Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Jul. 31, 2011	Apr. 30, 2012	Apr. 30, 2011
Goodwill And Intangible Assets [Abstract]
Goodwill before impairment losses, beginning balance	$ 459,039	$ 459,039	$ 453,884
Accumulated impairment losses, beginning balance	(24,888)	(24,888)	(2,188)
Goodwill, beginning balance	434,151	434,151	451,696
Acquisitions		5,377	15,441
Disposals and foreign currency changes		(4,553)	(10,286)
Impairments	(99,700)	(7,409)	(22,700)
Goodwill before impairment losses, ending balance		459,863	459,039
Accumulated impairment losses, ending balance		(32,297)	(24,888)
Goodwill, ending balance		$ 427,566	$ 434,151