Strategic Initiatives - Branch Closings (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Lease Termination and Associated Costs | Occupancy Expense, Net
Restructuring Cost and Reserve [Line Items]
Lease impairment charges	$ 1
Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Trading losses associated with exit of certain derivative contracts		$ 4
Allocated restructuring costs from affiliates	23	12
HSBC Group Restructuring Activities
Restructuring Cost and Reserve [Line Items]
Allocated restructuring costs from affiliates	$ 17	$ 7