Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 SFr / shares	Dec. 31, 2018 SFr / shares	Dec. 31, 2017 SFr / shares
Common shares, par value | SFr / shares			SFr 0.03	SFr 0.03
Stock Options [Member]
Issuance costs | $	$ 0.3	$ 0.4
Common Shares [Member]
Issuance costs | $	$ 25.1	$ 23.8
Common shares, par value | SFr / shares			SFr 0.03	SFr 0.03	SFr 0.03