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Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net loss	$ (7,121)	$ 6,974	$ (20,223)	$ (5,952)	$ (7,213)	$ (43,052)	$ (13,022)	$ (7,275)	$ (26,322)	$ (70,562)	$ (54,099)
Shares used in basic and diluted net loss per share (in shares)									126,564	122,677	119,994
Basic and diluted net loss per share (in dollars per share)	$ (0.05)	$ 0.05	$ (0.16)	$ (0.05)	$ (0.06)	$ (0.35)	$ (0.11)	$ (0.06)	$ (0.21)	$ (0.58)	$ (0.45)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS (in shares)									7,567	6,622
Stock options, RSU's and ESPP shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS (in shares)											8,978