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Cash and Investments in Marketable Securities - Portfolio of Cash and Investments in Marketable Securities (Detail) - USD ($) $ in Thousands | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Gross Unrealized Gains |  | $ 1,100
Gross Unrealized Losses |  | (200)
Cash | $ 14,056 | 6,285
Total cash and investments in marketable securities | 1,057,462 | 1,198,558
Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Amortized Cost | 896,784 |
Gross Unrealized Gains | 205 |
Gross Unrealized Losses | (127) |
Fair Value | 896,862 | 1,003,348
Corporate notes and bonds | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Amortized Cost | 403,490 |
Gross Unrealized Gains | 152 |
Gross Unrealized Losses | (91) |
Fair Value | 403,551 | 687,469
Corporate commercial paper | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Amortized Cost | 487,414 |
Gross Unrealized Gains | 51 |
Gross Unrealized Losses | (35) |
Fair Value | 487,430 | 313,497
Obligations of U.S. government agencies | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Amortized Cost | 5,880 |
Gross Unrealized Gains | 2 |
Gross Unrealized Losses | (1) |
Fair Value | 5,881 | 2,382
Money market funds | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Money market funds | 138,289 | 179,302
Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Money market funds | $ 8,255 | $ 9,623

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