Related Party Transactions - Information Regarding Loans (Detail) (HSBC Finance [Member], USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Revenue from External Customer [Line Items]
Loans serviced by HSBC Finance:					$ 21,200,000,000
Loans acquired on daily basis from Related Parties		8,100,000,000	9,900,000,000	23,700,000,000
Private Label Cards [Member]
Revenue from External Customer [Line Items]
Loans serviced by HSBC Finance:					12,500,000,000
Loans acquired on daily basis from Related Parties		3,700,000,000	4,400,000,000	10,500,000,000
Private Label Commercial and Closed End Loans [Member]
Revenue from External Customer [Line Items]
Loans serviced by HSBC Finance:					300,000,000
Loans acquired on daily basis from Related Parties
Credit Card General Motors [Member]
Revenue from External Customer [Line Items]
Loans serviced by HSBC Finance:					4,100,000,000
Loans acquired on daily basis from Related Parties		3,200,000,000	3,900,000,000	9,600,000,000
Credit Card Union Privilege [Member]
Revenue from External Customer [Line Items]
Loans serviced by HSBC Finance:					3,500,000,000
Loans acquired on daily basis from Related Parties		800,000,000	1,000,000,000	2,300,000,000
Credit Card Other [Member]
Revenue from External Customer [Line Items]
Loans serviced by HSBC Finance:					800,000,000
Loans acquired on daily basis from Related Parties		$ 400,000,000	$ 600,000,000	$ 1,300,000,000