Condensed Consolidated Balance Sheets - Unaudited (Parenthetical) - USD ($) $ in Millions	Sep. 29, 2017	Dec. 30, 2016
Current assets:
Allowance for doubtful accounts	$ 1.0	$ 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	31,776,356	31,059,038
Common stock, shares outstanding	31,669,830	30,925,496
Treasury stock, shares	106,526	133,542