Related Party Transactions - Fees Received and Paid (Detail) (HSBC USA, Inc. [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
HSBC USA, Inc. [Member]
Related Party Transaction [Line Items]
Fees received	$ 2	$ 2
Fees paid		$ 2