Other Current Assets and Other Long-Term Assets - Summary (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 5,043	$ 5,672
Deposits and other receivables	1,471	2,119
Interest receivable	1,813	1,566
Other current assets	8,327	9,357
Deposits paid for research and development	5,400	5,100
Long-term operating right-of-use asset	700	600
Security deposit for lease	$ 600	$ 300