Litigation and Regulatory Matters - Additional Information (Details) (USD $)	3 Months Ended		1 Months Ended		0 Months Ended	1 Months Ended			3 Months Ended	0 Months Ended	12 Months Ended			0 Months Ended	12 Months Ended			36 Months Ended			1 Months Ended		1 Months Ended
	Mar. 31, 2013 class_action	Sep. 30, 2011 Officers	Dec. 31, 2012 Bayerische Landesbank [Member]	Dec. 31, 2010 Madoff Litigation [Member]	Jun. 19, 2012 Knox Family Trust Litigation [Member] LegalMatter	Aug. 31, 2011 Knox Family Trust Litigation [Member] proceeding	May 31, 2011 Knox Family Trust Litigation [Member] proceeding	Nov. 30, 2010 Knox Family Trust Litigation [Member]	Mar. 31, 2013 Knox Family Trust Litigation [Member] proceeding	Feb. 28, 2013 Foreclosure Practices [Member] mortgage_servicer	Dec. 31, 2012 Foreclosure Practices [Member]	Feb. 29, 2012 Foreclosure Practices [Member] HSBC Bank USA [Member] Services state	Dec. 31, 2011 Foreclosure Practices [Member] HSBC Bank USA [Member]	Feb. 28, 2013 Foreclosure Practices [Member] Hsbc North America [Member]	Dec. 31, 2012 Foreclosure Practices [Member] Hsbc North America [Member]	Dec. 31, 2012 AML/BSA Related Litigation [Member] HSBC Bank USA [Member]	Dec. 31, 2012 AML/BSA Related Litigation [Member] Hsbc North America [Member]	Dec. 31, 2007 Mortgage Securitization Activity Related Litigation [Member] HSBC Securities [Member]	Mar. 31, 2013 Mortgage Securitization Activity Related Litigation [Member] HSBC Securities [Member]	Dec. 31, 2012 Mortgage Securitization Activity Related Litigation [Member] HSBC Securities [Member]	Jan. 31, 2012 Residential Mortgage Backed Securities Related Litigation [Member]	Mar. 31, 2013 Residential Mortgage Backed Securities Related Litigation [Member] Institution	Feb. 29, 2012 Residential Mortgage Backed Securities Related Litigation [Member] HSH Nordbank AG [Member]	Mar. 31, 2013 Residential Mortgage Backed Securities Related Litigation [Member] HSBC Securities [Member]
Loss Contingencies [Line Items]
Estimate of loss	$ 1,800,000,000
Percentage threshold	20.00%
Number of class actions	3
Damages and additional recoveries sought				9,000,000,000
Number of proceedings awarded for plaintiffs									7
Total damages								26,000,000
Amount of final judgments							25,000,000
Number of proceedings entered by court							2
Number of proceedings agreed by HSBC Bank USA							3
Loss contingency claims settled and dismissed number other							2
Proceedings agreed by HSBC Bank USA on appeal						1
Number of matters remitted to surrogate court by Appellate Division					3
Number of mortgage servicers										12
Cash payments mortgage servicers would pay in excess										9,300,000,000
Cash payment into a fund that will be used to make payments to borrowers														96,000,000
Recorded expenses of loss contingency											19,000,000				104,000,000
Number of states under different departments												49
Number of U.S. mortgage servicers with which settlement is announced												5
Accrual portion of HSBC North													38,000,000
Payments to authorities																1,381,000,000	1,921,000,000
Loans sold to HIS																		24,000,000,000
Outstanding principal balance on loan																			7,200,000,000	7,400,000,000
Number of former and current officers and directors		5
Unpaid principal balance of securities																								1,700,000,000
Number of financial institutions																						17
Alleged purchased by plaintiff			$ 75,000,000																		$ 122,400,000		$ 41,300,000