Available-for-Sale Marketable Securities

12 Months Ended

Dec. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Available-for-Sale Marketable Securities

3. Available-for-Sale Marketable Securities

As of December 31, 2015, the Company’s available-for-sale marketable securities consisted of money market mutual funds and debt securities issued by the U.S. government and government-sponsored entities and by investment grade institutions. As of December 31, 2014 and for the years ended December 31, 2014 and 2013, all of the Company’s funds were held in money market savings and checking accounts that were classified as cash equivalents and not as available-for-sale marketable securities.

The following table summarizes the Company’s available-for-sale marketable securities by major type of security as of December 31, 2015:

	Amortized Cost		Gross Unrealized					Estimated Fair Value
Type of Security			Gains		Losses
Money market mutual funds	$	42,017	$	—	$	(31	)	$	41,986
U.S. Treasury securities		2,528		—		—			2,528
Other U.S. government agency obligations		13,492		4		—			13,496
Corporate bonds		14,194		—		(6	)		14,188
Commercial paper		19,444		1		(3	)		19,442
Total available-for-sale marketable securities	$	91,675	$	5	$	(40	)	$	91,640

All available-for-sale marketable securities are classified in the Balance Sheets as Marketable Securities.

The Company classifies its marketable debt securities based on their contractual maturity dates. The marketable debt securities as of December 31, 2015 mature at various dates through September 2016. The fair values and amortized cost of marketable debt securities by contractual maturity were as follows. The table does not include money market funds that are classified as available-for-sale marketable securities.

	As of December 31,
	2015				2014
Contractual maturity	Fair Value		Amortized Cost		Fair Value		Amortized Cost
Less than one year	$	49,653	$	49,657	$	—	$	—

For the year ended December 31, 2015, there were no sales of available-for-sale marketable securities.

The following table shows the fair value of the Company’s available-for-sale marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual investments have been in a continuous unrealized loss position.

	Less than 12 Months					12 Months or Greater				Total
As of December 31, 2015	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Money market mutual funds	$	30,985	$	(31	)	$	—	$	—	$	30,985	$	(31	)
Corporate bonds		14,187		(6	)		—		—		14,187		(6	)
Commercial paper		11,960		(3	)		—		—		11,960		(3	)
Total	$	57,132	$	(40	)	$	—	$	—	$	57,132	$	(40	)

As of December 31, 2015, the Company held a total of 15 positions that were in an unrealized loss position, none of which had been in an unrealized loss position for 12 months or greater. Based on the Company’s review of these securities, the Company believes that the cost basis of its available-for-sale marketable securities is recoverable and that, therefore, it had no other-than-temporary impairments on these securities as of December 31, 2015. The Company does not intend to sell these debt securities and the Company believes it is not more likely than not that it will be required to sell these securities before the recovery of their amortized cost basis, which may be maturity.