Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Percentage of derivative contracts held by HSBC subsidiaries	99.60%	99.70%
Fair value of our agreements with affiliate counterparties required the affiliate to provide collateral	$ 347,000,000	$ 75,000,000
Notional values of derivative contracts	22,321,000,000	26,060,000,000
Increase in debt carrying value due to fair value hedge		7,000,000
Losses on current derivative instruments designated as cash flow hedges are reported in OCI net of tax and totaled a loss	164,000,000	329,000,000
Unrealized net losses on cash flow hedges	159,000,000
Unrealized net losses on cash flow hedges after tax	102,000,000
Termination of non-qualifying hedge	2,400,000,000
Notional Amount Of Derivatives Designated As Fair Value Hegde, Terminated During Period	300,000,000
Notional Amount Of Derivatives Designated As Cash Flow Hegde, Terminated During Period	1,000,000,000
Loss on cash flow hedge reclassified to income	199,000,000
HSBC Bank USA [Member]
Derivative [Line Items]
Notional values of derivative contracts	22,200,000,000	26,000,000,000
Fixed rate borrowings [Member] | HSBC USA, Inc. [Member]
Derivative [Line Items]
Debt Issued To Affiliate		1,500,000,000
Junior Subordinated Debt [Member] | HSBC Finance Capital Trust IX [Member]
Derivative [Line Items]
Long-term Debt, Gross		$ 1,000,000,000