Earnings Per Share (Schedule of Eanings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Sep. 25, 2016	Oct. 01, 2017	Sep. 25, 2016
Earnings Per Share [Abstract]
Net income (loss)	$ 2,802	$ 21	$ 2,087	$ (1,927)
Weighted average shares used to compute basic and diluted net income (loss) per share:
Weighted-average shares outstanding (in shares)	34,780	1,227	33,960	1,175
Less: weighted average shares subject to repurchase due to early exercise (in shares)	(46)	(70)	(53)	(127)
Weighted average shares used to compute basic net income (loss) per share (in shares)	34,734	1,157	33,907	1,048
Dilutive effect of convertible preferred stock, warrants to purchase preferred stock, stock options, common stock warrants, ESPP and RSUs (in shares)	3,791	28,817	4,512	0
Weighted average shares used to compute basic and diluted net income (loss) per share (in shares)	38,525	29,974	38,419	1,048
Net income (loss) per share:
Basic (usd per share)	$ 0.08	$ 0.02	$ 0.06	$ (1.84)
Diluted (usd per share)	$ 0.07	$ 0.00	$ 0.05	$ (1.84)