Going Concern - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Aug. 16, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss		$ (29,905,237)	$ (4,795,059)	$ (37,594,401)	$ (8,024,985)
Cash used to fund operations				(15,407,930)	(4,860,116)
Accumulated deficit		$ (68,853,850)		(68,853,850)		$ (31,259,449)
Proceeds from issuance of preferred stock and related common stock warrants, net of issuance costs	$ 13,018,570			$ 13,018,570	$ 5,673,680