Pensions and Other Postretirement Benefits-Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost – benefits earned during the period	$ 7	$ 4	$ 15
Interest cost	70	71	67
Expected return on assets	(87)	(83)	(91)
Amortization of net actuarial loss (gain)	34	49	46
Amortization of prior service cost (benefit)	0	0	(5)
Curtailment benefit recognized	0	0	31
Net periodic benefit cost	24	41	1
Postretirement Plans Other Than Pensions [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost – benefits earned during the period	0	1	1
Interest cost	3	2	3
Amortization of net actuarial loss (gain)	(1)	0
Amortization of transition obligation	0	0	2
Net periodic benefit cost	2	3	6
Hsbc North America [Member] | HSBC North America Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost – benefits earned during the period	16	11
Interest cost	$ 177	$ 176