Restricted financial assets (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Restricted Financial Assets [Line Items]
Pledged mortgage loans serve as collateral for existing liabilities against Swiss central mortgage institutions and for existing covered bond issuances	$ 12,456	$ 11,206
UBS AG
Restricted Financial Assets [Line Items]
Pledged mortgage loans serve as collateral for existing liabilities against Swiss central mortgage institutions and for existing covered bond issuances	$ 12,456	$ 11,206

The amount of pledged mortgage loans serve as collateral for existing liabilities against Swiss central mortgage institutions and for existing covered bond issuances.

No definition available.

Name:	ubs_MortgagesPledgedAsCollateralForLiabilitiesAgainstSwissCentralMortgageInstitutionsAndCoveredBondIssuances
Namespace Prefix:	ubs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant