Available-for-Sale Securities

6 Months Ended

Jun. 30, 2017

7. Available-for-Sale Securities

The following tables summarize the available-for-sale securities held at June 30, 2017 and December 31, 2016 (in thousands):


			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
June 30, 2017
U.S. Treasury securities	$	20,495	$	—	$	(5)	$	20,490
U.S. government-sponsored securities		70,292		—		(19)		70,273
Total	$	90,787	$	—	$	(24)	$	90,763


			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
December 31, 2016
U.S. Treasury securities	$	115,026	$	6	$	(11)	$	115,021
U.S. government-sponsored securities		136,193		10		(12)		136,191
Total	$	251,219	$	16	$	(23)	$	251,212

The contractual maturities of all securities held at June 30, 2017 are one year or less. There were 24 and 34 available-for-sale securities in an unrealized loss position at June 30, 2017 and December 31, 2016, respectively, none of which had been in an unrealized loss position for more than twelve months. The aggregate fair value of these securities at June 30, 2017 and December 31, 2016 was approximately $90.8 million and approximately $111.3 million, respectively. The Company reviews its investments for other-than-temporary impairment whenever the fair value of an investment is less than amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. To determine whether an impairment is other-than-temporary, the Company considers whether it has the ability and intent to hold the investment until a market price recovery and considers whether evidence indicating the cost of the investment is recoverable outweighs evidence to the contrary. The Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be maturity. The Company did not hold any securities with other-than-temporary impairment at June 30, 2017.

There were no sales of available-for-sale securities during each of the three and six months ended June 30, 2017 or 2016. Net unrealized holding gains or losses for the period that have been included in accumulated other comprehensive loss were not material to the Company’s condensed consolidated results of operations.