Pension and Other Postretirement Benefits-Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Postretirement Plans Other Than Pensions [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2	$ 2	$ 3
Amortization of net actuarial (gain) loss	0	0	(1)
Net periodic benefit cost	2	2	2
Hsbc North America [Member] | HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	70	70	70
Expected return on plan assets	(86)	(90)	(87)
Amortization of net actuarial (gain) loss	42	38	34
Administrative costs	4	5	7
Net periodic benefit cost	30	$ 23	$ 24
Out of period adjustment	$ 6