Related Party Transactions - Fees Received and Paid (Detail) (HSBC USA Inc [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
HSBC USA Inc [Member]
Related Party Transaction [Line Items]
Fees received	$ 6	$ 7	$ 7
Fees paid	$ 3	$ 10	$ 8