Acquisitions - Allocation of Purchase Price (Details) - USD ($) $ in Thousands	Apr. 30, 2015	Apr. 30, 2014
Liabilities assumed:
Goodwill	$ 127,046	$ 120,406
Series of Individually Immaterial Business Acquisitions
Assets acquired:
Inventories	2,863
Property and equipment	31,740
Total assets	34,603
Liabilities assumed:
Accrued expenses	86
Total liabilities	86
Net tangible assets acquired	34,517
Goodwill	6,640
Total consideration paid	$ 41,157