Derivative Financial Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Percentage of derivative contracts held by HSBC subsidiaries	99.70%	99.00%
Collateral held by third party swap		$ 10,000,000
Fair value of our agreements with affiliate counterparties required the affiliate to provide collateral	75,000,000	584,000,000
Notional values of derivative contracts	26,060,000,000	40,854,000,000
Increase in debt carrying value due to fair value hedge	7,000,000	36,000,000
Gains and losses on current derivative instruments designated as cash flow hedges are reported in OCI net of tax and totaled a loss	329,000,000	448,000,000
Unrealized net losses on cash flow hedges	189,000,000
Unrealized net losses on cash flow hedges after tax	122,000,000
Termination of non-qualifying hedge	4,200,000,000
HSBC Bank USA [Member]
Derivative [Line Items]
Notional values of derivative contracts	$ 26,000,000,000	$ 40,400,000,000