Fee Income from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		$ 311	$ 329
Other non-fee revenues		202	264
Total other revenues	[1],[2]	513	593
Deferred fee income		2		$ 1
Credit Card Fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		11	11
Interchange fees		21	19
Rewards program costs		12	9
Trust and Investment Management Fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		38	38
Account Services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		65	68
Credit Facilities [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		78	72
Custodial Fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		2	5
Other Fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		15	17
Total Other Fees and Commissions [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		160	162
Servicing and Other Fees from HSBC Affiliates [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		99	114
Insurance [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[3]	$ 3	$ 4

[1] Expenses for the segments include fully apportioned corporate overhead expenses.

[2] 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.

[3] Included as a component within other income in the consolidated statement of income (loss).