Pension and other post-retirement benefits (Details 11) - CHF (SFr) SFr in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Actuarial gains/(losses)
Increase (Decrease) in Accumulated other Comprehensive Income
OCI, before Reclassifications, Net of Tax, Attributable to Parent	SFr (42)	SFr (18)	SFr (40)
Net prior service credit/ (cost)
Increase (Decrease) in Accumulated other Comprehensive Income
OCI, before Reclassifications, Net of Tax, Attributable to Parent	SFr 0	SFr (10)	SFr 0

Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=118951672&loc=d3e1436-108581

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration