Warrants to Purchase Common Stock and CDIs - Additional Information (Detail) - $ / shares		9 Months Ended
	May 04, 2016	Sep. 30, 2018	May 30, 2018
2018 Senior Secured Convertible Promissory Note and Warrant
Class of Warrant or Right [Line Items]
Warrant expiration date			May 30, 2023
2018 Senior Secured Convertible Promissory Note and Warrant | CHESS Depositary Interests
Class of Warrant or Right [Line Items]
Common stock warrants, shares issued			97,222,200
Common stock warrant, exercise price			$ 0.018
Common stock | 2018 Senior Secured Convertible Promissory Note and Warrant
Class of Warrant or Right [Line Items]
Common stock warrants, shares issued			1,944,444
Consulting Agreement | Consultant Warrant
Class of Warrant or Right [Line Items]
Common stock warrants, shares issued	28,532
Common stock warrant, exercise price	$ 0.64
Vesting period of warrants	2 years
Contractual life of warrants	5 years
Common stock warrant, share reserved	28,532
Common stock warrant, shares exercised		0