Pension and Other Postretirement Benefits-Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 17	$ 16
Expected return on plan assets	(22)	(23)
Amortization of net actuarial (gain) loss	9	10
Administrative costs	2	1
Net periodic benefit cost	6	4
Postretirement Plans Other Than Pensions [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0	0	$ 1	$ 1
Net periodic benefit cost	$ 0	$ 0	1	1
Hsbc North America [Member] | HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost			35	33
Expected return on plan assets			(42)	(46)
Amortization of net actuarial (gain) loss			19	19
Administrative costs			3	3
Net periodic benefit cost			$ 15	$ 9