Fee Income from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		$ 262	$ 303	$ 545	$ 575
Other non-fee revenues		202	133	306	251
Total other revenues	[1]	464	436	851	826
Deferred fee income		3		3		$ 2
Credit card fees, net [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		9	18	20	30
Interchange fees		13	26	35	48
Rewards program costs		5	10	18	22
Trust and investment management fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		33	31	64	61
Account services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		58	68	119	133
Credit facilities [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		64	81	137	150
Other fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		15	13	32	26
Other fees and commissions [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		137	162	288	309
Servicing and other fees from HSBC affiliates [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		81	88	169	169
Insurance [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[2]	$ 2	$ 4	$ 4	$ 6

[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).