Fee Income from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		$ 283	$ 272
Other non-fee revenues		104	118
Total other revenues	[1]	387	390
Deferred fee income		3		$ 2
Credit card fees, net [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		11	12
Interchange fees		22	22
Rewards program costs		13	12
Trust and investment management fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		31	30
Account services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		61	65
Credit facilities [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		73	69
Other fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		17	13
Other fees and commissions [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		151	147
Servicing and other fees from HSBC affiliates [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		88	81
Insurance [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[2]	$ 2	$ 2

[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).