Strategic Initiatives - Restructuring Liability (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Restructuring Reserve [Roll Forward]
Restructuring liability at beginning of period	$ 0
Restructuring costs accrued during the period	57
Restructuring costs paid during the period	(24)
Restructuring liability at end of period	33
Severance and Other Employee Costs [Member]
Restructuring Reserve [Roll Forward]
Restructuring liability at beginning of period	0	[1]
Restructuring costs accrued during the period	28	[1]
Restructuring costs paid during the period	(18)	[1]
Restructuring liability at end of period	10	[1]
Lease Termination and Associated Costs [Member]
Restructuring Reserve [Roll Forward]
Restructuring liability at beginning of period	0	[2]
Restructuring costs accrued during the period	29	[2]
Restructuring costs paid during the period	(6)	[2]
Restructuring liability at end of period	$ 23	[2]

[1] Severance and other employee costs are included in salaries and employee benefits in the consolidated statement of income (loss). The majority of these costs were reported in the Wealth and Personal Banking and the Global Banking and Markets business segments. Not included in these costs are allocated severance costs from HSBC Technology & Services ("HTSU") discussed further below.

[2] Primarily includes real estate taxes, service charges and decommissioning costs. Lease termination and associated costs are included in occupancy expense, net in the consolidated statement of income (loss) and were reported in the Corporate Center business segment.