FVM - Transfers between Level 1 and Level 2 (Narrative) (Detail)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Fair Value Measurement [Line Items]
Statement that there were no transfers between Level 1 and Level 2 of fair value hierarchy, assets	Assets and liabilities transferred from Level 2 to Level 1 during 2020 were not material. Assets and liabilities transferred from Level 1 to Level 2 during 2020 were also not material.
Statement that there were no transfers between Level 1 and Level 2 of fair value hierarchy, liabilities	Assets and liabilities transferred from Level 2 to Level 1 during 2020 were not material. Assets and liabilities transferred from Level 1 to Level 2 during 2020 were also not material.
UBS AG
Disclosure Of Fair Value Measurement [Line Items]
Statement that there were no transfers between Level 1 and Level 2 of fair value hierarchy, assets	Assets and liabilities transferred from Level 2 to Level 1 during 2020 were not material. Assets and liabilities transferred from Level 1 to Level 2 during 2020 were also not material.
Statement that there were no transfers between Level 1 and Level 2 of fair value hierarchy, liabilities	Assets and liabilities transferred from Level 2 to Level 1 during 2020 were not material. Assets and liabilities transferred from Level 1 to Level 2 during 2020 were also not material.