Transactions With Related Parties - Facilities Rental (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Affiliated partnerships or entities \| Lease of warehouse facilities \| Selling, general and administrative expenses
Transactions with related parties
Rent expense	$ 0.2	$ 0.2	$ 0.6	$ 0.6

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