Post-employment benefits for associates - Weighted average actuarial assumptions (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Pension plans [member]
Disclosure of defined benefit plans [line items]
Discount rate	1.20%	1.70%
Expected rate of pension increase	1.10%	1.20%
Expected rate of salary increase	2.40%	3.30%
Interest on savings account	1.00%	1.00%
Current average life expectancy for a 65-year-old male (in years)	20 years	21 years
Current average life expectancy for a 65-year-old female (in years)	23 years	24 years
Pension plans [member] \| SWITZERLAND \| Country of domicile [member]
Disclosure of defined benefit plans [line items]
Discount rate	0.10%	0.30%
Pension plans [member] \| UNITED STATES \| Foreign countries [member]
Disclosure of defined benefit plans [line items]
Discount rate	2.40%	3.10%
Pension plans [member] \| GERMANY \| Foreign countries [member]
Disclosure of defined benefit plans [line items]
Discount rate	0.80%	1.10%
Pension plans [member] \| UNITED KINGDOM \| Foreign countries [member]
Disclosure of defined benefit plans [line items]
Discount rate	1.30%	2.00%
Other post-employment benefit plans [member]
Disclosure of defined benefit plans [line items]
Discount rate	2.30%	3.30%
Expected rate of pension increase
Expected rate of salary increase
Interest on savings account
Current average life expectancy for a 65-year-old male (in years)	20 years	21 years
Current average life expectancy for a 65-year-old female (in years)	22 years	23 years
Other post-employment benefit plans [member] \| UNITED STATES \| Foreign countries [member]
Disclosure of defined benefit plans [line items]
Discount rate	2.30%	3.30%

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- Definition

Actuarial Assumption Of Life Expectancy After Retirement, Female

+ References

No definition available.

+ Details

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- Definition

Actuarial Assumption Of Life Expectancy After Retirement, Male

+ References

No definition available.

+ Details

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- Definition

The discount rate used as the significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2020-01-01
-Paragraph 144
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2020-en-r&anchor=para_144&doctype=Standard
-URIDate 2020-01-01

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- Definition

The expected rate of increases in pension that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

+ Details

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- Definition

The expected rate of salary increases used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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