Retirement benefit plan - Change in other comprehensive gains (losses) (Details) - CHF (SFr) SFr in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Other comprehensive gains/(losses) [Abstract]
Effect of changes in demographic assumptions	SFr 29	SFr 0	SFr 1,428
Effect of changes in financial assumptions	8,397	156	(71)
Effect of changes in experience assumptions	(1,726)	(252)	(931)
Return on plan assets excluding interest income	(2,274)	1,052	300
Total other comprehensive gain	SFr 4,426	SFr 956	SFr 726
Weighted average duration period for defined benefit obligation	14 years 10 months 24 days	17 years 1 month 6 days

No definition available.

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- Definition

The amount of other comprehensive income, net of tax, resulting from actuarial gains (losses) arising from changes in demographic assumptions that result in remeasurements of the net defined benefit liability (asset). Demographic assumptions deal with matters such as: (a) mortality; (b) rates of employee turnover, disability and early retirement; (c) the proportion of plan members with dependants who will be eligible for benefits; (d) the proportion of plan members who will select each form of payment option available under the plan terms; and (e) claim rates under medical plans. [Refer: Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions]

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- Definition

The amount of other comprehensive income, net of tax, resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions]

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- Definition

The amount of other comprehensive income, net of tax, resulting from actuarial gains (losses) arising from experience adjustments that result in remeasurements of the net defined benefit liability (asset). Experience adjustments deal with the effects of differences between the previous actuarial assumptions and what has actually occurred. [Refer: Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from experience adjustments]

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- Definition

The amount of other comprehensive income, net of tax, related to gains (losses) on remeasurements of defined benefit plans, which comprise actuarial gains and losses; the return on plan assets, excluding amounts included in net interest on the net defined benefit liability (asset); and any change in the effect of the asset ceiling, excluding amounts included in net interest on the net defined benefit liability (asset). [Refer: Other comprehensive income; Defined benefit plans [member]; Plan assets [member]; Net defined benefit liability (asset)] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from gain (loss) on remeasurement in other comprehensive income]

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2021-01-01
-Paragraph 135
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_135_b&doctype=Standard
-URIDate 2021-03-24

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 91
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_91_a&doctype=Standard
-URIDate 2021-03-24

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 7
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_7&doctype=Standard
-URIDate 2021-03-24

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- Definition

The amount of other comprehensive income, net of tax, resulting from the return on plan assets, excluding amounts included in interest expense (income) arising from defined benefit plans. The return on plan assets is interest, dividends and other revenue derived from the plan assets, together with realised and unrealised gains or losses on the plan assets, less any costs of managing plan assets and less any tax payable by the plan itself, other than tax included in the actuarial assumptions used to measure the present value of the defined benefit obligation. [Refer: Other comprehensive income; Defined benefit plans [member]; Plan assets [member]; Other comprehensive income, net of tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from return on plan assets excluding interest income or expense]

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- Definition

The weighted average duration of a defined benefit obligation. [Refer: Weighted average [member]]

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2021-01-01
-Paragraph 147
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_147_c&doctype=Standard
-URIDate 2021-03-24

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