Investment securities - Maturities of amortized costs/FV/Avg yield (Details 5) SFr in Millions	Jun. 30, 2020 CHF (SFr)
Schedule of Held-to-maturity Securities [Line Items]
Due within 1 year, amortized cost	SFr 95
Debt securities held-to-maturity, amortized cost	95
Due within 1 year, fair value	95
Debt securities held-to-maturity, fair value	SFr 95
Due within 1 year, average yield (as a percent)	0.51%
Total, average yield (as a percent)	0.51%
Bank
Schedule of Held-to-maturity Securities [Line Items]
Due within 1 year, amortized cost	SFr 95
Debt securities held-to-maturity, amortized cost	95
Due within 1 year, fair value	95
Debt securities held-to-maturity, fair value	SFr 95
Due within 1 year, average yield (as a percent)	0.51%
Total, average yield (as a percent)	0.51%

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- Definition

Weighted average yield of investment in debt security measured at amortized cost (held-to-maturity) maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Industry Guide
-Number 3
-Section II
-Paragraph B

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- Definition

Amortized cost of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=120252992&loc=d3e62586-112803

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Section 50
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=121645371&loc=SL120269825-111563

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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27232-111563

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-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 3A
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-URI http://asc.fasb.org/extlink&oid=120252992&loc=SL120269850-112803

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-URI http://asc.fasb.org/extlink&oid=120252992&loc=d3e62586-112803

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- Definition

Amount of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

+ References

No definition available.

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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

No definition available.

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