Goodwill and intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2016	Jan. 03, 2015	Dec. 28, 2013
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill Opening	$ 29,082	$ 30,668
Goodwill, Acquired During Period	213,481
Goodwill, Translation Adjustments	(873)	(1,586)
Goodwill Ending	241,690	29,082	$ 30,668
Finite Lived Intangible Assets Accumulated Amortization	20,156	15,565
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	11,531
Finite-Lived Intangible Assets, Amortization Expense, Year Two	11,406
Finite-Lived Intangible Assets, Amortization Expense, Year Three	11,385
Finite-Lived Intangible Assets, Amortization Expense, Year Four	11,052
Finite-Lived Intangible Assets, Amortization Expense, Year Five	10,524
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	139,110
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	195,008
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net, Opening	13,755	16,282
Acquisitions	186,459
Intangible asset amortization	(4,951)	(2,036)	(2,182)
Impact of foreign exchange	(255)	(491)
Finite-Lived Intangible Assets, Net, Ending	195,008	13,755	16,282
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net, Opening	13,504	15,962
Acquisitions	186,251
Intangible asset amortization	(4,867)	(1,967)
Impact of foreign exchange	(255)	(491)
Finite-Lived Intangible Assets, Net, Ending	194,633	13,504	15,962
Patents And Trademark [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net, Opening	251	320
Acquisitions	0
Intangible asset amortization	(68)	(69)
Impact of foreign exchange	0	0
Finite-Lived Intangible Assets, Net, Ending	183	251	320
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net, Opening	0	0
Acquisitions	208
Intangible asset amortization	(16)	0
Impact of foreign exchange	0	0
Finite-Lived Intangible Assets, Net, Ending	$ 192	$ 0	$ 0