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CECL (Details 5) - CHF (SFr) SFr in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022
Debt securities issued by foreign governments |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Purchases | SFr 463 | SFr 971
Corporate debt securities |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Purchases | SFr 168 |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 + Details
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