Condensed Consolidated Balance Sheets - Unaudited (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 30, 2016
Current assets:
Allowance for doubtful accounts	$ 0.7	$ 0.7
Stockholders’ equity:
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	31,497,758	31,059,038
Common stock, shares outstanding	31,394,605	30,925,496
Treasury stock, shares	103,153	133,542