Assets - Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Short-term investments
Transfer of assets from Level 1 to Level 2	$ 0
Transfer of assets from Level 2 to Level 1	0
Transfer of Liabilities from Level 1 to Level 2	0
Transfer of Liabilities from Level 2 to Level 1	0
Measured at fair value on a recurring basis
Cash equivalents
Total Cash equivalents	83,999	$ 86,165
Short-term investments
Total Short-term investments	186,142	189,771
Measured at fair value on a recurring basis | U.S. treasuries
Short-term investments
Total Short-term investments	120,096	149,219
Measured at fair value on a recurring basis | Corporate debt
Short-term investments
Total Short-term investments	58,449	32,554
Measured at fair value on a recurring basis | Commercial paper
Short-term investments
Total Short-term investments	7,597	7,998
Measured at fair value on a recurring basis | Certificate of deposits and time deposits
Cash equivalents
Total Cash equivalents	80,062	59,168
Measured at fair value on a recurring basis | Corporate debt
Cash equivalents
Total Cash equivalents	2,002
Measured at fair value on a recurring basis | Commercial paper
Cash equivalents
Total Cash equivalents	950	2,000
Measured at fair value on a recurring basis | Money market cash
Cash equivalents
Total Cash equivalents	985
Measured at fair value on a recurring basis | U.S. treasuries
Cash equivalents
Total Cash equivalents		24,997
Measured at fair value on a recurring basis | Level 1
Cash equivalents
Total Cash equivalents	81,047	84,165
Short-term investments
Total Short-term investments	120,096	149,219
Measured at fair value on a recurring basis | Level 1 | U.S. treasuries
Short-term investments
Total Short-term investments	120,096	149,219
Measured at fair value on a recurring basis | Level 1 | Certificate of deposits and time deposits
Cash equivalents
Total Cash equivalents	80,062	59,168
Measured at fair value on a recurring basis | Level 1 | Money market cash
Cash equivalents
Total Cash equivalents	985
Measured at fair value on a recurring basis | Level 1 | U.S. treasuries
Cash equivalents
Total Cash equivalents		24,997
Measured at fair value on a recurring basis | Level 2
Cash equivalents
Total Cash equivalents	2,952	2,000
Short-term investments
Total Short-term investments	66,046	40,552
Measured at fair value on a recurring basis | Level 2 | Corporate debt
Short-term investments
Total Short-term investments	58,449	32,554
Measured at fair value on a recurring basis | Level 2 | Commercial paper
Short-term investments
Total Short-term investments	7,597	7,998
Measured at fair value on a recurring basis | Level 2 | Corporate debt
Cash equivalents
Total Cash equivalents	2,002
Measured at fair value on a recurring basis | Level 2 | Commercial paper
Cash equivalents
Total Cash equivalents	$ 950	$ 2,000