Share-based Compensation - Valuations Assumptions (Details) - $ / shares |
10 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Dec. 15, 2017 |
Sep. 30, 2018 |
Sep. 30, 2018 |
Sep. 30, 2016 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Dividend yield (percent) | 0.00% | |||
| Stock options | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Exercise price (in dollars per share) | $ 19.46 | $ 21.6595 | $ 21.6595 | |
| Volatility (percent) | 56.59% | 49.67% | ||
| Term (years) | 6 years 7 months 24 days | 5 years 10 months 10 days | ||
| Risk-free rate (percent) | 2.35% | 2.72% | ||
| Dividend yield (percent) | 0.00% | 0.00% | ||
| Predecessor | Stock options | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Exercise price (in dollars per share) | $ 1.83 | |||
| Volatility (percent) | 83.09% | |||
| Term (years) | 5 years | |||
| Risk-free rate (percent) | 1.53% | |||
| Dividend yield (percent) | 0.00% | 0.00% | ||
| Expiration period | 10 years | |||