Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Mar. 31, 2013	Sep. 30, 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		$ 818,000,000	$ 75,000,000
Notional values of derivative contracts		18,971,000,000	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		(119,000,000)	(329,000,000)
Unrealized net losses on cash flow hedges		(85,000,000)
Unrealized net losses on cash flow hedges after tax		(55,000,000)
Derivative, Notional Amount, Maturities		3,400,000,000
Termination of non-qualifying hedge		2,400,000,000
Notional amount of derivatives designated as fair value hedge, terminated during period		300,000,000
Notional amount of derivatives designated as cash flow hedge, terminated durding period	1,000,000,000
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Loss on cash flow hedge reclassified to income	199,000,000
Fixed rate borrowings [Member] | HSBC USA, Inc. [Member]
Derivative [Line Items]
Debt issued to affiliate	1,500,000,000		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
Parent Company [Member]
Derivative [Line Items]
Notional values of derivative contracts		$ 18,900,000,000	$ 26,000,000,000