Fee Income from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		$ 269	$ 298	$ 814	$ 873
Other non-fee revenues		87	188	393	439
Total other revenues	[1]	356	486	1,207	1,312
Deferred fee income		3		3		$ 2
Credit card fees, net [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		10	18	30	48
Interchange fees		18	25	53	73
Rewards program costs		10	11	28	33
Trust and investment management fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		34	34	98	95
Account services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		66	68	185	201
Credit facilities [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		67	73	204	223
Other fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		11	14	36	40
Other fees and commissions [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		144	155	425	464
Servicing and other fees from HSBC affiliates [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		79	88	255	257
Insurance [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[2]	$ 2	$ 3	$ 6	$ 9

[1] See Note 15, "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).