FAIR VALUE MEASUREMENTS - SECURITY TYPE (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Included in cash and cash equivalents:
Amortized Cost	$ 27,577	$ 31,706
Gross Unrealized Losses	(1)
Estimated Fair Value	27,576	31,706
Restricted cash:
Amortized Cost	364	364
Estimated Fair Value	364	364
Marketable securities:
Amortized Cost	147,001	177,675
Gross Unrealized Gains		4
Gross Unrealized Losses	(711)	(177)
Estimated Fair Value	146,290	177,502
Money market funds
Included in cash and cash equivalents:
Amortized Cost	15,327	24,207
Estimated Fair Value	15,327	24,207
Restricted cash:
Amortized Cost	93	93
Estimated Fair Value	93	93
Commercial paper
Included in cash and cash equivalents:
Amortized Cost	7,999	7,499
Estimated Fair Value	7,999	7,499
Corporate notes
Included in cash and cash equivalents:
Amortized Cost	4,251
Gross Unrealized Losses	(1)
Estimated Fair Value	4,250
Certificate of deposit
Restricted cash:
Amortized Cost	271	271
Estimated Fair Value	271	271
U.S. Treasury securities (due in less than one year)
Marketable securities:
Amortized Cost	20,650	15,585
Gross Unrealized Losses	(107)	(18)
Estimated Fair Value	20,543	15,567
U.S. Treasury securities (due in one to two years)
Marketable securities:
Amortized Cost		1,524
Gross Unrealized Losses		(3)
Estimated Fair Value		1,521
Municipal securities (due in less than one year)
Marketable securities:
Amortized Cost	3,000
Gross Unrealized Losses	(53)
Estimated Fair Value	2,947
Municipal securities (due in one to two years)
Marketable securities:
Amortized Cost		3,000
Gross Unrealized Losses		(15)
Estimated Fair Value		2,985
Government-sponsored enterprise securities (due in less than one year)
Marketable securities:
Amortized Cost	6,500	12,500
Gross Unrealized Losses	(39)	(7)
Estimated Fair Value	6,461	12,493
Commercial paper (due in less than one year)
Marketable securities:
Amortized Cost	69,434	84,398
Gross Unrealized Gains		2
Gross Unrealized Losses	(233)	(38)
Estimated Fair Value	69,201	84,362
Corporate notes (due in less than one year)
Marketable securities:
Amortized Cost	36,404	36,444
Gross Unrealized Gains		2
Gross Unrealized Losses	(211)	(17)
Estimated Fair Value	36,193	36,429
Corporate notes (due in one to two years)
Marketable securities:
Amortized Cost	11,013	24,224
Gross Unrealized Losses	(68)	(79)
Estimated Fair Value	$ 10,945	$ 24,145

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