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, 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)		5,776,611
Issuance of common stock	6,812		6,812
Stock-based compensation expense	41,093		41,093
Net loss	(147,983)				(147,983)
Other comprehensive income	329			329
Ending balance (in shares) at Jun. 29, 2019		258,139,452
Ending balance at Jun. 29, 2019	625,544	$ 25	1,092,306	263	(467,050)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition	(10,645)		(10,645)
Beginning balance (in shares) at Mar. 30, 2019		254,744,029
Beginning balance at Mar. 30, 2019	671,813	$ 25	1,070,224	96	(398,532)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		3,395,423
Issuance of common stock	5,881		5,881
Stock-based compensation expense	20,424		20,424
Taxes related to net share settlement of restricted stock units	(4,223)		(4,223)
Net loss	(68,518)				(68,518)
Other comprehensive income	167			167
Ending balance (in shares) at Jun. 29, 2019		258,139,452
Ending balance at Jun. 29, 2019	625,544	$ 25	1,092,306	263	(467,050)
Beginning balance (in shares) at Dec. 31, 2019		264,883,426
Beginning balance at Dec. 31, 2019	487,263	$ 26	1,126,827	188	(639,778)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		4,700,954
Issuance of common stock	1,003		1,002
Stock-based compensation expense	37,920		37,920
Net loss	(83,803)				(83,803)
Other comprehensive income	162			162
Ending balance (in shares) at Jul. 04, 2020		269,584,380
Ending balance at Jul. 04, 2020	430,316	$ 27	1,153,520	350	(723,581)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition	(12,229)		(12,229)
Beginning balance (in shares) at Apr. 04, 2020		266,806,999
Beginning balance at Apr. 04, 2020	521,055	$ 26	1,140,280	233	(619,484)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		2,777,381
Issuance of common stock	545	$ 1	544
Stock-based compensation expense	19,057		19,057
Taxes related to net share settlement of restricted stock units	(6,361)		(6,361)
Net loss	(104,097)				(104,097)
Other comprehensive income	117			117
Ending balance (in shares) at Jul. 04, 2020		269,584,380
Ending balance at Jul. 04, 2020	$ 430,316	$ 27	$ 1,153,520	$ 350	$ (723,581)