Pensions and Other Postretirement Benefits-Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Postretirement Plans Other Than Pensions [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 0	$ 1	$ 1	$ 2
Amortization of transition obligation	0	0	0	1
Net periodic benefit cost	0	1	1	3
Parent [Member] | HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost – benefits earned during the period	1	4	2	7
Interest cost on projected benefit obligation	17	18	34	35
Expected return on assets	(21)	(23)	(41)	(44)
Amortization of prior service cost (benefit)	0	(2)	0	(3)
Recognized losses	13	8	26	19
Net periodic benefit cost	$ 10	$ 5	$ 21	$ 14