Restructuring Liability (Schedule Of Changes In Restructuring Liability) (Details) (USD $)	3 Months Ended	6 Months Ended
Oct. 31, 2011	Oct. 31, 2011	Apr. 30, 2011
Liability, Beginning period	$ 3,820,000	$ 4,921,000
Reductions for cash payments	(680,000)	(1,707,000)
Exchange rate fluctuations	(64,000)	(138,000)
Liability, Ending period	3,076,000	3,076,000
Restructuring liability included in other long-term liabilities	1,300,000	1,300,000	2,100,000
Long-term restructuring liability, payment term	seven years	seven years
Severance [Member]
Liability, Beginning period	714,000	978,000
Reductions for cash payments	(76,000)	(331,000)
Exchange rate fluctuations	1,000	(8,000)
Liability, Ending period	639,000	639,000
Facilities [Member]
Liability, Beginning period	3,106,000	3,943,000
Reductions for cash payments	(604,000)	(1,376,000)
Exchange rate fluctuations	(65,000)	(130,000)
Liability, Ending period	$ 2,437,000	$ 2,437,000

Carrying amount as of the balance sheet date of known and estimated costs associated with exit from or disposal of business activities or restructurings pursuant to a duly authorized plan, which are expected to be paid after one year or beyond the next operating cycle, if longer. Costs of such activities include those for one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, and relocating employees, and costs associated with an ongoing benefit arrangement, but excludes costs associated with the retirement of a long-lived asset.

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Amount of cash paid in the period to fully or partially settle a specified, previously accrued type of restructuring cost.

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- Definition

Amount of foreign currency translation adjustment increasing or decreasing the accrual for a specified type of restructuring cost.

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