Stock-based Compensation - Warrants Granted to Non-Employees - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 05, 2014
Warrant information
Aggregate stock-based compensation expense	$ 15,656,372	$ 5,250,217	$ 416,624
Stock warrants exercised (in shares)	20,771	138,000
Proceeds from exercise of stock warrants	$ 53,350	$ 341,000
Research and development expenses
Warrant information
Aggregate stock-based compensation expense	5,988,231	1,293,841	$ 179,641
First Warrant | Pavilion
Warrant information
Grant date fair value	146,000
Warrants, exercise price (in dollars per share)				$ 2.47
First Warrant | Pavilion | Research and development expenses
Warrant information
Aggregate stock-based compensation expense	$ 0	$ 358,637
Common Stock | Non-Employee
Warrant information
Stock warrants vested ( in shares)	305,775	326,556
Stock warrants outstanding (in shares)	305,775	326,556
Warrants, exercise price (in dollars per share)	$ 2.57	$ 2.57