Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financial Assets
Financial assets, fair value	$ 47,919	$ 68,216
Money market funds
Financial Assets
Financial assets, fair value	9,026	7,023
Reverse repurchase agreements
Financial Assets
Financial assets, fair value		6,250
Commercial paper
Financial Assets
Financial assets, fair value	10,225	15,193
Corporate bonds
Financial Assets
Financial assets, fair value	28,668	39,750
Level 1
Financial Assets
Financial assets, fair value	9,026	7,023
Level 1 | Money market funds
Financial Assets
Financial assets, fair value	9,026	7,023
Level 2
Financial Assets
Financial assets, fair value	38,893	61,193
Level 2 | Reverse repurchase agreements
Financial Assets
Financial assets, fair value		6,250
Level 2 | Commercial paper
Financial Assets
Financial assets, fair value	10,225	15,193
Level 2 | Corporate bonds
Financial Assets
Financial assets, fair value	$ 28,668	$ 39,750