Stockholders' Equity - Warrants to Purchase Common Shares - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	9 Months Ended
	Jun. 26, 2018	Mar. 28, 2018	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Warrants issued in connection with term loan facility				0	486,812
Exercise price of issued warrants				$ 0	$ 1.23
Warrants, outstanding			486,812	486,812	486,812	486,812		0
Proceeds from exercise of warrants					$ 28,863
Second Tranche Warrants [Member]
Class of Stock [Line Items]
Exercise price of issued warrants			$ 1.43
Warrants, outstanding							20,184,224
Proceeds from exercise of warrants			$ 28,900
Warrants [Member] | Investor [Member]
Class of Stock [Line Items]
Weighted average remaining life of lender warrants				5 years 6 months 14 days
Senior Secured Term Loan [Member] | Warrants [Member]
Class of Stock [Line Items]
Warrants issued in connection with term loan facility	77,721	409,091
Exercise price of issued warrants	$ 1.93	$ 1.10
Warrants exercise period	7 years	7 years