Related Party Transactions - Summary of Related Party Transactions (Income - Expense) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Related Party Transaction [Line Items]
Interest income									$ 3,047		$ 2,979		$ 3,206
Interest expense									(743)		(938)		(1,048)
Net interest income	569	543	673	519	526	492	518	505	2,304	[1]	2,041	[1]	2,158	[1]
Servicing and other fees with HSBC affiliates:
Total affiliate income									199		202		202
Support services from HSBC affiliates:
Total support services from HSBC affiliates									(1,549)		(1,459)		(1,480)
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Interest income									71		46		13
Interest expense									(66)		(78)		(91)
Net interest income									5		(32)		(78)
Servicing and other fees with HSBC affiliates:
Total affiliate income									199		202		202
Support services from HSBC affiliates:
Total support services from HSBC affiliates									(1,549)		(1,459)		(1,480)
Stock based compensation expense with HSBC									(46)	[2]	(34)	[2]	(36)	[2]
Parent And Other Subsidiaries Of Common Parent [Member]
Servicing and other fees with HSBC affiliates:
Residential mortgage banking revenue									0		0		3
HSBC Finance Corporation [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates									(11)		(14)		(27)
HSBC Markets (USA) Inc. (HMUS) and subsidiaries [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates									(233)		(228)		(326)
Other Affiliates [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates									(202)		(217)		(215)
HSBC Technology and Services (USA) (HTSU) [Member]
Support services from HSBC affiliates:
Total support services from HSBC affiliates									(1,103)		(1,000)		(912)
Fees and Commissions [Member] | HSBC Finance Corporation [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income									77		86		72
Fees and Commissions [Member] | HSBC Markets (USA) Inc. (HMUS) and subsidiaries [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income									13		17		18
Fees and Commissions [Member] | Other Affiliates [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income									56		51		74
Other Fees [Member] | Affiliated Entity [Member]
Servicing and other fees with HSBC affiliates:
Total affiliate income									$ 53		$ 48		$ 38

[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 21, "Pension and Other Postretirement Benefits."