Basis of Presentation and Significant Accounting Policies - Summary of Option Activity (Detail) - $ / shares	9 Months Ended	12 Months Ended
	Jun. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding Beginning Balance (in shares)	1,602,822
Options, Granted (in shares)	315,020
Options, Exercised (in shares)	0
Options, Forfeited (in shares)	(84,314)
Options, Outstanding Ending Balance (in shares)	1,833,528	1,602,822
Options, Exercisable Ending Balance (in shares)	1,265,843
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding Beginning Balance (in usd per share)	$ 9.51
Weighted Average Exercise Price, Granted (in usd per share)	4.75
Weighted Average Exercise Price, Exercised (in usd per share)	0.00
Weighted Average Exercise Price, Forfeited (in usd per share)	16.81
Weighted Average Exercise Price, Outstanding Ending Balance (in usd per share)	8.36	$ 9.51
Weighted Average Exercise Price, Exercisable Ending Balance	$ 9.21
Weighted Average Remaining Contractual Period in Years, Outstanding Ending Balance	6 years 1 month	6 years 7 months 6 days
Weighted Average Remaining Contractual Period in Years, Granted	9 years 6 months
Weighted Average Remaining Contractual Period in Years, Exercised	0 years
Weighted Average Remaining Contractual Period in Years, Forfeited	4 years 11 months 6 days
Weighted Average Remaining Contractual Period in Years, Exercisable Ending Balance	5 years