Investments

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Investments

4. Investments

Our portfolio of fixed income securities consists of commercial paper, corporate debt securities and securities and obligations of U.S. government agencies. 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 December 31, 2016 and 2015 were as follows:

	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

	As of December 31, 2015
	Amortized						Fair
(in thousands)	cost		Gains		Losses		Value
Corporate debt securities	$	28,549	$	1	$	(30)	$	28,520
Commercial paper		24,187		1		(1)		24,187
Securities and obligations of U.S. government agencies		12,431		—		(5)		12,426
Total	$	65,167	$	2	$	(36)	$	65,133

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

	As of December 31,
(in thousands)	2016		2015
Cash equivalents	$	22,029	$	13,499
Short-term investments		36,184		49,574
Long-term investments		—		2,094
Total investments	$	58,213	$	65,167

The gross amortized cost and estimated fair value of our held-to-maturity investments at December 31, 2016 and 2015 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 December 31,
	2016				2015
	Gross				Gross
	Amortized		Fair		Amortized		Fair
(in thousands)	Cost		Value		Cost		Value
Due in one year or less	$	58,213	$	58,217	$	63,073	$	63,040
Due after one year through five years		—		—		2,094		2,093
Total	$	58,213	$	58,217	$	65,167	$	65,133

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 2016, we had an insignificant amount of unrealized gains or losses, and we did not recognize any other-than-temporary impairments.