Pension and Other Postretirement Benefits-Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Postretirement Plans Other Than Pensions [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost – benefits earned during the period	$ 0	$ 0	$ 1
Interest cost	2	3	2
Amortization of net actuarial (gain) loss	0	(1)	0
Net periodic benefit cost	2	2	3
Hsbc North America [Member] | HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost – benefits earned during the period	5	7	4
Interest cost	70	70	71
Expected return on plan assets	(90)	(87)	(83)
Amortization of net actuarial (gain) loss	38	34	49
Net periodic benefit cost	$ 23	$ 24	$ 41