Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Millions	3 Months Ended
	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 SFr / shares	Jun. 30, 2019 SFr / shares	Mar. 31, 2019 SFr / shares	Sep. 30, 2018 SFr / shares	Jun. 30, 2018 SFr / shares	Mar. 31, 2018 SFr / shares
Common shares, par value							SFr 0.03
Common Shares [Member]
Issuance costs | $	$ 2.3	$ 1.3	$ 1.2	$ 15.5	$ 0.0	$ 8.2
Common shares, par value							SFr 0.03	SFr 0.03	SFr 0.03	SFr 0.03	SFr 0.03	SFr 0.03