Loans - Summary of Nonaccrual Loans and Accruing Receivables 90 Days or More Delinquent (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	$ 896	$ 720
Accruing Loans Contractually Past Due 90 Days or More	49	151
Nonaccrual Loans With No Allowance For Credit Losses	162	139
Residential mortgage loans carried at lower of cost or fair value of the collateral less cost to sell	102	106
Commercial loans
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	720	541
Accruing Loans Contractually Past Due 90 Days or More	46	147
Nonaccrual Loans With No Allowance For Credit Losses	82	54
Commercial loans \| Real estate, including construction
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	384	261
Accruing Loans Contractually Past Due 90 Days or More	0	0
Nonaccrual Loans With No Allowance For Credit Losses	19	21
Commercial loans \| Business and corporate banking
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	336	280
Accruing Loans Contractually Past Due 90 Days or More	46	147
Nonaccrual Loans With No Allowance For Credit Losses	63	33
Consumer loans
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	176	179
Accruing Loans Contractually Past Due 90 Days or More	3	4
Nonaccrual Loans With No Allowance For Credit Losses	80	85
Consumer loans \| Residential mortgages
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	168	173
Accruing Loans Contractually Past Due 90 Days or More	0	0
Nonaccrual Loans With No Allowance For Credit Losses	74	80
Consumer loans \| Home equity mortgages
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	8	6
Accruing Loans Contractually Past Due 90 Days or More	0	0
Nonaccrual Loans With No Allowance For Credit Losses	6	5
Consumer loans \| Credit cards
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	0	0
Accruing Loans Contractually Past Due 90 Days or More	2	3
Nonaccrual Loans With No Allowance For Credit Losses	0	0
Consumer loans \| Other consumer
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	0	0
Accruing Loans Contractually Past Due 90 Days or More	1	1
Nonaccrual Loans With No Allowance For Credit Losses	$ 0	$ 0

Residential Mortgage Loan Nonaccrual Carried At Lower Of Amortized Cost Or Fair Value Less Cost To Sell

No definition available.

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

- Definition

Amortized cost excluding accrued interest, of financing receivable 90 days or more past due and still accruing. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-14

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 80
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-80

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=hsbcusa_BusinessandCorporateBankingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CreditCardReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: