Related Party Transactions - Receivable Portfolios (Detail) (HSBC Bank USA [Member], USD $) In Billions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables sold on daily basis	$ 2.5	$ 10.4
Private Label [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables sold on daily basis	1.1	4.4
General Motors [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables sold on daily basis	1.0	3.9
Union Plus [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables sold on daily basis	0.3	1.0
Other [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables sold on daily basis	$ 0.1	$ 1.1