INTANGIBLE AND OTHER ASSETS: (Details) - USD ($) $ in Thousands	Apr. 30, 2016	Apr. 30, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	$ 3,478	$ 21,197
Finite-Lived Intangible Assets, Accumulated Amortization	0	10,757
Customer Contracts and Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	7	16,986
Finite-Lived Intangible Assets, Accumulated Amortization	0	10,757
Prepaid Expenses [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	2,358	2,520
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Deferred Order Entry Costs [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	845	961
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Other [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	268	730
Finite-Lived Intangible Assets, Accumulated Amortization	$ 0	$ 0