Trading Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Derivatives included in trading assets, amount offset	$ 2,656		$ 2,797
Derivatives included in trading liabilities, amount offset	1,610		1,296
Dividend income on equity securities held for trading	48	$ 26
Trading Assets
Debt and Equity Securities, FV-NI [Line Items]
Derivatives included in trading assets, amount offset	2,033		1,419
Trading Liabilities
Debt and Equity Securities, FV-NI [Line Items]
Derivatives included in trading liabilities, amount offset	$ 1,610		$ 1,296

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958

+ Details

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

- Definition

Amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

+ Details

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

- Definition

Amount of dividend income on investment in equity security, classified as operating.

+ References

No definition available.

+ Details

Name:	us-gaap_DividendIncomeEquitySecuritiesOperating
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

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

- Details

Name:	us-gaap_BalanceSheetLocationAxis=hsbcusa_TradingAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_TradingLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: