Related Party Transactions - Additional Information (Details) (USD $)			1 Months Ended		3 Months Ended		24 Months Ended					3 Months Ended												3 Months Ended		12 Months Ended	3 Months Ended				1 Months Ended												3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Nov. 30, 2012 HSBC Finance [Member]	Jan. 31, 2009 HSBC Finance [Member]	Mar. 31, 2013 HSBC Finance [Member]	Mar. 31, 2012 HSBC Finance [Member]	Dec. 31, 2004 HSBC Finance [Member]	Mar. 31, 2013 HSBC Finance [Member] Residential Mortgage [Member]	Dec. 31, 2012 HSBC Finance [Member] Residential Mortgage [Member]	Mar. 29, 2012 HSBC Finance [Member] Credit Card Customer Relationship [Member]	Jul. 31, 2004 HSBC Finance [Member] Credit Card Customer Relationship [Member]	Mar. 31, 2012 HSBC Finance [Member] Credit Card Receivable [Member]	Jun. 30, 2012 HSBC Finance [Member] Extended uncommitted revolving credit facility	Dec. 31, 2011 HSBC Finance [Member] Extended uncommitted revolving credit facility	Mar. 31, 2013 HSBC Finance [Member] Extended uncommitted revolving credit facility	Dec. 31, 2012 HSBC Finance [Member] Extended uncommitted revolving credit facility	Mar. 31, 2013 HSBC Finance [Member] Extended uncommitted revolving credit facility Maturity Date, September 2017 [Member]	Dec. 31, 2012 HSBC Finance [Member] Extended uncommitted revolving credit facility Maturity Date, September 2017 [Member]	Mar. 31, 2013 HSBC Finance [Member] Extended uncommitted revolving credit facility Maturity Date, January 2018 [Member]	Dec. 31, 2012 HSBC Finance [Member] Extended uncommitted revolving credit facility Maturity Date, January 2018 [Member]	Mar. 31, 2013 HSBC Finance [Member] Extended committed revolving credit facility [Member]	Dec. 31, 2012 HSBC Finance [Member] Extended committed revolving credit facility [Member]	May 31, 2012 HSBC Finance [Member] Extended committed revolving credit facility [Member]	Mar. 31, 2013 HMUS [Member]	Mar. 31, 2012 HMUS [Member]	Dec. 31, 2012 HMUS [Member]	Mar. 31, 2013 HNAH [Member]	Mar. 31, 2012 HNAH [Member]	Apr. 30, 2011 HNAH [Member]	Aug. 31, 2009 HNAH [Member]	Apr. 30, 2011 HNAH [Member] Senior Notes [Member] installment	Aug. 31, 2009 HNAH [Member] Senior Notes [Member]	Mar. 31, 2013 Other Affiliates [Member]	Dec. 31, 2012 Other Affiliates [Member]	Mar. 31, 2013 HSBC Investment [Member]	Dec. 31, 2012 HSBC Investment [Member]	Mar. 31, 2013 HSBC Holdings Plc [Member]	Dec. 31, 2012 HSBC Holdings Plc [Member]	Mar. 31, 2013 Hsbc North America [Member]	Dec. 31, 2012 Hsbc North America [Member]	Mar. 31, 2013 Hsbc Finance And Other Hsbc Affiliates [Member]	Dec. 31, 2012 Hsbc Finance And Other Hsbc Affiliates [Member]	Mar. 31, 2013 Parent And Other Subsidiaries Of Common Parent [Member]	Mar. 31, 2012 Parent And Other Subsidiaries Of Common Parent [Member]	Mar. 31, 2013 HSBC Global Resourcing [Member]	Mar. 31, 2012 HSBC Global Resourcing [Member]	Mar. 31, 2013 Maximum [Member] HSBC Finance [Member]
Related Party Transaction [Line Items]
Credit card receivables										$ 108,000,000	$ 970,000,000
Credit card receivables purchased						7,400,000,000						492,000,000
Fee for servicing credit cards						5,000,000
Residential mortgage loans purchased							3,700,000,000
Residential mortgage loans servicing								1,100,000,000	1,200,000,000
Residential mortgage loans servicing fees					1,000,000	1,000,000
Services fee paid					2,000,000	2,000,000
Services fee received						2,000,000																																									1,000,000
Service revenue received against employee work for main bank					16,000,000	14,000,000
Extended secured uncommitted credit facility and loans and lines of credit					1,500,000,000																			3,800,000,000		3,800,000,000
Extended secured uncommitted credit facility to certain subsidiary (In days)			364 days		364 days
Extended line of credit														3,000,000,000									2,000,000,000
Extended unsecured uncommitted credit facility to certain subsidiary maturity														15 years
Amendment for increase extended unsecured uncommitted credit facility to certain subsidiary													4,000,000,000
Amount outstanding under the loan agreement															2,000,000,000	2,200,000,000					0	0
Maturing amount of credit agreement																	512,000,000	512,000,000	1,500,000,000	1,500,000,000
Purchase of Portfolios with an outstanding principal				12,400,000,000
Net premium of outstanding principal				113,000,000
Fees paid for servicing of components of income from discontinued operation						152,000,000
Loans and lines of credit amount outstanding																								250,000,000		310,000,000
Loans and lines of credit interest income																								1,000,000	1,000,000
Senior notes																													3,000,000,000	1,000,000,000
Term of floating rate debt																																5 years
Number of equal installments																															3
Notes mature installments period one																											1,000,000,000
Senior note interest rate period																											90 days
Interest expense on notes																											14,000,000	16,000,000
Related Party Marketable Securities																																	13,000,000	14,000,000
Loan and lease receivable unused line of credit facility																																			900,000,000	900,000,000	500,000,000	500,000,000	150,000,000	150,000,000
Extended loans and lines of credit																																	460,000,000	460,000,000
Line of credit amount outstanding																																	0	0
Senior Note Floating Rate Period																											Notes bear interest at 90 day USD Libor plus a spread
Notional value of interest rate derivative	3,537,700,000,000	3,244,000,000,000																																							1,213,000,000,000	1,066,500,000,000
Fair value of derivative receivables																																									673,000,000	691,000,000
Expense of stock compensation plans on a pre-tax basis																																											9,000,000	12,000,000
Support services expense																																													23,000,000	25,000,000
Dividends paid																											$ 0	$ 0