INVESTMENTS - By type (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Marketable securities by type
Cost	$ 61,717	$ 20,006
Gross Unrealized Gains	126	19
Gross Unrealized Losses	(37)	(21)
Estimated Fair Value	61,806	20,004
Commercial paper and corporate bonds
Marketable securities by type
Cost	15,765	7,540
Gross Unrealized Gains	13
Gross Unrealized Losses	(37)	(20)
Estimated Fair Value	15,741	7,520
U.S. government agency debt securities
Marketable securities by type
Cost	45,952	12,466
Gross Unrealized Gains	113	19
Gross Unrealized Losses		(1)
Estimated Fair Value	$ 46,065	$ 12,484

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).

+ References

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-Topic 320
-SubTopic 10
-Section 50
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Amount 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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