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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. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Earnings Per Share [Abstract]
Net loss	$ (7,213)	$ (43,052)	$ (13,022)	$ (7,275)	$ (8,164)	$ (12,414)	$ (13,810)	$ (19,711)	$ (70,562)	$ (54,099)	$ (159,233)
Shares used in basic and diluted net loss per share (in shares)									122,677	119,994	117,387
Basic and diluted net loss per share (in dollars per share)	$ (0.06)	$ (0.35)	$ (0.11)	$ (0.06)	$ (0.07)	$ (0.10)	$ (0.12)	$ (0.17)	$ (0.58)	$ (0.45)	$ (1.36)
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)									6,622	8,978	9,243