CASH EQUIVALENTS, INVESTMENTS AND FAIR VALUE MEASUREMENTS - Cost and fair value (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Amortized Cost	$ 412,252	$ 579,620
Gross Unrealized Gains		10
Gross Unrealized Losses	(2,695)	(612)
Fair Value	409,557	579,018
U.S. treasury securities
Amortized Cost	245,177	247,287
Gross Unrealized Losses	(2,526)	(520)
Fair Value	242,651	246,767
U.S. government agency securities
Amortized Cost	5,029	5,104
Gross Unrealized Losses	(17)	(7)
Fair Value	5,012	5,097
Corporate securities
Amortized Cost	6,002	35,627
Gross Unrealized Losses	(12)	(39)
Fair Value	5,990	35,588
Commercial paper
Amortized Cost	87,942	235,352
Gross Unrealized Gains		10
Gross Unrealized Losses	(140)	(46)
Fair Value	87,802	235,316
Money market funds
Amortized Cost	68,102	56,250
Fair Value	$ 68,102	$ 56,250

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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Amount, before tax, of unrealized loss 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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Amortized cost of 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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