Restructuring, acquisition and integration-related costs - Restructuring and Related Costs by Type of Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring, acquisition and integration-related costs			$ 27,099	$ 28,300
Cost of sales
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 8,309	$ 16,716	23,372	24,540
Acquisition integration-related costs	536	743	1,313	1,546
Restructuring, acquisition and integration-related costs	8,845	17,459	24,685	26,086
Selling, general and administrative expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs	2,437	2,060	3,727	3,760
Acquisition transaction-related costs	803	0	1,015	0
Acquisition integration-related costs	1,768	1,828	4,282	4,563
Restructuring, acquisition and integration-related costs	$ 5,008	$ 3,888	$ 9,024	$ 8,323