Other Current Liabilities - Accrued Warranty Activity (Details) $ in Thousands	3 Months Ended
	Mar. 30, 2018 USD ($)
Activity In Accrued Warranty And Service Liabilities Abstract
Balance, beginning of year	$ 10,535
Charged to expense	2,003
Margin on parts sales reversed	1,053
Reductions for claims settled	(2,483)
Balance, end of period	$ 11,108