Supplemental guarantor information (Narrative) (Detail) $ in Millions	6 Months Ended
Jun. 30, 2026 USD ($)
Supplemental Guarantor Information [Line Items]
Joint and several liability	$ 1,700
Increase decrease in joint and several liability	(100)
Joint and several liability for outstanding SEC-registered debt securities issued by Credit Suisse (USA), Inc.	$ 742

The amount of outstanding SEC-registered debt securities issued by Credit Suisse (USA), Inc., that has been fully and unconditionally guaranteed by UBS AG and UBS Group AG.

No definition available.

Name:	ubsag_JointAndSeveralLiabilityForOutstandingSecRegisteredDebtSecuritiesIssuedByIndirectSubsidiary
Namespace Prefix:	ubsag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant