Pension and other post-retirement benefits - Contributions (Details 7) - CHF (SFr) SFr in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Pension and Other Postretirement Plans Disclosure
Contributions made by the Entity to defined contribution pension plans	SFr 150	SFr 140	SFr 156
Contributions made by the Entity to the group defined benefit plan	SFr 338	SFr 377	SFr 379

Amount of cost for defined contribution plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration