Stockholders' Equity - Narrative (Details) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended
Jul. 04, 2020 USD ($) $ / shares shares
Stock options and RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to unvested awards \| $	$ 115.8
Unrecognized compensation expense related to unvested awards, estimated weighted average period	2 years
Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price (in dollars per share) \| $ / shares	$ 6.29
Common Class A \| 2015 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Class A common stock reserved for future issuance (in shares) \| shares	32.6

Aggregate number of common shares reserved for future issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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