Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 25, 2020	Dec. 27, 2019
Statement Of Financial Position [Abstract]
Account receivable, allowance for doubtful accounts	$ 0.3	$ 0.3
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000.0	10,000,000.0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	90,000,000.0	90,000,000.0
Common stock, shares issued	40,500,000	40,500,000
Common stock, shares outstanding	39,900,000	39,900,000
Treasury stock, shares	600,000	600,000