Other expense, net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Other Nonoperating Income (Expense) [Abstract]
Foreign currency losses, net	$ 3,568	$ 794	$ 6,253	$ 4,171
Release of indemnification asset	0	2,368	0	2,368
All other, net	(2,283)	677	(4,798)	(5,078)
Total other expense, net	$ 1,285	$ 3,839	$ 1,455	$ 1,461