Short-term Investments (Tables)

6 Months Ended

Jun. 30, 2020

Investments, Debt and Equity Securities [Abstract]

Summary of short-term investments

Short-term investments as of December 31, 2019 consisted of the following (in thousands):

			Gross
	Amortized		Unrealized		Estimated
	Cost		Losses		Fair Value
Municipal bonds and notes	$	2,986	$	—	$	2,986
Zero coupon bonds		33,919		—		33,919
Corporate bonds		19,509		(3)		19,506
Certificates of deposit		518		—		518
Total short-term investments	$	56,932	$	(3)	$	56,929

Short-term investments as of June 30, 2020 consisted of the following (in thousands):

			Gross
	Amortized		Unrealized		Estimated
	Cost		Gains		Fair Value
Zero coupon bonds	$	13,995	$	2	$	13,997
Corporate bonds		2,002		—		2,002
Certificates of deposit		530		—		530
Total short-term investments	$	16,527	$	2	$	16,529