Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Assets:
Cash	$ 967		$ 967		$ 215
Interest bearing deposits with banks	2,830		2,830		1,140
Securities purchased under agreements to resell	1,697		1,697		920
Derivative related assets	183		183
Other assets	1,278		1,278		1,312
Total assets	51,595		51,595		63,567
Liabilities:
Due to affiliates (includes $466 million and $447 million at June 30, 2012 and December 31, 2011, respectively, carried at fair value)	8,030		8,030		8,262
Derivative related liabilities					26
Other liabilities	1,287		1,287		1,688
Total liabilities	45,084		45,084		56,641
Income/(Expense):
Gain/(loss) on FVO debt with affiliate	92	245	(304)	216
Related Parties [Member]
Assets:
Cash	960		960		209
Interest bearing deposits with banks
Securities purchased under agreements to resell	1,397		1,397		920
Derivative related assets	180		180
Other assets	101		101		124
Total assets	2,638		2,638		1,253
Liabilities:
Due to affiliates (includes $466 million and $447 million at June 30, 2012 and December 31, 2011, respectively, carried at fair value)	8,030		8,030		8,262
Derivative related liabilities					25
Other liabilities	72		72		47
Total liabilities	8,102		8,102		8,334
HSBC affiliates [Member]
Income/(Expense):
Interest income from HSBC affiliates	1	2	2	4
Interest expense paid to HSBC affiliates(1)	(141)	(143)	(280)	(296)
Net interest income (loss)	(140)	(141)	(278)	(292)
Gain/(loss) on FVO debt with affiliate	(5)	5	(19)	(7)
Servicing and other fees from HSBC affiliates:
Real estate secured servicing and related fees from HSBC Bank USA	2	3	5	6
Other servicing, processing, origination and support revenues	3	3	5	5
HSBC Technology and Services (USA) Inc. ("HTSU") administrative fees and rental revenue(2)	4		8	2
Total servicing and other fees from HSBC affiliates	9	6	18	13
Support services from HSBC affiliates	(79)	(72)	(145)	(139)
Stock based compensation expense with HSBC	$ (2)	$ (2)	$ (4)	$ (4)