Stockholders' Equity - Summary of Changes in Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 26, 2016	Jun. 28, 2015	Jun. 26, 2016	Jun. 28, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders’ equity at beginning of period			$ 254.2	$ 224.3
Comprehensive loss:
Net loss	$ (10.4)	$ (15.0)	(32.6)	(31.3)
Change in cumulative translation adjustment	(0.1)	0.3	(0.1)	0.1
Comprehensive loss	(10.5)	(14.7)	(32.7)	(31.2)
Stock-based compensation			3.1	4.0
Issuance of common stock for employee stock purchase plan			1.3	1.8
Restricted stock units traded for taxes			(0.3)	(0.2)
Stockholders’ equity at end of period	$ 225.6	$ 198.7	$ 225.6	$ 198.7