Strategic Initiatives - Branch Closings (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) branch	Dec. 31, 2019 USD ($) branch	Dec. 31, 2021 USD ($)
Restructuring Cost and Reserve [Line Items]
Number of branches closing | branch	60	20
Lease impairment charges	$ 76	$ 13
Notional value of derivative contracts	2,021,133	4,807,851
Interest rate contracts [Member]
Restructuring Cost and Reserve [Line Items]
Notional value of derivative contracts	509,403	$ 3,051,548
Occupancy Expense, Net [Member]
Restructuring Cost and Reserve [Line Items]
Fixed asset impairment charges	16
Write Down of Lease Right-of-use Assets, Net of Estimated Sublease Income [Member] | Occupancy Expense, Net [Member]
Restructuring Cost and Reserve [Line Items]
Lease impairment charges	67
Lease Termination and Associated Costs [Member] | Occupancy Expense, Net [Member]
Restructuring Cost and Reserve [Line Items]
Lease impairment charges	9
2-year Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Trading losses associated with exit of certain derivative contracts	67
Allocated restructuring costs from affiliates	64
2-year Restructuring Plan [Member] | Interest rate contracts [Member]
Restructuring Cost and Reserve [Line Items]
Notional value of derivative contracts	64,600
2-year Restructuring Plan [Member] | Forecast [Member] | Interest rate contracts [Member]
Restructuring Cost and Reserve [Line Items]
Notional value of derivative contracts			$ 92,100
HSBC Group Restructuring Activities [Member]
Restructuring Cost and Reserve [Line Items]
Allocated restructuring costs from affiliates	$ 16