Related Party Transactions - Receivable Portfolios (Detail) (HSBC Bank USA [Member], USD $) In Billions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables serviced for HSBC Bank USA		$ 22.4
Receivables sold on daily basis	10.4	35.7	35.4
Private Label [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables serviced for HSBC Bank USA		12.8
Receivables sold on daily basis	4.4	15.4	14.6
General Motors [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables serviced for HSBC Bank USA		4.1
Receivables sold on daily basis	3.9	13.0	13.5
Union Privilege [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables serviced for HSBC Bank USA		3.5
Receivables sold on daily basis	1.0	3.2	3.2
Other [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables serviced for HSBC Bank USA		2.0
Receivables sold on daily basis	$ 1.1	$ 4.1	$ 4.1