Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 27, 2019	Dec. 28, 2018
Statement Of Financial Position [Abstract]
Accounts receivable and contract assets, allowance	$ 710	$ 1,441
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,250,000	1,250,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	57,137,480	56,607,622
Treasury stock, at cost, shares	27,280,200	27,086,782