Warranties (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Components of the warranty accrual [Roll Forward]
Balance as of beginning of period	$ 3,792	$ 3,484	$ 2,953	$ 3,426
Accruals for warranties issued during period	2,288	1,242	6,240	4,459
Settlements during the period	(1,789)	(1,736)	(4,902)	(4,895)
Balance as of end of period	$ 4,291	$ 2,990	$ 4,291	$ 2,990