Supplemental guarantor information (Narrative) (Detail) $ in Billions	6 Months Ended
Jun. 30, 2020 USD ($)
Supplemental Guarantor Information [Line Items]
Joint and several liability	$ 11
Increase decrease in joint and several liability	$ (6)

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

No definition available.

Name:	ubs_SupplementalGuarantorInformationLineItems
Namespace Prefix:	ubs_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration