Pensions and Other Postretirement Benefits-Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost – benefits earned during the period	$ 2	$ 1
Interest cost	17	18
Expected return on assets	(23)	(20)
Amortization of net actuarial loss (gain)	9	9
Net periodic benefit cost	5	8
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]
Contributions by employer			$ 46