Related Party Transactions - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended	12 Months Ended
		Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Jun. 30, 2015
Related Party Transaction [Line Items]
Long-term debt		$ 37,739,000,000		$ 37,739,000,000	$ 33,509,000,000
Derivative, notional amount		4,135,130,000,000		4,135,130,000,000	4,212,040,000,000
Hnah [Member]
Related Party Transaction [Line Items]
Long-term debt		4,900,000,000		4,900,000,000	1,900,000,000
Maximum borrowing capacity		150,000,000		150,000,000
Amount outstanding under the loan agreement		0		0
HSBC Finance Corporation [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		2,501,000,000		2,501,000,000	3,014,000,000
HSBC Finance Corporation [Member] | Extended Uncommitted Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Extended loans and lines of credit		5,000,000,000.0		$ 5,000,000,000.0	5,000,000,000.0
Debt term				364 days
Maximum maturity for borrowings under uncommitted revolving credit agreement				5 years
Amount outstanding on line of credit		2,500,000,000.0		$ 2,500,000,000.0	3,000,000,000
Amount prepaid on credit agreement		512,000,000
Credit agreement, prepayment fee paid		6,000,000
Credit agreement amount maturing January 2018		1,500,000,000		1,500,000,000
Credit agreement amount maturing September 2018		1,000,000,000		1,000,000,000
HSBC Finance Corporation [Member] | Extended committed revolving credit facility [Member]
Related Party Transaction [Line Items]
Extended loans and lines of credit		0		0	1,000,000,000
Amount outstanding on line of credit		0		0	0
HMUS [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		563,000,000		563,000,000	978,000,000
Extended loans and lines of credit		5,900,000,000		5,900,000,000	10,700,000,000
Amount outstanding on line of credit		563,000,000		563,000,000	978,000,000
HSBC Mexico [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		195,000,000		195,000,000	725,000,000
Extended loans and lines of credit		1,200,000,000		1,200,000,000	1,200,000,000
Other Affiliates [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		15,000,000		15,000,000	40,000,000
Extended loans and lines of credit		3,100,000,000		3,100,000,000
Amount outstanding on line of credit		0		0	0
Regency [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties	[1]	0		0	58,000,000
Notional amount of liquidity facilities					3,400,000,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Long-term debt		4,834,000,000		4,834,000,000	1,827,000,000
Loans and leases receivable from related parties		3,274,000,000		3,274,000,000	4,815,000,000
Derivative, notional amount		878,500,000,000		878,500,000,000	1,004,100,000,000
Fair value of derivative assets and liabilities		29,000,000		29,000,000	216,000,000
Floating Rate Note Maturing December 2016 [Member] | Hnah [Member] | Senior debt [Member]
Related Party Transaction [Line Items]
Debt issued								$ 1,000,000,000
Floating Rate Note Maturing August 2021 [Member] | Hnah [Member] | Senior debt [Member]
Related Party Transaction [Line Items]
Debt issued							$ 2,000,000,000
Floating Rate Note Maturing May 2025 [Member] | Hnah [Member] | Subordinated Debt [Member]
Related Party Transaction [Line Items]
Debt issued								$ 900,000,000
Floating Rate Note Maturing August 2026 [Member] | Hnah [Member] | Senior debt [Member]
Related Party Transaction [Line Items]
Debt issued							$ 2,000,000,000
Residential Mortgage [Member] | HSBC Finance Corporation [Member]
Related Party Transaction [Line Items]
Carrying amount of residential mortgage loans		$ 558,000,000		558,000,000	696,000,000
Support Services From Affiliates [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Rent from related party				$ 60,000,000	$ 58,000,000	$ 55,000,000
6.0% Non-Cumulative Preferred Stock, Series I ($1,000,000 stated value)
Related Party Transaction [Line Items]
HSBC USA preferred stock dividend rate (percent)				6.00%
6.0% Non-Cumulative Preferred Stock, Series I ($1,000,000 stated value) | Hnah [Member]
Related Party Transaction [Line Items]
HSBC USA preferred stock issued			$ 1,265,000,000
HSBC USA preferred stock dividend rate (percent)			6.00%

[1] An asset-backed commercial paper conduit consolidated by an HSBC affiliate.