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Shareholders' equity Dividends declared (Details) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 $ / shares | Sep. 30, 2017 SFr / shares | Sep. 30, 2016 $ / shares | Sep. 30, 2016 SFr / shares | Sep. 30, 2017 $ / shares | Sep. 30, 2017 SFr / shares | Sep. 30, 2016 $ / shares | Sep. 30, 2016 SFr / shares
Dividends Declared [Abstract] |  |  |  |  |  |  |  |
Common Stock, Dividend Rate Declared | (per share) | $ 0.71 | SFr 0.68 | $ 0.69 | SFr 0.67 | $ 2.11 | SFr 2.06 | $ 2.05 | SFr 2.01

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- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
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