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Property And Equipment (Narrative) (Details) (USD $)	12 Months Ended
Property And Equipment (Narrative) (Details) (USD $)	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Property, Plant and Equipment [Line Items]
Tax incentives received relating to corporate headquarters building	$ 7,300,000	$ 7,600,000	$ 6,500,000
Depreciation and amortization	$ 68,192,000	$ 61,390,000	$ 61,557,000

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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