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Balance Sheet Components - Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | $ 354,431 | $ 8,272
Gross Unrealized Holding Gains | 153 | 119
Gross Unrealized Holding Losses | (73) | (3)
Fair Value | 354,511 | 8,388
Corporate bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 127,005 |
Gross Unrealized Holding Gains | 35 |
Gross Unrealized Holding Losses | (46) |
Fair Value | 126,994 |
Commercial paper [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 95,402 |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 0 |
Fair Value | 95,402 |
U.S. government bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 73,119 |
Gross Unrealized Holding Gains | 5 |
Gross Unrealized Holding Losses | (16) |
Fair Value | 73,108 |
Agency bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 23,399 |
Gross Unrealized Holding Gains | 4 |
Gross Unrealized Holding Losses | (4) |
Fair Value | 23,399 |
Asset-backed securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 27,261 |
Gross Unrealized Holding Gains | 2 |
Gross Unrealized Holding Losses | (7) |
Fair Value | 27,256 |
Foreign government bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 8,127 |
Gross Unrealized Holding Gains | 0 |
Gross Unrealized Holding Losses | 0 |
Fair Value | 8,127 |
Bond and mutual funds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost |  | 8,147
Gross Unrealized Holding Gains |  | 0
Gross Unrealized Holding Losses |  | (3)
Fair Value |  | 8,144
Equity investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 118 | 125
Gross Unrealized Holding Gains | 107 | 119
Gross Unrealized Holding Losses | 0 | 0
Fair Value | $ 225 | $ 244

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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
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