Investments

9 Months Ended

Sep. 30, 2017

Investments, Debt and Equity Securities [Abstract]

Investments

4.Investments

Our portfolio of fixed income securities consists of commercial paper, corporate debt securities and obligations of foreign government related entities. All our investments in fixed income securities are classified as held-to-maturity. These investments are carried at amortized cost.

Our investments in fixed income securities as of September 30, 2017 and December 31, 2016 were as follows:

	As of September 30, 2017
	Amortized						Fair
(in thousands)	Cost		Gains		Losses		Value
Corporate debt securities	$	5,525	$	—	$	—	$	5,525
Commercial paper		52,256		—		(4)		52,252
Government debt securities		900		—		—		900
Total	$	58,681	$	—	$	(4)	$	58,677

	As of December 31, 2016
	Amortized						Fair
(in thousands)	Cost		Gains		Losses		Value
Corporate debt securities	$	10,740	$	—	$	(2)	$	10,738
Commercial paper		47,473		8		(2)		47,479
Total	$	58,213	$	8	$	(4)	$	58,217

The following table summarizes the balance sheet classification of our investments:

	As of September 30,		As of December 31,
(in thousands)	2017		2016
Cash equivalents	$	56,081	$	22,029
Short-term investments		2,600		36,184
Total investments	$	58,681	$	58,213

The gross amortized cost and estimated fair value of our held-to-maturity investments by contractual maturity are shown below. Actual maturities may differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties.

	As of September 30, 2017				As of December 31, 2016
	Gross				Gross
	Amortized		Fair		Amortized		Fair
(in thousands)	Cost		Value		Cost		Value
Due in one year or less	$	58,681	$	58,677	$	58,213	$	58,217
Due after one year through five years		—		—		—		—
Total	$	58,681	$	58,677	$	58,213	$	58,217

We monitor our investment portfolio for impairment on a periodic basis. In order to determine whether a decline in fair value is other-than-temporary, we evaluate, among other factors: the duration and extent to which the fair value has been less than the carrying value; our financial condition and business outlook, including key operational and cash flow metrics, current market conditions and future trends in our industry; our relative competitive position within the industry; and our intent and ability to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value. A decline in the fair value of the security below amortized cost that is deemed other-than-temporary is charged to earnings, resulting in the establishment of a new cost basis for the affected securities. In the three and nine months ended September 30, 2017, we had an insignificant amount of unrealized gains or losses, and we did not recognize any other-than-temporary impairments.