Goodwill and intangible assets (Summary of Changes - Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017		Dec. 31, 2016		Jan. 02, 2016
Indefinite Lived Intangible Assets By Major Class [Line Items]
Goodwill Opening	$ 223,611		$ 241,690
Goodwill, Impairment Loss	(115,000)		(17,540)		$ 0
Goodwill, Foreign Currency Translation Gain (Loss)	922		(539)
Goodwill Ending	109,533		223,611		241,690
Global Ingredients [Member]
Indefinite Lived Intangible Assets By Major Class [Line Items]
Goodwill Opening	8,255		25,990
Goodwill, Impairment Loss	0		(17,540)	[1]
Goodwill, Foreign Currency Translation Gain (Loss)	922		(195)
Goodwill Ending	9,177		8,255		25,990
Consumer Products [Member]
Indefinite Lived Intangible Assets By Major Class [Line Items]
Goodwill Opening	215,356		215,700
Goodwill, Impairment Loss	(115,000)	[2]	0
Goodwill, Foreign Currency Translation Gain (Loss)	0		(344)
Goodwill Ending	$ 100,356		$ 215,356		$ 215,700

[1] Based on the results of the annual impairment test performed for the year ended December 31, 2016 , the Company determined that the carrying value of the goodwill associated with the Sunflower reporting unit of the Raw Material Sourcing and Supply operating segment exceeded its implied fair value, reflecting lower anticipated sales demand and higher ex pected production and capital costs as a result of the sunflower recall. As a result, the Company recognized a goodwill impairment charge of $17.5 mi llion in 2016.

[2] Based on the results of the annual impairment test performed for the year ended December 30, 2017 , the Company determined that the carrying value of the Healthy Fruit reporting unit of the Consumer Products operating segment exceeded its fair value, reflecting lower-than-expected sales and operating performance for frozen fruit since the Sunr ise Acquisition, and uncertainty of future sales due to lost customer volumes and declining consumer consumption trends in 2017. As a result, the Company recognized a goodwill impairment charge of $115.0 million in 2017.