FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Available-for-sale Securities (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 49,350
Gross Unrealized Gains	2
Gross Unrealized Losses	(48)
Aggregate Estimated Fair Value	49,304
U.S. government agency-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,382
Gross Unrealized Gains	2
Gross Unrealized Losses	(1)
Aggregate Estimated Fair Value	7,383
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	41,968
Gross Unrealized Gains	0
Gross Unrealized Losses	(47)
Aggregate Estimated Fair Value	$ 41,921

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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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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