FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of financial instruments measured at fair value on recurring basis

	December 31, 2018
	Fair Value Measurements Using
	Quoted Prices  in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Money market accounts	$	81,425	—		—		$	81,425
U.S. Treasury securities	—		13,930		$	—	13,930
Total assets at fair value (2)	$	81,425	$	13,930	$	—	$	95,355

(2) The above table excludes $29.6 million of cash held in banks.

Financial instruments measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 are classified based on the valuation technique in the table below (in thousands):

	March 31, 2019
	Fair Value Measurements Using
	Quoted Prices  in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Money market accounts	$	70,848	—		—		$	70,848
U.S. Treasury securities	—		14,959		$	—	14,959
Total assets at fair value (1)	$	70,848	$	14,959	$	—	$	85,807

(1) The above table excludes $31.8 million of cash held in banks.

Schedule of short-term investments

Short-term investments as of March 31, 2019 and December 31, 2018 consists of the following (in thousands):

	March 31, 2019
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
U.S. Treasury securities	$	14,960	$	—	$	(1	)	$	14,959
Total	$	14,960	$	—	$	(1	)	$	14,959

	December 31, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
U.S. Treasury securities	$	13,936	$	—	$	(6	)	$	13,930
Total	$	13,936	$	—	$	(6	)	$	13,930