INVESTMENT SECURITIES - Summary of investment securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized cost, as adjusted	$ 26,284	$ 27,798
Gross unrealized holding gains	106	28
Gross unrealized holding losses	0	0
Estimated fair value	26,390	27,826
Short-term Investments [Member] \| Obligations of domestic governmental agencies [Member]
Amortized cost, as adjusted	26,284	27,798
Gross unrealized holding gains	106	28
Gross unrealized holding losses	0	0
Estimated fair value	$ 26,390	$ 27,826

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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