Equity - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Total stock-based compensation expense	$ 1,688	$ 5,151	$ 3,393	$ 7,017
Research and Development Expense [Member]
Total stock-based compensation expense	571	98	1,200	178
General and Administrative Expense [Member]
Total stock-based compensation expense	$ 1,117	$ 5,053	$ 2,193	$ 6,839