Pension and Other Postretirement Benefits - Net Periodic Benefit Cost (Detail) - HSBC North America - HSBC North America Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 57	$ 57	$ 52
Expected return on plan assets	(67)	(65)	(56)
Amortization of net actuarial loss	3	5	3
Administrative costs	3	3	3
Pension (income) expense	$ (4)	$ 0	$ 2