Related Party Transactions - Summary of Related Party Transactions (Income - Expense) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Related Party Transaction [Line Items]
Interest income	$ 725		$ 785		$ 2,222		$ 2,428
Interest expense	(233)		(275)		(707)		(796)
Net interest income	492	[1]	510	[1]	1,515	[1]	1,632	[1]
Servicing and other fees with HSBC affiliates:
Total affiliate income	41		63		154		165
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(378)		(372)		(1,064)		(1,143)
Parent And Other Subsidiaries Of Common Parent [Member]
Related Party Transaction [Line Items]
Interest income	31		19		143		117
Interest expense	(19)		(23)		(59)		(70)
Net interest income	12		(4)		84		47
Servicing and other fees with HSBC affiliates:
Residential mortgage banking revenue	0		0		0		3
Support services from HSBC affiliates:
Stock based compensation expense with HSBC	(7)	[2]	(8)	[2]	(29)	[2]	(27)	[2]
Hsbc Finance And Other Hsbc Affiliates [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	41		63		154		165
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(378)		(372)		(1,064)		(1,143)
HSBC Finance Corporation [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	20		21		67		51
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(2)		(5)		(11)		(22)
HSBC Markets [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	4		4		13		14
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(58)		(87)		(164)		(248)
Other HSBC Affiliates [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	9		17		39		59
Support services from HSBC affiliates:
Total support services from HSBC affiliates	(44)		(43)		(140)		(162)
Other HSBC Affiliates Income [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income	8		21		35		41
HSBC Technology and Services [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates	$ (274)		$ (237)		$ (749)		$ (711)

[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 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 (loss). Employees also participate in a defined benefit pension plan and other postretirement plans sponsored by HSBC North America which are discussed in Note 13, “Pension and Other Postretirement Benefits.”