Nature of Business and Basis of Presentation - Additional Information (Details) |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Apr. 30, 2018 |
Apr. 30, 2017 |
Apr. 30, 2018 |
Apr. 30, 2017 |
|
| POSCO Energy [Member] | ||||
| Nature Of Business And Basis Of Presentation [Line Items] | ||||
| Common stock ownership percentage | 3.00% | 3.00% | ||
| Significant customer revenue percentage | 4.00% | 7.00% | 3.00% | 8.00% |
| NRG Energy, Inc. [Member] | ||||
| Nature Of Business And Basis Of Presentation [Line Items] | ||||
| Common stock ownership percentage | 2.00% | 2.00% | ||
| Significant customer revenue percentage | 52.00% | 0.30% | 18.10% | 0.40% |