INTANGIBLE AND OTHER ASSETS: (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Apr. 30, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	$ 23,702	$ 23,259
Finite-Lived Intangible Assets, Accumulated Amortization	9,576	8,284
Deferred Order Entry Costs [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	1,168	1,278
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Prepaid Expenses [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	4,365	3,859
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Customer Contracts and Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	16,986	17,048
Finite-Lived Intangible Assets, Accumulated Amortization	9,342	7,917
Other Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	1,183	1,074
Finite-Lived Intangible Assets, Accumulated Amortization	$ 234	$ 367