Deposits held for sale.

No definition available.

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Namespace Prefix:	hsbcusa_
Data Type:	xbrli:monetaryItemType
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- Definition

Short Term Financial Assets

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Short-term Financial Liabilities

+ References

No definition available.

+ Details

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- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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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

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- Definition

Includes: (1) the amount outstanding of funds lent to other depository institutions, securities brokers, or securities dealers in the form of Federal Funds sold; for example, immediately available funds lent under agreements or contracts that mature in one business day or roll over under a continuing contract, regardless of the nature of the transaction or the collateral involved, excluding overnight lending for commercial and industrial purposes. Also include Federal Funds sold under agreements to resell on a gross basis, excluding (1) sales of term Federal Funds, (2) due bills representing purchases of securities or other assets by the reporting bank that have not yet been delivered and similar instruments, (3) resale agreements that mature in more than one business day involving assets other than securities, and (4) yield maintenance dollar repurchase agreements (Federal Funds Sold) and (2) the dollar amount outstanding of funds lent in the form of security resale agreements regardless of maturity, if the agreement requires the bank to resell the identical security purchased or a security that meets the definition of substantially the same in the case of a dollar roll. Also include purchases of participations in pools of securities, regardless of maturity (Securities Purchased Under Agreements to Re-sell).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(m)(2)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SX 210.9-03(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562

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-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
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-Name Accounting Standards Codification
-Topic 942
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

- Definition

The face amount of loans that will be sold to other entities.

+ References

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
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+ Details

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

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
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Namespace Prefix:
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Balance Type:
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- Details

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- Details

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- Details

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Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Federal funds sold and securities purchased under agreements to resell	$ 17,838	$ 10,168
Securities held-to-maturity	13,293	14,670
Loans, net of allowance for credit losses	67,916	68,437	$ 71,882
Loans held for sale	289	512
Deposits	119,693	110,955	$ 118,702
Deposits held for sale	0	10
Long-term debt	26,697	30,628
Commercial Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	212	394
Consumer Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	77	118
Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	77	65
Consumer Loans [Member] \| Other consumer [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	0	53
Level 1 [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets	1,744	1,514
Federal funds sold and securities purchased under agreements to resell	0	0
Securities held-to-maturity	0	0
Short-term financial liabilities	0	0
Deposits held for sale		0
Long-term debt	0	0
Level 1 [Member] \| Commercial Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	0	0
Loans held for sale	0	0
Level 1 [Member] \| Consumer Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	0	0
Level 1 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	0	0
Level 1 [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		0
Level 1 [Member] \| Deposits Without Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	0	0
Level 1 [Member] \| Deposits With Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	0	0
Level 2 [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets	2,038	15,700
Federal funds sold and securities purchased under agreements to resell	17,838	10,168
Securities held-to-maturity	13,431	14,443
Short-term financial liabilities	3,286	3,626
Deposits held for sale		10
Long-term debt	16,696	19,688
Level 2 [Member] \| Commercial Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	0	0
Loans held for sale	34	285
Level 2 [Member] \| Consumer Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	0	0
Level 2 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	77	65
Level 2 [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		0
Level 2 [Member] \| Deposits Without Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	96,161	91,794
Level 2 [Member] \| Deposits With Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	16,264	10,933
Level 3 [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets	18	23
Federal funds sold and securities purchased under agreements to resell	0	0
Securities held-to-maturity	0	0
Short-term financial liabilities	18	23
Deposits held for sale		0
Long-term debt	0	0
Level 3 [Member] \| Commercial Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	49,252	50,671
Loans held for sale	0	0
Level 3 [Member] \| Consumer Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	19,889	18,878
Level 3 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	1	0
Level 3 [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		53
Level 3 [Member] \| Deposits Without Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	0	0
Level 3 [Member] \| Deposits With Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	0	0
Carrying Value [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets	3,800	17,237
Federal funds sold and securities purchased under agreements to resell	17,838	10,168
Securities held-to-maturity	13,293	14,670
Short-term financial liabilities	3,304	3,643
Deposits held for sale		10
Long-term debt	16,350	19,379
Carrying Value [Member] \| Commercial Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	47,704	48,884
Loans held for sale	34	285
Carrying Value [Member] \| Consumer Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	20,212	19,553
Carrying Value [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	77	65
Carrying Value [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		53
Carrying Value [Member] \| Deposits Without Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	96,161	91,794
Carrying Value [Member] \| Deposits With Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	16,323	10,996
Estimate of fair value [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Short-term financial assets	3,800	17,237
Federal funds sold and securities purchased under agreements to resell	17,838	10,168
Securities held-to-maturity	13,431	14,443
Short-term financial liabilities	3,304	3,649
Deposits held for sale		10
Long-term debt	16,696	19,688
Estimate of fair value [Member] \| Commercial Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	49,252	50,671
Loans held for sale	34	285
Estimate of fair value [Member] \| Consumer Loans [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans, net of allowance for credit losses	19,889	18,878
Estimate of fair value [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale	78	65
Estimate of fair value [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Loans held for sale		53
Estimate of fair value [Member] \| Deposits Without Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	96,161	91,794
Estimate of fair value [Member] \| Deposits With Fixed Maturities [Member]
Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]
Deposits	$ 16,264	$ 10,933