Hedge accounting (Narrative) (Detail)	12 Months Ended
Dec. 31, 2020
Disclosure Of Detailed Information About Hedging Instruments [Line Items]
Maximum maturity of aggregate principal balances and interest cash flows that are hedged with interest rate swaps	10 years
UBS AG [Member]
Disclosure Of Detailed Information About Hedging Instruments [Line Items]
Maximum maturity of aggregate principal balances and interest cash flows that are hedged with interest rate swaps	10 years

Maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments.

No definition available.

Name:	ubs_MaximumLengthOfTimeHedgedInCashFlowHedge
Namespace Prefix:	ubs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration