CASH EQUIVALENTS, INVESTMENTS AND FAIR VALUE MEASUREMENTS - Fair value of company's financial assets (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Total	$ 489,203	$ 579,018
U.S. treasury securities
Total	246,484	246,767
U.S. government agency securities
Total	5,046	5,097
Corporate securities
Total	34,329	35,588
Commercial paper
Total	158,095	235,316
Money market funds
Total	45,249	56,250
Level 1
Total	291,733	303,017
Level 1 | U.S. treasury securities
Total	246,484	246,767
Level 1 | Money market funds
Total	45,249	56,250
Level 2
Total	197,470	276,001
Level 2 | U.S. government agency securities
Total	5,046	5,097
Level 2 | Corporate securities
Total	34,329	35,588
Level 2 | Commercial paper
Total	$ 158,095	$ 235,316