Group Reporting Basis Increase (Decrease) to Profit (Loss) Before Income Tax Expense

No definition available.

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Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Group Reporting Basis, Increase (Decrease) to Segment Assets

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Increase (Decrease) in Banking Deposits

+ References

No definition available.

+ Details

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Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the estimated amount of gains and losses from fair value changes included in earnings that are attributable to changes in the instrument-specific credit risk of liabilities with fair values that have been significantly affected during the reporting period by changes in the instrument-specific credit risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14172-108612

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Term of lessor's sales-type lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888428&loc=SL77919359-209981

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of lessor's sales-type lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
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

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Business Segments Additional Information (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2017 segment	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment		5
Lease, term of contract		10 years
Lease, extension term		5 years
Operating Segments [Member] \| RBWM [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the three months ended September 30:	$ 1		$ 1
Increase (decrease) in segment total assets at September 30:			(611)
Increase (decrease) in segment total deposits at September 30:			0
Operating Segments [Member] \| CMB [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the three months ended September 30:	3		9
Increase (decrease) in segment total assets at September 30:			0
Increase (decrease) in segment total deposits at September 30:			0
Operating Segments [Member] \| GBM [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the three months ended September 30:	(50)		(131)
Increase (decrease) in segment total assets at September 30:			(107,318)
Increase (decrease) in segment total deposits at September 30:			(6,672)
Operating Segments [Member] \| PB [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the three months ended September 30:	0		0
Increase (decrease) in segment total assets at September 30:			0
Increase (decrease) in segment total deposits at September 30:			0
Operating Segments [Member] \| CC (as compared with previously reported Other) [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the three months ended September 30:	46		121
Increase (decrease) in segment total assets at September 30:			107,929
Increase (decrease) in segment total deposits at September 30:			6,672
Group Reporting Basis, Other Operating Income [Member]
Segment Reporting Information [Line Items]
Gain from change in fair value of debt attributable to credit spread	$ 5		$ 113