Variable Interest Entities - Summary of Assets and Liabilities Related to Consolidated Variable Interest Entities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Variable interest entities [Member]
Variable Interest Entity [Line Items]
Consolidated Assets	$ 231	$ 320
Consolidated Liabilities	139	160
Other assets [Member] \| Low income housing limited partnership investments [Member]
Variable Interest Entity [Line Items]
Consolidated Assets	231	320
Long-term debt [Member] \| Low income housing limited partnership investments [Member]
Variable Interest Entity [Line Items]
Consolidated Liabilities	79	92
Interest, taxes and other liabilities [Member] \| Low income housing limited partnership investments [Member]
Variable Interest Entity [Line Items]
Consolidated Liabilities	$ 60	$ 68

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5710-111685

+ Details

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

- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

+ Details

Name:	us-gaap_VariableInterestEntityConsolidatedCarryingAmountLiabilities
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

No definition available.

+ Details

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

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=hsbcusa_LowIncomeHousingLimitedLiabilityPartnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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