Revenue Recognition - Sales Returns (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017
Sales Return Liability [Roll Forward]
Balance at beginning of year	$ 19,270	$ 15,222
Additions that reduce net sales	57,296	55,720
Deductions from reserves	(56,031)	(52,494)
Balance at end of period	$ 20,535	$ 18,448