Financial Instruments (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Summary of assets measured at fair value on a recurring basis
Total assets	$ 42,999	$ 33,714
Level 1
Summary of assets measured at fair value on a recurring basis
Total assets	22,999	5,432
Level 2
Summary of assets measured at fair value on a recurring basis
Total assets	20,000	28,282
Money market fund
Summary of assets measured at fair value on a recurring basis
Cash and cash equivalents	22,999	5,432
Money market fund | Level 1
Summary of assets measured at fair value on a recurring basis
Cash and cash equivalents	22,999	5,432
Commercial paper
Summary of assets measured at fair value on a recurring basis
Short-term investments		1,993
Commercial paper | Level 2
Summary of assets measured at fair value on a recurring basis
Short-term investments		1,993
Corporate debt securities
Summary of assets measured at fair value on a recurring basis
Cash and cash equivalents		1,937
Short-term investments		3,352
Corporate debt securities | Level 2
Summary of assets measured at fair value on a recurring basis
Cash and cash equivalents		1,937
Short-term investments		3,352
Reverse repurchase agreements
Summary of assets measured at fair value on a recurring basis
Short-term investments	20,000	21,000
Reverse repurchase agreements | Level 2
Summary of assets measured at fair value on a recurring basis
Short-term investments	$ 20,000	$ 21,000