Related Party Transactions - Summary of Related Party Transactions (Income - Expense) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Related Party Transaction [Line Items]
Interest income										$ 3,910		$ 3,501		$ 3,047
Interest expense										(1,426)		(1,031)		(743)
Net interest income		$ 588	$ 604	$ 638	$ 654	$ 621	$ 617	$ 626	$ 606	2,484	[1]	2,470	[1]	2,304	[1]
Trading revenue (expense)										227		74		105
Servicing and other fees with HSBC affiliates:
Total affiliate income										217		213		199
Gain (loss) on instruments designated at fair value and related derivatives										(71)		264		75
Support services from HSBC affiliates:
Total support services from HSBC affiliates										(1,363)		(1,435)		(1,549)
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Interest income										122		117		71
Interest expense										(166)		(63)		(66)
Net interest income										(44)		54		5
Trading revenue (expense)										(1,297)		402		(676)
Servicing and other fees with HSBC affiliates:
Total affiliate income										217		213		199
Gain (loss) on instruments designated at fair value and related derivatives										467		(116)		453
Support services from HSBC affiliates:
Total support services from HSBC affiliates										(1,363)		(1,435)		(1,549)
Stock based compensation expense with HSBC	[2]									(39)		(49)		(46)
HSBC Bank Plc [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income										95		82		49
HSBC Finance Corporation [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income										40		53		81
HSBC Markets (USA) Inc. (HMUS) and subsidiaries [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income										23		25		22
Support services from HSBC affiliates:
Total support services from HSBC affiliates										(176)		(256)		(248)
Other Affiliates [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income										59		53		47
Support services from HSBC affiliates:
Total support services from HSBC affiliates										(193)		(180)		(198)
HSBC Technology and Services (USA) (HTSU) [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates										$ (994)		$ (999)		$ (1,103)

[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 the 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. Certain employees are also eligible to participate in a defined benefit pension plan and other postretirement plans sponsored by HSBC North America which are discussed in Note 20, "Pension and Other Postretirement Benefits.