Related Party Transactions - Related Party Balances and Income and (Expense) Generated by Related Party Transactions (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Assets:
Cash	$ 173				$ 173				$ 175
Securities purchased under agreements to resell	4,841				4,841				6,924
Other assets	1,353				1,353				1,417
Total assets	32,648				32,648				37,872
Liabilities
Due to affiliates	6,940				6,940				8,742
Other liabilities	1,168				1,168				1,299
Total liabilities	25,539				25,539				31,211
Income/(Expense):
Servicing and other fees from HSBC affiliates	6		6		20		19
Support services from HSBC affiliates	(65)		(78)		(198)		(213)
HSBC affiliates [Member]
Assets:
Cash	173				173				172
Securities purchased under agreements to resell	4,841	[1]			4,841	[1]			6,924	[1]
Other assets	159				159				86
Total assets	5,173				5,173				7,182
Liabilities
Due to affiliates	6,940	[2]			6,940	[2]			8,742	[2]
Other liabilities	40				40				51
Total liabilities	6,980				6,980				8,793
Income/(Expense):
Interest income from HSBC affiliates	1		1		4		3
Interest expense paid to HSBC affiliates	(76)	[3]	(113)	[3]	(231)	[3]	(371)	[3]
Net interest income (loss)	(75)		(112)		(227)		(368)
Servicing and other fees from HSBC affiliates	6		6		20		19
Support services from HSBC affiliates	(65)		(78)		(198)		(213)
Stock based compensation expense with HSBC	(1)	[4]	1	[4]	(4)	[4]	(3)	[4]
HSBC affiliates [Member] | Borrowings [Member]
Income/(Expense):
Gain (loss) on FVO debt with affiliate	$ 10		$ (16)		$ (10)		$ 21

[1] Securities under an agreement to resell are purchased from HSI and generally have terms of 120 days or less. The collateral underlying the securities purchased under agreements to resell, however, is with an unaffiliated third party. Interest income recognized on these securities is reflected as interest income from HSBC affiliate in the table below.

[2] Due to affiliates includes amounts owed to HSBC and its subsidiaries as a result of direct debt issuances as well as HSBC's ownership of our subordinated debt and excludes preferred stock.

[3] Includes interest expense paid to HSBC affiliates for debt held by HSBC affiliates as well as net interest paid to or received from HSBC affiliates on risk management hedges related to non-affiliated debt.

[4] Employees participate in one or more stock compensation plans sponsored by HSBC. These expenses are included in Salary and employee benefits in our consolidated statement of income. Employees also participate in a defined benefit pension plan and other postretirement benefit plans sponsored by HSBC North America which are discussed in Note 10, “Pension and Other Postretirement Benefits.”