Related Party Transactions - Additional Information (Detail)		1 Months Ended					3 Months Ended	7 Months Ended	12 Months Ended
		Dec. 31, 2016 USD ($)	Oct. 31, 2016 USD ($)	Jul. 31, 2016 USD ($) borrowing	Nov. 30, 2013 USD ($)	Oct. 31, 2013 USD ($)	Dec. 31, 2010 shares	Jul. 31, 2016 USD ($) borrowing	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Due to affiliates		$ 3,300,000,000							$ 3,300,000,000	$ 5,925,000,000
Long-term debt		4,340,000,000							4,340,000,000	9,510,000,000
Notional values of derivative contracts		1,765,000,000							1,765,000,000	8,933,000,000
Fair value of our agreements with affiliate counterparties required the affiliate to provide collateral		317,000,000							317,000,000	491,000,000
Interest bearing deposits with banks		1,500,000,000							1,500,000,000	0
Fair value of derivative related liability		12,000,000							12,000,000	57,000,000
Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Borrowing capacity of credit facility		3,000,000							$ 3,000,000
Debt instrument, term									364 days
HSBC USA, Inc. [Member]
Related Party Transaction [Line Items]
Due to affiliates		2,500,000,000							$ 2,500,000,000	3,012,000,000
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
Maximum maturity period for borrowings									5 years
Loss on extinguishment of debt		6,000,000
HSBC Holdings plc [Member]
Related Party Transaction [Line Items]
Due to affiliates		800,000,000							$ 800,000,000	813,000,000
HSBC North America [Member]
Related Party Transaction [Line Items]
Due to affiliates		0							0	1,600,000,000
Annual fee to guarantor										4,000,000	$ 6,000,000
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		$ 1,000,000,000
Debt instrument, term									364 days
Loan agreement repaid			$ 1,000,000,000
Amount of credit facility outstanding		0							$ 0	0
HSBC affiliates [Member]
Related Party Transaction [Line Items]
Due to affiliates	[1]	3,300,000,000							3,300,000,000	5,925,000,000
Interest bearing deposits with banks		1,500,000,000							1,500,000,000	0	2,000,000,000
Interest income on deposits									0
Cash received from sale of data center										54,000,000
HSBC Securities (USA) Inc. [Member]
Related Party Transaction [Line Items]
Receivable transaction assistance fees									10,000,000	2,000,000	2,000,000
HSBC Bank USA [Member]
Related Party Transaction [Line Items]
Notional values of derivative contracts		1,800,000,000							1,800,000,000	8,900,000,000
Receivables services to affiliates		559,000,000							559,000,000	696,000,000
Series C Preferred Stock [Member]
Related Party Transaction [Line Items]
Number of shares of stock issued (shares) | shares							1,000
Dividend paid on preferred stock									86,000,000	86,000,000	$ 86,000,000
Credit Agreement Maturing September 2017 [Member] | HSBC USA, Inc. [Member] | Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Loan agreement repaid		512,000,000
Credit Agreement Maturing January 2018 [Member] | HSBC USA, Inc. [Member] | Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Due to affiliates		1,500,000,000							1,500,000,000
Credit Agreement Maturing September 2018 [Member] | HSBC USA, Inc. [Member] | Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Due to affiliates		1,000,000,000							1,000,000,000
Terminated September 2016 [Member] | HSBC USA, Inc. [Member] | Revolving Credit Facility [Member]
Related Party Transaction [Line Items]
Borrowing capacity of credit facility										$ 1,000,000,000
Debt instrument, term										364 days
Amount of credit facility outstanding		0							0	$ 0
Subordinated Debt [Member] | Public Subordinated Debt Issue Maturing 2021 [Member]
Related Party Transaction [Line Items]
Long-term debt		3,000,000,000							3,000,000,000
Delayed Draw Term Loan [Member] | HSBC North America [Member]
Related Party Transaction [Line Items]
Number of draws allowed | borrowing				3				3
Amount per draw				$ 200,000,000				$ 200,000,000
Loan agreement repaid				$ 600,000,000
Delayed Draw Term Loan [Member] | Minimum [Member] | HSBC North America [Member]
Related Party Transaction [Line Items]
Maturity year of long term debt								2034
Delayed Draw Term Loan [Member] | Maximum [Member] | HSBC North America [Member]
Related Party Transaction [Line Items]
Maturity year of long term debt								2035
Securities Litigation [Member]
Related Party Transaction [Line Items]
Litigation judgment claims					$ 2,500,000,000	$ 2,500,000,000
Visa Class B Shares [Member] | HSBC USA, Inc. [Member]
Related Party Transaction [Line Items]
Notional values of derivative contracts		50,000,000							50,000,000
Fair value of derivative related liability		$ 5,000,000							$ 5,000,000

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