Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Apr. 01, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Reserves for accounts receivable	$ 1,664	$ 1,568
Common stock, par value	$ 0.002	$ 0.002
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	172,948,000	173,507,000
Common stock, shares outstanding	172,948,000	173,507,000