Cash and Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 22,575	$ 38,022
Debt securities, available-for-sale, amortized cost	137,854	118,119
Debt Securities, available-for-sale, accumulated gross unrealized gain, before tax	52	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(2)	0
Short-term investments	137,904	118,119
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	13,588	38,022
Commercial paper
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	8,987
Cash Equivalents
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	22,575	38,022
Commercial paper
Cash and Cash Equivalents [Line Items]
Debt securities, available-for-sale, amortized cost	61,371	79,634
Debt Securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	0	0
Short-term investments	61,371	79,634
Corporate Bond Securities
Cash and Cash Equivalents [Line Items]
Debt securities, available-for-sale, amortized cost	23,856	16,119
Debt Securities, available-for-sale, accumulated gross unrealized gain, before tax	14	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(1)	0
Short-term investments	23,869	16,119
US Treasury and Government
Cash and Cash Equivalents [Line Items]
Debt securities, available-for-sale, amortized cost	52,627	22,366
Debt Securities, available-for-sale, accumulated gross unrealized gain, before tax	38	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(1)	0
Short-term investments	$ 52,664	$ 22,366