Stock-Based Compensation - Assumptions Used to Value Stock Options (Detail) - $ / shares |
6 Months Ended | |
---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||
Risk-free interest rate, minimum | 2.10% | 1.30% |
Risk-free interest rate, maximum | 2.70% | 2.10% |
Volatility | 110.00% | 79.00% |
Expected life (in years) | 6 years 3 months | |
Weighted average grant date fair value per share of options granted | $ 3.47 | $ 1.36 |
Minimum | ||
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||
Expected life (in years) | 5 years 9 months | |
Maximum | ||
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||
Expected life (in years) | 6 years 3 months |