Significant Accounting Policies - Summary of the Inventory Values (Details) - USD ($) $ in Thousands	Apr. 30, 2017	Apr. 30, 2016
Inventory
Inventory	$ 201,644	$ 204,988
Fuel
Inventory
Inventory	60,833	57,840
Merchandise
Inventory
Inventory	$ 140,811	$ 147,148

Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.6(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_InventoryGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant