Fair Value of Investments (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value

Summary of fair value financial assets measured on a recurring basis

	Quoted Prices in Active Markets for Indentical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	12,947	$	—	$	—	$	12,947
U.S. government securities		15,923		—		—		15,923
Corporate bonds		—		31,495		—		31,495
Commerical paper		—		27,869		—		27,869
Asset-backed securities		—		17,025		—		17,025
Total assets	$	28,870	$	76,389	$	—	$	105,259