Fee Income from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		$ 288	$ 283
Other non-fee revenues		96	104
Total other revenues	[1]	384	387
Deferred fee income		3		$ 3
Credit card fees, net [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		10	11
Interchange fees		18	22
Rewards program costs		11	13
Trust and investment management fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		29	31
Account services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		70	61
Credit facilities [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		83	73
Other fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		12	17
Other fees and commissions [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		165	151
Servicing and other fees from HSBC affiliates [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		83	88
Insurance [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[2]	$ 1	$ 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 in the consolidated statement of income (loss).