Provisions - Sensitivity analysis of inbound and outbound claims (Details) $ in Millions	Dec. 31, 2017 USD ($) policy
Other Provisions, Contingent Liabilities And Contingent Assets [Abstract]
Reasonably possible increase in number of inbound claims	100,000
Reasonably possible decrease in number of inbound claims	100,000
Increase (decrease) in redress provision due to reasonably possible increase in inbound claims \| $	$ 194

Increase (Decrease) In Redress Provision Due To Reasonably Possible Increase In Inbound Claims

No definition available.

Name:	hsbc_IncreaseDecreaseInRedressProvisionDueToReasonablyPossibleIncreaseInInboundClaims
Namespace Prefix:	hsbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant