Related Party Transactions - Additional Information (Detail) (USD $)	9 Months Ended				3 Months Ended		9 Months Ended					3 Months Ended	9 Months Ended					3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended			3 Months Ended		9 Months Ended					3 Months Ended		9 Months Ended			9 Months Ended							3 Months Ended		9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Residential Mortgage [Member]	Dec. 31, 2011 Residential Mortgage [Member]	Sep. 30, 2012 HSBC Finance [Member]	Sep. 30, 2011 HSBC Finance [Member]	Sep. 30, 2012 HSBC Finance [Member]	Sep. 30, 2011 HSBC Finance [Member]	Dec. 31, 2011 HSBC Finance [Member]	Sep. 30, 2012 HSBC Finance [Member] Credit Card Customer Relationship [Member]	Mar. 29, 2012 HSBC Finance [Member] Credit Card Customer Relationship [Member]	Sep. 30, 2011 HSBC Finance [Member] Credit Card Receivables [Member]	Sep. 30, 2012 HSBC Finance [Member] Credit Card Receivables [Member]	Sep. 30, 2011 HSBC Finance [Member] Credit Card Receivables [Member]	Dec. 31, 2011 HSBC Finance [Member] Credit Card Receivables [Member]	Sep. 30, 2012 HSBC Finance [Member] Extended committed revolving credit facility [Member]	May 31, 2012 HSBC Finance [Member] Extended committed revolving credit facility [Member]	Sep. 30, 2012 HSBC Finance [Member] Extended uncommitted revolving credit facility	Jun. 30, 2012 HSBC Finance [Member] Extended uncommitted revolving credit facility	Sep. 30, 2012 HSBC Finance [Member] Extended uncommitted revolving credit facility	Dec. 31, 2011 HSBC Finance [Member] Extended uncommitted revolving credit facility	Sep. 30, 2012 HMUS [Member]	Sep. 30, 2011 HMUS [Member]	Sep. 30, 2012 HMUS [Member]	Sep. 30, 2011 HMUS [Member]	Dec. 31, 2011 HMUS [Member]	Jan. 31, 2011 Halbis Capital Management (USA) [Member]	Apr. 30, 2012 Halbis Capital Management (USA) [Member] European Banknotes Business [Member]	Sep. 30, 2012 HNAH [Member]	Sep. 30, 2011 HNAH [Member]	Sep. 30, 2012 HNAH [Member]	Sep. 30, 2011 HNAH [Member]	Dec. 31, 2011 HNAH [Member]	Apr. 30, 2011 HNAH [Member]	Aug. 31, 2009 HNAH [Member]	Sep. 30, 2012 Other Affiliates [Member]	Sep. 30, 2011 Other Affiliates [Member]	Sep. 30, 2012 Other Affiliates [Member]	Sep. 30, 2011 Other Affiliates [Member]	Dec. 31, 2011 Other Affiliates [Member]	Sep. 30, 2012 HSBC France [Member]	Dec. 31, 2011 HSBC France [Member]	Sep. 30, 2012 HSBC Investment [Member]	Sep. 30, 2012 HSBC North America Inc. [Member]	Dec. 31, 2011 HSBC North America Inc. [Member]	Sep. 30, 2012 HSBC Finance and other HSBC Affiliates [Member]	Dec. 31, 2011 HSBC Finance and other HSBC Affiliates [Member]	Sep. 30, 2012 HSBC Global Resourcing [Member]	Sep. 30, 2011 HSBC Global Resourcing [Member]	Sep. 30, 2012 HSBC Global Resourcing [Member]	Sep. 30, 2011 HSBC Global Resourcing [Member]
Related Party Transaction [Line Items]
Credit card receivables										$ 970,000,000	$ 108,000,000
Credit card receivables purchased						8,100,000,000	9,900,000,000	23,700,000,000				582,000,000	492,000,000	1,700,000,000
Credit card servicing															1,200,000,000
Fee for servicing credit cards						4,000,000	7,000,000	11,000,000
Residential mortgage loans purchased	3,700,000,000
Residential mortgage loans servicing			1,200,000,000	1,300,000,000
Residential mortgage loans servicing fees					1,000,000	1,000,000	3,000,000	3,000,000
Services fee paid					2,000,000	2,000,000	5,000,000	5,000,000
Services fee received					1,000,000	3,000,000	3,000,000	7,000,000
Service revenue received against employee work for main bank					14,000,000		42,000,000
Service revenue received against employee work for main bank last year						15,000,000		47,000,000
Extended secured uncommitted credit facility and loans and lines of credit							1,500,000,000																	2,800,000,000		2,800,000,000
Extended secured uncommitted credit facility to certain subsidiary (In days)							364 days
Extended line of credit																	2,000,000,000				3,000,000,000
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																0		512,000,000		512,000,000
Interest income received																		1,000,000		1,000,000
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						149,000,000	199,000,000	447,000,000
Line of Credit					1,000,000,000		1,000,000,000
Line of credit amount outstanding									0																											0		0		0
Extended unsecured credit facility	1,000,000,000
Extended line of credit amount outstanding		0
Loans and lines of credit amount outstanding																						270,000,000		270,000,000		229,000,000
Loans and lines of credit interest income																						1,000,000	1,000,000	3,000,000	5,000,000
Increase in additional paid-in-capital																											21,000,000
Sale of our European Banknotes Business with assets		21,454,000,000																										123,000,000
Senior notes																																		3,000,000,000	1,000,000,000
Notes mature installments period one																													1,000,000,000		1,000,000,000
Notes mature installments period two																													1,000,000,000		1,000,000,000
Notes mature installments period three																													1,000,000,000		1,000,000,000
Senior note floating rate period																															Notes bear interest at 90 day USD Libor plus a spread
Senior note interest rate period																															90 days
Interest expense on notes																													16,000,000	14,000,000	49,000,000	31,000,000
Marketable securities																													15,000,000		15,000,000		8,500,000,000
Notional value of credit derivatives transactions	526,000,000,000	657,300,000,000																																		45,900,000,000		45,900,000,000		45,100,000,000
Derivative Liabilities																																				1,200,000,000		1,200,000,000		1,000,000,000
Loan and lease receivable unused line of credit facility																																										2,500,000,000	500,000,000	150,000,000	150,000,000
Loan and lease receivable unused line of credit facility termination date																																									Jul. 30, 2012
Extended loans and lines of credit																																				460,000,000		460,000,000		460,000,000
Loans and lines of credit interest income																																				0	0	0	0
Notional value of interest rate derivative	3,176,200,000,000	2,782,600,000,000																																												1,023,000,000,000	887,000,000,000
Fair value of derivative receivables																																														22,700,000,000	22,400,000,000
Expense of stock compensation plans on a pre-tax basis																																				7,000,000	14,000,000	27,000,000	38,000,000
Support services expense																																																5,000,000		18,000,000
Prior year professional and contract services expense																																																	$ 7,000,000		$ 21,000,000