FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value

The following table represents the fair value of the Company’s financial instruments, including those measured at fair value on a recurring basis and those held-to-maturity as of December 31, 2017 and 2016 (in thousands):

	December 31, 2017								December 31, 2016
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Cash Equivalents:
Money market funds	$	217,838	$	—	$	—	$	217,838	$	152,423	$	—	$	—	$	152,423
Commercial paper	—		46,927		—		46,927		—		—		—		—
Marketable Securities:
Commercial paper	—		138,412		—		138,412		—		45,894		—		45,894
Agency bonds	—		78,913		—		78,913		—		152,394		—		152,394
Corporate bonds	—		69,926		—		69,926		—		9,006		—		9,006
Agency discount notes	—		10,989		—		10,989		—		—		—		—
Total cash equivalents and marketable securities	$	217,838	$	345,167	$	—	$	563,005	$	152,423	$	207,294	$	—	$	359,717