Shareholders' equity (Details) - SFr / shares		9 Months Ended
Aug. 03, 2020	Sep. 30, 2020	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Common Shares, par value		SFr 24.15	SFr 24.15
Common Shares in treasury, shares		26,229,070	27,812,297
Treasury Stock, Shares, Retired	2,178,600
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		1,670,777

Face amount or stated value per share of common stock.

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Number of shares issued during the period related to Restricted Stock Awards, net of any shares forfeited.

+ References

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- References

No definition available.

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- Definition

Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

+ References

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Number of shares of common and preferred stock retired from treasury during the period.

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