4. Investments

The following table summarizes the Company’s investments as of June 30, 2016 (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss			Fair Value
Current:
Corporate debt securities	$	63,265	$	31	$	(12	)	$	63,284
Commercial paper		20,697		36		—			20,733
U.S. government and agency securities		1,000		1		—			1,001
Non-current:
Corporate debt securities (one to two year maturity)		38,273		160		—			38,433
U.S. government and agency securities (one to two year maturity)		4,500		1		—			4,501

	$	127,735	$	229	$	(12	)	$	127,952

The following table summarizes the Company’s investments as of December 31, 2015 (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Loss			Fair Value
Current:
Corporate debt securities	$	86,515	$	4	$	(72	)	$	86,447
Commercial paper		29,808		20		—			29,828
U.S. government and agency securities		1,000		—		—			1,000
Non-current:
Corporate debt securities (one to two year maturity)		34,019		2		(143	)		33,878

	$	151,342	$	26	$	(215	)	$	151,153

At June 30, 2016 and December 31, 2015, the Company held 19 and 69 debt securities that were in an unrealized loss position for less than one year, respectively. The aggregate fair value of debt securities in an unrealized loss position at June 30, 2016 and December 31, 2015 was $25,406 and $117,851, respectively. There were no individual securities that were in a significant unrealized loss position or that had been in an unrealized loss position for greater than one year as of June 30, 2016 or December 31, 2015.

The Company reviews investments for other-than-temporary impairment whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time.

Other-than-temporary impairments of investments are recognized in the condensed consolidated statements of operations if the Company has experienced a credit loss and has the intent to sell the investment or if it is more likely than not that the Company will be required to sell the investment before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period.