Business Combinations (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Jul. 31, 2012
Changes in goodwill
Balance, as of April 30,2012
Increase in goodwill related to acquisition	112,700
Balance, as of July 31, 2012, Gross	112,700
Accumulated impairment loss
Balance, as of July 31, 2012, net	$ 112,700

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

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+ Details

- Definition

Change in the carrying value of goodwill. The change could be the result of new goodwill acquired, goodwill impairment, if any, goodwill written off related to the sale of a business or other adjustments to goodwill.

+ References+ Details