Current Liabilities - Other Current Liabilities (Details) - USD ($) $ in Thousands	Jul. 04, 2015	Apr. 04, 2015	Dec. 31, 2014		Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2013
Accounts Payable and Accrued Liabilities, Current [Abstract]
Salaries and benefits	$ 5,672		$ 6,619
Warranty accrual	1,766	$ 1,737	1,501		$ 1,083	$ 1,055	$ 1,142
Advanced billings	79		202
Capital lease, current portion	817		796
Other	3,625		2,184
Balance, end of the period	$ 11,959		$ 11,302	[1]

[1] The balance sheet as of December 31, 2014 has been derived from the audited financial statements at that date.