Stock-Based Compensation - Assumptions Used to Value Stock Options (Detail) - $ / shares |
12 Months Ended | ||
---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2013 |
|
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
Risk-free interest rate, minimum | 1.46% | 1.80% | 0.70% |
Risk-free interest rate, maximum | 1.89% | 2.40% | 2.30% |
Volatility | 75.00% | 69.00% | 69.00% |
Weighted average grant date fair value per share of options granted | $ 4.24 | $ 8.92 | $ 1.88 |
Minimum | |||
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
Expected life (in years) | 6 years | 6 years 3 months | 5 years 6 months |
Maximum | |||
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
Expected life (in years) | 6 years 3 months | 9 years 5 months 19 days | 6 years 3 months |