFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of other assets.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherAssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of other liabilities.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherLiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_StudentLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_LoansReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=hsbcusa_ShareRepurchaseAssetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_BorrowingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=hsbcusa_StructuredNoteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_DepositsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=hsbcusa_ShareRepurchaseLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: