INTANGIBLE AND OTHER ASSETS: (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2013	Apr. 30, 2012
Finite-Lived Intangible Assets, Cost	$ 23,259	$ 23,270
Finite-Lived Intangible Assets, Accumulated Amortization	8,284	9,290
Software and Software Development Costs [Member]
Finite-Lived Intangible Assets, Cost	0	1,964
Finite-Lived Intangible Assets, Accumulated Amortization	0	1,905
Deferred Order Entry Costs [Member]
Finite-Lived Intangible Assets, Cost	1,278	1,320
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Prepaid Expenses [Member]
Finite-Lived Intangible Assets, Cost	3,859	3,315
Finite-Lived Intangible Assets, Accumulated Amortization	0	0
Customer Contracts and Relationships [Member]
Finite-Lived Intangible Assets, Cost	17,048	15,000
Finite-Lived Intangible Assets, Accumulated Amortization	7,917	6,612
Other Intangible Assets [Member]
Finite-Lived Intangible Assets, Cost	1,074	1,671
Finite-Lived Intangible Assets, Accumulated Amortization	$ 367	$ 773