Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2012	Apr. 30, 2012
Goodwill And Intangible Assets [Abstract]
Goodwill before impairment losses, beginning balance	$ 459,863
Accumulated impairment losses, beginning balance	(32,297)
Goodwill	434,492	427,566
Acquisitions	6,922
Disposals and foreign currency changes, net	4
Goodwill before impairment losses, ending balance	466,789
Accumulated impairment losses, ending balance	$ (32,297)