Expected credit loss measurement - Credit impaired financial instruments at amortized cost (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Foreclosed Property [Line Items]
Foreclosed Assets	$ 86	$ 60
UBS AG
Disclosure Of Foreclosed Property [Line Items]
Foreclosed Assets	$ 86	$ 60

Carrying amount as of the balance sheet date of all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance; includes real and personal property; equity interests in corporations, partnerships, and joint ventures; and beneficial interests in trusts.

No definition available.

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