Related Party Transactions - Summary of Related Party Transactions (Income - Expense) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Related Party Transaction [Line Items]
Interest income		$ 980	$ 869	$ 1,960	$ 1,702
Interest expense		(342)	(243)	(668)	(470)
Net interest income	[1]	638	626	1,292	1,232
Trading revenue		49	24	65	57
Servicing and other fees with HSBC affiliates:
Total affiliate income		51	53	105	109
Gain (loss) on instruments designated at fair value and related derivatives		(38)	56	178	141
Support services from HSBC affiliates:
Total support services from HSBC affiliates		(355)	(385)	(675)	(737)
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Interest income		30	28	60	58
Interest expense		(35)	(8)	(64)	(22)
Net interest income		(5)	20	(4)	36
Trading revenue		956	221	799	369
Servicing and other fees with HSBC affiliates:
Gain (loss) on instruments designated at fair value and related derivatives		79	(128)	35	130
Support services from HSBC affiliates:
Total support services from HSBC affiliates		(355)	(385)	(675)	(737)
Stock based compensation expense with HSBC	[2]	(11)	(15)	(17)	(28)
HSBC Markets (USA) Inc. (HMUS) and subsidiaries [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates		(55)	(69)	(108)	(133)
Other Affiliates [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates		(47)	(52)	(85)	(100)
HSBC Technology and Services (USA) (HTSU) [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates		(253)	(264)	(482)	(504)
Fees and Commissions [Member] | HSBC Bank Plc [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income		26	18	48	37
Fees and Commissions [Member] | HSBC Finance Corporation [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income		8	13	21	29
Fees and Commissions [Member] | HSBC Markets (USA) Inc. (HMUS) and subsidiaries [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income		4	6	10	13
Fees and Commissions [Member] | Other Affiliates [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income		13	16	26	30
Other Fees [Member] | Affiliated Entity [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income		$ 51	$ 53	$ 105	$ 109

[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 Balance Sheet Management 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 (loss). Employees also may 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."