Share-based compensation - Fair Value and Valuation Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 30, 2023	Dec. 31, 2022	Jan. 01, 2022
—SARs
Share-based Compensation Arrangement by Share-based Payment Award
Assumed fair value exercise price (in usd per share)	$ 6.57	$ 6.94	$ 6.66
Expected volatility (as a percent)	42.80%	43.50%	46.10%
Expected option life (in years)	6 years	6 years	6 years
Risk-free interest rate (as a percent)	4.03%	1.91%	0.95%
—Share options
Share-based Compensation Arrangement by Share-based Payment Award
Assumed fair value exercise price (in usd per share)			$ 6.66
Expected volatility (as a percent)			46.10%
Expected option life (in years)			6 years
Risk-free interest rate (as a percent)			0.95%
—Premium-priced options
Share-based Compensation Arrangement by Share-based Payment Award
Assumed fair value exercise price (in usd per share)			$ 6.36
Expected volatility (as a percent)			46.10%
Expected option life (in years)			6 years
Risk-free interest rate (as a percent)			0.95%
—RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Assumed fair value exercise price (in usd per share)	$ 13.79	$ 13.67	$ 15.16
—PRSUs
Share-based Compensation Arrangement by Share-based Payment Award
Assumed fair value exercise price (in usd per share)	$ 15.88	$ 17.23	$ 17.92
Expected volatility (as a percent)	37.70%	49.10%	50.80%
Risk-free interest rate (as a percent)	4.60%	1.72%	0.27%