Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Short-term investments available-for-sale

Our short-term investments are classified as available-for-sale and consist of the following:

	December 31, 2018
	Amortized		Unrealized Gross				Aggregate
	Cost		Gains		Losses		Fair Value
Commercial paper	$	27,898	$	—	$	—	$	27,898
Corporate bonds	28,043		—		(31)		28,012
Asset-backed securities	17,074		—		(19)		17,055
U.S. government securities	17,959		—		(2)		17,957
Short-term investments	$	90,974	$	—	$	(52)	$	90,922

	December 31, 2017
	Amortized		Unrealized Gross				Aggregate
	Cost		Gains		Losses		Fair Value
Commercial paper	$	5,384	$	—	$	—	$	5,384
Corporate bonds	1,804		—		—		1,804
Short-term investments	$	7,188	$	—	$	—	$	7,188