Shareholders' equity - Accumulated other comprehensive income into income expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 02, 2023	Jun. 26, 2022	Jul. 02, 2023	Jun. 26, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of goods sold	$ 335,436	$ 315,709	$ 654,988	$ 611,191
Total before tax	126,955	123,967	224,435	217,307
(Benefit) tax	(15,532)	(18,412)	(35,716)	(34,385)
Income from continuing operations	111,423	105,555	188,719	182,922
Reclassification out of accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total reclassifications, net of tax	(604)	1,127	(2,059)	2,868
Reclassification out of accumulated other comprehensive income | Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total before tax	2,069	1,989	4,135	3,989
Reclassification out of accumulated other comprehensive income | Prior-service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total before tax	(252)	(252)	(504)	(504)
Reclassification out of accumulated other comprehensive income | Pension and Other Postretirement Benefits Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total before tax	1,817	1,737	3,631	3,485
(Benefit) tax	(418)	(405)	(835)	(812)
Income from continuing operations	1,399	1,332	2,796	2,673
Reclassification out of accumulated other comprehensive income | Foreign exchange contract | Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of goods sold	(2,181)	(229)	(5,235)	169
Total before tax	(2,181)	(229)	(5,235)	169
(Benefit) tax	178	24	380	26
Income from continuing operations	$ (2,003)	$ (205)	$ (4,855)	$ 195