Current Liabilities - Warranty Accrual (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Apr. 02, 2016
Accounts Payable and Accrued Liabilities, Current [Abstract]
New product warranty period	12 months
Refurbished product warranty period	3 months
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Balance, beginning of the period	$ 1,884
Liabilities accrued for warranties issued	813	$ 653
Warranty claims paid and utilized	(558)	(548)
Changes in accrued warranty liabilities	(13)	(21)
Balance, end of the period	$ 2,126	$ 1,884