Investments (Tables)

9 Months Ended

Sep. 30, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments in Fixed Income Securities

	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

Summary of the Balance Sheet Classification of 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

Schedule of Held-to-Maturity Investments by Contractual Maturity

	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