Stockholders' Equity Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Sep. 29, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Loss, Net of Tax
Balance, beginning of year			$ (61,673)			$ (46,198)	$ (61,673)	$ (46,198)
Current-period other comprehensive income (loss)	$ (2,297)	$ 3,835	6,025	$ 5,315	$ (4,325)	(5,927)	7,563	(4,937)
Balance, end of the period	(54,110)			(51,135)			(54,110)	(51,135)
Foreign Currency Translation
Accumulated Other Comprehensive Loss, Net of Tax
Balance, beginning of year			(61,673)			(45,149)	(61,673)	(45,149)
Current-period other comprehensive income (loss)							7,563	(5,054)
Balance, end of the period	(54,110)			(50,203)			(54,110)	(50,203)
Pension
Accumulated Other Comprehensive Loss, Net of Tax
Balance, beginning of year			$ 0			$ (1,049)	0	(1,049)
Current-period other comprehensive income (loss)							0	117
Balance, end of the period	$ 0			$ (932)			$ 0	$ (932)