Related Party Transactions - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Loss on extinguishment of debt				$ 287,000,000	$ 0
Due to affiliates		$ 0		0		$ 3,300,000,000
Notional values of derivative contracts		419,000,000		419,000,000		1,765,000,000
Interest bearing deposits with banks		0		0		1,500,000,000
Purchase of senior subordinated debt held by non-affiliates		1,100,000,000
Derivative related liabilities		1,000,000		1,000,000		12,000,000
Derivative related expense		1,000,000	$ 3,000,000	4,000,000	(109,000,000)
HSBC USA, Inc. [Member]
Related Party Transaction [Line Items]
Due to affiliates		0		0		2,500,000,000
Interest bearing deposits with banks						1,500,000,000
HSBC USA, Inc. [Member] | Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Borrowing capacity of credit facility		5,000,000,000		$ 5,000,000,000
Debt instrument, term				364 days
Repayments of Lines of Credit				$ 2,500,000,000
Loss on extinguishment of debt				28,000,000
HSBC Holdings plc [Member]
Related Party Transaction [Line Items]
Loss on extinguishment of debt		85,000,000		85,000,000
Due to affiliates		0		0		800,000,000
HSBC North America [Member] | Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Borrowing capacity of credit facility		1,000,000,000		$ 1,000,000,000		1,000,000,000
Debt instrument, term				364 days
Amount of credit facility outstanding		0		$ 0		0
HSBC Bank USA [Member]
Related Party Transaction [Line Items]
Notional values of derivative contracts		419,000,000		419,000,000		1,800,000,000
Fair value of our agreements with affiliate counterparties required the affiliate to provide collateral		35,000,000		35,000,000		317,000,000
Receivables services to affiliates		1,000,000		1,000,000		559,000,000
HSBC affiliates [Member]
Related Party Transaction [Line Items]
Loss on extinguishment of debt		85,000,000	0	113,000,000	0
Due to affiliates	[1]	0		0		3,300,000,000
Interest bearing deposits with banks		0		0
HSBC Securities (USA) Inc. [Member]
Related Party Transaction [Line Items]
Receivable transaction assistance fees		2,000,000	1,000,000	7,000,000	5,000,000
Transaction assistance fees		3,000,000		3,000,000
Discontinued Operations [Member]
Related Party Transaction [Line Items]
Derivative related expense		1,000,000		2,000,000
Series C Preferred Stock [Member]
Related Party Transaction [Line Items]
Dividend paid on preferred stock		21,000,000	$ 21,000,000	64,000,000	$ 64,000,000
Discontinued Operations [Member] | Visa Class B Shares [Member] | HSBC USA, Inc. [Member]
Related Party Transaction [Line Items]
Notional values of derivative contracts		68,000,000		68,000,000		50,000,000
Derivative related liabilities		$ 6,000,000		$ 6,000,000		$ 5,000,000
HSBC North America [Member] | Series C Preferred Stock [Member]
Related Party Transaction [Line Items]
Share held by parent company (shares)		1,000		1,000

[1] Due to affiliates includes amounts owed to HSBC and its subsidiaries as a result of direct debt issuances and excludes preferred stock.