Transactions With Related Parties - Facilities Rental (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Affiliated partnerships or entities \| Lease of office and warehouse facilities \| Selling, general and administrative expenses
Transactions with related parties
Rent expense	$ 0.2	$ 0.4	$ 0.2	$ 0.4

Amount of selling, general and administrative expenses resulting from transactions, excluding transactions that are eliminated in consolidated or combined financial statements, with related party.

No definition available.

Name:	us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration