Earnings per share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Earnings Per Share [Abstract]
Net income attributable to shareholders	$ 41.9	$ 35.5	$ 55.1	$ 670.7
Weighted average number of shares outstanding (in shares)	290,769,392	290,109,231	290,634,292	290,032,416
Dilutive effect of share-based awards (in shares)	1,672,207	1,003,871	1,249,143	1,634,515
Diluted weighted average number of shares outstanding (in shares)	292,441,599	291,113,102	291,883,435	291,666,931
Number of anti-dilutive shares excluded from diluted (loss) earnings per share calculation (in shares)	3,896,143	3,623,701	5,811,571	3,686,986
Basic earnings per share (in usd per share)	$ 0.14	$ 0.12	$ 0.19	$ 2.31
Diluted earnings per share (in usd per share)	$ 0.14	$ 0.12	$ 0.19	$ 2.30