Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Summary of short-term investments

Short-term investments as of December 31, 2018 consisted of the following (in thousands):

			Gross
	Amortized		Unrealized		Estimated
	Cost		Losses		Fair Value
Municipal bonds and notes	$	9,210	$	(19)	$	9,191
Zero coupon bonds		29,823		(28)		29,795
Corporate bonds		26,175		(22)		26,153
Certificates of deposit		507		—		507
Total short-term investments	$	65,715	$	(69)	$	65,646

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