Long-Term Debt Long-Term Debt Additioanl Information (Details) (USD $)	12 Months Ended											12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 HSBC North America [Member]	Sep. 30, 2012 Senior Notes [Member]	Jul. 31, 2011 Senior Notes [Member]	Dec. 31, 2012 Delayed Draw Term Loan [Member] HSBC North America [Member]	Jul. 31, 2011 Delayed Draw Term Loan [Member] HSBC North America [Member] Draw	Dec. 31, 2012 Trust Preferred Securities Subject to Mandatory Redemption [Member]	Dec. 31, 2012 Carrying (Reported) Amount, Fair Value Disclosure [Member]	Dec. 31, 2011 Carrying (Reported) Amount, Fair Value Disclosure [Member]	Dec. 31, 2012 Minimum [Member] Delayed Draw Term Loan [Member] HSBC North America [Member]	Dec. 31, 2012 Maximum [Member] Delayed Draw Term Loan [Member] HSBC North America [Member]	Dec. 31, 2012 Revolving Credit Facility [Member] Amended Credit Agreement [Member] HSBC USA, Inc. [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage									5.91%
Long Term Debt, Cumulative Carrying Value Adjustments, Derivative Financial Instruments	$ 17,000,000	$ 46,000,000
Change in Carrying Value of Foreign Denominated Long Term Debt Resulting from Foreign Currency Translation Adjustments	828,000,000	1,300,000,000
Long-term debt carried at fair value	9,700,000,000	13,700,000,000								9,725,000,000	13,664,000,000
Interest Expense for long-term debt for continuing operations	1,600,000,000	2,200,000,000	2,900,000,000
Maturity year of long term debt												2034	2035
Weighted average interest rate on long-term debt	4.48%	4.50%
Long-term debt	28,426,000,000	39,790,000,000		600,000,000			600,000,000			18,701,000,000	26,126,000,000			512,000,000
Debt Instrument, Repurchased Face Amount					512,000,000	600,000,000
Loan agreements with affiliates								600,000,000	1,000,000,000					512,000,000
Number of draws allowed								3
Amount per draw							200,000,000
Loans Pledged as Collateral	4,900,000,000	5,300,000,000
Long-term debt collateralized by receivables	$ 2,900,000,000	$ 3,300,000,000
Preferred Stock callable at par									$ 25
Preferred Securities have a liquidation value per preferred security									$ 25