Debt - Accounts Receivable Securitization Facility (Details) - USD ($)	6 Months Ended
Oct. 31, 2019	Apr. 30, 2019
Energy Services \| Receivables Facility \| Energy Services Receivables Facility
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 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.

No definition available.

Name:	us-gaap_ShortTermDebtLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration