Restructuring, acquisition and integration-related costs - Restructuring and Related Costs by Type of Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 18,182	$ 3,025
Cost of sales
Restructuring Cost and Reserve [Line Items]
Restructuring costs	14,090	2,898
Acquisition integration-related costs	408	(86)
Restructuring, acquisition and integration-related costs	14,498	2,812
Selling, general and administrative expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs	4,092	127
Acquisition integration-related costs	3,514	1,039
Restructuring, acquisition and integration-related costs	$ 7,606	$ 1,166