Sale of Certain Private Banking Client Relationships (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	8 Months Ended
	Aug. 31, 2017	Sep. 30, 2017	Mar. 31, 2018		Dec. 31, 2017	Mar. 31, 2017
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Client deposit			$ 117,953	[1]	$ 118,702	$ 129,258
Client investments transferred during the fourth quarter			1,100
Client deposits transferred during the fourth quarter			600
Client deposits held for sale			291		673
Portion of Latin America Portfolio [Member] | PB [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Client investments	$ 3,500
Client deposit	$ 1,700
Fee, as percent of assets transferred during first 2 years of agreement (percent)	0.50%
Client deposits held for sale			300		$ 700
Additional deposits conditionally eligible for transfer			$ 200
Other assets [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Contingent consideration receivable		$ 15
Other Income (Loss) [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Pre-tax gain on sale		$ 8

[1] In addition to the changes discussed above, in conjunction with HSBC's adoption of the requirements of IFRS 9 we also adopted changes in presentation under the Group Reporting Basis related to affiliate loans and deposits as well as cash collateral posted and received. Beginning January 1, 2018, affiliate loans have been reclassified from other assets to loans, affiliate deposits have been reclassified from other liabilities to deposits, cash collateral posted has been reclassified from loans to other assets and cash collateral received has been reclassified from deposits to other liabilities. As a result of these changes, total loans, net and total deposits in the GB&M segment increased $0.2 billion and $10.8 billion, respectively, and total loans, net and total deposits in the CC segment decreased $3.0 billion and $0.9 billion, respectively, at March 31, 2018.