Pension and Other Postretirement Benefits-Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Postretirement Plans Other Than Pensions [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1	$ 1
Net periodic benefit cost	1	1
Hsbc North America [Member] | HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	18	18
Expected return on plan assets	(21)	(20)
Amortization of net actuarial (gain) loss	10	10
Administrative costs	1	1
Net periodic benefit cost	$ 8	$ 9