Fee Income from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		$ 272	$ 311
Other non-fee revenues		118	202
Total other revenues	[1],[2]	390	513
Deferred fee income		2		$ 2
Credit card fees, net [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		12	11
Interchange fees		22	21
Rewards program costs		12	12
Trust and investment management fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		30	38
Account services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[3]	65	69
Credit facilities [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		69	78
Other fees [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[3]	13	13
Other fees and commissions [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		147	160
Servicing and other fees from HSBC affiliates [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers		81	99
Insurance [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers	[4]	$ 2	3
Reclassified Amount [Member] | Account services [Member]
Disaggregation of Revenue [Line Items]
Fee income from contracts with customers			$ 4

[1] Represents adjustments associated with differences between U.S. GAAP and the Group Reporting Basis.

[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] During the fourth quarter of 2018, we concluded that certain wire transfer fees would be better presented in account services as opposed to other fees. As a result, we have reclassified $4 million of wire transfer fees from other fees to account services during the three months ended March 31, 2018 to conform with the current year presentation.

[4] Included within other income (loss) in the consolidated statement of income (loss).