MARKETABLE SECURITIES

9 Months Ended

Sep. 30, 2017

Marketable Securities [Abstract]

Marketable Securities

MARKETABLE SECURITIES

The amortized cost, gross unrealized gains and losses, and fair value of securities held-to-maturity, all of which mature within one year, as of September 30, 2017 and December 31, 2016 were as follows (in thousands):

	September 30, 2017
Short-term marketable securities:	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Agency bonds	$	128,005	$	1	$	(53	)	$	127,953
Commercial paper	41,817		1		—			41,818
Agency discount notes	15,948		1		—			15,949
Corporate bonds	9,998		—		(5		)	9,993
Total marketable securities	$	195,768	$	3	$	(58	)	$	195,713
	December 31, 2016
Short-term marketable securities:	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Agency bonds	$	152,429	$	18	$	(53	)	$	152,394
Commercial paper	45,894		—		—			45,894
Corporate bonds	9,009		—		(3		)	9,006
Total marketable securities	$	207,332	$	18	$	(56	)	$	207,294

The following tables present gross unrealized losses and fair values for those securities that were in an unrealized loss position as of September 30, 2017 and December 31, 2016, aggregated by investment category and the length of time that the individual securities have been in a continuous loss position (in thousands):

	September 30, 2017
	Less Than 12 Months					12 Months or Greater				Total
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Agency bonds	$	122,948	$	(53	)	$	—	$	—	$	122,948	$	(53	)
Corporate bonds	9,993		(5		)	—		—		9,993		(5		)
Total	$	132,941	$	(58	)	$	—	$	—	$	132,941	$	(58	)
	December 31, 2016
	Less Than 12 Months					12 Months or Greater				Total
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Agency bonds	$	92,018	$	(53	)	$	—	$	—	$	92,018	$	(53	)
Corporate bonds	8,006		(3		)	—		—		8,006		(3		)
Total	$	100,024	$	(56	)	$	—	$	—	$	100,024	$	(56	)

The Company periodically reviews its investment portfolio for other-than-temporary impairment. The Company considers such factors as the duration, severity and reason for the decline in value, and the potential recovery period. The Company also considers whether it is more likely than not that it will be required to sell the securities before the recovery of their amortized cost basis, and whether the amortized cost basis cannot be recovered as a result of credit losses. During the three and nine months ended September 30, 2017 and 2016, the Company did not recognize any other-than-temporary impairment loss.