Employee benefits: variable compensation (Narrative) (Detail 2) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of when the majority of awards were granted	February 2021
Weighted average discount for share and performance share awards granted	23.80%	22.60%
Carrying amount of liability related to cash-settled share-based awards	$ 36	$ 34
Unvested share-based awards
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Weighted average remaining contractual term (years)	2.9
UBS AG
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of when the majority of awards were granted	February 2021
Weighted average discount for share and performance share awards granted	23.80%	22.60%
Carrying amount of liability related to cash-settled share-based awards	$ 1	$ 1
UBS AG \| Unvested share-based awards
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Weighted average remaining contractual term (years)	2.9

The date on which share-based payment arrangements are granted. [Refer: Share-based payment arrangements [member]]

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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.

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The amount of liabilities arising from share-based payment transactions. Share-based payment transactions are transactions in which the entity: (a) receives goods or services from the supplier of those goods or services (including an employee) in a share-based payment arrangement; or (b) incurs an obligation to settle the transaction with the supplier in a share-based payment arrangement when another group entity receives those goods or services. [Refer: Share-based payment arrangements [member]]

+ References

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- Definition

The weighted average discount rate for share and performance share awards granted during the reporting period.

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- Definition

The weighted average remaining contractual life of outstanding shares.

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