Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense (income)	$ 4,148,025	$ 888,556	$ 6,281,555	$ 2,144,866
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense (income)	1,037,530	264,731	1,671,905	366,432
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense (income)	$ 3,110,495	$ 623,825	$ 4,609,650	$ 1,778,434