Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2017		238,756,522
Beginning balance at Dec. 31, 2017	$ 823,963	$ 24	$ 956,060	$ (9)	$ (132,112)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		8,854,756
Issuance of common stock	11,646	$ 1	11,645
Stock-based compensation expense	73,783		73,783
Taxes related to net share settlement of restricted stock units	(15,685)		(15,685)
Net loss	(201,201)				(201,201)
Other comprehensive loss	3,342			3,342
Ending balance (in shares) at Sep. 29, 2018		247,611,278
Ending balance at Sep. 29, 2018	694,721	$ 25	1,025,803	3,333	(334,440)
Beginning balance (in shares) at Jun. 30, 2018		245,041,726
Beginning balance at Jun. 30, 2018	678,959	$ 25	1,006,639	4,679	(332,384)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		2,569,552
Issuance of common stock	908	$ 0	908
Stock-based compensation expense	23,954		23,954
Taxes related to net share settlement of restricted stock units	(5,698)		(5,698)
Net loss	(2,056)				(2,056)
Other comprehensive loss	(1,346)			(1,346)
Ending balance (in shares) at Sep. 29, 2018		247,611,278
Ending balance at Sep. 29, 2018	694,721	$ 25	1,025,803	3,333	(334,440)
Beginning balance (in shares) at Dec. 31, 2018		252,362,841
Beginning balance at Dec. 31, 2018	735,938	$ 25	1,055,046	(66)	(319,067)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		7,522,885
Issuance of common stock	7,045	$ 1	7,044
Stock-based compensation expense	59,064		59,064
Taxes related to net share settlement of restricted stock units	(13,495)		(13,495)
Net loss	(199,876)				(199,876)
Other comprehensive loss	298			298
Ending balance (in shares) at Sep. 28, 2019		259,885,726
Ending balance at Sep. 28, 2019	588,974	$ 26	1,107,659	232	(518,943)
Beginning balance (in shares) at Jun. 29, 2019		258,139,452
Beginning balance at Jun. 29, 2019	625,544	$ 25	1,092,306	263	(467,050)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		1,746,274
Issuance of common stock	233		232
Stock-based compensation expense	17,971		17,971
Taxes related to net share settlement of restricted stock units	(2,850)		(2,850)
Net loss	(51,893)
Other comprehensive loss	(31)			(31)
Ending balance (in shares) at Sep. 28, 2019		259,885,726
Ending balance at Sep. 28, 2019	$ 588,974	$ 26	$ 1,107,659	$ 232	$ (518,943)