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Cash equivalents and available for Sale Securities Amortized Cost

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Cash equivalents and available for sale securities, gross unrealized gain, before tax.

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Cash equivalents and available for sale securities, gross unrealized loss, before Tax

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Cash Equivalents, Gross Unrealized Loss, Before Tax

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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CASH EQUIVALENTS AND MARKETABLE SECURITIES - Summary of Cash Equivalents and Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
ASSETS
Cash equivalents, Amortized Cost	$ 176,954	$ 131,329	$ 259,393	$ 80,428
Available-for-sale securities, Amortized Cost	342,080	560,575
Available-for-sale securities, Gross Unrealized Gains	57	86
Available-for-sale securities, Gross Unrealized (Losses)	(47)	(37)
Available-for-sale securities, Estimated Fair Value	342,090	560,624
Total cash equivalents and available-for-sale securities, Amortized Cost	466,672	613,740
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	57	86
Total cash equivalents and available-for-sale securities, Gross Unrealized (Losses)	(47)	(37)
Total cash equivalents and available-for-sale securities, Estimated Fair Value	466,682	613,789
Money market funds
ASSETS
Cash equivalents, Amortized Cost	124,592	53,165
Cash equivalents, Gross Unrealized Gains	0	0
Cash equivalents, Gross Unrealized (Losses)	0	0
Cash equivalents, Estimated Fair Value	124,592	53,165
Cash equivalents
ASSETS
Cash equivalents, Amortized Cost	124,592	53,165
Cash equivalents, Gross Unrealized Gains	0	0
Cash equivalents, Gross Unrealized (Losses)	0	0
Cash equivalents, Estimated Fair Value	124,592	53,165
U.S. government-sponsored entity debt securities
ASSETS
Available-for-sale securities, Amortized Cost	87,159	257,284
Available-for-sale securities, Gross Unrealized Gains	12	19
Available-for-sale securities, Gross Unrealized (Losses)	(4)	(5)
Available-for-sale securities, Estimated Fair Value	87,167	257,298
Commercial paper securities
ASSETS
Available-for-sale securities, Amortized Cost	98,046	213,500
Available-for-sale securities, Gross Unrealized Gains	24	41
Available-for-sale securities, Gross Unrealized (Losses)	(5)	(8)
Available-for-sale securities, Estimated Fair Value	98,065	213,533
Corporate debt securities
ASSETS
Available-for-sale securities, Amortized Cost	33,697	59,575
Available-for-sale securities, Gross Unrealized Gains	3	16
Available-for-sale securities, Gross Unrealized (Losses)	(6)	(17)
Available-for-sale securities, Estimated Fair Value	33,694	59,574
Asset-backed securities
ASSETS
Available-for-sale securities, Amortized Cost	74,350	17,905
Available-for-sale securities, Gross Unrealized Gains	7	10
Available-for-sale securities, Gross Unrealized (Losses)	(31)	(7)
Available-for-sale securities, Estimated Fair Value	74,326	17,908
Certificates of deposit
ASSETS
Available-for-sale securities, Amortized Cost	48,828	12,311
Available-for-sale securities, Gross Unrealized Gains	11	0
Available-for-sale securities, Gross Unrealized (Losses)	(1)	0
Available-for-sale securities, Estimated Fair Value	$ 48,838	$ 12,311