Net Loss Per Share - Summary of Number of Ordinary Shares Excluded from Computation of Earnings Per Share (Detail) - shares	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Ordinary shares issuable excluded from computation of earnings per share	3,374,810	2,609,480
Exercise Of Options To Purchase Ordinary Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Ordinary shares issuable excluded from computation of earnings per share	2,207,722	1,806,668
Restricted Share Units Awarded, Including Multi-Year Performance
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Ordinary shares issuable excluded from computation of earnings per share	991,563	627,287
Exercise Of Warrants At $16.14 Per Share
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Ordinary shares issuable excluded from computation of earnings per share	111,525	111,525
Exercise Of Warrants At $9.37 Per Share
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Ordinary shares issuable excluded from computation of earnings per share	64,000	64,000