Energy Services Accounts Receivable Securitization Facility - Narrative (Details) - USD ($)	6 Months Ended
Oct. 31, 2017	Apr. 30, 2017
Forecast \| Maximum
Accounts, Notes, Loans and Financing Receivable
Receivables facility	$ 75,000,000	$ 150,000,000

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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