Related Party Transactions - Summary of Related Party Transactions (Income - Expense) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Related Party Transaction [Line Items]
Interest income	$ 762		$ 757		$ 1,507		$ 1,497
Interest expense	(89)		(239)		(315)		(474)
Net interest income	673	[1]	518	[1]	1,192	[1]	1,023	[1]
Servicing and other fees with HSBC affiliates:
Total affiliate income	51		59		98		113
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(385)		(362)		(739)		(686)
Parent And Other Subsidiaries Of Common Parent [Member]
Related Party Transaction [Line Items]
Interest income	86		83		123		105
Interest expense	(19)		(19)		(37)		(39)
Net interest income	67		64		86		66
Support services from HSBC affiliates:
Stock based compensation expense with HSBC	(10)	[2]	(13)	[2]	(18)	[2]	(22)	[2]
Hsbc Finance And Other Hsbc Affiliates [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	51		59		98		113
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(385)		(362)		(739)		(686)
HSBC Finance Corporation [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	23		26		38		47
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(3)		(5)		(6)		(9)
HSBC Markets (USA) Inc. (HMUS) and subsidiaries [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	1		4		5		9
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(51)		(54)		(104)		(106)
Other HSBC Affiliates [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	12		14		31		30
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(60)		(61)		(105)		(96)
Other HSBC Affiliates Income [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	15		15		24		27
HSBC Technology and Services (USA) (HTSU) [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates	$ (271)		$ (242)		$ (524)		$ (475)

[1] Net interest income of each segment represents the difference between actual interest earned on assets and interest paid on liabilities of the segment adjusted for a funding charge or credit. Segments are charged a cost to fund assets (e.g. customer loans) and receive a funding credit for funds provided (e.g. customer deposits) based on equivalent market rates. The objective of these charges/credits is to transfer interest rate risk from the segments to one centralized unit in Treasury and more appropriately reflect the profitability of segments.

[2] Employees may participate in one or more stock compensation plans sponsored by HSBC. These expenses are included in Salaries and employee benefits in our consolidated statement of income. Employees also may participate in a defined benefit pension plan and other postretirement plans sponsored by HSBC North America which are discussed in Note 12, "Pension and Other Postretirement Benefits."