Net Loss Per Share - Summary of Number of Ordinary Shares Excluded from Computation of Earnings Per Share (Detail) (Parenthetical) - $ / shares	Sep. 30, 2017	Sep. 30, 2016
Exercise Of Warrants At $16.14 Per Share
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Exercise price of warrants per share	$ 16.14	$ 16.14
Exercise Of Warrants At $9.37 Per Share
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Exercise price of warrants per share	$ 9.37	$ 9.37