Intangible assets (Schedule of major components) (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Jan. 01, 2022
Finite-Lived Intangible Assets [Line Items]
Cost	$ 203,815	$ 216,399
Accumulated amortization	68,169	67,959
Net book value	135,646	148,440
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	177,996	189,407
Accumulated amortization	64,578	64,867
Net book value	113,418	124,540
Brand names [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	25,073	25,073
Accumulated amortization	2,845	1,173
Net book value	22,228	23,900
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	746	1,919
Accumulated amortization	746	1,919
Net book value	$ 0	$ 0