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%