Equity Incentive Plans - Recorded Stock-Based Compensation Expense in the Condensed Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement, Expensed [Line Items]
Stock-based compensation expense	$ 48,626	$ 13,333	$ 2,658
Cost of revenue
Share-based Payment Arrangement, Expensed [Line Items]
Stock-based compensation expense	1,551	325	85
Research and development
Share-based Payment Arrangement, Expensed [Line Items]
Stock-based compensation expense	19,623	5,721	1,030
Selling, general and administrative
Share-based Payment Arrangement, Expensed [Line Items]
Stock-based compensation expense	$ 27,452	$ 7,287	$ 1,543

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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Balance Type:	debit
Period Type:	duration