Provisions (Detail) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Disclosure Of Other Provisions [Line Items]
Provisions other than provisions for expected credit losses	$ 3,098	$ 3,217
Provisions for expected credit losses	443	347
Total provisions	$ 3,541	$ 3,564

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

No definition available.

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of liabilities of uncertain timing or amount, including provisions for employee benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 54
-Subparagraph l
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_54_l&doctype=Standard
-URIDate 2025-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of the provisions for expected credit losses on loan commitments and financial guarantee contracts.

+ References

No definition available.

+ Details

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Namespace Prefix:	ubsag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of provisions other than provisions for expected credit losses.

+ References

No definition available.

+ Details

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Namespace Prefix:	ubsag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant