Fee Income from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		$ 267	$ 269	$ 837	$ 814
Other non-fee revenues		(25)	87	93	393
Total other revenues	[1]	242	356	930	1,207
Deferred fee income		5		5		$ 3
Credit card fees, net [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		0	10	23	30
Interchange fees		24	18	68	53
Rewards program costs		26	10	50	28
Trust and investment management fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		26	34	81	98
Account services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		73	66	216	185
Credit facilities [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		76	67	248	204
Other fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		11	11	32	36
Other fees and commissions [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		160	144	496	425
Servicing and other fees from HSBC affiliates [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		79	79	232	255
Insurance [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[2]	$ 2	$ 2	$ 5	$ 6

[1] See Note 16, "Business Segments," for a reconciliation of total other revenues on a U.S. GAAP basis to other operating income for each business segment under the Group Reporting Basis.

[2] Included within other income (loss) in the consolidated statement of income (loss).